[PATCH v3 3/3] objtool: check: Make SP memory operation match PUSH/POP semantics

[Julien Thierry]

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 <jthie...@redhat.com>
---
 tools/objtool/check.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 815aeb770930..32ee9902ade2 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2003,6 +2003,14 @@ 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) {
 
@@ -2024,6 +2032,12 @@ 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;
@@ -2101,6 +2115,12 @@ 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;
-- 
2.25.4