11:06 p.m.
Currently, the kernel has supported Rust, and it has been
enabled in some distributions by default. So the crash tool
can not resolve the mangled Rust symbols on such vmcores.
For example:
crash> bt
PID: 3520 TASK: ffff8f240f670000 CPU: 1 COMMAND: "insmod"
#0 [ffffd08c4f063a20] machine_kexec at ffffffff9575e60e
#1 [ffffd08c4f063a40] __crash_kexec at ffffffff958db711
#2 [ffffd08c4f063b00] panic at ffffffff9560cede
#3 [ffffd08c4f063b80] _RNvCscb18lrEyTSA_10rust_panic10area_in_hp at ffffffffc07fe107
[rust_panic]
#4 [ffffd08c4f063c20] _RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two at
ffffffffc07fe160 [rust_panic]
#5 [ffffd08c4f063cf0] do_one_initcall at ffffffff956c7aaa
...
The patchset will solve the current issues, the crash tool
reuses the rust demangle lib in gdb to demangle the mangled
Rust symbol into human-readable symbol.
With the patchset:
crash> bt
PID: 3520 TASK: ffff8f240f670000 CPU: 1 COMMAND: "insmod"
#0 [ffffd08c4f063a20] machine_kexec at ffffffff9575e60e
#1 [ffffd08c4f063a40] __crash_kexec at ffffffff958db711
#2 [ffffd08c4f063b00] panic at ffffffff9560cede
#3 [ffffd08c4f063b80] rust_panic::area_in_hp at ffffffffc07fe107 [rust_panic]
#4 [ffffd08c4f063c20] <rust_panic::HelloPanic>::step_two at ffffffffc07fe160
[rust_panic]
#5 [ffffd08c4f063cf0] do_one_initcall at ffffffff956c7aaa
...
crash> sym "rust_panic::area_in_hp"
ffffffffc07fe010 (t) rust_panic::area_in_hp [rust_panic]
/root/linux-6.16.3/samples/rust/rust_panic.rs: 22
crash> dis "rust_panic::area_in_hp"
0xffffffffc07fe010 <rust_panic::area_in_hp>::area_in_hp>: push %rbx
0xffffffffc07fe011 <rust_panic::area_in_hp+1>::area_in_hp+1>: sub
$0x90,%rsp
0xffffffffc07fe018 <rust_panic::area_in_hp+8>::area_in_hp+8>: mov
%rdi,%rbx
0xffffffffc07fe01b <rust_panic::area_in_hp+11>::area_in_hp+11>: movq
$0xffffffffc0bd5020,(%rsp)
0xffffffffc07fe023 <rust_panic::area_in_hp+19>::area_in_hp+19>: movq
$0x1,0x8(%rsp)
0xffffffffc07fe02c <rust_panic::area_in_hp+28>::area_in_hp+28>: movq
$0x0,0x20(%rsp)
0xffffffffc07fe035 <rust_panic::area_in_hp+37>::area_in_hp+37>: movq
$0x8,0x10(%rsp)
0xffffffffc07fe03e <rust_panic::area_in_hp+46>::area_in_hp+46>: movq
$0x0,0x18(%rsp)
0xffffffffc07fe047 <rust_panic::area_in_hp+55>::area_in_hp+55>: mov
%rsp,%rcx
0xffffffffc07fe04a <rust_panic::area_in_hp+58>::area_in_hp+58>: mov
$0xc,%edx
0xffffffffc07fe04f <rust_panic::area_in_hp+63>::area_in_hp+63>: mov
$0xffffffff96afb62c,%rdi
0xffffffffc07fe056 <rust_panic::area_in_hp+70>::area_in_hp+70>: mov
$0xffffffffc0bd5118,%rsi
0xffffffffc07fe05d <rust_panic::area_in_hp+77>::area_in_hp+77>: call
0xffffffff95fcb2e0 <kernel::print::call_printk>
0xffffffffc07fe062 <rust_panic::area_in_hp+82>::area_in_hp+82>: movq
$0xffffffffc0bd50d0,0x30(%rsp)
...
crash> gdb bt
#0 0xffffffff958db684 in crash_setup_regs (newregs=0xffffd08c4f063a48, oldregs=0x0) at
./arch/x86/include/asm/kexec.h:108
#1 0xffffffff958db711 in __crash_kexec (regs=regs@entry=0x0) at
kernel/crash_core.c:122
#2 0xffffffff9560cede in panic (fmt=<optimized out>) at kernel/panic.c:401
#3 0xffffffffc07fe107 in rust_panic::HelloPanic::trigger_panic (self=0x1) at
rust_panic.rs:59
#4 rust_panic::HelloPanic::step_three (self=0x1) at rust_panic.rs:53
#5 rust_panic::area_in_hp (rectangle=0xffffd08c4f063c38) at rust_panic.rs:24
#6 0xffffffffc07fe160 in rust_panic::HelloPanic::step_two (self=<optimized out>)
at rust_panic.rs:46
#7 0xffffffffc0c5d067 in ?? ()
crash> frame 5
#5 rust_panic::area_in_hp (rectangle=0xffffd08c4f063c38) at rust_panic.rs:24
24 in rust_panic.rs
crash> whatis rectangle
*mut rust_panic::RectangleHP
crash> p *rectangle
$2 = rust_panic::RectangleHP {
width: 30,
height: 50
}
crash> struct RectangleHP
struct rust_panic::RectangleHP {
width: u32,
height: u32,
}
SIZE: 8
crash>
Anyway, there are still many limitations of debugging complex, nested
data type about Rust code in kernel. I do not expect patches to always
work well in the real world, but it can get improved over time. As you
know, also some challenges come from the compilers, they may have
different behavior, for example:
crash> gdb bt
#0 rust_helper_BUG () at rust/helpers/bug.c:7
#1 0xffffffff98b5a92a in kernel::panic (info=0xffffcf05880d7800) at
rust/kernel/lib.rs:202
#2 0xffffffff9840e310 in core::panicking::panic_fmt (fmt=...) at
/home/llvm-20.1.8-rust-1.88.0-x86_64/lib/rustlib/src/rust/library/core/src/panicking.rs:75
#3 0xffffffffc12e71ec in ?? ()
#4 0xffffcf05880d7880 in ?? ()
#5 0xffffffffc14680a8 in ?? ()
crash>
Note: The above kernel is compiled with the clang(clang version 20.1.8
(https://github.com/llvm/llvm-project.git 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)), the
gdb stack unwind looks incomplete.
BTW: I did not see the similar issues on the kernel that compiled by the gcc (GCC)
14.3.1.
Note: the rust_panic is a Rust kernel module, which is used to test the
current patchset. If anyone needs it, I can share it via email.
Lianbo Jiang (3):
Add a rustfilt command to demangle a mangled Rust symbol
Enable demangling a mangled Rust support
Enable resolving mangled Rust symbol in lockless ring buffer
Makefile | 2 +-
defs.h | 2 ++
global_data.c | 1 +
help.c | 10 +++++++
printk.c | 28 +++++++++++++++++-
symbols.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++
6 files changed, 119 insertions(+), 2 deletions(-)
--
2.50.1
11:06 p.m.
