[PATCH v5 00/13] Add build ID to stacktraces

[PATCH v5 00/13] Add build ID to stacktraces

[Stephen Boyd]

This series adds the kernel's build ID[1] to the stacktrace header printed
in oops messages, warnings, etc. and the build ID for any module that
appears in the stacktrace after the module name. The goal is to make the
stacktrace more self-contained and descriptive by including the relevant
build IDs in the kernel logs when something goes wrong. This can be used
by post processing tools like script/decode_stacktrace.sh and kernel
developers to easily locate the debug info associated with a kernel
crash and line up what line and file things started falling apart at.

To show how this can be used I've included a patch to
decode_stacktrace.sh that downloads the debuginfo from a debuginfod
server.

This also includes some patches to make the buildid.c file use more
const arguments and consolidate logic into buildid.c from kdump. These
are left to the end as they were mostly cleanup patches. I don't know
who exactly maintains this so I guess Andrew is the best option to merge
all this code.

Here's an example lkdtm stacktrace on arm64.

 WARNING: CPU: 4 PID: 3255 at drivers/misc/lkdtm/bugs.c:83 lkdtm_WARNING+0x28/0x30 [lkdtm]
 Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE
 CPU: 4 PID: 3255 Comm: bash Not tainted 5.11 #3 aa23f7a1231c229de205662d5a9e0d4c580f19a1
 Hardware name: Google Lazor (rev3+) with KB Backlight (DT)
 pstate: 00400009 (nzcv daif +PAN -UAO -TCO BTYPE=--)
 pc : lkdtm_WARNING+0x28/0x30 [lkdtm]
 lr : lkdtm_do_action+0x24/0x40 [lkdtm]
 sp : ffffffc0134fbca0
 x29: ffffffc0134fbca0 x28: ffffff92d53ba240
 x27: 0000000000000000 x26: 0000000000000000
 x25: 0000000000000000 x24: ffffffe3622352c0
 x23: 0000000000000020 x22: ffffffe362233366
 x21: ffffffe3622352e0 x20: ffffffc0134fbde0
 x19: 0000000000000008 x18: 0000000000000000
 x17: ffffff929b6536fc x16: 0000000000000000
 x15: 0000000000000000 x14: 0000000000000012
 x13: ffffffe380ed892c x12: ffffffe381d05068
 x11: 0000000000000000 x10: 0000000000000000
 x9 : 0000000000000001 x8 : ffffffe362237000
 x7 : aaaaaaaaaaaaaaaa x6 : 0000000000000000
 x5 : 0000000000000000 x4 : 0000000000000001
 x3 : 0000000000000008 x2 : ffffff93fef25a70
 x1 : ffffff93fef15788 x0 : ffffffe3622352e0
 Call trace:
  lkdtm_WARNING+0x28/0x30 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
  direct_entry+0x16c/0x1b4 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
  full_proxy_write+0x74/0xa4
  vfs_write+0xec/0x2e8
  ksys_write+0x84/0xf0
  __arm64_sys_write+0x24/0x30
  el0_svc_common+0xf4/0x1c0
  do_el0_svc_compat+0x28/0x3c
  el0_svc_compat+0x10/0x1c
  el0_sync_compat_handler+0xa8/0xcc
  el0_sync_compat+0x178/0x180
 ---[ end trace 3d95032303e59e68 ]---

Changes from v4 (https://lore.kernel.org/r/20210410015300.3764485-1-swboyd@chromium.org):
 * Stubbed out more code when CONFIG_STACKTRACE_BUILD_ID=n
 * Use static_assert instead of BUILD_BUG_ON()
 * Dropped bad printk change to IP on x86

Changes from v3 (https://lore.kernel.org/r/20210331030520.3816265-1-swboyd@chromium.org):
 * Fixed compilation warnings due to config changes
 * Fixed kernel-doc on init_vmlinx_build_id()
 * Totally removed add_build_id_vmcoreinfo()
 * Added another printk format %pBb to help x86 print backtraces
 * Some BUILD_BUG_ON() checks to make sure the buildid doesn't get bigger or smaller

