From c8b056a3b4ebb33adbb873cab152ed499d1a1dcb Mon Sep 17 00:00:00 2001 From: Petr Pavlu Date: Tue, 11 Jul 2023 11:19:51 +0200 Subject: [PATCH] x86/retpoline,kprobes: Fix position of thunk sections with CONFIG_LTO_CLANG 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 Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Nathan Chancellor Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20230711091952.27944-2-petr.pavlu@suse.com Signed-off-by: Greg Kroah-Hartman --- 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(-) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 6b137c0027788..78ccb5ec3c0e7 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -134,7 +134,7 @@ SECTIONS KPROBES_TEXT ALIGN_ENTRY_TEXT_BEGIN #ifdef CONFIG_CPU_SRSO - *(.text.__x86.rethunk_untrain) + *(.text..__x86.rethunk_untrain) #endif ENTRY_TEXT @@ -145,7 +145,7 @@ 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 SOFTIRQENTRY_TEXT @@ -154,8 +154,8 @@ SECTIONS #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 } :text =0xcccc diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index 5a55ee2e80f0b..65c5c44f006bc 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -11,7 +11,7 @@ #include #include - .section .text.__x86.indirect_thunk + .section .text..__x86.indirect_thunk .macro RETPOLINE reg ANNOTATE_INTRA_FUNCTION_CALL @@ -91,7 +91,7 @@ SYM_CODE_END(__x86_indirect_thunk_array) * 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 @@ -102,7 +102,7 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) 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) @@ -120,7 +120,7 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE) 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 diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 8ec97762b6076..7c4e61cbefaa4 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -379,7 +379,7 @@ static int decode_instructions(struct objtool_file *file) if (!strcmp(sec->name, ".noinstr.text") || !strcmp(sec->name, ".entry.text") || - !strncmp(sec->name, ".text.__x86.", 12)) + !strncmp(sec->name, ".text..__x86.", 13)) sec->noinstr = true; for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {