From: Petr Pavlu petr.pavlu@suse.com
commit 79cd2a11224eab86d6673fe8a11d2046ae9d2757 upstream.
The linker script arch/x86/kernel/vmlinux.lds.S matches the thunk sections ".text.__x86.*" from arch/x86/lib/retpoline.S as follows:
.text { [...] TEXT_TEXT [...] __indirect_thunk_start = .; *(.text.__x86.*) __indirect_thunk_end = .; [...] }
Macro TEXT_TEXT references TEXT_MAIN which normally expands to only ".text". However, with CONFIG_LTO_CLANG, TEXT_MAIN becomes ".text .text.[0-9a-zA-Z_]*" which wrongly matches also the thunk sections. The output layout is then different than expected. For instance, the currently defined range [__indirect_thunk_start, __indirect_thunk_end] becomes empty.
Prevent the problem by using ".." as the first separator, for example, ".text..__x86.indirect_thunk". This pattern is utilized by other explicit section names which start with one of the standard prefixes, such as ".text" or ".data", and that need to be individually selected in the linker script.
[ nathan: Fix conflicts with SRSO and fold in fix issue brought up by Andrew Cooper in post-review: https://lore.kernel.org/20230803230323.1478869-1-andrew.cooper3@citrix.com ]
Fixes: dc5723b02e52 ("kbuild: add support for Clang LTO") Signed-off-by: Petr Pavlu petr.pavlu@suse.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Nathan Chancellor nathan@kernel.org Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Link: https://lore.kernel.org/r/20230711091952.27944-2-petr.pavlu@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/vmlinux.lds.S | 8 ++++---- arch/x86/lib/retpoline.S | 8 ++++---- tools/objtool/check.c | 2 +- 3 files changed, 9 insertions(+), 9 deletions(-)
--- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -134,15 +134,15 @@ SECTIONS SOFTIRQENTRY_TEXT #ifdef CONFIG_RETPOLINE __indirect_thunk_start = .; - *(.text.__x86.indirect_thunk) - *(.text.__x86.return_thunk) + *(.text..__x86.indirect_thunk) + *(.text..__x86.return_thunk) __indirect_thunk_end = .; #endif STATIC_CALL_TEXT
ALIGN_ENTRY_TEXT_BEGIN #ifdef CONFIG_CPU_SRSO - *(.text.__x86.rethunk_untrain) + *(.text..__x86.rethunk_untrain) #endif
ENTRY_TEXT @@ -153,7 +153,7 @@ SECTIONS * definition. */ . = srso_alias_untrain_ret | (1 << 2) | (1 << 8) | (1 << 14) | (1 << 20); - *(.text.__x86.rethunk_safe) + *(.text..__x86.rethunk_safe) #endif ALIGN_ENTRY_TEXT_END *(.gnu.warning) --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -13,7 +13,7 @@ #include <asm/frame.h> #include <asm/nops.h>
- .section .text.__x86.indirect_thunk + .section .text..__x86.indirect_thunk
.macro POLINE reg @@ -148,7 +148,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_a * As a result, srso_alias_safe_ret() becomes a safe return. */ #ifdef CONFIG_CPU_SRSO - .section .text.__x86.rethunk_untrain + .section .text..__x86.rethunk_untrain
SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) UNWIND_HINT_FUNC @@ -159,7 +159,7 @@ SYM_START(srso_alias_untrain_ret, SYM_L_ SYM_FUNC_END(srso_alias_untrain_ret) __EXPORT_THUNK(srso_alias_untrain_ret)
- .section .text.__x86.rethunk_safe + .section .text..__x86.rethunk_safe #else /* dummy definition for alternatives */ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) @@ -177,7 +177,7 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLO int3 SYM_FUNC_END(srso_alias_safe_ret)
- .section .text.__x86.return_thunk + .section .text..__x86.return_thunk
SYM_CODE_START(srso_alias_return_thunk) UNWIND_HINT_FUNC --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -429,7 +429,7 @@ static int decode_instructions(struct ob if (!strcmp(sec->name, ".noinstr.text") || !strcmp(sec->name, ".entry.text") || !strcmp(sec->name, ".cpuidle.text") || - !strncmp(sec->name, ".text.__x86.", 12)) + !strncmp(sec->name, ".text..__x86.", 13)) sec->noinstr = true;
/*