diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2022-06-14 23:15:48 +0200 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2022-06-27 10:33:59 +0200 |
| commit | a149180fbcf336e97ce4eb2cdc13672727feb94d (patch) | |
| tree | 465e0b2ebf7a147d686abed224a732907c475c1b /tools/objtool | |
| parent | 951ddecf435659553ed15a9214e153a3af43a9a1 (diff) | |
x86: Add magic AMD return-thunk
Note: needs to be in a section distinct from Retpolines such that the
Retpoline RET substitution cannot possibly use immediate jumps.
ORC unwinding for zen_untrain_ret() and __x86_return_thunk() is a
little tricky but works due to the fact that zen_untrain_ret() doesn't
have any stack ops and as such will emit a single ORC entry at the
start (+0x3f).
Meanwhile, unwinding an IP, including the __x86_return_thunk() one
(+0x40) will search for the largest ORC entry smaller or equal to the
IP, these will find the one ORC entry (+0x3f) and all works.
[ Alexandre: SVM part. ]
[ bp: Build fix, massages. ]
Suggested-by: Andrew Cooper <Andrew.Cooper3@citrix.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Diffstat (limited to 'tools/objtool')
| -rw-r--r-- | tools/objtool/check.c | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index b98fd68013c3..4252cd05dfc4 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1302,7 +1302,7 @@ static void add_retpoline_call(struct objtool_file *file, struct instruction *in annotate_call_site(file, insn, false); } -static void add_return_call(struct objtool_file *file, struct instruction *insn) +static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add) { /* * Return thunk tail calls are really just returns in disguise, @@ -1311,7 +1311,8 @@ static void add_return_call(struct objtool_file *file, struct instruction *insn) insn->type = INSN_RETURN; insn->retpoline_safe = true; - list_add_tail(&insn->call_node, &file->return_thunk_list); + if (add) + list_add_tail(&insn->call_node, &file->return_thunk_list); } static bool same_function(struct instruction *insn1, struct instruction *insn2) @@ -1367,7 +1368,7 @@ static int add_jump_destinations(struct objtool_file *file) add_retpoline_call(file, insn); continue; } else if (reloc->sym->return_thunk) { - add_return_call(file, insn); + add_return_call(file, insn, true); continue; } else if (insn->func) { /* @@ -1387,6 +1388,21 @@ static int add_jump_destinations(struct objtool_file *file) jump_dest = find_insn(file, dest_sec, dest_off); if (!jump_dest) { + struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off); + + /* + * This is a special case for zen_untrain_ret(). + * It jumps to __x86_return_thunk(), but objtool + * can't find the thunk's starting RET + * instruction, because the RET is also in the + * middle of another instruction. Objtool only + * knows about the outer instruction. + */ + if (sym && sym->return_thunk) { + add_return_call(file, insn, false); + continue; + } + WARN_FUNC("can't find jump dest instruction at %s+0x%lx", insn->sec, insn->offset, dest_sec->name, dest_off); |