[tip: objtool/core] objtool: Generate ORC data for __pfx code

[tip-bot2 for Josh Poimboeuf]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     5743654f5e2ebd56df99f56fca5ba4b23fe3c815
Gitweb:        https://git.kernel.org/tip/5743654f5e2ebd56df99f56fca5ba4b23fe3c815
Author:        Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate:    Wed, 12 Apr 2023 13:26:15 -07:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 14 Apr 2023 16:08:30 +02:00

objtool: Generate ORC data for __pfx code

Allow unwinding from prefix code by copying the CFI from the starting
instruction of the corresponding function.  Even when the NOPs are
replaced, they're still stack-invariant instructions so the same ORC
entry can be reused everywhere.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/bc3344e51f3e87102f1301a0be0f72a7689ea4a4.1681331135.git.jpoimboe@xxxxxxxxxx
---
 tools/objtool/check.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 8ee4d51..df634da 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4117,6 +4117,7 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
 {
 	struct instruction *insn, *prev;
+	struct cfi_state *cfi;
 
 	insn = find_insn(file, func->sec, func->offset);
 	if (!insn)
@@ -4145,6 +4146,19 @@ static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
 	if (!prev)
 		return -1;
 
+	if (!insn->cfi) {
+		/*
+		 * This can happen if stack validation isn't enabled or the
+		 * function is annotated with STACK_FRAME_NON_STANDARD.
+		 */
+		return 0;
+	}
+
+	/* Propagate insn->cfi to the prefix code */
+	cfi = cfi_hash_find_or_add(insn->cfi);
+	for (; prev != insn; prev = next_insn_same_sec(file, prev))
+		prev->cfi = cfi;
+
 	return 0;
 }