Re: [PATCH 5.15 45/76] modpost: Add '.ltext' and '.ltext.*' to TEXT_SECTIONS

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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@xxxxxxxxxx>

[ 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@xxxxxxxxxxxxxxx
Closes: https://github.com/ClangBuiltLinux/linux/issues/1981
Link: https://github.com/llvm/llvm-project/commit/4bf8a688956a759b7b6b8d94f42d25c13c7af130
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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




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