From 724c8a23d589d8a002d2e39633c2f9a5a429616f Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 18 Feb 2021 17:14:10 +0100 Subject: [PATCH] objtool: Fix stack-swizzle for FRAME_POINTER=y When objtool encounters the stack-swizzle: mov %rsp, (%[tos]) mov %[tos], %rsp ... pop %rsp Inside a FRAME_POINTER=y build, things go a little screwy because clearly we're not adjusting the cfa->base. This then results in the pop %rsp not being detected as a restore of cfa->base so it will turn into a regular POP and offset the stack, resulting in: kernel/softirq.o: warning: objtool: do_softirq()+0xdb: return with modified stack frame Therefore, have "mov %[tos], %rsp" act like a PUSH (it sorta is anyway) to balance the things out. We're not too concerned with the actual stack_size for frame-pointer builds, since we don't generate ORC data for them anyway. Fixes: aafeb14e9da2 ("objtool: Support stack-swizzle") Reported-by: kernel test robot Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Acked-by: Josh Poimboeuf Link: https://lkml.kernel.org/r/YC6UC+rc9KKmQrkd@hirez.programming.kicks-ass.net --- tools/objtool/check.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 8e74210..2087974 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1983,6 +1983,20 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, } } + else if (op->dest.reg == CFI_SP && + cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && + cfi->vals[op->src.reg].offset == cfa->offset) { + + /* + * The same stack swizzle case 2) as above. But + * because we can't change cfa->base, case 3) + * will become a regular POP. Pretend we're a + * PUSH so things don't go unbalanced. + */ + cfi->stack_size += 8; + } + + break; case OP_SRC_ADD: -- 2.7.4