This is a note to let you know that I've just added the patch titled
kallsyms: Fix kallsyms_selftest failure
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kallsyms-fix-kallsyms_selftest-failure.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 33f0467fe06934d5e4ea6e24ce2b9c65ce618e26 Mon Sep 17 00:00:00 2001
From: Yonghong Song <yonghong.song@xxxxxxxxx>
Date: Thu, 24 Aug 2023 20:46:59 -0700
Subject: kallsyms: Fix kallsyms_selftest failure
From: Yonghong Song <yonghong.song@xxxxxxxxx>
commit 33f0467fe06934d5e4ea6e24ce2b9c65ce618e26 upstream.
Kernel test robot reported a kallsyms_test failure when clang lto is
enabled (thin or full) and CONFIG_KALLSYMS_SELFTEST is also enabled.
I can reproduce in my local environment with the following error message
with thin lto:
[ 1.877897] kallsyms_selftest: Test for 1750th symbol failed: (tsc_cs_mark_unstable) addr=ffffffff81038090
[ 1.877901] kallsyms_selftest: abort
It appears that commit 8cc32a9bbf29 ("kallsyms: strip LTO-only suffixes
from promoted global functions") caused the failure. Commit 8cc32a9bbf29
changed cleanup_symbol_name() based on ".llvm." instead of '.' where
".llvm." is appended to a before-lto-optimization local symbol name.
We need to propagate such knowledge in kallsyms_selftest.c as well.
Further more, compare_symbol_name() in kallsyms.c needs change as well.
In scripts/kallsyms.c, kallsyms_names and kallsyms_seqs_of_names are used
to record symbol names themselves and index to symbol names respectively.
For example:
kallsyms_names:
...
__amd_smn_rw._entry <== seq 1000
__amd_smn_rw._entry.5 <== seq 1001
__amd_smn_rw.llvm.<hash> <== seq 1002
...
kallsyms_seqs_of_names are sorted based on cleanup_symbol_name() through, so
the order in kallsyms_seqs_of_names actually has
index 1000: seq 1002 <== __amd_smn_rw.llvm.<hash> (actual symbol comparison using '__amd_smn_rw')
index 1001: seq 1000 <== __amd_smn_rw._entry
index 1002: seq 1001 <== __amd_smn_rw._entry.5
Let us say at a particular point, at index 1000, symbol '__amd_smn_rw.llvm.<hash>'
is comparing to '__amd_smn_rw._entry' where '__amd_smn_rw._entry' is the one to
search e.g., with function kallsyms_on_each_match_symbol(). The current implementation
will find out '__amd_smn_rw._entry' is less than '__amd_smn_rw.llvm.<hash>' and
then continue to search e.g., index 999 and never found a match although the actual
index 1001 is a match.
To fix this issue, let us do cleanup_symbol_name() first and then do comparison.
In the above case, comparing '__amd_smn_rw' vs '__amd_smn_rw._entry' and
'__amd_smn_rw._entry' being greater than '__amd_smn_rw', the next comparison will
be > index 1000 and eventually index 1001 will be hit an a match is found.
For any symbols not having '.llvm.' substr, there is no functionality change
for compare_symbol_name().
Fixes: 8cc32a9bbf29 ("kallsyms: strip LTO-only suffixes from promoted global functions")
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202308232200.1c932a90-oliver.sang@xxxxxxxxx
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
Reviewed-by: Song Liu <song@xxxxxxxxxx>
Reviewed-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230825034659.1037627-1-yonghong.song@xxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/kallsyms.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -188,16 +188,13 @@ static bool cleanup_symbol_name(char *s)
static int compare_symbol_name(const char *name, char *namebuf)
{
- int ret;
-
- ret = strcmp(name, namebuf);
- if (!ret)
- return ret;
-
- if (cleanup_symbol_name(namebuf) && !strcmp(name, namebuf))
- return 0;
-
- return ret;
+ /* The kallsyms_seqs_of_names is sorted based on names after
+ * cleanup_symbol_name() (see scripts/kallsyms.c) if clang lto is enabled.
+ * To ensure correct bisection in kallsyms_lookup_names(), do
+ * cleanup_symbol_name(namebuf) before comparing name and namebuf.
+ */
+ cleanup_symbol_name(namebuf);
+ return strcmp(name, namebuf);
}
static int kallsyms_lookup_names(const char *name,
Patches currently in stable-queue which might be from yonghong.song@xxxxxxxxx are
queue-6.1/kallsyms-fix-kallsyms_selftest-failure.patch
