Messages in this thread Patch in this message | | | Date | Tue, 23 Jan 2018 16:42:36 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 00/24] objtool: retpoline and asm-goto validation |
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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 <peterz@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) <peterz@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 */ /*
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