forge/linux-uconsole
1
0
Fork 0
Code Issues 1 Pull requests Projects Releases Packages Wiki Activity Actions

kbuild: lto: Merge module sections if and only if CONFIG_LTO_CLANG is enabled

Browse source 
commit 6a3193cdd5 upstream.

Merge module sections only when using Clang LTO. With ld.bfd, merging
sections does not appear to update the symbol tables for the module,
e.g. 'readelf -s' shows the value that a symbol would have had, if
sections were not merged. ld.lld does not show this problem.

The stale symbol table breaks gdb's function disassembler, and presumably
other things, e.g.

  gdb -batch -ex "file arch/x86/kvm/kvm.ko" -ex "disassemble kvm_init"

reads the wrong bytes and dumps garbage.

Fixes: dd2776222a ("kbuild: lto: merge module sections")
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210322234438.502582-1-seanjc@google.com
Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sean Christopherson 2021-03-22 16:44:38 -07:00 • committed by Greg Kroah-Hartman
commit 44b81136e8
1 changed files with 2 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

2
scripts/module.lds.S
View file

@ -26,6 +26,7 @@ SECTIONS {
__patchable_function_entries : { *(__patchable_function_entries) }
#ifdef CONFIG_LTO_CLANG
/*
* With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and
* -ffunction-sections, which increases the size of the final module.
@ -47,6 +48,7 @@ SECTIONS {
}
.text : { *(.text .text.[0-9a-zA-Z_]*) }
#endif
}
/* bring in arch-specific sections */