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SubjectRe: [PATCH 18/20] objtool: Add UACCESS validation
On Fri, Mar 08, 2019 at 03:02:09PM -0600, Josh Poimboeuf wrote:

> These gotos make my head spin. Again I would much prefer a small amount
> of code duplication over this.

something like so then?

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1888,6 +1888,23 @@ static inline const char *insn_dest_name
return "{dynamic}";
}

+static int validate_call(struct instruction *insn, struct insn_state *state)
+{
+ if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
+ WARN_FUNC("call to %s() with UACCESS enabled",
+ insn->sec, insn->offset, insn_dest_name(insn));
+ return 1;
+ }
+
+ if (state->df) {
+ WARN_FUNC("call to %s() with DF set",
+ insn->sec, insn->offset, insn_dest_name(insn));
+ return 1;
+ }
+
+ return 0;
+}
+
/*
* Follow the branch starting at the given instruction, and recursively follow
* any other branches (jumps). Meanwhile, track the frame pointer state at
@@ -2036,25 +2053,9 @@ static int validate_branch(struct objtoo

case INSN_CALL:
case INSN_CALL_DYNAMIC:
-do_call:
- if (state.uaccess && !func_uaccess_safe(insn->call_dest)) {
- WARN_FUNC("call to %s() with UACCESS enabled",
- sec, insn->offset, insn_dest_name(insn));
- return 1;
- }
-
- if (state.df) {
- WARN_FUNC("call to %s() with DF set",
- sec, insn->offset, insn_dest_name(insn));
- return 1;
- }
-
- if (insn->type == INSN_JUMP_UNCONDITIONAL ||
- insn->type == INSN_JUMP_DYNAMIC)
- return 0;
-
- if (insn->type == INSN_JUMP_CONDITIONAL)
- break;
+ ret = validate_call(insn, &state);
+ if (ret)
+ return ret;

if (insn->type == INSN_CALL) {
if (is_fentry_call(insn))
@@ -2077,13 +2078,15 @@ static int validate_branch(struct objtoo
case INSN_JUMP_CONDITIONAL:
case INSN_JUMP_UNCONDITIONAL:
if (func && !insn->jump_dest) {
-do_sibling_call:
+ /* sibling call */
if (has_modified_stack_frame(&state)) {
WARN_FUNC("sibling call from callable instruction with modified stack frame",
sec, insn->offset);
return 1;
}
- goto do_call;
+ ret = validate_call(insn, &state);
+ if (ret)
+ return ret;

} else if (insn->jump_dest &&
(!func || !insn->jump_dest->func ||
@@ -2104,8 +2107,17 @@ static int validate_branch(struct objtoo
break;

case INSN_JUMP_DYNAMIC:
- if (func && list_empty(&insn->alts))
- goto do_sibling_call;
+ if (func && list_empty(&insn->alts)) {
+ /* sibling call */
+ if (has_modified_stack_frame(&state)) {
+ WARN_FUNC("sibling call from callable instruction with modified stack frame",
+ sec, insn->offset);
+ return 1;
+ }
+ ret = validate_call(insn, &state);
+ if (ret)
+ return ret;
+ }

return 0;

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