Changes from v2 (https://lore.kernel.org/r/20210324020443.1815557-1-swboyd@chromium.org):
 * Renamed symbol printing function to indicate build IDness
 * Put build ID information behind Kconfig knob
 * Build ID for vmlinux is calculated in early init instead of on demand
 * printk format is %pS[R]b

Changes from v1 (https://lore.kernel.org/r/20210301174749.1269154-1-swboyd@chromium.org):
 * New printk format %pSb and %pSr
 * Return binary format instead of hex format string from build ID APIs
 * Some new patches to cleanup buildid/decode_stacktrace.sh
 * A new patch to decode_stacktrace.sh to parse output

[1] https://fedoraproject.org/wiki/Releases/FeatureBuildId

Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Evan Green <evgreen@chromium.org>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: <kexec@lists.infradead.org>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: <linux-doc@vger.kernel.org>
Cc: <linux-kernel@vger.kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: <x86@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: peter enderborg <peter.
Stephen Boyd (13):
  buildid: Only consider GNU notes for build ID parsing
  buildid: Add API to parse build ID out of buffer
  buildid: Stash away kernels build ID on init
  dump_stack: Add vmlinux build ID to stack traces
  module: Add printk formats to add module build ID to stacktraces
  arm64: stacktrace: Use %pSb for backtrace printing
  x86/dumpstack: Use %pSb/%pBb for backtrace printing
  scripts/decode_stacktrace.sh: Support debuginfod
  scripts/decode_stacktrace.sh: Silence stderr messages from
    addr2line/nm
  scripts/decode_stacktrace.sh: Indicate 'auto' can be used for base
    path
  buildid: Mark some arguments const
  buildid: Fix kernel-doc notation
  kdump: Use vmlinux_build_id to simplify

 Documentation/core-api/printk-formats.rst |  11 +++
 arch/arm64/kernel/stacktrace.c            |   2 +-
 arch/x86/kernel/dumpstack.c               |   2 +-
 include/linux/buildid.h                   |   8 ++
 include/linux/crash_core.h                |  12 +--
 include/linux/kallsyms.h                  |  20 ++++-
 include/linux/module.h                    |   8 +-
 init/main.c                               |   1 +
 kernel/crash_core.c                       |  50 +----------
 kernel/kallsyms.c                         | 101 +++++++++++++++++-----
 kernel/module.c                           |  31 ++++++-
 lib/Kconfig.debug                         |  11 +++
 lib/buildid.c                             |  74 ++++++++++++----
 lib/dump_stack.c                          |  13 ++-
 lib/vsprintf.c                            |   8 +-
 scripts/decode_stacktrace.sh              |  89 +++++++++++++++----
 16 files changed, 327 insertions(+), 114 deletions(-)


base-commit: a38fd8748464831584a19438cbb3082b5a2dab15
-- 
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[PATCH v5 03/13] buildid: Stash away kernels build ID on init

[Stephen Boyd]

Parse the kernel's build ID at initialization so that other code can
print a hex format string representation of the running kernel's build
ID. This will be used in the kdump and dump_stack code so that
developers can easily locate the vmlinux debug symbols for a
crash/stacktrace.

Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Evan Green <evgreen@chromium.org>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: <kexec@lists.infradead.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 include/linux/buildid.h |  3 +++
 init/main.c             |  1 +
 lib/buildid.c           | 15 +++++++++++++++
 3 files changed, 19 insertions(+)

diff --git a/include/linux/buildid.h b/include/linux/buildid.h
index ebce93f26d06..f375900cf9ed 100644
--- a/include/linux/buildid.h
+++ b/include/linux/buildid.h
@@ -10,4 +10,7 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
 		   __u32 *size);
 int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size);
 
