From: Josh Poimboeuf <jpoimboe@redhat.com>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Nick Desaulniers <ndesaulniers@google.com>,
Arnd Bergmann <arnd@arndb.de>, Jann Horn <jannh@google.com>,
Randy Dunlap <rdunlap@infradead.org>
Subject: [PATCH v2 22/22] objtool: Support conditional retpolines
Date: Wed, 17 Jul 2019 20:36:57 -0500 [thread overview]
Message-ID: <30d4c758b267ef487fb97e6ecb2f148ad007b554.1563413318.git.jpoimboe@redhat.com> (raw)
In-Reply-To: <cover.1563413318.git.jpoimboe@redhat.com>
A Clang-built kernel is showing the following warning:
arch/x86/kernel/platform-quirks.o: warning: objtool: x86_early_init_platform_quirks()+0x84: unreachable instruction
That corresponds to this code:
7e: 0f 85 00 00 00 00 jne 84 <x86_early_init_platform_quirks+0x84>
80: R_X86_64_PC32 __x86_indirect_thunk_r11-0x4
84: c3 retq
This is a conditional retpoline sibling call, which is now possible
thanks to retpolines. Objtool hasn't seen that before. It's
incorrectly interpreting the conditional jump as an unconditional
dynamic jump.
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
---
tools/objtool/arch.h | 1 +
tools/objtool/check.c | 12 ++++++++++--
2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index 50448c0c4bca..ced3765c4f44 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -15,6 +15,7 @@ enum insn_type {
INSN_JUMP_CONDITIONAL,
INSN_JUMP_UNCONDITIONAL,
INSN_JUMP_DYNAMIC,
+ INSN_JUMP_DYNAMIC_CONDITIONAL,
INSN_CALL,
INSN_CALL_DYNAMIC,
INSN_RETURN,
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 381e36dc587c..a93ecce40641 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -575,7 +575,11 @@ static int add_jump_destinations(struct objtool_file *file)
* Retpoline jumps are really dynamic jumps in
* disguise, so convert them accordingly.
*/
- insn->type = INSN_JUMP_DYNAMIC;
+ if (insn->type == INSN_JUMP_UNCONDITIONAL)
+ insn->type = INSN_JUMP_DYNAMIC;
+ else
+ insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
+
insn->retpoline_safe = true;
continue;
} else {
@@ -2114,13 +2118,17 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
break;
case INSN_JUMP_DYNAMIC:
+ case INSN_JUMP_DYNAMIC_CONDITIONAL:
if (func && is_sibling_call(insn)) {
ret = validate_sibling_call(insn, &state);
if (ret)
return ret;
}
- return 0;
+ if (insn->type == INSN_JUMP_DYNAMIC)
+ return 0;
+
+ break;
case INSN_CONTEXT_SWITCH:
if (func && (!next_insn || !next_insn->hint)) {
--
2.20.1
next prev parent reply other threads:[~2019-07-18 1:37 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-18 1:36 [PATCH v2 00/22] x86, objtool: several fixes/improvements Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 01/22] x86/paravirt: Fix callee-saved function ELF sizes Josh Poimboeuf
2019-07-18 19:07 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 02/22] x86/kvm: Fix fastop function ELF metadata Josh Poimboeuf
2019-07-18 19:08 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 03/22] x86/kvm: Replace vmx_vmenter()'s call to kvm_spurious_fault() with UD2 Josh Poimboeuf
2019-07-18 8:17 ` Paolo Bonzini
2019-07-18 19:08 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 04/22] x86/kvm: Don't call kvm_spurious_fault() from .fixup Josh Poimboeuf
2019-07-18 8:22 ` Paolo Bonzini
2019-07-18 13:16 ` Sean Christopherson
2019-07-18 13:18 ` Paolo Bonzini
2019-07-18 14:12 ` Josh Poimboeuf
2019-07-18 14:13 ` Paolo Bonzini
2019-07-18 14:03 ` Josh Poimboeuf
2019-07-18 19:09 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 05/22] x86/entry: Fix thunk function ELF sizes Josh Poimboeuf
2019-07-18 19:10 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 06/22] x86/head/64: Annotate start_cpu0() as non-callable Josh Poimboeuf
2019-07-18 19:11 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 07/22] x86/uaccess: Remove ELF function annotation from copy_user_handle_tail() Josh Poimboeuf
2019-07-18 19:11 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 08/22] x86/uaccess: Don't leak AC flag into fentry from mcsafe_handle_tail() Josh Poimboeuf
2019-07-18 19:12 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 09/22] x86/uaccess: Remove redundant CLACs in getuser/putuser error paths Josh Poimboeuf
2019-07-18 19:13 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 10/22] bpf: Disable GCC -fgcse optimization for ___bpf_prog_run() Josh Poimboeuf
2019-07-18 19:14 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2020-04-29 21:51 ` BPF vs objtool again Josh Poimboeuf
2020-04-29 22:01 ` Arvind Sankar
2020-04-29 23:41 ` Alexei Starovoitov
2020-04-30 0:13 ` Josh Poimboeuf
2020-04-30 2:10 ` Alexei Starovoitov
2020-04-30 3:53 ` Josh Poimboeuf
2020-04-30 4:24 ` Alexei Starovoitov
2020-04-30 4:43 ` Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 11/22] objtool: Add mcsafe_handle_tail() to the uaccess safe list Josh Poimboeuf
2019-07-18 19:14 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 12/22] objtool: Track original function across branches Josh Poimboeuf
2019-07-18 19:15 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 13/22] objtool: Refactor function alias logic Josh Poimboeuf
2019-07-18 19:16 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 14/22] objtool: Warn on zero-length functions Josh Poimboeuf
2019-07-18 19:17 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 15/22] objtool: Change dead_end_function() to return boolean Josh Poimboeuf
2019-07-18 19:17 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 16/22] objtool: Do frame pointer check before dead end check Josh Poimboeuf
2019-07-18 19:18 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 17/22] objtool: Refactor sibling call detection logic Josh Poimboeuf
2019-07-18 19:19 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 18/22] objtool: Refactor jump table code Josh Poimboeuf
2019-07-18 19:20 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 19/22] objtool: Support repeated uses of the same C jump table Josh Poimboeuf
2019-07-18 19:20 ` [tip:core/urgent] " tip-bot for Jann Horn
2019-07-18 1:36 ` [PATCH v2 20/22] objtool: Fix seg fault on bad switch table entry Josh Poimboeuf
2019-07-18 19:21 ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` [PATCH v2 21/22] objtool: convert insn type to enum Josh Poimboeuf
2019-07-18 19:22 ` [tip:core/urgent] objtool: Convert " tip-bot for Josh Poimboeuf
2019-07-18 1:36 ` Josh Poimboeuf [this message]
2019-07-18 19:23 ` [tip:core/urgent] objtool: Support conditional retpolines tip-bot for Josh Poimboeuf
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