[PATCH v2] arm64: support an X86_64 target on an ARM64 host
by Alexandr Boyko
Allow "make target=X86_64" on an arm64 host to analyze x86_64 dumpfiles,
mirroring the existing "make target=ARM64" support on an x86_64 host.
The only host dependency was in the LKCD dump headers, which embed a
"struct pt_regs" from <asm/ptrace.h>. The arm64 uapi header exports
"struct user_pt_regs" instead, so add lkcd_x86_64_pt_regs.h, a copy of
the x86_64 uapi definition used only when the X86_64 target is built on
a non-x86_64 host.
Also make the sticky target logic host aware, and reject live system
debugging of an X86/X86_64 binary on an arm64 host.
Assisted-by: Github Copilot CLI:claude-opus-5
Signed-off-by: Alexander Boyko <boy1284(a)gmail.com>
---
Makefile | 2 +-
README | 2 ++
configure.c | 36 +++++++++++++++++++++++++++---
filesys.c | 4 ++++
lkcd_vmdump_v1.h | 4 ++++
lkcd_vmdump_v2_v3.h | 4 ++++
lkcd_x86_64_pt_regs.h | 51 +++++++++++++++++++++++++++++++++++++++++++
7 files changed, 99 insertions(+), 4 deletions(-)
create mode 100644 lkcd_x86_64_pt_regs.h
diff --git a/Makefile b/Makefile
index 46c43a4..22154af 100644
--- a/Makefile
+++ b/Makefile
@@ -98,7 +98,7 @@ GENERIC_HFILES=defs.h xen_hyper_defs.h xen_dom0.h
MCORE_HFILES=va_server.h vas_crash.h
REDHAT_HFILES=netdump.h diskdump.h makedumpfile.h xendump.h kvmdump.h qemu-load.h vmcore.h
LKCD_DUMP_HFILES=lkcd_vmdump_v1.h lkcd_vmdump_v2_v3.h lkcd_dump_v5.h \
- lkcd_dump_v7.h lkcd_dump_v8.h
+ lkcd_dump_v7.h lkcd_dump_v8.h lkcd_x86_64_pt_regs.h
LKCD_OBSOLETE_HFILES=lkcd_fix_mem.h
LKCD_TRACE_HFILES=lkcd_x86_trace.h
IBM_HFILES=ibm_common.h
diff --git a/README b/README
index 69232eb..5c4d8f2 100644
--- a/README
+++ b/README
@@ -113,6 +113,8 @@
riscv64 dumpfiles may be built by typing "make target=RISCV64".
o On an x86_64 host, an x86_64 binary that can be used to analyze
loongarch64 dumpfiles may be built by typing "make target=LOONGARCH64".
+ o On an arm64 host, an arm64 binary that can be used to analyze
+ x86_64 dumpfiles may be built by typing "make target=X86_64".
Traditionally when vmcores are compressed via the makedumpfile(8) facility
the libz compression library is used, and by default the crash utility
diff --git a/configure.c b/configure.c
index fd7b533..1732001 100644
--- a/configure.c
+++ b/configure.c
@@ -182,6 +182,7 @@ void add_extra_lib(char *);
#define GDB_TARGET_MIPS_ON_X86_64 "GDB_CONF_FLAGS=--target=mipsel-elf-linux CFLAGS=-m32 CXXFLAGS=-m32"
#define GDB_TARGET_RISCV64_ON_X86_64 "GDB_CONF_FLAGS=--target=riscv64-unknown-linux-gnu"
#define GDB_TARGET_LOONGARCH64_ON_X86_64 "GDB_CONF_FLAGS=--target=loongarch64-unknown-linux-gnu"
+#define GDB_TARGET_X86_64_ON_ARM64 "GDB_CONF_FLAGS=--target=x86_64-pc-linux-gnu"
/*
* The original plan was to allow the use of a particular version
@@ -474,6 +475,12 @@ get_current_configuration(struct supported_gdb_version *sp)
* Build an ARM64 crash binary on an X86_64 host.
*/
target_data.target = ARM64;
+ } else if ((target_data.target == ARM64) &&
+ (name_to_target((char *)target_data.target_as_param) == X86_64)) {
+ /*
+ * Build an X86_64 crash binary on an ARM64 host.
+ */
+ target_data.target = X86_64;
} else if ((target_data.target == X86_64) &&
(name_to_target((char *)target_data.target_as_param) == PPC64)) {
/*
@@ -570,11 +577,32 @@ get_current_configuration(struct supported_gdb_version *sp)
(target_data.initial_gdb_target != X86))
arch_mismatch(sp);
+ if ((target_data.initial_gdb_target == X86_64) &&
+ (target_data.target != X86_64) &&
+ (target_data.host == ARM64)) {
+ if (target_data.target == ARM64) {
+ /*
+ * An X86_64 cross gdb built on an ARM64 host is sticky.
+ */
+ target_data.target = X86_64;
+ } else
+ arch_mismatch(sp);
+ }
+
if ((target_data.initial_gdb_target == ARM64) &&
(target_data.target != ARM64)) {
- if (target_data.target == X86_64)
+ if (target_data.host == ARM64) {
+ /*
+ * The gdb in this tree is a native ARM64 gdb; it cannot
+ * serve any other target, so a clean rebuild is required.
+ */
+ arch_mismatch(sp);
+ } else if (target_data.host == X86_64 && target_data.target == X86_64) {
+ /*
+ * An ARM64 cross gdb built on an X86_64 host is sticky.
+ */
target_data.target = ARM64;
- else
+ } else
arch_mismatch(sp);
}
if ((target_data.target == ARM64) &&
@@ -787,7 +815,9 @@ build_configure(struct supported_gdb_version *sp)
break;
case X86_64:
target = TARGET_X86_64;
- target_CFLAGS = TARGET_CFLAGS_X86_64;
+ target_CFLAGS = TARGET_CFLAGS_X86_64;
+ if (target_data.host == ARM64)
+ gdb_conf_flags = GDB_TARGET_X86_64_ON_ARM64;
break;
case ARM:
target = TARGET_ARM;
diff --git a/filesys.c b/filesys.c
index 7ff4787..f5b79e7 100644
--- a/filesys.c
+++ b/filesys.c
@@ -4574,4 +4574,8 @@ check_live_arch_mismatch(void)
if (machine_type("PPC"))
error(FATAL, "compiled for the PPC architecture\n");
#endif
+#ifdef __aarch64__
+ if (machine_type("X86_64"))
+ error(FATAL, "compiled for the X86_64 architecture\n");
+#endif
}
diff --git a/lkcd_vmdump_v1.h b/lkcd_vmdump_v1.h
index 3ffb219..0540a1f 100644
--- a/lkcd_vmdump_v1.h
+++ b/lkcd_vmdump_v1.h
@@ -35,8 +35,12 @@
#endif
#ifndef IA64
typedef unsigned int u32;
+#if defined(X86_64) && !defined(__x86_64__)
+#include "lkcd_x86_64_pt_regs.h" /* for pt_regs */
+#else
#include <asm/ptrace.h> /* for pt_regs */
#endif
+#endif
/* necessary header definitions in all cases */
#define DUMP_KIOBUF_NUMBER 0xdeadbeef /* special number for kiobuf maps */
diff --git a/lkcd_vmdump_v2_v3.h b/lkcd_vmdump_v2_v3.h
index f215446..2b47141 100644
--- a/lkcd_vmdump_v2_v3.h
+++ b/lkcd_vmdump_v2_v3.h
@@ -104,8 +104,12 @@ typedef struct _dump_header_asm_s {
#ifndef IA64
typedef unsigned int u32;
+#if defined(X86_64) && !defined(__x86_64__)
+#include "lkcd_x86_64_pt_regs.h" /* for pt_regs */
+#else
#include <asm/ptrace.h> /* for pt_regs */
#endif
+#endif
/* definitions */
#define DUMP_ASM_MAGIC_NUMBER 0xdeaddeadULL /* magic number */
diff --git a/lkcd_x86_64_pt_regs.h b/lkcd_x86_64_pt_regs.h
new file mode 100644
index 0000000..39240d0
--- /dev/null
+++ b/lkcd_x86_64_pt_regs.h
@@ -0,0 +1,51 @@
+/* lkcd_x86_64_pt_regs.h - core analysis suite
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+/*
+ * The LKCD dump headers embed the host kernel's "struct pt_regs", which is
+ * normally picked up from <asm/ptrace.h>. When the X86_64 target is built
+ * on a non-x86_64 host, that header describes the host architecture and does
+ * not export an x86_64 "struct pt_regs" at all, so the definition below is
+ * used instead. It is a verbatim copy of "struct pt_regs" from
+ * arch/x86/include/uapi/asm/ptrace.h, which keeps the LKCD dump
+ * header layout identical to a native x86_64 build.
