On 2020-06-17, Nick Desaulniers wrote:
ld.bfd's internal linker script considers .text.hot AND .text.hot.* to be part of .text, as well as .text.unlikely and .text.unlikely.*.
ld.lld will produce .text.hot.*/.text.unlikely.* sections.
Correction to this sentence. lld is not relevant here. -ffunction-sections combined with profile-guided optimization can produce .text.hot.* .text.unlikely.* sections. Newer clang may produce .text.hot. .text.unlikely. (without suffix, but with a trailing dot) when -fno-unique-section-names is specified, as an optimization to make .strtab smaller. We've already seen that GCC can place main in .text.startup without -ffunction-sections. There may be other non -ffunction-sections cases for .text.hot.* or .text.unlikely.*. So it is definitely a good idea to be more specific even if we don't care about -ffunction-sections for now.
Make sure to group these together. Otherwise these orphan sections may be placed outside of the the _stext/_etext boundaries. Cc: sta...@vger.kernel.org Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=add44f8d5c5c05e08b11e033127a744d61c26aee Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=1de778ed23ce7492c523d5850c6c6dbb34152655 Link: https://reviews.llvm.org/D79600 Reported-by: Jian Cai <jian...@google.com> Debugged-by: Luis Lozano <lloz...@google.com> Suggested-by: Fāng-ruì Sòng <mask...@google.com> Tested-by: Luis Lozano <lloz...@google.com> Tested-by: Manoj Gupta <manojgu...@google.com> Signed-off-by: Nick Desaulniers <ndesaulni...@google.com> --- include/asm-generic/vmlinux.lds.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index d7c7c7f36c4a..fe5aaef169e3 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -560,7 +560,9 @@ */ #define TEXT_TEXT \ ALIGN_FUNCTION(); \ - *(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \ + *(.text.hot .text.hot.*) \ + *(TEXT_MAIN .text.fixup) \ + *(.text.unlikely .text.unlikely.*) \ NOINSTR_TEXT \ *(.text..refcount) \ *(.ref.text) \ -- 2.27.0.290.gba653c62da-goog
