From: Nathan Chancellor <nathan@kernel.org>

[ Upstream commit 397586506c3da005b9333ce5947ad01e8018a3be ]

After the linked LLVM change, building ARCH=um defconfig results in a
segmentation fault in modpost. Prior to commit a23e7584ecf3 ("modpost:
unify 'sym' and 'to' in default_mismatch_handler()"), there was a
warning:

  WARNING: modpost: vmlinux.o(__ex_table+0x88): Section mismatch in reference to the .ltext:(unknown)
  WARNING: modpost: The relocation at __ex_table+0x88 references
  section ".ltext" which is not in the list of
  authorized sections.  If you're adding a new section
  and/or if this reference is valid, add ".ltext" to the
  list of authorized sections to jump to on fault.
  This can be achieved by adding ".ltext" to
  OTHER_TEXT_SECTIONS in scripts/mod/modpost.c.

The linked LLVM change moves global objects to the '.ltext' (and
'.ltext.*' with '-ffunction-sections') sections with '-mcmodel=large',
which ARCH=um uses. These sections should be handled just as '.text'
and '.text.*' are, so add them to TEXT_SECTIONS.

Cc: stable@vger.kernel.org
Closes: https://github.com/ClangBuiltLinux/linux/issues/1981
Link: https://github.com/llvm/llvm-project/commit/4bf8a688956a759b7b6b8d94f42d25c13c7af130
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 scripts/mod/modpost.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 43bacdee5cc5d..201ac1bf5030d 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -937,7 +937,8 @@ static void check_section(const char *modname, struct elf_info *elf,
 
 #define DATA_SECTIONS ".data", ".data.rel"
 #define TEXT_SECTIONS ".text", ".text.*", ".sched.text", \
-		".kprobes.text", ".cpuidle.text", ".noinstr.text"
+		".kprobes.text", ".cpuidle.text", ".noinstr.text", \
+		".ltext", ".ltext.*"
 #define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \
 		".fixup", ".entry.text", ".exception.text", \
 		".coldtext", ".softirqentry.text"
-- 
2.43.0

Hi Sasha,

On Wed, Mar 13, 2024 at 12:41:52PM -0400, Sasha Levin wrote:
> From: Nathan Chancellor <nathan@kernel.org>
> 
> [ Upstream commit 397586506c3da005b9333ce5947ad01e8018a3be ]
> 
> After the linked LLVM change, building ARCH=um defconfig results in a
> segmentation fault in modpost. Prior to commit a23e7584ecf3 ("modpost:
> unify 'sym' and 'to' in default_mismatch_handler()"), there was a
> warning:
> 
>   WARNING: modpost: vmlinux.o(__ex_table+0x88): Section mismatch in reference to the .ltext:(unknown)
>   WARNING: modpost: The relocation at __ex_table+0x88 references
>   section ".ltext" which is not in the list of
>   authorized sections.  If you're adding a new section
>   and/or if this reference is valid, add ".ltext" to the
>   list of authorized sections to jump to on fault.
>   This can be achieved by adding ".ltext" to
>   OTHER_TEXT_SECTIONS in scripts/mod/modpost.c.
> 
> The linked LLVM change moves global objects to the '.ltext' (and
> '.ltext.*' with '-ffunction-sections') sections with '-mcmodel=large',
> which ARCH=um uses. These sections should be handled just as '.text'
> and '.text.*' are, so add them to TEXT_SECTIONS.
> 
> Cc: stable@vger.kernel.org
> Closes: https://github.com/ClangBuiltLinux/linux/issues/1981
> Link: https://github.com/llvm/llvm-project/commit/4bf8a688956a759b7b6b8d94f42d25c13c7af130
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

This causes a warning when building with HOSTCC=clang:

  scripts/mod/modpost.c:1123:37: warning: excess elements in array initializer [-Wexcess-initializers]
   1123 |         .good_tosec = {ALL_TEXT_SECTIONS , NULL},
        |                                            ^~~~
  .../lib/clang/17/include/stddef.h:89:16: note: expanded from macro 'NULL'
     89 | #  define NULL ((void*)0)
        |                ^~~~~~~~~~
  1 warning generated.

Same comment as on the other UML clang-18 patch, I do not think this is
necessary right now in 5.15 and earlier. The other modpost patch can go
as well, as it is only a prerequisite change.

Cheers,
Nathan

On Wed, Mar 13, 2024 at 10:12:29AM -0700, Nathan Chancellor wrote:
>Hi Sasha,
>
>On Wed, Mar 13, 2024 at 12:41:52PM -0400, Sasha Levin wrote:
>> From: Nathan Chancellor <nathan@kernel.org>
>>
>> [ Upstream commit 397586506c3da005b9333ce5947ad01e8018a3be ]
>>
>> After the linked LLVM change, building ARCH=um defconfig results in a
>> segmentation fault in modpost. Prior to commit a23e7584ecf3 ("modpost:
>> unify 'sym' and 'to' in default_mismatch_handler()"), there was a
>> warning:
>>
>>   WARNING: modpost: vmlinux.o(__ex_table+0x88): Section mismatch in reference to the .ltext:(unknown)
>>   WARNING: modpost: The relocation at __ex_table+0x88 references
>>   section ".ltext" which is not in the list of
>>   authorized sections.  If you're adding a new section
>>   and/or if this reference is valid, add ".ltext" to the
>>   list of authorized sections to jump to on fault.
>>   This can be achieved by adding ".ltext" to
>>   OTHER_TEXT_SECTIONS in scripts/mod/modpost.c.
>>
>> The linked LLVM change moves global objects to the '.ltext' (and
>> '.ltext.*' with '-ffunction-sections') sections with '-mcmodel=large',
>> which ARCH=um uses. These sections should be handled just as '.text'
>> and '.text.*' are, so add them to TEXT_SECTIONS.
>>
>> Cc: stable@vger.kernel.org
>> Closes: https://github.com/ClangBuiltLinux/linux/issues/1981
>> Link: https://github.com/llvm/llvm-project/commit/4bf8a688956a759b7b6b8d94f42d25c13c7af130
>> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
>> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>
>This causes a warning when building with HOSTCC=clang:
>
>  scripts/mod/modpost.c:1123:37: warning: excess elements in array initializer [-Wexcess-initializers]
>   1123 |         .good_tosec = {ALL_TEXT_SECTIONS , NULL},
>        |                                            ^~~~
>  .../lib/clang/17/include/stddef.h:89:16: note: expanded from macro 'NULL'
>     89 | #  define NULL ((void*)0)
>        |                ^~~~~~~~~~
>  1 warning generated.
>
>Same comment as on the other UML clang-18 patch, I do not think this is
>necessary right now in 5.15 and earlier. The other modpost patch can go
>as well, as it is only a prerequisite change.

Dropped, thanks!

-- 
Thanks,
Sasha