+ vmcoreinfo-include-kallsyms-symbols.patch added to mm-nonmm-unstable branch

+ vmcoreinfo-include-kallsyms-symbols.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: vmcoreinfo: include kallsyms symbols
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     vmcoreinfo-include-kallsyms-symbols.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/vmcoreinfo-include-kallsyms-symbols.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Stephen Brennan <stephen.s.brennan@oracle.com>
Subject: vmcoreinfo: include kallsyms symbols
Date: Mon, 16 May 2022 17:05:08 -0700

The internal kallsyms tables contain information which could be quite
useful to a debugging tool in the absence of other debuginfo.  If kallsyms
is enabled, then a debugging tool could parse it and use it as a fallback
symbol table.  Combined with BTF data, live & post-mortem debuggers can
support basic operations without needing a large DWARF debuginfo file
available.  As many as five symbols are necessary to properly parse
kallsyms names and addresses.  Add these to the vmcoreinfo note.

CONFIG_KALLSYMS_ABSOLUTE_PERCPU does impact the computation of symbol
addresses.  However, a debugger can infer this configuration value by
comparing the address of _stext in the vmcoreinfo with the address
computed via kallsyms.  So there's no need to include information about
this config value in the vmcoreinfo note.

To verify that we're still well below the maximum of 4096 bytes, I created
a script[1] to compute a rough upper bound on the possible size of
vmcoreinfo.  On v5.18-rc7, the script reports 3106 bytes, and with this
patch, the maximum become 3370 bytes.

[1]: https://github.com/brenns10/kernel_stuff/blob/master/vmcoreinfosize/

Link: https://lkml.kernel.org/r/20220517000508.777145-3-stephen.s.brennan@oracle.com
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Bixuan Cui <cuibixuan@huawei.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: David Vernet <void@manifault.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/crash_core.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

--- a/kernel/crash_core.c~vmcoreinfo-include-kallsyms-symbols
+++ a/kernel/crash_core.c
@@ -15,6 +15,8 @@
 
 #include <crypto/sha1.h>
 
+#include "kallsyms_internal.h"
+
 /* vmcoreinfo stuff */
 unsigned char *vmcoreinfo_data;
 size_t vmcoreinfo_size;
@@ -480,6 +482,18 @@ static int __init crash_save_vmcoreinfo_
 	VMCOREINFO_NUMBER(PAGE_OFFLINE_MAPCOUNT_VALUE);
 #endif
 
+#ifdef CONFIG_KALLSYMS
+	VMCOREINFO_SYMBOL(kallsyms_names);
+	VMCOREINFO_SYMBOL(kallsyms_token_table);
+	VMCOREINFO_SYMBOL(kallsyms_token_index);
+#ifdef CONFIG_KALLSYMS_BASE_RELATIVE
+	VMCOREINFO_SYMBOL(kallsyms_offsets);
+	VMCOREINFO_SYMBOL(kallsyms_relative_base);
+#else
+	VMCOREINFO_SYMBOL(kallsyms_addresses);
+#endif /* CONFIG_KALLSYMS_BASE_RELATIVE */
+#endif /* CONFIG_KALLSYMS */
+
 	arch_crash_save_vmcoreinfo();
 	update_vmcoreinfo_note();
 
_

Patches currently in -mm which might be from stephen.s.brennan@oracle.com are

kallsyms-move-declarations-to-internal-header.patch
vmcoreinfo-include-kallsyms-symbols.patch