From: Josh Poimboeuf jpoimboe@kernel.org
[ Upstream commit e27e5bea956ce4d3eb15112de5fa5a3b77c2f488 ]
Add a macro which prevents a function from getting sealed if there are no compile-time references to it.
Signed-off-by: Josh Poimboeuf jpoimboe@kernel.org Message-Id: 20220818213927.e44fmxkoq4yj6ybn@treble Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/include/asm/ibt.h | 11 +++++++++++ tools/objtool/check.c | 3 ++- 2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/ibt.h b/arch/x86/include/asm/ibt.h index 689880eca9ba..9b08082a5d9f 100644 --- a/arch/x86/include/asm/ibt.h +++ b/arch/x86/include/asm/ibt.h @@ -31,6 +31,16 @@
#define __noendbr __attribute__((nocf_check))
+/* + * Create a dummy function pointer reference to prevent objtool from marking + * the function as needing to be "sealed" (i.e. ENDBR converted to NOP by + * apply_ibt_endbr()). + */ +#define IBT_NOSEAL(fname) \ + ".pushsection .discard.ibt_endbr_noseal\n\t" \ + _ASM_PTR fname "\n\t" \ + ".popsection\n\t" + static inline __attribute_const__ u32 gen_endbr(void) { u32 endbr; @@ -84,6 +94,7 @@ extern __noendbr void ibt_restore(u64 save); #ifndef __ASSEMBLY__
#define ASM_ENDBR +#define IBT_NOSEAL(name)
#define __noendbr
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index b341f8a8c7c5..31c719f99f66 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -4096,7 +4096,8 @@ static int validate_ibt(struct objtool_file *file) * These sections can reference text addresses, but not with * the intent to indirect branch to them. */ - if (!strncmp(sec->name, ".discard", 8) || + if ((!strncmp(sec->name, ".discard", 8) && + strcmp(sec->name, ".discard.ibt_endbr_noseal")) || !strncmp(sec->name, ".debug", 6) || !strcmp(sec->name, ".altinstructions") || !strcmp(sec->name, ".ibt_endbr_seal") ||