New subject: [PATCH 1/3] Add a rustfilt command to demangle a mangled Rust symbol
For example:
crash> rustfilt _RNvXsh_NtCskljHLvcz3xy_4core3fmteNtB5_7Display3fmt
<str as core::fmt::Display>::fmt
Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
---
defs.h | 2 ++
global_data.c | 1 +
help.c | 10 ++++++++++
symbols.c | 33 +++++++++++++++++++++++++++++++++
4 files changed, 46 insertions(+)
diff --git a/defs.h b/defs.h
index 4fecb8388229..156ac0232906 100644
--- a/defs.h
+++ b/defs.h
@@ -5508,6 +5508,7 @@ void cmd_s390dbf(void);
#endif
void cmd_map(void); /* kvmdump.c */
void cmd_ipcs(void); /* ipcs.c */
+void cmd_rustfilt(void); /* symbols.c */
/*
* main.c
@@ -6115,6 +6116,7 @@ extern char *help_wr[];
extern char *help_s390dbf[];
#endif
extern char *help_map[];
+extern char *help_rustfilt[];
/*
* task.c
diff --git a/global_data.c b/global_data.c
index f9bb7d079f51..889103d35f82 100644
--- a/global_data.c
+++ b/global_data.c
@@ -125,6 +125,7 @@ struct command_table_entry linux_command_table[] = {
#if defined(S390) || defined(S390X)
{"s390dbf", cmd_s390dbf, help_s390dbf, 0},
#endif
+ {"rustfilt", cmd_rustfilt, help_rustfilt, MINIMAL},
{(char *)NULL}
};
diff --git a/help.c b/help.c
index 5d61e0d57229..4f071e0bd0a0 100644
--- a/help.c
+++ b/help.c
@@ -8186,6 +8186,16 @@ char *help_net[] = {
NULL
};
+char *help_rustfilt[] = {
+"rustfilt",
+"demangle a mangled Rust symbol to human readable symbol",
+"<symbol>",
+" This command converts a mangled Rust symbol to human readable symbol.",
+"\nEXAMPLES",
+" crash> rustfilt _RNvNtCshc5sK6KjdJJ_6kernel5print11call_printk",
+" kernel::print::call_printk",
+NULL
+};
char *help_waitq[] = {
"waitq",
diff --git a/symbols.c b/symbols.c
index 794519ad4126..052196265be0 100644
--- a/symbols.c
+++ b/symbols.c
@@ -22,6 +22,7 @@
#include "config.h"
#endif
#include "bfd.h"
+#include "demangle.h"
static void store_symbols(bfd *, int, void *, long, unsigned int);
static void store_sysmap_symbols(void);
@@ -4887,6 +4888,38 @@ do_multiples:
cmd_usage(pc->curcmd, SYNOPSIS);
}
+/*
+ * Demangle a mangled Rust symbol to human readable symbol
+ */
+void cmd_rustfilt(void)
+{
+ int c;
+
+ while ((c = getopt(argcnt, args, "")) != EOF) {
+ switch(c)
+ {
+ default:
+ argerrs++;
+ break;
+ }
+ }
+
+ if (argerrs)
+ cmd_usage(pc->curcmd, SYNOPSIS);
+
+ if (args[optind]) {
+ char *buf;
+
+ buf = rust_demangle(args[optind], DMGL_RUST);
+ if (buf) {
+ fprintf(fp, "%s", buf);
+ free(buf);
+ } else
+ fprintf(fp, "Not a rust symbol: \n%s", args[optind]);
+ } else
+ cmd_usage(pc->curcmd, SYNOPSIS);
+}
+
/*
* Common symbol display for cmd_sym().
*/
--
2.50.1
12:12 a.m.
New subject: [PATCH 1/3] Add a rustfilt command to demangle a mangled Rust symbol
For this patch, LGTM, ack.
Thanks,
Tao Liu
On Wed, Aug 27, 2025 at 4:08 PM Lianbo Jiang <lijiang(a)redhat.com> wrote:
For example:
crash> rustfilt _RNvXsh_NtCskljHLvcz3xy_4core3fmteNtB5_7Display3fmt
<str as core::fmt::Display>::fmt
Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
---
defs.h | 2 ++
global_data.c | 1 +
help.c | 10 ++++++++++
symbols.c | 33 +++++++++++++++++++++++++++++++++
4 files changed, 46 insertions(+)
diff --git a/defs.h b/defs.h
index 4fecb8388229..156ac0232906 100644
--- a/defs.h
+++ b/defs.h
@@ -5508,6 +5508,7 @@ void cmd_s390dbf(void);
#endif
void cmd_map(void); /* kvmdump.c */
void cmd_ipcs(void); /* ipcs.c */
+void cmd_rustfilt(void); /* symbols.c */
/*
* main.c
@@ -6115,6 +6116,7 @@ extern char *help_wr[];
extern char *help_s390dbf[];
#endif
extern char *help_map[];
+extern char *help_rustfilt[];
/*
* task.c
diff --git a/global_data.c b/global_data.c
index f9bb7d079f51..889103d35f82 100644
--- a/global_data.c
+++ b/global_data.c
@@ -125,6 +125,7 @@ struct command_table_entry linux_command_table[] = {
#if defined(S390) || defined(S390X)
{"s390dbf", cmd_s390dbf, help_s390dbf, 0},
#endif
+ {"rustfilt", cmd_rustfilt, help_rustfilt, MINIMAL},
{(char *)NULL}
};
diff --git a/help.c b/help.c
index 5d61e0d57229..4f071e0bd0a0 100644
--- a/help.c
+++ b/help.c
@@ -8186,6 +8186,16 @@ char *help_net[] = {
NULL
};
+char *help_rustfilt[] = {
+"rustfilt",
+"demangle a mangled Rust symbol to human readable symbol",
+"<symbol>",
+" This command converts a mangled Rust symbol to human readable symbol.",
+"\nEXAMPLES",
+" crash> rustfilt _RNvNtCshc5sK6KjdJJ_6kernel5print11call_printk",
+" kernel::print::call_printk",
+NULL
+};
char *help_waitq[] = {
"waitq",
diff --git a/symbols.c b/symbols.c
index 794519ad4126..052196265be0 100644
--- a/symbols.c
+++ b/symbols.c
@@ -22,6 +22,7 @@
#include "config.h"
#endif
#include "bfd.h"
+#include "demangle.h"
static void store_symbols(bfd *, int, void *, long, unsigned int);
static void store_sysmap_symbols(void);
@@ -4887,6 +4888,38 @@ do_multiples:
cmd_usage(pc->curcmd, SYNOPSIS);
}
+/*
+ * Demangle a mangled Rust symbol to human readable symbol
+ */
+void cmd_rustfilt(void)
+{
+ int c;
+
+ while ((c = getopt(argcnt, args, "")) != EOF) {
+ switch(c)
+ {
+ default:
+ argerrs++;
+ break;
+ }
+ }
+
+ if (argerrs)
+ cmd_usage(pc->curcmd, SYNOPSIS);
+
+ if (args[optind]) {
+ char *buf;
+
+ buf = rust_demangle(args[optind], DMGL_RUST);
+ if (buf) {
+ fprintf(fp, "%s", buf);
+ free(buf);
+ } else
+ fprintf(fp, "Not a rust symbol: \n%s", args[optind]);
+ } else
+ cmd_usage(pc->curcmd, SYNOPSIS);
+}
+
/*
* Common symbol display for cmd_sym().
*/
--
2.50.1
--
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11:06 p.m.
New subject: [PATCH 2/3] Enable demangling a mangled Rust support
Without the patch:
crash> bt
PID: 3520 TASK: ffff8f240f670000 CPU: 1 COMMAND: "insmod"
#0 [ffffd08c4f063a20] machine_kexec at ffffffff9575e60e
#1 [ffffd08c4f063a40] __crash_kexec at ffffffff958db711
#2 [ffffd08c4f063b00] panic at ffffffff9560cede
#3 [ffffd08c4f063b80] _RNvCscb18lrEyTSA_10rust_panic10area_in_hp at ffffffffc07fe107
[rust_panic]
#4 [ffffd08c4f063c20] _RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two at
ffffffffc07fe160 [rust_panic]
...
crash> sym _RNvCscb18lrEyTSA_10rust_panic10area_in_hp
ffffffffc07fe010 (t) _RNvCscb18lrEyTSA_10rust_panic10area_in_hp [rust_panic]
/root/linux-6.16.3/samples/rust/rust_panic.rs: 22
With the patch:
crash> bt
PID: 3520 TASK: ffff8f240f670000 CPU: 1 COMMAND: "insmod"
#0 [ffffd08c4f063a20] machine_kexec at ffffffff9575e60e
#1 [ffffd08c4f063a40] __crash_kexec at ffffffff958db711
#2 [ffffd08c4f063b00] panic at ffffffff9560cede
#3 [ffffd08c4f063b80] rust_panic::area_in_hp at ffffffffc07fe107 [rust_panic]
#4 [ffffd08c4f063c20] <rust_panic::HelloPanic>::step_two at ffffffffc07fe160
[rust_panic]
...
