Re: [PATCH] vmlinux.lds: consider .text.{hot|unlikely}.* part of .text too

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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: stable@xxxxxxxxxxxxxxx
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 <jiancai@xxxxxxxxxx>
Debugged-by: Luis Lozano <llozano@xxxxxxxxxx>
Suggested-by: Fāng-ruì Sòng <maskray@xxxxxxxxxx>
Tested-by: Luis Lozano <llozano@xxxxxxxxxx>
Tested-by: Manoj Gupta <manojgupta@xxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
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




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