+extern unsigned char vmlinux_build_id[BUILD_ID_SIZE_MAX];
+void init_vmlinux_build_id(void);
+
 #endif
diff --git a/init/main.c b/init/main.c
index 53b278845b88..eaede2f41327 100644
--- a/init/main.c
+++ b/init/main.c
@@ -857,6 +857,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
 	set_task_stack_end_magic(&init_task);
 	smp_setup_processor_id();
 	debug_objects_early_init();
+	init_vmlinux_build_id();
 
 	cgroup_init_early();
 
diff --git a/lib/buildid.c b/lib/buildid.c
index 6aea1c4e5e85..1103ed46214f 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/buildid.h>
+#include <linux/cache.h>
 #include <linux/elf.h>
 #include <linux/kernel.h>
 #include <linux/pagemap.h>
@@ -172,3 +173,17 @@ int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size)
 {
 	return parse_build_id_buf(build_id, NULL, buf, buf_size);
 }
+
+unsigned char vmlinux_build_id[BUILD_ID_SIZE_MAX] __ro_after_init;
+
+/**
+ * init_vmlinux_build_id - Compute and stash the running kernel's build ID
+ */
+void __init init_vmlinux_build_id(void)
+{
+	extern const void __start_notes __weak;
+	extern const void __stop_notes __weak;
+	unsigned int size = &__stop_notes - &__start_notes;
+
+	build_id_parse_buf(&__start_notes, vmlinux_build_id, size);
+}
-- 
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[PATCH v5 13/13] kdump: Use vmlinux_build_id to simplify

[Stephen Boyd]

We can use the vmlinux_build_id array here now instead of open coding
it. This mostly consolidates code.

Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Evan Green <evgreen@chromium.org>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: <kexec@lists.infradead.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 include/linux/crash_core.h | 12 ++++-----
 kernel/crash_core.c        | 50 ++------------------------------------
 2 files changed, 8 insertions(+), 54 deletions(-)

diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index 206bde8308b2..de62a722431e 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -38,8 +38,12 @@ phys_addr_t paddr_vmcoreinfo_note(void);
 
 #define VMCOREINFO_OSRELEASE(value) \
 	vmcoreinfo_append_str("OSRELEASE=%s\n", value)
-#define VMCOREINFO_BUILD_ID(value) \
-	vmcoreinfo_append_str("BUILD-ID=%s\n", value)
+#define VMCOREINFO_BUILD_ID()						\
+	({								\
+		static_assert(sizeof(vmlinux_build_id) == 20);		\
+		vmcoreinfo_append_str("BUILD-ID=%20phN\n", vmlinux_build_id); \
+	})
+
 #define VMCOREINFO_PAGESIZE(value) \
 	vmcoreinfo_append_str("PAGESIZE=%ld\n", value)
 #define VMCOREINFO_SYMBOL(name) \
@@ -69,10 +73,6 @@ extern unsigned char *vmcoreinfo_data;
 extern size_t vmcoreinfo_size;
 extern u32 *vmcoreinfo_note;
 
-/* raw contents of kernel .notes section */
-extern const void __start_notes __weak;
-extern const void __stop_notes __weak;
-
 Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
 			  void *data, size_t data_len);
 void final_note(Elf_Word *buf);
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 825284baaf46..29cc15398ee4 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -4,6 +4,7 @@
  * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
  */
 
+#include <linux/buildid.h>
 #include <linux/crash_core.h>
 #include <linux/utsname.h>
 #include <linux/vmalloc.h>
@@ -378,53 +379,6 @@ 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);
-	}
-}
-
 static int __init crash_save_vmcoreinfo_init(void)
 {
 	vmcoreinfo_data = (unsigned char *)get_zeroed_page(GFP_KERNEL);
@@ -443,7 +397,7 @@ static int __init crash_save_vmcoreinfo_init(void)
 	}
 
 	VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
-	add_build_id_vmcoreinfo();
+	VMCOREINFO_BUILD_ID();
 	VMCOREINFO_PAGESIZE(PAGE_SIZE);
 
 	VMCOREINFO_SYMBOL(init_uts_ns);
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Re: [PATCH v5 03/13] buildid: Stash away kernels build ID on init

[Baoquan He]

On 04/20/21 at 02:49pm, Stephen Boyd wrote:
> Parse the kernel's build ID at initialization so that other code can
> print a hex format string representation of the running kernel's build
> ID. This will be used in the kdump and dump_stack code so that
> developers can easily locate the vmlinux debug symbols for a
> crash/stacktrace.
> 
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Jessica Yu <jeyu@kernel.org>
> Cc: Evan Green <evgreen@chromium.org>
> Cc: Hsin-Yi Wang <hsinyi@chromium.org>
> Cc: Dave Young <dyoung@redhat.com>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Vivek Goyal <vgoyal@redhat.com>
> Cc: <kexec@lists.infradead.org>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
>  include/linux/buildid.h |  3 +++
>  init/main.c             |  1 +
>  lib/buildid.c           | 15 +++++++++++++++
>  3 files changed, 19 insertions(+)
> 
> diff --git a/include/linux/buildid.h b/include/linux/buildid.h
> index ebce93f26d06..f375900cf9ed 100644
> --- a/include/linux/buildid.h
> +++ b/include/linux/buildid.h
> @@ -10,4 +10,7 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
>  		   __u32 *size);
>  int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size);
>  
> +extern unsigned char vmlinux_build_id[BUILD_ID_SIZE_MAX];
> +void init_vmlinux_build_id(void);
> +
>  #endif
> diff --git a/init/main.c b/init/main.c
> index 53b278845b88..eaede2f41327 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -857,6 +857,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
>  	set_task_stack_end_magic(&init_task);
>  	smp_setup_processor_id();
>  	debug_objects_early_init();
> +	init_vmlinux_build_id();
>  
>  	cgroup_init_early();
>  
> diff --git a/lib/buildid.c b/lib/buildid.c
> index 6aea1c4e5e85..1103ed46214f 100644
> --- a/lib/buildid.c
> +++ b/lib/buildid.c
> @@ -1,6 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0
>  
>  #include <linux/buildid.h>
> +#include <linux/cache.h>
>  #include <linux/elf.h>
>  #include <linux/kernel.h>
>  #include <linux/pagemap.h>
> @@ -172,3 +173,17 @@ int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size)
>  {
>  	return parse_build_id_buf(build_id, NULL, buf, buf_size);
>  }
> +
> +unsigned char vmlinux_build_id[BUILD_ID_SIZE_MAX] __ro_after_init;
> +
> +/**
> + * init_vmlinux_build_id - Compute and stash the running kernel's build ID
> + */
> +void __init init_vmlinux_build_id(void)
> +{
> +	extern const void __start_notes __weak;
> +	extern const void __stop_notes __weak;
> +	unsigned int size = &__stop_notes - &__start_notes;
> +
> +	build_id_parse_buf(&__start_notes, vmlinux_build_id, size);
> +}

LGTM, thx.

Acked-by: Baoquan He <bhe@redhat.com>


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Re: [PATCH v5 13/13] kdump: Use vmlinux_build_id to simplify

[Baoquan He]

On 04/20/21 at 02:50pm, Stephen Boyd wrote:
> We can use the vmlinux_build_id array here now instead of open coding
> it. This mostly consolidates code.
> 
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Jessica Yu <jeyu@kernel.org>
> Cc: Evan Green <evgreen@chromium.org>
> Cc: Hsin-Yi Wang <hsinyi@chromium.org>
> Cc: Dave Young <dyoung@redhat.com>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Vivek Goyal <vgoyal@redhat.com>
> Cc: <kexec@lists.infradead.org>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
>  include/linux/crash_core.h | 12 ++++-----
>  kernel/crash_core.c        | 50 ++------------------------------------
>  2 files changed, 8 insertions(+), 54 deletions(-)
> 
> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> index 206bde8308b2..de62a722431e 100644
> --- a/include/linux/crash_core.h
> +++ b/include/linux/crash_core.h
> @@ -38,8 +38,12 @@ phys_addr_t paddr_vmcoreinfo_note(void);
>  
>  #define VMCOREINFO_OSRELEASE(value) \
>  	vmcoreinfo_append_str("OSRELEASE=%s\n", value)
> -#define VMCOREINFO_BUILD_ID(value) \
> -	vmcoreinfo_append_str("BUILD-ID=%s\n", value)
> +#define VMCOREINFO_BUILD_ID()						\
> +	({								\
> +		static_assert(sizeof(vmlinux_build_id) == 20);		\
> +		vmcoreinfo_append_str("BUILD-ID=%20phN\n", vmlinux_build_id); \

Since there has been static_assert at above, can we remove the magic
number '20'? 