crash> sym "rust_panic::area_in_hp"
ffffffffc07fe010 (t) rust_panic::area_in_hp [rust_panic]
/root/linux-6.16.3/samples/rust/rust_panic.rs: 22
Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
---
symbols.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/symbols.c b/symbols.c
index 052196265be0..7e9f57be7cec 100644
--- a/symbols.c
+++ b/symbols.c
@@ -3277,6 +3277,46 @@ load_module_filter(char *s, int type)
#define AVERAGE_SYMBOL_SIZE (16)
+static size_t rust_demangle_symbol(const char *symbol, char *out, size_t out_size)
+{
+ int i;
+ size_t loc = 0;
+ size_t len = strlen(symbol);
+ char *buf = NULL;
+ /*
+ * Rust symbols always start with _R (v0) or _ZN (legacy)
+ */
+ const char *mangled_rust[] = {
+ "_R",
+ "_ZN",
+ NULL
+ };
+
+ if (!out || out_size < len)
+ return 0;
+
+ for (i = 0; mangled_rust[i]; i++) {
+ size_t sz = strlen(mangled_rust[i]);
+ char *p = memmem(symbol, len, mangled_rust[i], sz);
+ if (p) {
+ loc = p - symbol;
+ if (loc)
+ memcpy(out, symbol, loc);
+ break;
+ }
+ }
+
+ buf = rust_demangle(symbol + loc, DMGL_RUST);
+ if (buf) {
+ memcpy(out + loc, buf, strlen(buf));
+ free(buf);
+ return 1;
+ } else if (loc != 0)
+ memset(out, 0, loc);
+
+ return 0;
+}
+
static int
namespace_ctl(int cmd, struct symbol_namespace *ns, void *nsarg1, void *nsarg2)
{
@@ -3315,9 +3355,14 @@ namespace_ctl(int cmd, struct symbol_namespace *ns, void *nsarg1,
void *nsarg2)
return TRUE;
case NAMESPACE_INSTALL:
+ char demangled[BUFSIZE] = {0};
sp = (struct syment *)nsarg1;
name = (char *)nsarg2;
len = strlen(name)+1;
+ if (rust_demangle_symbol(name, demangled, sizeof(demangled))) {
+ len = strlen(demangled) + 1;
+ name = demangled;
+ }
if ((ns->index + len) >= ns->size) {
if (!(addr = realloc(ns->address, ns->size*2)))
error(FATAL, "symbol name space malloc: %s\n",
--
2.50.1
12:11 a.m.
New subject: [PATCH 2/3] Enable demangling a mangled Rust support
On Wed, Aug 27, 2025 at 4:09 PM Lianbo Jiang <lijiang(a)redhat.com> wrote:
Without the patch:
crash> bt
PID: 3520 TASK: ffff8f240f670000 CPU: 1 COMMAND: "insmod"
#0 [ffffd08c4f063a20] machine_kexec at ffffffff9575e60e
#1 [ffffd08c4f063a40] __crash_kexec at ffffffff958db711
#2 [ffffd08c4f063b00] panic at ffffffff9560cede
#3 [ffffd08c4f063b80] _RNvCscb18lrEyTSA_10rust_panic10area_in_hp at ffffffffc07fe107
[rust_panic]
#4 [ffffd08c4f063c20] _RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two at
ffffffffc07fe160 [rust_panic]
...
crash> sym _RNvCscb18lrEyTSA_10rust_panic10area_in_hp
ffffffffc07fe010 (t) _RNvCscb18lrEyTSA_10rust_panic10area_in_hp [rust_panic]
/root/linux-6.16.3/samples/rust/rust_panic.rs: 22
With the patch:
crash> bt
PID: 3520 TASK: ffff8f240f670000 CPU: 1 COMMAND: "insmod"
#0 [ffffd08c4f063a20] machine_kexec at ffffffff9575e60e
#1 [ffffd08c4f063a40] __crash_kexec at ffffffff958db711
#2 [ffffd08c4f063b00] panic at ffffffff9560cede
#3 [ffffd08c4f063b80] rust_panic::area_in_hp at ffffffffc07fe107 [rust_panic]
#4 [ffffd08c4f063c20] <rust_panic::HelloPanic>::step_two at ffffffffc07fe160
[rust_panic]
...
crash> sym "rust_panic::area_in_hp"
ffffffffc07fe010 (t) rust_panic::area_in_hp [rust_panic]
/root/linux-6.16.3/samples/rust/rust_panic.rs: 22
Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
---
symbols.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/symbols.c b/symbols.c
index 052196265be0..7e9f57be7cec 100644
--- a/symbols.c
+++ b/symbols.c
@@ -3277,6 +3277,46 @@ load_module_filter(char *s, int type)
#define AVERAGE_SYMBOL_SIZE (16)
+static size_t rust_demangle_symbol(const char *symbol, char *out, size_t out_size)
+{
+ int i;
+ size_t loc = 0;
+ size_t len = strlen(symbol);
+ char *buf = NULL;
+ /*
+ * Rust symbols always start with _R (v0) or _ZN (legacy)
+ */
+ const char *mangled_rust[] = {
+ "_R",
+ "_ZN",
+ NULL
+ };
+
+ if (!out || out_size < len)
+ return 0;
+
+ for (i = 0; mangled_rust[i]; i++) {
+ size_t sz = strlen(mangled_rust[i]);
+ char *p = memmem(symbol, len, mangled_rust[i], sz);
+ if (p) {
+ loc = p - symbol;
+ if (loc)
+ memcpy(out, symbol, loc);
+ break;
+ }
+ }
+
+ buf = rust_demangle(symbol + loc, DMGL_RUST);
+ if (buf) {
+ memcpy(out + loc, buf, strlen(buf));
I guess this one is fine, "out" is a 1500 size buf, and it only deals
with symbol names, so after demangle it hardly exceeds 1.5k size, so
we can leave it for now.
So for this one, ack.
+ free(buf);
+ return 1;
+ } else if (loc != 0)
+ memset(out, 0, loc);
+
+ return 0;
+}
+
static int
namespace_ctl(int cmd, struct symbol_namespace *ns, void *nsarg1, void *nsarg2)
{
@@ -3315,9 +3355,14 @@ namespace_ctl(int cmd, struct symbol_namespace *ns, void *nsarg1,
void *nsarg2)
return TRUE;
case NAMESPACE_INSTALL:
+ char demangled[BUFSIZE] = {0};
sp = (struct syment *)nsarg1;
name = (char *)nsarg2;
len = strlen(name)+1;
+ if (rust_demangle_symbol(name, demangled, sizeof(demangled))) {
+ len = strlen(demangled) + 1;
+ name = demangled;
+ }
if ((ns->index + len) >= ns->size) {
if (!(addr = realloc(ns->address, ns->size*2)))
error(FATAL, "symbol name space malloc: %s\n",
--
2.50.1
--
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12:14 a.m.
