On Sun, Jul 28, 2024 at 01:29:56PM -0700, Rong Xu 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 "..". 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 | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index 5703526d6ebf..f3de66bda293 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -582,9 +582,21 @@ > * 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 \ > + *(.text.asan.* .text.tsan.*) \ > + *(.text.unknown .text.unknown.*) \ > + *(.text.unlikely .text.unlikely.*) \ > + ALIGN_FUNCTION(); \ Why leave the above text sections unaligned? > + *(.text.hot .text.hot.*) \ > + *(TEXT_MAIN .text.fixup) \ > + NOINSTR_TEXT \ > + *(.ref.text) \ > + MEM_KEEP(init.text*) > +#else > #define TEXT_TEXT \ > ALIGN_FUNCTION(); \ > *(.text.hot .text.hot.*) \ > @@ -594,7 +606,8 @@ > NOINSTR_TEXT \ > *(.ref.text) \ > *(.text.asan.* .text.tsan.*) \ > - MEM_KEEP(init.text*) \ > + MEM_KEEP(init.text*) > +#endif > > > /* sched.text is aling to function alignment to secure we have same > -- > 2.46.0.rc1.232.g9752f9e123-goog >