And I checked format_decode(), didn't find which type corresponds to
'N', could you tell?

Other than these, this patch looks good to me, thanks for the effort.

Thanks
Baoquan

> +	})
> +
>  #define VMCOREINFO_PAGESIZE(value) \
>  	vmcoreinfo_append_str("PAGESIZE=%ld\n", value)
>  #define VMCOREINFO_SYMBOL(name) \
> @@ -69,10 +73,6 @@ extern unsigned char *vmcoreinfo_data;
>  extern size_t vmcoreinfo_size;
>  extern u32 *vmcoreinfo_note;
>  
> -/* raw contents of kernel .notes section */
> -extern const void __start_notes __weak;
> -extern const void __stop_notes __weak;
> -
>  Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
>  			  void *data, size_t data_len);
>  void final_note(Elf_Word *buf);
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 825284baaf46..29cc15398ee4 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -4,6 +4,7 @@
>   * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
>   */
>  
> +#include <linux/buildid.h>
>  #include <linux/crash_core.h>
>  #include <linux/utsname.h>
>  #include <linux/vmalloc.h>
> @@ -378,53 +379,6 @@ 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);
> -	}
> -}
> -
>  static int __init crash_save_vmcoreinfo_init(void)
>  {
>  	vmcoreinfo_data = (unsigned char *)get_zeroed_page(GFP_KERNEL);
> @@ -443,7 +397,7 @@ static int __init crash_save_vmcoreinfo_init(void)
>  	}
>  
>  	VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
> -	add_build_id_vmcoreinfo();
> +	VMCOREINFO_BUILD_ID();
>  	VMCOREINFO_PAGESIZE(PAGE_SIZE);
>  
>  	VMCOREINFO_SYMBOL(init_uts_ns);
> -- 
> https://chromeos.dev
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
> 


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Re: [PATCH v5 13/13] kdump: Use vmlinux_build_id to simplify

[Stephen Boyd]

Quoting Baoquan He (2021-04-28 03:13:55)
> On 04/20/21 at 02:50pm, Stephen Boyd wrote:
> > We can use the vmlinux_build_id array here now instead of open coding
> > it. This mostly consolidates code.
> >
> > Cc: Jiri Olsa <jolsa@kernel.org>
> > Cc: Alexei Starovoitov <ast@kernel.org>
> > Cc: Jessica Yu <jeyu@kernel.org>
> > Cc: Evan Green <evgreen@chromium.org>
> > Cc: Hsin-Yi Wang <hsinyi@chromium.org>
> > Cc: Dave Young <dyoung@redhat.com>
> > Cc: Baoquan He <bhe@redhat.com>
> > Cc: Vivek Goyal <vgoyal@redhat.com>
> > Cc: <kexec@lists.infradead.org>
> > Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> > ---
> >  include/linux/crash_core.h | 12 ++++-----
> >  kernel/crash_core.c        | 50 ++------------------------------------
> >  2 files changed, 8 insertions(+), 54 deletions(-)
> >
> > diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> > index 206bde8308b2..de62a722431e 100644
> > --- a/include/linux/crash_core.h
> > +++ b/include/linux/crash_core.h
> > @@ -38,8 +38,12 @@ phys_addr_t paddr_vmcoreinfo_note(void);
> >
> >  #define VMCOREINFO_OSRELEASE(value) \
> >       vmcoreinfo_append_str("OSRELEASE=%s\n", value)
> > -#define VMCOREINFO_BUILD_ID(value) \
> > -     vmcoreinfo_append_str("BUILD-ID=%s\n", value)
> > +#define VMCOREINFO_BUILD_ID()                                                \
> > +     ({                                                              \
> > +             static_assert(sizeof(vmlinux_build_id) == 20);          \
> > +             vmcoreinfo_append_str("BUILD-ID=%20phN\n", vmlinux_build_id); \
>
> Since there has been static_assert at above, can we remove the magic
> number '20'?
>
> And I checked format_decode(), didn't find which type corresponds to
> 'N', could you tell?