New subject: [PATCH 2/3] Enable demangling a mangled Rust support
Hi Lianbo,
On Wed, Aug 27, 2025 at 4:09 PM Lianbo Jiang <lijiang(a)redhat.com> wrote:
Without the patch:
crash> bt
PID: 3520 TASK: ffff8f240f670000 CPU: 1 COMMAND: "insmod"
#0 [ffffd08c4f063a20] machine_kexec at ffffffff9575e60e
#1 [ffffd08c4f063a40] __crash_kexec at ffffffff958db711
#2 [ffffd08c4f063b00] panic at ffffffff9560cede
#3 [ffffd08c4f063b80] _RNvCscb18lrEyTSA_10rust_panic10area_in_hp at ffffffffc07fe107
[rust_panic]
#4 [ffffd08c4f063c20] _RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two at
ffffffffc07fe160 [rust_panic]
...
crash> sym _RNvCscb18lrEyTSA_10rust_panic10area_in_hp
ffffffffc07fe010 (t) _RNvCscb18lrEyTSA_10rust_panic10area_in_hp [rust_panic]
/root/linux-6.16.3/samples/rust/rust_panic.rs: 22
With the patch:
crash> bt
PID: 3520 TASK: ffff8f240f670000 CPU: 1 COMMAND: "insmod"
#0 [ffffd08c4f063a20] machine_kexec at ffffffff9575e60e
#1 [ffffd08c4f063a40] __crash_kexec at ffffffff958db711
#2 [ffffd08c4f063b00] panic at ffffffff9560cede
#3 [ffffd08c4f063b80] rust_panic::area_in_hp at ffffffffc07fe107 [rust_panic]
#4 [ffffd08c4f063c20] <rust_panic::HelloPanic>::step_two at ffffffffc07fe160
[rust_panic]
...
crash> sym "rust_panic::area_in_hp"
ffffffffc07fe010 (t) rust_panic::area_in_hp [rust_panic]
/root/linux-6.16.3/samples/rust/rust_panic.rs: 22
Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
---
symbols.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/symbols.c b/symbols.c
index 052196265be0..7e9f57be7cec 100644
--- a/symbols.c
+++ b/symbols.c
@@ -3277,6 +3277,46 @@ load_module_filter(char *s, int type)
#define AVERAGE_SYMBOL_SIZE (16)
+static size_t rust_demangle_symbol(const char *symbol, char *out, size_t out_size)
+{
+ int i;
+ size_t loc = 0;
+ size_t len = strlen(symbol);
+ char *buf = NULL;
+ /*
+ * Rust symbols always start with _R (v0) or _ZN (legacy)
+ */
+ const char *mangled_rust[] = {
+ "_R",
+ "_ZN",
+ NULL
+ };
+
+ if (!out || out_size < len)
+ return 0;
+
+ for (i = 0; mangled_rust[i]; i++) {
+ size_t sz = strlen(mangled_rust[i]);
+ char *p = memmem(symbol, len, mangled_rust[i], sz);
+ if (p) {
+ loc = p - symbol;
+ if (loc)
+ memcpy(out, symbol, loc);
+ break;
+ }
+ }
+
+ buf = rust_demangle(symbol + loc, DMGL_RUST);
+ if (buf) {
+ memcpy(out + loc, buf, strlen(buf));
+ free(buf);
+ return 1;
+ } else if (loc != 0)
+ memset(out, 0, loc);
+
+ return 0;
+}
+
static int
namespace_ctl(int cmd, struct symbol_namespace *ns, void *nsarg1, void *nsarg2)
{
@@ -3315,9 +3355,14 @@ namespace_ctl(int cmd, struct symbol_namespace *ns, void *nsarg1,
void *nsarg2)
return TRUE;
case NAMESPACE_INSTALL:
+ char demangled[BUFSIZE] = {0};
Just found a compiling error on this in rhel8: gcc version 8.5.0
gcc -c -g -DX86_64 -DLZO -DSNAPPY -DZSTD -DGDB_16_2 symbols.c
-I./gdb-16.2/bfd -I./gdb-16.2/include
symbols.c: In function ‘namespace_ctl’:
symbols.c:3358:3: error: a label can only be part of a statement and a
declaration is not a statement
char demangled[BUFSIZE] = {0};
^~~~
make[4]: *** [Makefile:403: symbols.o] Error 1
Looks "char demangled[]" cannot follow the "case XX:" tag in older
gcc.
I have merged your rust patchset, because the github test pipeline
doesn't find this issue, maybe due to the gcc is newer. Could you
please fix this issue, as well as the ci pipeline?
Thanks,
Tao Liu
sp = (struct syment *)nsarg1;
name = (char *)nsarg2;
len = strlen(name)+1;
+ if (rust_demangle_symbol(name, demangled, sizeof(demangled))) {
+ len = strlen(demangled) + 1;
+ name = demangled;
+ }
if ((ns->index + len) >= ns->size) {
if (!(addr = realloc(ns->address, ns->size*2)))
error(FATAL, "symbol name space malloc: %s\n",
--
2.50.1
--
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1:42 a.m.
New subject: [PATCH 2/3] Enable demangling a mangled Rust support
On Mon, Sep 15, 2025 at 1:14 PM Tao Liu <ltao(a)redhat.com> wrote:
Hi Lianbo,
On Wed, Aug 27, 2025 at 4:09 PM Lianbo Jiang <lijiang(a)redhat.com> wrote:
>
> Without the patch:
> crash> bt
> PID: 3520 TASK: ffff8f240f670000 CPU: 1 COMMAND: "insmod"
> #0 [ffffd08c4f063a20] machine_kexec at ffffffff9575e60e
> #1 [ffffd08c4f063a40] __crash_kexec at ffffffff958db711
> #2 [ffffd08c4f063b00] panic at ffffffff9560cede
> #3 [ffffd08c4f063b80] _RNvCscb18lrEyTSA_10rust_panic10area_in_hp at
ffffffffc07fe107 [rust_panic]
> #4 [ffffd08c4f063c20]
_RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two at
ffffffffc07fe160 [rust_panic]
> ...
>
> crash> sym _RNvCscb18lrEyTSA_10rust_panic10area_in_hp
> ffffffffc07fe010 (t) _RNvCscb18lrEyTSA_10rust_panic10area_in_hp
[rust_panic] /root/linux-6.16.3/samples/rust/rust_panic.rs: 22
>
> With the patch:
> crash> bt
> PID: 3520 TASK: ffff8f240f670000 CPU: 1 COMMAND: "insmod"
> #0 [ffffd08c4f063a20] machine_kexec at ffffffff9575e60e
> #1 [ffffd08c4f063a40] __crash_kexec at ffffffff958db711
> #2 [ffffd08c4f063b00] panic at ffffffff9560cede
> #3 [ffffd08c4f063b80] rust_panic::area_in_hp at ffffffffc07fe107
[rust_panic]
> #4 [ffffd08c4f063c20] <rust_panic::HelloPanic>::step_two at
ffffffffc07fe160 [rust_panic]
> ...
>
> crash> sym "rust_panic::area_in_hp"
> ffffffffc07fe010 (t) rust_panic::area_in_hp [rust_panic]
/root/linux-6.16.3/samples/rust/rust_panic.rs: 22
>
> Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
> ---
> symbols.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 45 insertions(+)
>
> diff --git a/symbols.c b/symbols.c
> index 052196265be0..7e9f57be7cec 100644
> --- a/symbols.c
> +++ b/symbols.c
> @@ -3277,6 +3277,46 @@ load_module_filter(char *s, int type)
>
> #define AVERAGE_SYMBOL_SIZE (16)
>
> +static size_t rust_demangle_symbol(const char *symbol, char *out,
size_t out_size)
> +{
> + int i;
> + size_t loc = 0;
> + size_t len = strlen(symbol);
> + char *buf = NULL;
> + /*
> + * Rust symbols always start with _R (v0) or _ZN (legacy)
> + */
> + const char *mangled_rust[] = {
> + "_R",
> + "_ZN",
> + NULL
> + };
> +
> + if (!out || out_size < len)
> + return 0;
> +
> + for (i = 0; mangled_rust[i]; i++) {
> + size_t sz = strlen(mangled_rust[i]);
> + char *p = memmem(symbol, len, mangled_rust[i], sz);
> + if (p) {
> + loc = p - symbol;
> + if (loc)
> + memcpy(out, symbol, loc);
> + break;
> + }
> + }
> +
> + buf = rust_demangle(symbol + loc, DMGL_RUST);
> + if (buf) {
> + memcpy(out + loc, buf, strlen(buf));
> + free(buf);
> + return 1;
> + } else if (loc != 0)
> + memset(out, 0, loc);
> +
> + return 0;
> +}
> +
> static int
> namespace_ctl(int cmd, struct symbol_namespace *ns, void *nsarg1, void
*nsarg2)
> {
> @@ -3315,9 +3355,14 @@ namespace_ctl(int cmd, struct symbol_namespace
*ns, void *nsarg1, void *nsarg2)
> return TRUE;
>
> case NAMESPACE_INSTALL:
> + char demangled[BUFSIZE] = {0};
Just found a compiling error on this in rhel8: gcc version 8.5.0
gcc -c -g -DX86_64 -DLZO -DSNAPPY -DZSTD -DGDB_16_2 symbols.c
-I./gdb-16.2/bfd -I./gdb-16.2/include
symbols.c: In function ‘namespace_ctl’:
symbols.c:3358:3: error: a label can only be part of a statement and a
declaration is not a statement
char demangled[BUFSIZE] = {0};
^~~~
make[4]: *** [Makefile:403: symbols.o] Error 1
Looks "char demangled[]" cannot follow the "case XX:" tag in older
gcc.
