2021-03-01 23:24:52

by Stephen Boyd

Subject: [PATCH 7/7] kdump: Use vmlinux_build_id() to simplify

We can use the vmlinux_build_id() helper here now instead of open coding
it. This consolidates code and possibly avoids calculating the build ID
twice in the case of a crash with a stacktrace.

Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
---
kernel/crash_core.c | 46 ++++++++-------------------------------------
1 file changed, 8 insertions(+), 38 deletions(-)

diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 825284baaf46..07d3e1109a8c 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -4,6 +4,7 @@
* Copyright (C) 2002-2004 Eric Biederman <[email protected]>
*/

+#include <linux/buildid.h>
#include <linux/crash_core.h>
#include <linux/utsname.h>
#include <linux/vmalloc.h>
@@ -378,51 +379,20 @@ phys_addr_t __weak paddr_vmcoreinfo_note(void)
}
EXPORT_SYMBOL(paddr_vmcoreinfo_note);

-#define NOTES_SIZE (&__stop_notes - &__start_notes)
-#define BUILD_ID_MAX SHA1_DIGEST_SIZE
-#define NT_GNU_BUILD_ID 3
-
-struct elf_note_section {
- struct elf_note n_hdr;
- u8 n_data[];
-};
-
/*
* Add build ID from .notes section as generated by the GNU ld(1)
* or LLVM lld(1) --build-id option.
*/
static void add_build_id_vmcoreinfo(void)
{
- char build_id[BUILD_ID_MAX * 2 + 1];
- int n_remain = NOTES_SIZE;
-
- while (n_remain >= sizeof(struct elf_note)) {
- const struct elf_note_section *note_sec =
- &__start_notes + NOTES_SIZE - n_remain;
- const u32 n_namesz = note_sec->n_hdr.n_namesz;
-
- if (note_sec->n_hdr.n_type == NT_GNU_BUILD_ID &&
- n_namesz != 0 &&
- !strcmp((char *)&note_sec->n_data[0], "GNU")) {
- if (note_sec->n_hdr.n_descsz <= BUILD_ID_MAX) {
- const u32 n_descsz = note_sec->n_hdr.n_descsz;
- const u8 *s = &note_sec->n_data[n_namesz];
-
- s = PTR_ALIGN(s, 4);
- bin2hex(build_id, s, n_descsz);
- build_id[2 * n_descsz] = '\0';
- VMCOREINFO_BUILD_ID(build_id);
- return;
- }
- pr_warn("Build ID is too large to include in vmcoreinfo: %u > %u\n",
- note_sec->n_hdr.n_descsz,
- BUILD_ID_MAX);
- return;
- }
- n_remain -= sizeof(struct elf_note) +
- ALIGN(note_sec->n_hdr.n_namesz, 4) +
- ALIGN(note_sec->n_hdr.n_descsz, 4);
+ const char *build_id = vmlinux_build_id();
+
+ if (build_id[0] == '\0') {
+ pr_warn("Build ID cannot be included in vmcoreinfo\n");
+ return;
}
+
+ VMCOREINFO_BUILD_ID(build_id);
}