It is documented in Documentation/core-api/printk-formats.rst (see "Raw
buffer as a hex string") where the '20' replaces the '*' to specify a
fixed size buffer to format. We could pass the 20 as an argument instead
of encoding it in the format, but then it would still be there twice. We
could use a #define but then it would have to be passed as an argument.

I don't know of a good way to enforce in printk that the buffer is the
size that matches the format size. Maybe it shouldn't be an option to
have a size in the format string if it's a problem to put the size of
the buffer in there.

>
> Other than these, this patch looks good to me, thanks for the effort.
>

Thanks.

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Re: [PATCH v5 13/13] kdump: Use vmlinux_build_id to simplify

[Baoquan He]

On 04/29/21 at 01:14am, Stephen Boyd wrote:
> Quoting Baoquan He (2021-04-28 03:13:55)
> > On 04/20/21 at 02:50pm, Stephen Boyd wrote:
> > > We can use the vmlinux_build_id array here now instead of open coding
> > > it. This mostly consolidates code.
> > >
> > > Cc: Jiri Olsa <jolsa@kernel.org>
> > > Cc: Alexei Starovoitov <ast@kernel.org>
> > > Cc: Jessica Yu <jeyu@kernel.org>
> > > Cc: Evan Green <evgreen@chromium.org>
> > > Cc: Hsin-Yi Wang <hsinyi@chromium.org>
> > > Cc: Dave Young <dyoung@redhat.com>
> > > Cc: Baoquan He <bhe@redhat.com>
> > > Cc: Vivek Goyal <vgoyal@redhat.com>
> > > Cc: <kexec@lists.infradead.org>
> > > Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> > > ---
> > >  include/linux/crash_core.h | 12 ++++-----
> > >  kernel/crash_core.c        | 50 ++------------------------------------
> > >  2 files changed, 8 insertions(+), 54 deletions(-)
> > >
> > > diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> > > index 206bde8308b2..de62a722431e 100644
> > > --- a/include/linux/crash_core.h
> > > +++ b/include/linux/crash_core.h
> > > @@ -38,8 +38,12 @@ phys_addr_t paddr_vmcoreinfo_note(void);
> > >
> > >  #define VMCOREINFO_OSRELEASE(value) \
> > >       vmcoreinfo_append_str("OSRELEASE=%s\n", value)
> > > -#define VMCOREINFO_BUILD_ID(value) \
> > > -     vmcoreinfo_append_str("BUILD-ID=%s\n", value)
> > > +#define VMCOREINFO_BUILD_ID()                                                \
> > > +     ({                                                              \
> > > +             static_assert(sizeof(vmlinux_build_id) == 20);          \
> > > +             vmcoreinfo_append_str("BUILD-ID=%20phN\n", vmlinux_build_id); \
> >
> > Since there has been static_assert at above, can we remove the magic
> > number '20'?
> >
> > And I checked format_decode(), didn't find which type corresponds to
> > 'N', could you tell?
> 
> It is documented in Documentation/core-api/printk-formats.rst (see "Raw
> buffer as a hex string") where the '20' replaces the '*' to specify a
> fixed size buffer to format. We could pass the 20 as an argument instead
> of encoding it in the format, but then it would still be there twice. We
> could use a #define but then it would have to be passed as an argument.

Thanks for telling, I can see 'phN' is used in many places, but haven't
figured out how it's parsed, e.g in format_decode() it's not related.
Anyway, I may need dig further or search to get it.

> 
> I don't know of a good way to enforce in printk that the buffer is the
> size that matches the format size. Maybe it shouldn't be an option to
> have a size in the format string if it's a problem to put the size of
> the buffer in there.

Oh, I meant that we may not need to enforce that because the size of
vmlinux_build_id can be guaranteed, always 20, we do not need to specify
the '20'? Afaik, we usually specify the format size when the string size
is variable, and we want to add '0' to make the width of printing is
fixed. Anyway, this dones't matter much.