+ */
+
+#ifndef _LKCD_X86_64_PT_REGS_H
+#define _LKCD_X86_64_PT_REGS_H
+
+struct pt_regs {
+ unsigned long r15;
+ unsigned long r14;
+ unsigned long r13;
+ unsigned long r12;
+ unsigned long rbp;
+ unsigned long rbx;
+ unsigned long r11;
+ unsigned long r10;
+ unsigned long r9;
+ unsigned long r8;
+ unsigned long rax;
+ unsigned long rcx;
+ unsigned long rdx;
+ unsigned long rsi;
+ unsigned long rdi;
+ unsigned long orig_rax;
+ unsigned long rip;
+ unsigned long cs;
+ unsigned long eflags;
+ unsigned long rsp;
+ unsigned long ss;
+};
+
+#endif /* _LKCD_X86_64_PT_REGS_H */
--
2.43.0
15 hours, 16 minutes
- 2
- 1
[PATCH RFC 00/11] crash build refinements
by Dave Young
The embedded gdb module dominates a crash build. Until now it was built with
everything its own configure enables by default, and with debug information
for crash and gdb alike, even though crash uses neither gdb's full-screen TUI
nor the libctf and libbacktrace libraries. At the same time crash's own
configure rewrote the tracked top-level Makefile in place: the tree was dirty
after every build, and it was easy to end up with objects built with stale
flags, since make cannot see that a flag changed.
This series builds only what crash needs, and tidies the interface around the
build and the release targets. Patches 1-4 trim the build, 5-8 rework the
configure and release machinery, and 9-11 document and harden the result.
Trimming the build:
build: make debug information optional, off by default
build: don't build the embedded gdb TUI
build: don't build the unused libctf and libbacktrace libraries
build: remove the unused gdb_files, glink, name and ref targets
-g is now opt-in with "make DEBUG=1", for crash and the embedded gdb both.
The gdb build no longer compiles its TUI (crash has its own CLI), nor
libctf and libbacktrace: 68 source files in all. A full native build now
compiles 599 objects and produces a ~14 MB crash binary.
Reworking configure and the release targets:
build: write the configure variables to Makefile.inc
build: add a separate srpm target, release only builds the tarball
build: remove the redundant tar target
build: make README a static source file
configure no longer edits the Makefile. It writes the variables it manages
to a generated Makefile.inc, which the Makefile includes after its own
defaults, so the tracked file is never modified and unconfiguring is just
removing that file: "make unconfig", or "make distclean", which also removes
the extracted gdb tree, the generated configure files and any release
tarball/spec/source RPM. The release step is split so that "make release"
only produces the source tarball and "make srpm" builds the source RPM from
it, the redundant "make tar" is gone, and README is a normal source file
rather than something a release regenerates from the built binary.
Documenting and hardening:
build: add a "make help" target
README: document the new cleanup and packaging targets
build: recover from an interrupted embedded-gdb configure
"make help" lists the targets and options, including which target= values a
given host accepts. gdb's configure creates config.status early but
gdb/Makefile late, so an interrupted configure used to look like a complete
one; a .configured marker written when configure finishes makes the next
build reconfigure instead, and the remaining failure paths now point at
"make distclean". README describes the new targets and the cleanup rules.
Testing:
- fresh native (x86_64) build: 599 objects, ~14 MB crash binary, runs and
reports crash 9.0.3++;
- fresh "make target=ARM64" build: links and runs;
- configure leaves the tracked Makefile untouched, and "make files" no
longer rewrites README;
- "make clean", "make unconfig" and "make distclean" verified, including
that distclean keeps CFLAGS.extra/LDFLAGS.extra and the downloaded gdb
tarball;
- the series applies in order to the current master.
