5.15-stable review patch. If anyone has any objections, please let me know.
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From: Song Liu song@kernel.org
[ Upstream commit 75b2f7e4c9e0fd750a5a27ca9736d1daa7a3762a ]
-flto* implies -ffunction-sections. With LTO enabled, ld.lld generates multiple .text sections for purgatory.ro:
$ readelf -S purgatory.ro | grep " .text" [ 1] .text PROGBITS 0000000000000000 00000040 [ 7] .text.purgatory PROGBITS 0000000000000000 000020e0 [ 9] .text.warn PROGBITS 0000000000000000 000021c0 [13] .text.sha256_upda PROGBITS 0000000000000000 000022f0 [15] .text.sha224_upda PROGBITS 0000000000000000 00002be0 [17] .text.sha256_fina PROGBITS 0000000000000000 00002bf0 [19] .text.sha224_fina PROGBITS 0000000000000000 00002cc0
This causes WARNING from kexec_purgatory_setup_sechdrs():
WARNING: CPU: 26 PID: 110894 at kernel/kexec_file.c:919 kexec_load_purgatory+0x37f/0x390
Fix this by disabling LTO for purgatory.
[ AFAICT, x86 is the only arch that supports LTO and purgatory. ]
We could also fix this with an explicit linker script to rejoin .text.* sections back into .text. However, given the benefit of LTOing purgatory is small, simply disable the production of more .text.* sections for now.
Fixes: b33fff07e3e3 ("x86, build: allow LTO to be selected") Signed-off-by: Song Liu song@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Nick Desaulniers ndesaulniers@google.com Reviewed-by: Sami Tolvanen samitolvanen@google.com Link: https://lore.kernel.org/r/20230914170138.995606-1-song@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/purgatory/Makefile | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile index dc0b91c1db04b..7a7701d1e18d0 100644 --- a/arch/x86/purgatory/Makefile +++ b/arch/x86/purgatory/Makefile @@ -19,6 +19,10 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS # optimization flags. KBUILD_CFLAGS := $(filter-out -fprofile-sample-use=% -fprofile-use=%,$(KBUILD_CFLAGS))
+# When LTO is enabled, llvm emits many text sections, which is not supported +# by kexec. Remove -flto=* flags. +KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO),$(KBUILD_CFLAGS)) + # When linking purgatory.ro with -r unresolved symbols are not checked, # also link a purgatory.chk binary without -r to check for unresolved symbols. PURGATORY_LDFLAGS := -e purgatory_start -nostdlib -z nodefaultlib