Acked-by: Baoquan He <bhe@redhat.com>

Thanks
Baoquan

> 
> >
> > Other than these, this patch looks good to me, thanks for the effort.
> >
> 
> Thanks.
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
> 


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Re: [PATCH v5 13/13] kdump: Use vmlinux_build_id to simplify

[Baoquan He]

On 05/07/21 at 11:54am, Baoquan He wrote:
> On 04/29/21 at 01:14am, Stephen Boyd wrote:
> > Quoting Baoquan He (2021-04-28 03:13:55)
> > > On 04/20/21 at 02:50pm, Stephen Boyd wrote:
> > > > We can use the vmlinux_build_id array here now instead of open coding
> > > > it. This mostly consolidates code.
> > > >
> > > > Cc: Jiri Olsa <jolsa@kernel.org>
> > > > Cc: Alexei Starovoitov <ast@kernel.org>
> > > > Cc: Jessica Yu <jeyu@kernel.org>
> > > > Cc: Evan Green <evgreen@chromium.org>
> > > > Cc: Hsin-Yi Wang <hsinyi@chromium.org>
> > > > Cc: Dave Young <dyoung@redhat.com>
> > > > Cc: Baoquan He <bhe@redhat.com>
> > > > Cc: Vivek Goyal <vgoyal@redhat.com>
> > > > Cc: <kexec@lists.infradead.org>
> > > > Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> > > > ---
> > > >  include/linux/crash_core.h | 12 ++++-----
> > > >  kernel/crash_core.c        | 50 ++------------------------------------
> > > >  2 files changed, 8 insertions(+), 54 deletions(-)
> > > >
> > > > diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> > > > index 206bde8308b2..de62a722431e 100644
> > > > --- a/include/linux/crash_core.h
> > > > +++ b/include/linux/crash_core.h
> > > > @@ -38,8 +38,12 @@ phys_addr_t paddr_vmcoreinfo_note(void);
> > > >
> > > >  #define VMCOREINFO_OSRELEASE(value) \
> > > >       vmcoreinfo_append_str("OSRELEASE=%s\n", value)
> > > > -#define VMCOREINFO_BUILD_ID(value) \
> > > > -     vmcoreinfo_append_str("BUILD-ID=%s\n", value)
> > > > +#define VMCOREINFO_BUILD_ID()                                                \
> > > > +     ({                                                              \
> > > > +             static_assert(sizeof(vmlinux_build_id) == 20);          \
> > > > +             vmcoreinfo_append_str("BUILD-ID=%20phN\n", vmlinux_build_id); \
> > >
> > > Since there has been static_assert at above, can we remove the magic
> > > number '20'?
> > >
> > > And I checked format_decode(), didn't find which type corresponds to
> > > 'N', could you tell?
> > 
> > It is documented in Documentation/core-api/printk-formats.rst (see "Raw
> > buffer as a hex string") where the '20' replaces the '*' to specify a
> > fixed size buffer to format. We could pass the 20 as an argument instead
> > of encoding it in the format, but then it would still be there twice. We
> > could use a #define but then it would have to be passed as an argument.
> 
> Thanks for telling, I can see 'phN' is used in many places, but haven't
> figured out how it's parsed, e.g in format_decode() it's not related.
> Anyway, I may need dig further or search to get it.
> 
> > 
> > I don't know of a good way to enforce in printk that the buffer is the
> > size that matches the format size. Maybe it shouldn't be an option to
> > have a size in the format string if it's a problem to put the size of
> > the buffer in there.
> 
> Oh, I meant that we may not need to enforce that because the size of
> vmlinux_build_id can be guaranteed, always 20, we do not need to specify
> the '20'? Afaik, we usually specify the format size when the string size
> is variable, and we want to add '0' to make the width of printing is
                                  ~'space' I meant
> fixed. Anyway, this dones't matter much.
> 
> Acked-by: Baoquan He <bhe@redhat.com>
> 
> Thanks
> Baoquan
> 
> > 
> > >
> > > Other than these, this patch looks good to me, thanks for the effort.
> > >
> > 
> > Thanks.
> > 
> > _______________________________________________
> > kexec mailing list
> > kexec@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> > 
> 
> 
> _______________________________________________
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> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
> 


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