Re: [PATCH v2] kbuild: Makefile.lib: fix offsets generation with debug info

[Nathan Chancellor <nathan@kernel.org>]

On Fri, Oct 16, 2026 at 09:02:07PM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] kbuild: unanchored sed substitutions in sed-offsets can break build
> --
> 
> commit 48672ceb9d59753178f125f7c16956dd57252dcd
> Author: Dmitry Kandybka <d.kandybka@gmail.com>
> 
> kbuild: Makefile.lib: fix offsets generation with debug info
> 
> This commit fixes offset generation when debug information is enabled by
> making the sed pattern matching stricter and adding a BLANK() macro for
> readability. It prevents debug metadata from leaking into generated header
> files and breaking the build.
> 
> > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> > index 19e96b30a122f..173bc3aa4247f 100644
> > --- a/scripts/Makefile.lib
> > +++ b/scripts/Makefile.lib
> > @@ -493,9 +493,9 @@ quiet_cmd_zstd22_with_size = ZSTD22  $@
> >  # the .ascii directive whereas GCC keeps the <space> as-is.
> >  define sed-offsets
> >  	's:^[[:space:]]*\.ascii[[:space:]]*"\(.*\)".*:\1:; \
> > -	/^->/{s:->#\(.*\):/* \1 */:; \
> > -	s:^->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; \
> > -	s:->::; p;}'
> > +	/^->/{s:->#\(.*\):/* \1 */:p; \
> > +	s:^->\([[:alnum:]_]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:p; \
> > +	s:->BLANK()::p;}'
> 
> [Severity: Low]
> Could this unanchored sed substitution break the build under certain
> conditions?
> 
> If the kernel is built with debug info (e.g., -ggdb3), the compiler may emit
> .ascii directives containing debug strings from source code. If a string
> literal from an included header starts with -> and contains -># or ->BLANK()
> mid-string (for example, ->foo ->BLANK()), the unanchored sed substitution
> will match mid-string.
> 
> Because of the :p flag, wouldn't it print the partially modified pattern space
> (e.g., ->foo ), resulting in invalid C code being written to
> include/generated/asm-offsets.h?
> 
> Should the pattern be anchored (e.g., s:^->BLANK()$::p;) to ensure it only
> matches the intended kbuild macros?
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20261015210149.78470-1-d.kandybka@gmail.com?part=1

This definitely feels a little contrived but anchoring at the beginning
would avoid this and seems to match the rest of the macro.

  s:^->BLANK()::p;}'

-- 
Cheers,
Nathan