[RFC v5 16/57] objtool: Support restoring BP from the stack without POP

[Julien Thierry]

Support instruction that set BP to its previous value (base on the
current CFA state) from the stack without modifying the stack pointer.

Signed-off-by: Julien Thierry <jthierry@xxxxxxxxxx>
---
 tools/objtool/check.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5b2539eaccba..0a5c51e4e24c 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1507,6 +1507,12 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
 				cfa->base = state->drap_reg;
 				cfa->offset = 0;
 				state->drap_offset = -1;
+			} else if (!state->drap && op->src.reg == CFI_SP &&
+				op->dest.reg == cfa->base) {
+
+				/* mov disp(%rsp), %rbp */
+				cfa->base = CFI_SP;
+				cfa->offset += op->src.offset;
 			}
 
 			if (state->drap && op->src.reg == CFI_BP &&
-- 
2.21.0