static int __init crash_save_vmcoreinfo_init(void)
--
https://chromeos.dev

2021-03-02 20:47:41

by Baoquan He

Subject: Re: [PATCH 7/7] kdump: Use vmlinux_build_id() to simplify

On 03/01/21 at 09:47am, Stephen Boyd wrote:
> We can use the vmlinux_build_id() helper here now instead of open coding
> it. This consolidates code and possibly avoids calculating the build ID
> twice in the case of a crash with a stacktrace.
>
> Cc: Jiri Olsa <[email protected]>
> Cc: Alexei Starovoitov <[email protected]>
> Cc: Jessica Yu <[email protected]>
> Cc: Evan Green <[email protected]>
> Cc: Hsin-Yi Wang <[email protected]>
> Cc: Dave Young <[email protected]>
> Cc: Baoquan He <[email protected]>
> Cc: Vivek Goyal <[email protected]>
> Cc: <[email protected]>
> Signed-off-by: Stephen Boyd <[email protected]>
> ---
> kernel/crash_core.c | 46 ++++++++-------------------------------------
> 1 file changed, 8 insertions(+), 38 deletions(-)
>
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 825284baaf46..07d3e1109a8c 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -4,6 +4,7 @@
> * Copyright (C) 2002-2004 Eric Biederman <[email protected]>
> */
>
> +#include <linux/buildid.h>
> #include <linux/crash_core.h>
> #include <linux/utsname.h>
> #include <linux/vmalloc.h>
> @@ -378,51 +379,20 @@ phys_addr_t __weak paddr_vmcoreinfo_note(void)
> }
> EXPORT_SYMBOL(paddr_vmcoreinfo_note);
>
> -#define NOTES_SIZE (&__stop_notes - &__start_notes)
> -#define BUILD_ID_MAX SHA1_DIGEST_SIZE
> -#define NT_GNU_BUILD_ID 3
> -
> -struct elf_note_section {
> - struct elf_note n_hdr;
> - u8 n_data[];
> -};
> -
> /*
> * Add build ID from .notes section as generated by the GNU ld(1)
> * or LLVM lld(1) --build-id option.
> */
> static void add_build_id_vmcoreinfo(void)
> {
> - char build_id[BUILD_ID_MAX * 2 + 1];
> - int n_remain = NOTES_SIZE;
> -
> - while (n_remain >= sizeof(struct elf_note)) {
> - const struct elf_note_section *note_sec =
> - &__start_notes + NOTES_SIZE - n_remain;
> - const u32 n_namesz = note_sec->n_hdr.n_namesz;
> -
> - if (note_sec->n_hdr.n_type == NT_GNU_BUILD_ID &&
> - n_namesz != 0 &&
> - !strcmp((char *)&note_sec->n_data[0], "GNU")) {
> - if (note_sec->n_hdr.n_descsz <= BUILD_ID_MAX) {
> - const u32 n_descsz = note_sec->n_hdr.n_descsz;
> - const u8 *s = &note_sec->n_data[n_namesz];
> -
> - s = PTR_ALIGN(s, 4);
> - bin2hex(build_id, s, n_descsz);
> - build_id[2 * n_descsz] = '\0';
> - VMCOREINFO_BUILD_ID(build_id);
> - return;
> - }
> - pr_warn("Build ID is too large to include in vmcoreinfo: %u > %u\n",
> - note_sec->n_hdr.n_descsz,
> - BUILD_ID_MAX);
> - return;
> - }
> - n_remain -= sizeof(struct elf_note) +
> - ALIGN(note_sec->n_hdr.n_namesz, 4) +
> - ALIGN(note_sec->n_hdr.n_descsz, 4);
> + const char *build_id = vmlinux_build_id();

It's strange that I can only see the cover letter and this patch 7,
couldn't find the patch where vmlinux_build_id() is introduced in lkml.

> +
> + if (build_id[0] == '\0') {
> + pr_warn("Build ID cannot be included in vmcoreinfo\n");
> + return;
> }
> +
> + VMCOREINFO_BUILD_ID(build_id);
> }
>
> static int __init crash_save_vmcoreinfo_init(void)
> --
> https://chromeos.dev
>
>
> _______________________________________________
> kexec mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/kexec
>

2021-03-04 07:42:02

by Stephen Boyd

Subject: Re: [PATCH 7/7] kdump: Use vmlinux_build_id() to simplify

Quoting Baoquan He (2021-03-02 00:19:09)
> On 03/01/21 at 09:47am, Stephen Boyd wrote:
> > - note_sec->n_hdr.n_descsz,
> > - BUILD_ID_MAX);
> > - return;
> > - }
> > - n_remain -= sizeof(struct elf_note) +
> > - ALIGN(note_sec->n_hdr.n_namesz, 4) +
> > - ALIGN(note_sec->n_hdr.n_descsz, 4);
> > + const char *build_id = vmlinux_build_id();
>
> It's strange that I can only see the cover letter and this patch 7,
> couldn't find the patch where vmlinux_build_id() is introduced in lkml.
>

Hmm not sure. Maybe spam stuff? I will Cc you on the first patch for v2.