linux-kernel - [RFC v5 15/57] objtool: Support addition to set frame pointer

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Message-Id: <20200109160300.26150-16-jthierry@redhat.com>
Date:   Thu,  9 Jan 2020 16:02:18 +0000
From:   Julien Thierry <jthierry@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     jpoimboe@...hat.com, peterz@...radead.org, raphael.gault@....com,
        catalin.marinas@....com, will@...nel.org,
        Julien Thierry <jthierry@...hat.com>
Subject: [RFC v5 15/57] objtool: Support addition to set frame pointer

Support updating the frame pointer by adding an immediate value to the
stack pointer in the CFA tracking code.

Signed-off-by: Julien Thierry <jthierry@...hat.com>
---
 tools/objtool/check.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 19e96c4ad0a3..5b2539eaccba 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1394,6 +1394,18 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
 				break;
 			}
 
+			if (op->src.reg == CFI_SP && cfa->base == CFI_SP &&
+			    op->dest.reg == CFI_BP &&
+			    regs[CFI_BP].base == CFI_CFA &&
+			    regs[CFI_BP].offset == -cfa->offset + op->src.offset) {
+
+				/* lea disp(%rsp), %rbp */
+				cfa->base = CFI_BP;
+				cfa->offset -= op->src.offset;
+				state->bp_scratch = false;
+				break;
+			}
+
 			if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
 
 				/* drap: lea disp(%rsp), %drap */
-- 
2.21.0