I have merged your rust patchset, because the github test pipeline
doesn't find this issue, maybe due to the gcc is newer. Could you
please fix this issue, as well as the ci pipeline?
Thank you for pointing out this issue, Tao.
I did not build it with the old gcc . I'll check it.
Thanks
Lianbo
Thanks,
Tao Liu
11:06 p.m.
New subject: [PATCH 3/3] Enable resolving mangled Rust symbol in lockless ring buffer
Without the patch:
crash> log
...
[ 2174.308966] Call Trace:
[ 2174.311693] <TASK>
[ 2174.314033] dump_stack_lvl+0x5d/0x80
[ 2174.318125] panic+0x156/0x32a
[ 2174.321539] _RNvCscb18lrEyTSA_10rust_panic10area_in_hp+0xf7/0x120 [rust_panic]
[ 2174.329700] ? console_unlock+0x9c/0x140
[ 2174.334080] ? irq_work_queue+0x2d/0x50
[ 2174.338352] ? __pfx_init_module+0x10/0x10 [rust_panic]
[ 2174.344183] _RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two+0x20/0xe0
[rust_panic]
[ 2174.353698] ? _printk+0x6b/0x90
...
With the patch:
crash> log
...
[ 2174.308966] Call Trace:
[ 2174.311693] <TASK>
[ 2174.314033] dump_stack_lvl+0x5d/0x80
[ 2174.318125] panic+0x156/0x32a
[ 2174.321539] rust_panic::area_in_hp+0xf7/0x120 [rust_panic]
[ 2174.329700] ? console_unlock+0x9c/0x140
[ 2174.334080] ? irq_work_queue+0x2d/0x50
[ 2174.338352] ? __pfx_init_module+0x10/0x10 [rust_panic]
[ 2174.344183] <rust_panic::HelloPanic>::step_two+0x20/0xe0 [rust_panic]
[ 2174.353698] ? _printk+0x6b/0x90
...
Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
---
Makefile | 2 +-
printk.c | 28 +++++++++++++++++++++++++++-
2 files changed, 28 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index fc1c9588dcfa..b277129f6df2 100644
--- a/Makefile
+++ b/Makefile
@@ -421,7 +421,7 @@ kernel.o: ${GENERIC_HFILES} kernel.c
${CC} -c ${CRASH_CFLAGS} kernel.c -I${BFD_DIRECTORY} -I${GDB_INCLUDE_DIRECTORY}
${WARNING_OPTIONS} ${WARNING_ERROR}
printk.o: ${GENERIC_HFILES} printk.c
- ${CC} -c ${CRASH_CFLAGS} printk.c ${WARNING_OPTIONS} ${WARNING_ERROR}
+ ${CC} -c ${CRASH_CFLAGS} printk.c -I${GDB_INCLUDE_DIRECTORY} ${WARNING_OPTIONS}
${WARNING_ERROR}
gdb_interface.o: ${GENERIC_HFILES} gdb_interface.c
${CC} -c ${CRASH_CFLAGS} gdb_interface.c ${WARNING_OPTIONS} ${WARNING_ERROR}
diff --git a/printk.c b/printk.c
index 95db7e607e4c..6a87a790b892 100644
--- a/printk.c
+++ b/printk.c
@@ -1,5 +1,6 @@
#include "defs.h"
#include <ctype.h>
+#include "demangle.h"
/* convenience struct for passing many values to helper functions */
struct prb_map {
@@ -205,10 +206,35 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags)
if (*p == '\n')
fprintf(fp, "\n%s", space(ilen));
else if (isprint(*p) || isspace(*p))
- fputc(*p, fp);
+ sprintf(&buf[i], "%c", *p);
else
fputc('.', fp);
}
+ /*
+ * Try to demangle a mangled Rust symbol(calltrace) from log buffer
+ */
+ char *p1 = strstr(buf, "_R");
+ if (!p1)
+ p1 = strstr(buf, "_ZN");
+ char *p2 = strchrnul(buf, '+');
+ if (p1 && p2) {
+ char mangled[BUFSIZE] = {0};
+ char demangled[BUFSIZE] = {0};
+ char *res;
+ size_t slen = p1 - buf;
+
+ if (slen)
+ memcpy(demangled, buf, slen);
+
+ memcpy(mangled, p1, p2-p1);
+ res = rust_demangle(mangled, DMGL_RUST);
+ if (res) {
+ sprintf(demangled+slen, "%s%s", res,p2);
+ fprintf(fp, "%s",demangled);
+ free(res);
+ }
+ } else
+ fprintf(fp, "%s", buf);
if (msg_flags & SHOW_LOG_DICT) {
text = info + OFFSET(printk_info_dev_info) +
--
2.50.1
12:07 a.m.
New subject: [PATCH 3/3] Enable resolving mangled Rust symbol in lockless ring buffer
Hi lianbo,
Just some nits.
On Wed, Aug 27, 2025 at 4:10 PM Lianbo Jiang <lijiang(a)redhat.com> wrote:
Without the patch:
crash> log
...
[ 2174.308966] Call Trace:
[ 2174.311693] <TASK>
[ 2174.314033] dump_stack_lvl+0x5d/0x80
[ 2174.318125] panic+0x156/0x32a
[ 2174.321539] _RNvCscb18lrEyTSA_10rust_panic10area_in_hp+0xf7/0x120 [rust_panic]
[ 2174.329700] ? console_unlock+0x9c/0x140
[ 2174.334080] ? irq_work_queue+0x2d/0x50
[ 2174.338352] ? __pfx_init_module+0x10/0x10 [rust_panic]
[ 2174.344183] _RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two+0x20/0xe0
[rust_panic]
[ 2174.353698] ? _printk+0x6b/0x90
...
With the patch:
crash> log
...
[ 2174.308966] Call Trace:
[ 2174.311693] <TASK>
[ 2174.314033] dump_stack_lvl+0x5d/0x80
[ 2174.318125] panic+0x156/0x32a
[ 2174.321539] rust_panic::area_in_hp+0xf7/0x120 [rust_panic]
[ 2174.329700] ? console_unlock+0x9c/0x140
[ 2174.334080] ? irq_work_queue+0x2d/0x50
[ 2174.338352] ? __pfx_init_module+0x10/0x10 [rust_panic]
[ 2174.344183] <rust_panic::HelloPanic>::step_two+0x20/0xe0 [rust_panic]
[ 2174.353698] ? _printk+0x6b/0x90
...
Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
---
Makefile | 2 +-
printk.c | 28 +++++++++++++++++++++++++++-
2 files changed, 28 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index fc1c9588dcfa..b277129f6df2 100644
--- a/Makefile
+++ b/Makefile
@@ -421,7 +421,7 @@ kernel.o: ${GENERIC_HFILES} kernel.c
${CC} -c ${CRASH_CFLAGS} kernel.c -I${BFD_DIRECTORY} -I${GDB_INCLUDE_DIRECTORY}
${WARNING_OPTIONS} ${WARNING_ERROR}
printk.o: ${GENERIC_HFILES} printk.c
- ${CC} -c ${CRASH_CFLAGS} printk.c ${WARNING_OPTIONS} ${WARNING_ERROR}
+ ${CC} -c ${CRASH_CFLAGS} printk.c -I${GDB_INCLUDE_DIRECTORY} ${WARNING_OPTIONS}
${WARNING_ERROR}
gdb_interface.o: ${GENERIC_HFILES} gdb_interface.c
${CC} -c ${CRASH_CFLAGS} gdb_interface.c ${WARNING_OPTIONS} ${WARNING_ERROR}
diff --git a/printk.c b/printk.c
index 95db7e607e4c..6a87a790b892 100644
--- a/printk.c
+++ b/printk.c
@@ -1,5 +1,6 @@
#include "defs.h"
#include <ctype.h>
+#include "demangle.h"
/* convenience struct for passing many values to helper functions */
struct prb_map {
@@ -205,10 +206,35 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags)
if (*p == '\n')
fprintf(fp, "\n%s", space(ilen));
else if (isprint(*p) || isspace(*p))
- fputc(*p, fp);
+ sprintf(&buf[i], "%c", *p);
else
fputc('.', fp);
}
+ /*
+ * Try to demangle a mangled Rust symbol(calltrace) from log buffer
+ */
+ char *p1 = strstr(buf, "_R");
+ if (!p1)
+ p1 = strstr(buf, "_ZN");
+ char *p2 = strchrnul(buf, '+');
+ if (p1 && p2) {
+ char mangled[BUFSIZE] = {0};
+ char demangled[BUFSIZE] = {0};
+ char *res;
+ size_t slen = p1 - buf;
+
+ if (slen)
+ memcpy(demangled, buf, slen);
+
+ memcpy(mangled, p1, p2-p1);
+ res = rust_demangle(mangled, DMGL_RUST);
+ if (res) {
+ sprintf(demangled+slen, "%s%s", res,p2);
The (de)mangled buf size is 1500. First copied slen chars into
demangled, then sprintf res and p2 into demangled buf without length
check.Though this might be a rare case, but I guess a snprintf with a
length check is safer for preventing overflow, since we are within
ringbuffer buf, I'm not sure how much slen it may be.
The rest of the patch are good to me.
Thanks,
Tao Liu
+ fprintf(fp, "%s",demangled);
+ free(res);
+ }
+ } else
+ fprintf(fp, "%s", buf);
if (msg_flags & SHOW_LOG_DICT) {
text = info + OFFSET(printk_info_dev_info) +
--
2.50.1
--
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9:54 p.m.
New subject: [PATCH 3/3] Enable resolving mangled Rust symbol in lockless ring buffer
Hi, Tao
Thank you for the review.
On Thu, Sep 4, 2025 at 1:08 PM Tao Liu <ltao(a)redhat.com> wrote:
Hi lianbo,
Just some nits.
On Wed, Aug 27, 2025 at 4:10 PM Lianbo Jiang <lijiang(a)redhat.com> wrote:
>
> Without the patch:
> crash> log
> ...
> [ 2174.308966] Call Trace:
> [ 2174.311693] <TASK>
> [ 2174.314033] dump_stack_lvl+0x5d/0x80
> [ 2174.318125] panic+0x156/0x32a
> [ 2174.321539] _RNvCscb18lrEyTSA_10rust_panic10area_in_hp+0xf7/0x120
[rust_panic]
> [ 2174.329700] ? console_unlock+0x9c/0x140
> [ 2174.334080] ? irq_work_queue+0x2d/0x50
> [ 2174.338352] ? __pfx_init_module+0x10/0x10 [rust_panic]
> [ 2174.344183]
_RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two+0x20/0xe0
[rust_panic]
> [ 2174.353698] ? _printk+0x6b/0x90
> ...
>
> With the patch:
> crash> log
> ...
> [ 2174.308966] Call Trace:
> [ 2174.311693] <TASK>
> [ 2174.314033] dump_stack_lvl+0x5d/0x80
> [ 2174.318125] panic+0x156/0x32a
> [ 2174.321539] rust_panic::area_in_hp+0xf7/0x120 [rust_panic]
> [ 2174.329700] ? console_unlock+0x9c/0x140
> [ 2174.334080] ? irq_work_queue+0x2d/0x50
> [ 2174.338352] ? __pfx_init_module+0x10/0x10 [rust_panic]
> [ 2174.344183] <rust_panic::HelloPanic>::step_two+0x20/0xe0
[rust_panic]
> [ 2174.353698] ? _printk+0x6b/0x90
> ...
>
> Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
> ---
> Makefile | 2 +-
> printk.c | 28 +++++++++++++++++++++++++++-
> 2 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index fc1c9588dcfa..b277129f6df2 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -421,7 +421,7 @@ kernel.o: ${GENERIC_HFILES} kernel.c
> ${CC} -c ${CRASH_CFLAGS} kernel.c -I${BFD_DIRECTORY}
-I${GDB_INCLUDE_DIRECTORY} ${WARNING_OPTIONS} ${WARNING_ERROR}
>
> printk.o: ${GENERIC_HFILES} printk.c
> - ${CC} -c ${CRASH_CFLAGS} printk.c ${WARNING_OPTIONS}
${WARNING_ERROR}
> + ${CC} -c ${CRASH_CFLAGS} printk.c -I${GDB_INCLUDE_DIRECTORY}
${WARNING_OPTIONS} ${WARNING_ERROR}
>
> gdb_interface.o: ${GENERIC_HFILES} gdb_interface.c
> ${CC} -c ${CRASH_CFLAGS} gdb_interface.c ${WARNING_OPTIONS}
${WARNING_ERROR}
> diff --git a/printk.c b/printk.c
> index 95db7e607e4c..6a87a790b892 100644
> --- a/printk.c
> +++ b/printk.c
> @@ -1,5 +1,6 @@
> #include "defs.h"
> #include <ctype.h>
> +#include "demangle.h"
>
> /* convenience struct for passing many values to helper functions */
> struct prb_map {
> @@ -205,10 +206,35 @@ dump_record(struct prb_map *m, unsigned long id,
int msg_flags)
> if (*p == '\n')
> fprintf(fp, "\n%s", space(ilen));
> else if (isprint(*p) || isspace(*p))
> - fputc(*p, fp);
> + sprintf(&buf[i], "%c", *p);
> else
> fputc('.', fp);
> }
> + /*
> + * Try to demangle a mangled Rust symbol(calltrace) from log
buffer
> + */
> + char *p1 = strstr(buf, "_R");
> + if (!p1)
> + p1 = strstr(buf, "_ZN");
> + char *p2 = strchrnul(buf, '+');
> + if (p1 && p2) {
> + char mangled[BUFSIZE] = {0};
> + char demangled[BUFSIZE] = {0};
> + char *res;
> + size_t slen = p1 - buf;
> +
> + if (slen)
> + memcpy(demangled, buf, slen);
> +
> + memcpy(mangled, p1, p2-p1);
> + res = rust_demangle(mangled, DMGL_RUST);
> + if (res) {
> + sprintf(demangled+slen, "%s%s", res,p2);
The (de)mangled buf size is 1500. First copied slen chars into
demangled, then sprintf res and p2 into demangled buf without length
check.Though this might be a rare case, but I guess a snprintf with a
Theoretically yes, but actually I never saw a very long string in the
printk buffer because it would have bad readability.
Anyway, how about the following changes?
diff --git a/printk.c b/printk.c
index 6a87a790b892..c547ea8c3f9f 100644
--- a/printk.c
+++ b/printk.c
@@ -202,6 +202,11 @@ dump_record(struct prb_map *m, unsigned long id, int
msg_flags)
text = m->text_data + begin;
+ if (text_len > BUFSIZE) {
+ error(WARNING, "\nThe messages could be truncated!\n");
+ text_len = BUFSIZE;
+ }
+
for (i = 0, p = text; i < text_len; i++, p++) {
if (*p == '\n')
fprintf(fp, "\n%s", space(ilen));
@@ -229,7 +234,7 @@ dump_record(struct prb_map *m, unsigned long id, int
msg_flags)
memcpy(mangled, p1, p2-p1);
res = rust_demangle(mangled, DMGL_RUST);
if (res) {
- sprintf(demangled+slen, "%s%s", res,p2);
+ snprintf(demangled+slen, BUFSIZE, "%s%s", res, p2);
fprintf(fp, "%s",demangled);
free(res);
}
Thanks
Lianbo
length check is safer for preventing overflow, since we are within
ringbuffer buf, I'm not sure how much slen it may be.
