objtool: Make SP memory operation match PUSH/POP semantics

Architectures without PUSH/POP instructions will always access the stack
though memory operations (SRC/DEST_INDIRECT). Make those operations have
the same effect on the CFA as PUSH/POP, with no stack pointer
modification.

Signed-off-by: Julien Thierry <jthierry@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 00d00f9045366d4b00a9caf79119239a9e36306d..270adc38d896b4fc3d4c41eed8bf45995eb41af3 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2065,6 +2065,14 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
                        break;
 
                case OP_SRC_REG_INDIRECT:
+                       if (!cfi->drap && op->dest.reg == cfa->base &&
+                           op->dest.reg == CFI_BP) {
+
+                               /* mov disp(%rsp), %rbp */
+                               cfa->base = CFI_SP;
+                               cfa->offset = cfi->stack_size;
+                       }
+
                        if (cfi->drap && op->src.reg == CFI_BP &&
                            op->src.offset == cfi->drap_offset) {
 
@@ -2086,6 +2094,12 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
                                /* mov disp(%rbp), %reg */
                                /* mov disp(%rsp), %reg */
                                restore_reg(cfi, op->dest.reg);
+
+                       } else if (op->src.reg == CFI_SP &&
+                                  op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
+
+                               /* mov disp(%rsp), %reg */
+                               restore_reg(cfi, op->dest.reg);
                        }
 
                        break;
@@ -2163,6 +2177,12 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
                        /* mov reg, disp(%rsp) */
                        save_reg(cfi, op->src.reg, CFI_CFA,
                                 op->dest.offset - cfi->cfa.offset);
+
+               } else if (op->dest.reg == CFI_SP) {
+
+                       /* mov reg, disp(%rsp) */
+                       save_reg(cfi, op->src.reg, CFI_CFA,
+                                op->dest.offset - cfi->stack_size);
                }
 
                break;