[Crash-utility] Re: [PATCH v2] Add "log -R" to display human readable Rust symbol name

On Thu, Sep 18, 2025 at 9:50 AM HAGIO KAZUHITO(萩尾　一仁) <k-hagio-ab(a)nec.com&gt; wrote: > > On 2025/09/17 23:15, Lianbo Jiang wrote: > > Currently, the log command will display human readable Rust > > symbol name by default if any, but, sometimes still want to > > print the original messages from the log buffer(do not demangle). > > > > In addition, if the log buffer has lines like "_R ... +" which > > are not Rust symbols unexpectedly, probably the output will be > > missed, that is unexpected. > > > > To fix above cases, add "log -R" to display human readable Rust > > symbol name, otherwise still print the original messages. > > > > With the patch: > > crash> log -R > > ... > > [ 2174.289360] Tainted: [S]=CPU_OUT_OF_SPEC, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE > > [ 2174.297322] Hardware name: Intel Corporation S2600CWR/S2600CWR, BIOS SE5C610.86B.01.01.0018.072020161249 07/20/2016 > > [ 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 > > [ 2174.357303] init_module+0x57/0xff0 [rust_panic] > > [ 2174.362456] ? __pfx_init_module+0x10/0x10 [rust_panic] > > ... > > > > Suggested-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > > Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com&gt; > > Thank you for the patch, Lianbo. It looks good to me and cleans my worries. > Np. This looks better to me. Lianbo > > Thanks, > Kazu > > > --- > > defs.h | 1 + > > help.c | 24 +++++++++++++++++++++++- > > kernel.c | 5 ++++- > > printk.c | 53 +++++++++++++++++++++++++++++------------------------ > > 4 files changed, 57 insertions(+), 26 deletions(-) > > > > diff --git a/defs.h b/defs.h > > index 156ac0232906..997145cba9d2 100644 > > --- a/defs.h > > +++ b/defs.h > > @@ -6227,6 +6227,7 @@ void parse_kernel_version(char *); > > #define SHOW_LOG_CTIME (0x10) > > #define SHOW_LOG_SAFE (0x20) > > #define SHOW_LOG_CALLER (0x40) > > +#define SHOW_LOG_RUST (0x80) > > void set_cpu(int); > > void clear_machdep_cache(void); > > struct stack_hook *gather_text_list(struct bt_info *); > > diff --git a/help.c b/help.c > > index 4f071e0bd0a0..78d7a5c70e30 100644 > > --- a/help.c > > +++ b/help.c > > @@ -4026,7 +4026,7 @@ NULL > > char *help_log[] = { > > "log", > > "dump system message buffer", > > -"[-Ttdmasc]", > > +"[-TtdmascR]", > > " This command dumps the kernel log_buf contents in chronological order. The", > > " command supports the older log_buf formats, which may or may not contain a", > > " timestamp inserted prior to each message, as well as the newer variable-length", > > @@ -4053,6 +4053,8 @@ char *help_log[] = { > > " the CPU id (if in CPU context) that called printk(), if available.", > > " Generally available on Linux 5.1 to 5.9 kernels configured with", > > " CONFIG_PRINTK_CALLER or Linux 5.10 and later kernels.", > > +" -R Display the message text with human readable Rust symbol name if any,", > > +" otherwise still print the original message text.", > > " ", > > "\nEXAMPLES", > > " Dump the kernel message buffer:\n", > > @@ -4231,6 +4233,26 @@ char *help_log[] = { > > " [ 0.014179] [ T29] RAMDISK: [mem 0x3cf4f000-0x437bbfff]", > > " [ 0.198789] [ C0] DMAR: DRHD: handling fault status reg 3", > > " ...", > > +" ", > > +" Display the message text with human readable Rust symbol name if any,", > > +" otherwise still print the original message text.\n", > > +" %s> log -R", > > +" ...", > > +" [ 2174.289360] Tainted: [S]=CPU_OUT_OF_SPEC, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE", > > +" [ 2174.297322] Hardware name: Intel Corporation S2600CWR/S2600CWR, BIOS SE5C610.86B.01.01.0018.072020161249 07/20/2016", > > +" [ 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", > > +" [ 2174.357303] init_module+0x57/0xff0 [rust_panic]", > > +" [ 2174.362456] ? __pfx_init_module+0x10/0x10 [rust_panic]", > > +" ...", > > > > NULL > > }; > > diff --git a/kernel.c b/kernel.c > > index e4213d7a663e..e077275d7ed6 100644 > > --- a/kernel.c > > +++ b/kernel.c > > @@ -5136,7 +5136,7 @@ cmd_log(void) > > > > msg_flags = 0; > > > > - while ((c = getopt(argcnt, args, "Ttdmasc")) != EOF) { > > + while ((c = getopt(argcnt, args, "TtdmascR")) != EOF) { > > switch(c) > > { > > case 'T': > > @@ -5160,6 +5160,9 @@ cmd_log(void) > > case 'c': > > msg_flags |= SHOW_LOG_CALLER; > > break; > > + case 'R': > > + msg_flags |= SHOW_LOG_RUST; > > + break; > > default: > > argerrs++; > > break; > > diff --git a/printk.c b/printk.c > > index 51b618e2a434..b8fcc8e58160 100644 > > --- a/printk.c > > +++ b/printk.c > > @@ -202,7 +202,7 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags) > > > > text = m->text_data + begin; > > > > - if (text_len > BUFSIZE) { > > + if ((msg_flags & SHOW_LOG_RUST) && (text_len > BUFSIZE)) { > > error(WARNING, "\nThe messages could be truncated!\n"); > > text_len = BUFSIZE; > > } > > @@ -210,36 +210,41 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags) > > for (i = 0, p = text; i < text_len; i++, p++) { > > if (*p == '\n') > > fprintf(fp, "\n%s", space(ilen)); > > - else if (isprint(*p) || isspace(*p)) > > + else if ((msg_flags & SHOW_LOG_RUST) && (isprint(*p) || isspace(*p))) > > sprintf(&buf[i], "%c", *p); > > + else if (isprint(*p) || isspace(*p)) > > + fputc(*p, fp); > > 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 = strrchr(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) { > > - snprintf(demangled+slen, BUFSIZE-slen, "%s%s", res, p2); > > - fprintf(fp, "%s",demangled); > > - free(res); > > - } > > - } else > > - fprintf(fp, "%s", buf); > > + if (msg_flags & SHOW_LOG_RUST) { > > + char *p1 = strstr(buf, "_R"); > > + if (!p1) > > + p1 = strstr(buf, "_ZN"); > > + char *p2 = strrchr(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) { > > + snprintf(demangled+slen, BUFSIZE-slen, "%s%s", res, p2); > > + fprintf(fp, "%s",demangled); > > + free(res); > > + } else > > + fprintf(fp, "%s", buf); > > + } else > > + fprintf(fp, "%s", buf); > > + } > > > > if (msg_flags & SHOW_LOG_DICT) { > > text = info + OFFSET(printk_info_dev_info) +