The rest of the patch are good to me.
Thanks,
Tao Liu
> + fprintf(fp, "%s",demangled);
> + free(res);
> + }
> + } else
> + fprintf(fp, "%s", buf);
>
> if (msg_flags & SHOW_LOG_DICT) {
> text = info + OFFSET(printk_info_dev_info) +
> --
> 2.50.1
> --
> Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io
> To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io
> https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/
> Contribution Guidelines: https://github.com/crash-utility/crash/wiki
10:22 p.m.
New subject: [PATCH 3/3] Enable resolving mangled Rust symbol in lockless ring buffer
On Mon, Sep 8, 2025 at 2:55 PM lijiang <lijiang(a)redhat.com> wrote:
Hi, Tao
Thank you for the review.
On Thu, Sep 4, 2025 at 1:08 PM Tao Liu <ltao(a)redhat.com> wrote:
>
> Hi lianbo,
>
> Just some nits.
>
> On Wed, Aug 27, 2025 at 4:10 PM Lianbo Jiang <lijiang(a)redhat.com> wrote:
> >
> > Without the patch:
> > crash> log
> > ...
> > [ 2174.308966] Call Trace:
> > [ 2174.311693] <TASK>
> > [ 2174.314033] dump_stack_lvl+0x5d/0x80
> > [ 2174.318125] panic+0x156/0x32a
> > [ 2174.321539] _RNvCscb18lrEyTSA_10rust_panic10area_in_hp+0xf7/0x120
[rust_panic]
> > [ 2174.329700] ? console_unlock+0x9c/0x140
> > [ 2174.334080] ? irq_work_queue+0x2d/0x50
> > [ 2174.338352] ? __pfx_init_module+0x10/0x10 [rust_panic]
> > [ 2174.344183]
_RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two+0x20/0xe0 [rust_panic]
> > [ 2174.353698] ? _printk+0x6b/0x90
> > ...
> >
> > With the patch:
> > crash> log
> > ...
> > [ 2174.308966] Call Trace:
> > [ 2174.311693] <TASK>
> > [ 2174.314033] dump_stack_lvl+0x5d/0x80
> > [ 2174.318125] panic+0x156/0x32a
> > [ 2174.321539] rust_panic::area_in_hp+0xf7/0x120 [rust_panic]
> > [ 2174.329700] ? console_unlock+0x9c/0x140
> > [ 2174.334080] ? irq_work_queue+0x2d/0x50
> > [ 2174.338352] ? __pfx_init_module+0x10/0x10 [rust_panic]
> > [ 2174.344183] <rust_panic::HelloPanic>::step_two+0x20/0xe0
[rust_panic]
> > [ 2174.353698] ? _printk+0x6b/0x90
> > ...
> >
> > Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
> > ---
> > Makefile | 2 +-
> > printk.c | 28 +++++++++++++++++++++++++++-
> > 2 files changed, 28 insertions(+), 2 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index fc1c9588dcfa..b277129f6df2 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -421,7 +421,7 @@ kernel.o: ${GENERIC_HFILES} kernel.c
> > ${CC} -c ${CRASH_CFLAGS} kernel.c -I${BFD_DIRECTORY}
-I${GDB_INCLUDE_DIRECTORY} ${WARNING_OPTIONS} ${WARNING_ERROR}
> >
> > printk.o: ${GENERIC_HFILES} printk.c
> > - ${CC} -c ${CRASH_CFLAGS} printk.c ${WARNING_OPTIONS} ${WARNING_ERROR}
> > + ${CC} -c ${CRASH_CFLAGS} printk.c -I${GDB_INCLUDE_DIRECTORY}
${WARNING_OPTIONS} ${WARNING_ERROR}
> >
> > gdb_interface.o: ${GENERIC_HFILES} gdb_interface.c
> > ${CC} -c ${CRASH_CFLAGS} gdb_interface.c ${WARNING_OPTIONS}
${WARNING_ERROR}
> > diff --git a/printk.c b/printk.c
> > index 95db7e607e4c..6a87a790b892 100644
> > --- a/printk.c
> > +++ b/printk.c
> > @@ -1,5 +1,6 @@
> > #include "defs.h"
> > #include <ctype.h>
> > +#include "demangle.h"
> >
> > /* convenience struct for passing many values to helper functions */
> > struct prb_map {
> > @@ -205,10 +206,35 @@ dump_record(struct prb_map *m, unsigned long id, int
msg_flags)
> > if (*p == '\n')
> > fprintf(fp, "\n%s", space(ilen));
> > else if (isprint(*p) || isspace(*p))
> > - fputc(*p, fp);
> > + sprintf(&buf[i], "%c", *p);
> > else
> > fputc('.', fp);
> > }
> > + /*
> > + * Try to demangle a mangled Rust symbol(calltrace) from log buffer
> > + */
> > + char *p1 = strstr(buf, "_R");
> > + if (!p1)
> > + p1 = strstr(buf, "_ZN");
> > + char *p2 = strchrnul(buf, '+');
> > + if (p1 && p2) {
> > + char mangled[BUFSIZE] = {0};
> > + char demangled[BUFSIZE] = {0};
> > + char *res;
> > + size_t slen = p1 - buf;
> > +
> > + if (slen)
> > + memcpy(demangled, buf, slen);
> > +
> > + memcpy(mangled, p1, p2-p1);
> > + res = rust_demangle(mangled, DMGL_RUST);
> > + if (res) {
> > + sprintf(demangled+slen, "%s%s", res,p2);
>
> The (de)mangled buf size is 1500. First copied slen chars into
> demangled, then sprintf res and p2 into demangled buf without length
> check.Though this might be a rare case, but I guess a snprintf with a
Theoretically yes, but actually I never saw a very long string in the printk buffer
because it would have bad readability.
Anyway, how about the following changes?
diff --git a/printk.c b/printk.c
index 6a87a790b892..c547ea8c3f9f 100644
--- a/printk.c
+++ b/printk.c
@@ -202,6 +202,11 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags)
text = m->text_data + begin;
+ if (text_len > BUFSIZE) {
+ error(WARNING, "\nThe messages could be truncated!\n");
+ text_len = BUFSIZE;
+ }
+
OK.
for (i = 0, p = text; i < text_len; i++, p++) {
if (*p == '\n')
fprintf(fp, "\n%s", space(ilen));
@@ -229,7 +234,7 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags)
memcpy(mangled, p1, p2-p1);
res = rust_demangle(mangled, DMGL_RUST);
if (res) {
- sprintf(demangled+slen, "%s%s", res,p2);
+ snprintf(demangled+slen, BUFSIZE, "%s%s", res, p2);
I think it should be:
snprintf(demangled+slen, BUFSIZE - slen, "%s%s", res, p2);
Because demangled[BUFSIZE], with slen offset from demangled, the left
space is BUFSIZE - slen.
fprintf(fp, "%s",demangled);
free(res);
}
Thanks
Lianbo
> length check is safer for preventing overflow, since we are within
> ringbuffer buf, I'm not sure how much slen it may be.
>
> The rest of the patch are good to me.
>
> Thanks,
> Tao Liu
>
> > + fprintf(fp, "%s",demangled);
> > + free(res);
> > + }
> > + } else
> > + fprintf(fp, "%s", buf);
> >
> > if (msg_flags & SHOW_LOG_DICT) {
> > text = info + OFFSET(printk_info_dev_info) +
> > --
> > 2.50.1
> > --
> > Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io
> > To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io
> > https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/
> > Contribution Guidelines: https://github.com/crash-utility/crash/wiki
>
3:28 a.m.
