On Tue, Jan 23, 2018 at 04:25:39PM +0100, Peter Zijlstra wrote:
> This series adds two features to objtool:
>
> - retpoline validation; it verifies no indirect jumps/calls are left in
> CONFIG_RETPOLINE=y builds.
>
> includes fixups for kvm and others
>
> - asm-goto validation; allows asserting that a block of code is not reachable
> through a dynamic branch.
>
> After this it forces an asm-goto capable compiler to build arch/x86 and
> removes
> the fallback code for static_cpu_has(). After which we can use
> static_cpu_has()
> to guarantee a lack of dynamic branches, which is a requested feature for
> various spectre related things.
x86_64-allmodconfig -KCOV -KASAN +patch gives:
drivers/infiniband/hw/bnxt_re/.tmp_qplib_fp.o: warning: objtool:
bnxt_qplib_poll_cq()+0xf8: sibling call from callable instruction with modified
stack frame
drivers/watchdog/.tmp_hpwdt.o: warning: objtool: .text+0x24: indirect call
found in RETPOLINE build
---
Subject: jump_label: Add static assertion to every static_branch
From: Peter Zijlstra <pet...@infradead.org>
Date: Tue Jan 16 15:27:36 CET 2018
For testing only.. can't use in general because people do:
static_branch() || more-cond
which confuses the living daylight out of objtool validation and
really isn't fixable.
DO NOT MERGE
Not-signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
arch/x86/include/asm/jump_label.h | 1 +
include/linux/cgroup.h | 2 +-
include/linux/jump_label.h | 15 +++++++++++++--
3 files changed, 15 insertions(+), 3 deletions(-)
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -76,6 +76,7 @@ static __always_inline bool arch_static_
*
* Also works with static_cpu_has().
*/
+#define arch_static_assert arch_static_assert
static __always_inline void arch_static_assert(void)
{
asm volatile ("1:\n\t"
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -88,7 +88,7 @@ extern struct css_set init_css_set;
* @ss: subsystem in question
*/
#define cgroup_subsys_on_dfl(ss)
\
- static_branch_likely(&ss ## _on_dfl_key)
+ __static_branch_likely(&ss ## _on_dfl_key)
bool css_has_online_children(struct cgroup_subsys_state *css);
struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -323,6 +323,10 @@ extern bool ____wrong_branch_error(void)
#ifdef HAVE_JUMP_LABEL
+#ifndef arch_static_assert
+#define arch_static_assert (void)
+#endif
+
/*
* Combine the right initial value (type) with the right branch order
* to generate the desired result.
@@ -379,7 +383,7 @@ extern bool ____wrong_branch_error(void)
* See jump_label_type() / jump_label_init_type().
*/
-#define static_branch_likely(x)
\
+#define __static_branch_likely(x)
\
({
\
bool branch;
\
if (__builtin_types_compatible_p(typeof(*x), struct static_key_true))
\
@@ -391,7 +395,9 @@ extern bool ____wrong_branch_error(void)
likely(branch);
\
})
-#define static_branch_unlikely(x)
\
+#define static_branch_likely(x) (__static_branch_likely(x) &&
(arch_static_assert(), true))
+
+#define __static_branch_unlikely(x)
\
({
\
bool branch;
\
if (__builtin_types_compatible_p(typeof(*x), struct static_key_true))
\
@@ -403,11 +409,16 @@ extern bool ____wrong_branch_error(void)
unlikely(branch);
\
})
+#define static_branch_unlikely(x) (__static_branch_unlikely(x) &&
(arch_static_assert(), true))
+
#else /* !HAVE_JUMP_LABEL */
#define static_branch_likely(x)
likely(static_key_enabled(&(x)->key))
#define static_branch_unlikely(x) unlikely(static_key_enabled(&(x)->key))
+#define __static_branch_likely(x)
likely(static_key_enabled(&(x)->key))
+#define __static_branch_unlikely(x) unlikely(static_key_enabled(&(x)->key))
+
#endif /* HAVE_JUMP_LABEL */
/*
