From ba08abca66d46381df60842f64f70099d5482b92 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 8 Mar 2021 15:46:04 +0100 Subject: [PATCH] objtool,x86: Fix uaccess PUSHF/POPF validation Commit ab234a260b1f ("x86/pv: Rework arch_local_irq_restore() to not use popf") replaced "push %reg; popf" with something like: "test $0x200, %reg; jz 1f; sti; 1:", which breaks the pushf/popf symmetry that commit ea24213d8088 ("objtool: Add UACCESS validation") relies on. The result is: drivers/gpu/drm/amd/amdgpu/si.o: warning: objtool: si_common_hw_init()+0xf36: PUSHF stack exhausted Meanwhile, commit c9c324dc22aa ("objtool: Support stack layout changes in alternatives") makes that we can actually use stack-ops in alternatives, which means we can revert 1ff865e343c2 ("x86,smap: Fix smap_{save,restore}() alternatives"). That in turn means we can limit the PUSHF/POPF handling of ea24213d8088 to those instructions that are in alternatives. Fixes: ab234a260b1f ("x86/pv: Rework arch_local_irq_restore() to not use popf") Reported-by: Borislav Petkov Signed-off-by: Peter Zijlstra (Intel) Acked-by: Josh Poimboeuf Link: https://lkml.kernel.org/r/YEY4rIbQYa5fnnEp@hirez.programming.kicks-ass.net --- arch/x86/include/asm/smap.h | 10 ++++------ tools/objtool/check.c | 3 +++ 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/smap.h b/arch/x86/include/asm/smap.h index 8b58d6975d5d..0bc9b0895f33 100644 --- a/arch/x86/include/asm/smap.h +++ b/arch/x86/include/asm/smap.h @@ -58,9 +58,8 @@ static __always_inline unsigned long smap_save(void) unsigned long flags; asm volatile ("# smap_save\n\t" - ALTERNATIVE("jmp 1f", "", X86_FEATURE_SMAP) - "pushf; pop %0; " __ASM_CLAC "\n\t" - "1:" + ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC "\n\t", + X86_FEATURE_SMAP) : "=rm" (flags) : : "memory", "cc"); return flags; @@ -69,9 +68,8 @@ static __always_inline unsigned long smap_save(void) static __always_inline void smap_restore(unsigned long flags) { asm volatile ("# smap_restore\n\t" - ALTERNATIVE("jmp 1f", "", X86_FEATURE_SMAP) - "push %0; popf\n\t" - "1:" + ALTERNATIVE("", "push %0; popf\n\t", + X86_FEATURE_SMAP) : : "g" (flags) : "memory", "cc"); } diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 068cdb41f76f..5e5388a38e2a 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2442,6 +2442,9 @@ static int handle_insn_ops(struct instruction *insn, struct insn_state *state) if (update_cfi_state(insn, &state->cfi, op)) return 1; + if (!insn->alt_group) + continue; + if (op->dest.type == OP_DEST_PUSHF) { if (!state->uaccess_stack) { state->uaccess_stack = 1;