New subject: [PATCH 3/3] Enable resolving mangled Rust symbol in lockless ring buffer
On Mon, Sep 8, 2025 at 11:23 AM Tao Liu <ltao(a)redhat.com> wrote:
On Mon, Sep 8, 2025 at 2:55 PM lijiang <lijiang(a)redhat.com>
wrote:
>
> Hi, Tao
> Thank you for the review.
>
> On Thu, Sep 4, 2025 at 1:08 PM Tao Liu <ltao(a)redhat.com> wrote:
>>
>> Hi lianbo,
>>
>> Just some nits.
>>
>> On Wed, Aug 27, 2025 at 4:10 PM Lianbo Jiang <lijiang(a)redhat.com>
wrote:
>> >
>> > Without the patch:
>> > crash> log
>> > ...
>> > [ 2174.308966] Call Trace:
>> > [ 2174.311693] <TASK>
>> > [ 2174.314033] dump_stack_lvl+0x5d/0x80
>> > [ 2174.318125] panic+0x156/0x32a
>> > [ 2174.321539]
_RNvCscb18lrEyTSA_10rust_panic10area_in_hp+0xf7/0x120 [rust_panic]
>> > [ 2174.329700] ? console_unlock+0x9c/0x140
>> > [ 2174.334080] ? irq_work_queue+0x2d/0x50
>> > [ 2174.338352] ? __pfx_init_module+0x10/0x10 [rust_panic]
>> > [ 2174.344183]
_RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two+0x20/0xe0
[rust_panic]
>> > [ 2174.353698] ? _printk+0x6b/0x90
>> > ...
>> >
>> > With the patch:
>> > crash> log
>> > ...
>> > [ 2174.308966] Call Trace:
>> > [ 2174.311693] <TASK>
>> > [ 2174.314033] dump_stack_lvl+0x5d/0x80
>> > [ 2174.318125] panic+0x156/0x32a
>> > [ 2174.321539] rust_panic::area_in_hp+0xf7/0x120 [rust_panic]
>> > [ 2174.329700] ? console_unlock+0x9c/0x140
>> > [ 2174.334080] ? irq_work_queue+0x2d/0x50
>> > [ 2174.338352] ? __pfx_init_module+0x10/0x10 [rust_panic]
>> > [ 2174.344183] <rust_panic::HelloPanic>::step_two+0x20/0xe0
[rust_panic]
>> > [ 2174.353698] ? _printk+0x6b/0x90
>> > ...
>> >
>> > Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
>> > ---
>> > Makefile | 2 +-
>> > printk.c | 28 +++++++++++++++++++++++++++-
>> > 2 files changed, 28 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/Makefile b/Makefile
>> > index fc1c9588dcfa..b277129f6df2 100644
>> > --- a/Makefile
>> > +++ b/Makefile
>> > @@ -421,7 +421,7 @@ kernel.o: ${GENERIC_HFILES} kernel.c
>> > ${CC} -c ${CRASH_CFLAGS} kernel.c -I${BFD_DIRECTORY}
-I${GDB_INCLUDE_DIRECTORY} ${WARNING_OPTIONS} ${WARNING_ERROR}
>> >
>> > printk.o: ${GENERIC_HFILES} printk.c
>> > - ${CC} -c ${CRASH_CFLAGS} printk.c ${WARNING_OPTIONS}
${WARNING_ERROR}
>> > + ${CC} -c ${CRASH_CFLAGS} printk.c -I${GDB_INCLUDE_DIRECTORY}
${WARNING_OPTIONS} ${WARNING_ERROR}
>> >
>> > gdb_interface.o: ${GENERIC_HFILES} gdb_interface.c
>> > ${CC} -c ${CRASH_CFLAGS} gdb_interface.c ${WARNING_OPTIONS}
${WARNING_ERROR}
>> > diff --git a/printk.c b/printk.c
>> > index 95db7e607e4c..6a87a790b892 100644
>> > --- a/printk.c
>> > +++ b/printk.c
>> > @@ -1,5 +1,6 @@
>> > #include "defs.h"
>> > #include <ctype.h>
>> > +#include "demangle.h"
>> >
>> > /* convenience struct for passing many values to helper functions */
>> > struct prb_map {
>> > @@ -205,10 +206,35 @@ dump_record(struct prb_map *m, unsigned long
id, int msg_flags)
>> > if (*p == '\n')
>> > fprintf(fp, "\n%s", space(ilen));
>> > else if (isprint(*p) || isspace(*p))
>> > - fputc(*p, fp);
>> > + sprintf(&buf[i], "%c", *p);
>> > else
>> > fputc('.', fp);
>> > }
>> > + /*
>> > + * Try to demangle a mangled Rust symbol(calltrace) from log
buffer
>> > + */
>> > + char *p1 = strstr(buf, "_R");
>> > + if (!p1)
>> > + p1 = strstr(buf, "_ZN");
>> > + char *p2 = strchrnul(buf, '+');
>> > + if (p1 && p2) {
>> > + char mangled[BUFSIZE] = {0};
>> > + char demangled[BUFSIZE] = {0};
>> > + char *res;
>> > + size_t slen = p1 - buf;
>> > +
>> > + if (slen)
>> > + memcpy(demangled, buf, slen);
>> > +
>> > + memcpy(mangled, p1, p2-p1);
>> > + res = rust_demangle(mangled, DMGL_RUST);
>> > + if (res) {
>> > + sprintf(demangled+slen, "%s%s", res,p2);
>>
>> The (de)mangled buf size is 1500. First copied slen chars into
>> demangled, then sprintf res and p2 into demangled buf without length
>> check.Though this might be a rare case, but I guess a snprintf with a
>
>
> Theoretically yes, but actually I never saw a very long string in the
printk buffer because it would have bad readability.
> Anyway, how about the following changes?
>
> diff --git a/printk.c b/printk.c
> index 6a87a790b892..c547ea8c3f9f 100644
> --- a/printk.c
> +++ b/printk.c
> @@ -202,6 +202,11 @@ dump_record(struct prb_map *m, unsigned long id,
int msg_flags)
>
> text = m->text_data + begin;
>
> + if (text_len > BUFSIZE) {
> + error(WARNING, "\nThe messages could be truncated!\n");
> + text_len = BUFSIZE;
> + }
> +
OK.
> for (i = 0, p = text; i < text_len; i++, p++) {
> if (*p == '\n')
> fprintf(fp, "\n%s", space(ilen));
> @@ -229,7 +234,7 @@ dump_record(struct prb_map *m, unsigned long id, int
msg_flags)
> memcpy(mangled, p1, p2-p1);
> res = rust_demangle(mangled, DMGL_RUST);
> if (res) {
> - sprintf(demangled+slen, "%s%s", res,p2);
> + snprintf(demangled+slen, BUFSIZE, "%s%s", res,
p2);
I think it should be:
snprintf(demangled+slen, BUFSIZE - slen, "%s%s", res, p2);
Because demangled[BUFSIZE], with slen offset from demangled, the left
space is BUFSIZE - slen.
Totally agree.
Lianbo
> fprintf(fp, "%s",demangled);
> free(res);
> }
>
> Thanks
> Lianbo
>
>> length check is safer for preventing overflow, since we are within
>> ringbuffer buf, I'm not sure how much slen it may be.
>>
>> The rest of the patch are good to me.
>>
>> Thanks,
>> Tao Liu
>>
>> > + fprintf(fp, "%s",demangled);
>> > + free(res);
>> > + }
>> > + } else
>> > + fprintf(fp, "%s", buf);
>> >
>> > if (msg_flags & SHOW_LOG_DICT) {
>> > text = info + OFFSET(printk_info_dev_info) +
>> > --
>> > 2.50.1
>> > --
>> > Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io
>> > To unsubscribe send an email to
devel-leave(a)lists.crash-utility.osci.io
>> > https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/
>> > Contribution Guidelines: https://github.com/crash-utility/crash/wiki
>>
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3 comments
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participants (1)
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lijiang
-
Tao Liu