Notes:
- "make tar" produced an unversioned, gdb-less crash.tar.gz next to the
versioned, gdb-bundled crash-<version>.tar.gz from "make release". If the
gdb-less variant is still wanted, it belongs as an option of release
rather than as a second target.
- README no longer mirrors help.c's built-in README text; "crash -h README"
still substitutes the crash and gdb versions and the date at run time.
- "make srpm" still triggers rpmbuild's "%source_date_epoch_from_changelog is
set, but %changelog has no entries" warning on Fedora/RHEL, because the
generated spec carries no %changelog. It is cosmetic and left as is.
- These series were assited by LLM. I have a plan to continue to improve
the code later, for example remove dead code, maintain the documents
including the white paper within the git tree. I'd like to convert the
static html into .rst files, and generate html/pdf dynamically.
- I'd appreciate for inputs and comments.
Dave Young (11):
build: remove the unused gdb_files, glink, name and ref targets
build: make debug information optional, off by default
build: don't build the embedded gdb TUI
build: don't build the unused libctf and libbacktrace libraries
build: write the configure variables to Makefile.inc
build: add a separate srpm target, release only builds the tarball
build: remove the redundant tar target
build: make README a static source file
build: add a "make help" target
README: document the new cleanup and packaging targets
build: recover from an interrupted embedded-gdb configure
.gitignore | 2 +
Makefile | 174 ++++++++++++++++-----
README | 32 +++-
configure.c | 412 +++++++++++++++++++++++++------------------------
gdb-16.2.patch | 22 ++-
5 files changed, 398 insertions(+), 244 deletions(-)
--
2.51.1
2 days, 13 hours
- 2
- 12
Re: [PATCH] arm64: support an X86_64 target on an ARM64 host
by Dave Young
Added the missing list address in cc.
On 10/5/26 9:23 AM, Dave Young wrote:
> Hi Boiko,
>
> On 10/5/26 3:44 AM, Boiko Alex wrote:
>> On Sat, Oct 3, 2026 at 9:26 AM Dave Young <yangrr.2009(a)tsinghua.org.cn>
>> wrote:
>>
>>>
>>>
>>> On 10/3/26 3:20 PM, Dave Young wrote:
>>>>
>>>>
>>>> On 10/3/26 1:32 PM, Dave Young wrote:
>>>>> Hi Boiko,
>>>>>
>>>>> I will review it. But please resend via either embed the patch in
>>> email body via email client (not an attachment), or send it via git
>>> send-email.
>>>>
>>>> Copy some comments here, but please make sure to send plain text inline
>>> patch as above (use git send-email for safe if you are not sure how to
>>> setup email clients).
>>>>
>>>> /* necessary header files */
>>>> typedef unsigned int u32;
>>>> +#if defined(X86_64) && !defined(__x86_64__)
>>>> +#include "lkcd_x86_64_pt_regs.h" /* for pt_regs
>>> */
>>>> +#else
>>>> #include <asm/ptrace.h> /* for pt_regs
>>> */
>>>> +#endif
>>>>
>>>>
>>>> Above chunk is unreachable. That #include sits inside below if condition:
>>>> #if defined(ARM) || defined(X86) || defined(PPC) || defined(S390) || \
>>>> defined(S390X) || defined(ARM64) || defined(MIPS) || \
>>>> defined(MIPS64) || defined(SPARC64) || defined(RISCV64) || \
>>>> defined(LOONGARCH64)
>>>>
>>>>
>>>> 2. Remove TARGET_CFLAGS_X86_64_ON_ARM64 as it is identical to the
>>> TARGET_CFLAGS_X86_64
>>>>
>>>> 3. machine_type("X86") in filesys.c is unreachable: configure.c never
>>> allows target=X86 on an arm64 host. Harmless defensive symmetry.
>>>>
>>>>
>>>> 4. lkcd_x86_64_pt_regs.h: Copyright line is wrong (2025), please remove
>>> or update it.
>>>
>>>
>>> 5. below chunk is not for supporting x86_64 on arm64, please separate it
>>> in another patch:
>>> if ((target_data.initial_gdb_target == ARM64) &&
>>> (target_data.target != ARM64)) {
>>> - if (target_data.target == X86_64)
>>> + if ((target_data.target == X86_64) &&
>>> + (target_data.host == X86_64))
>>> target_data.target = ARM64;
>>> else
>>> arch_mismatch(sp);
>>>
>>
>> without it, would be wrong gdb arch and wrong build after native arm64
>> build, so it directly related
>
>
> Ok, it confuses sometimes, I thought about the host checking. how about make it clearer like below:
> if ((target_data.initial_gdb_target == ARM64) &&
> (target_data.target != ARM64)) {
> if (target_data.host == ARM64) {
> /*
> * The gdb in this tree is a native ARM64 gdb; it cannot
> * serve any other target, so a clean rebuild is required.
> */
> arch_mismatch(sp);
> } else if (target_data.host == X86_64 && target_data.target == X86_64) {
> /*
> * An ARM64 cross gdb built on an X86_64 host is sticky.
> */
> target_data.target = ARM64;
> } else
> arch_mismatch(sp);
> }
>
>>
>> $ make target=x86_64 lzo snappy zstd
>>>
>>> TARGET: ARM64
>>>
>>> CRASH: 9.0.3++
>>>
>>> GDB: 16.2
>>>
>>>
>>>
>>> gcc -c -g -DARM64 -DLZO -DSNAPPY -DZSTD -DGDB_16_2 build_data.c
>>>
>>> gcc -c -g -DARM64 -DLZO -DSNAPPY -DZSTD -DGDB_16_2 diskdump.c
>>>
>>> ar -rs crashlib.a main.o tools.o global_data.o memory.o filesys.o help.o
>>> task.o build_data.o kernel.o test.o gdb_interface.o net.o dev.o bpf.o
>>> printk.o alpha.o x86.o ppc.o ia64.o s390.o s390x.o s390dbf.o ppc64.o
>>> x86_64.o arm.o arm64.o mips.o mips64.o riscv64.o loongarch64.o sparc64.o
>>> extensions.o remote.o va_server.o va_server_v1.o symbols.o cmdline.o
>>> lkcd_common.o lkcd_v1.o lkcd_v2_v3.o lkcd_v5.o lkcd_v7.o lkcd_v8.o
>>> lkcd_fix_mem.o s390_dump.o netdump.o diskdump.o makedumpfile.o xendump.o
>>> lkcd_x86_trace.o unwind_v1.o unwind_v2.o unwind_v3.o unwind_x86_32_64.o
>>> unwind_arm.o xen_hyper.o xen_hyper_command.o xen_hyper_global_data.o
>>> xen_hyper_dump_tables.o kvmdump.o qemu.o qemu-load.o sadump.o ipcs.o
>>> ramdump.o vmware_vmss.o vmware_guestdump.o xen_dom0.o kaslr_helper.o
>>> sbitmap.o maple_tree.o lzorle_decompress.o
>>> make[4]: warning: Clock skew detected. Your build may be incomplete.
>>>
>>> CXXLD gdb
>>>
>>
>>
>>
>> instead of
>>
>>
>>> $make target=x86_64 lzo snappy zstd
>>>
>>>
>>>
>>> The initial build in this source tree was for the ARM64 architecture.
>>>
>>>
>>>
>>> In order to build a crash binary for the X86_64 architecture:
>>>
>>> 1. remove the gdb-16.2 subdirectory
>>>
>>> 2. perform a "make clean"
>>>
>>> 3. retry the build
>>>
>>
>>
>>
>> make: *** [Makefile:306: all] Error 1
>>
>>>
>>>>
>>>>
>>>>>
>>>>> On 10/2/26 10:33 PM, Boiko Alex wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io
>>>>>> To unsubscribe send an email to
>>> devel-leave(a)lists.crash-utility.osci.io
>>>>>> https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/
>>>>>> Contribution Guidelines: https://github.com/crash-utility/crash/wiki
>>>>> --
>>>>> 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://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/
>>>>> Contribution Guidelines: https://github.com/crash-utility/crash/wiki
>>>> --
>>>> Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io
>>>> To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io
>>>> https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/
>>>> Contribution Guidelines: https://github.com/crash-utility/crash/wiki
>>>
>>>
>>
>
>
>
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