On Tue, Oct 15, 2024 at 6:33 AM Rong Xu <xur@xxxxxxxxxx> wrote: > > When the -ffunction-sections compiler option is enabled, each function > is placed in a separate section named .text.function_name rather than > putting all functions in a single .text section. > > However, using -function-sections can cause problems with the > linker script. The comments included in include/asm-generic/vmlinux.lds.h > note these issues.: > “TEXT_MAIN here will match .text.fixup and .text.unlikely if dead > code elimination is enabled, so these sections should be converted > to use ".." first.” > > It is unclear whether there is a straightforward method for converting > a suffix to "..". Why not for ".text.fixup"? $ git grep --name-only '\.text\.fixup' | xargs sed -i 's/\.text\.fixup/.text..fixup/g' I do not know how to rename other sections that are generated by compilers. > This patch modifies the order of subsections within the > text output section when the -ffunction-sections flag is enabled. > Specifically, it repositions sections with certain fixed patterns (for > example .text.unlikely) before TEXT_MAIN, ensuring that they are grouped > and matched together. > > Note that the limitation arises because the linker script employs glob > patterns instead of regular expressions for string matching. While there > is a method to maintain the current order using complex patterns, this > significantly complicates the pattern and increases the likelihood of > errors. > > Co-developed-by: Han Shen <shenhan@xxxxxxxxxx> > Signed-off-by: Han Shen <shenhan@xxxxxxxxxx> > Signed-off-by: Rong Xu <xur@xxxxxxxxxx> > Suggested-by: Sriraman Tallam <tmsriram@xxxxxxxxxx> > Suggested-by: Krzysztof Pszeniczny <kpszeniczny@xxxxxxxxxx> > --- > include/asm-generic/vmlinux.lds.h | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index eeadbaeccf88..5df589c60401 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -554,9 +554,21 @@ > * during second ld run in second ld pass when generating System.map > * > * TEXT_MAIN here will match .text.fixup and .text.unlikely if dead > - * code elimination is enabled, so these sections should be converted > - * to use ".." first. > + * code elimination or function-section is enabled. Match these symbols > + * first when in these builds. > */ > +#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) > +#define TEXT_TEXT \ Why did you do this conditionally? You are making this even more unmaintainable. > + ALIGN_FUNCTION(); \ > + *(.text.asan.* .text.tsan.*) \ > + *(.text.unknown .text.unknown.*) \ > + *(.text.unlikely .text.unlikely.*) \ > + . = ALIGN(PAGE_SIZE); \ > + *(.text.hot .text.hot.*) \ > + *(TEXT_MAIN .text.fixup) \ > + NOINSTR_TEXT \ > + *(.ref.text) > +#else > #define TEXT_TEXT \ > ALIGN_FUNCTION(); \ > *(.text.hot .text.hot.*) \ > @@ -566,6 +578,7 @@ > NOINSTR_TEXT \ > *(.ref.text) \ > *(.text.asan.* .text.tsan.*) > +#endif > > > /* sched.text is aling to function alignment to secure we have same > -- > 2.47.0.rc1.288.g06298d1525-goog > > -- Best Regards Masahiro Yamada
