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Date: Thu, 23 Jul 2015 15:14:13 -0400
From: Jason Baron <jasonbaron0@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: Borislav Petkov <bp@...en8.de>,
Andy Lutomirski <luto@...capital.net>,
Thomas Gleixner <tglx@...utronix.de>,
Mikulas Patocka <mpatocka@...hat.com>,
Paul Mackerras <paulus@...ba.org>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Kees Cook <keescook@...omium.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Vince Weaver <vince@...ter.net>,
"hillf.zj" <hillf.zj@...baba-inc.com>,
Valdis Kletnieks <Valdis.Kletnieks@...edu>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Steven Rostedt <rostedt@...dmis.org>
Subject: Re: Kernel broken on processors without performance counters
On 07/23/2015 10:49 AM, Peter Zijlstra wrote:
> On Thu, Jul 23, 2015 at 04:33:08PM +0200, Peter Zijlstra wrote:
>> Lemme finish this and I'll post it.
> Compile tested on x86_64 only..
>
> Please have a look, I think you said I got some of the logic wrong, I've
> not double checked that.
>
> I'll go write comments and double check things.
>
> ---
> arch/arm/include/asm/jump_label.h | 22 +++++++-
> arch/arm64/include/asm/jump_label.h | 22 +++++++-
> arch/mips/include/asm/jump_label.h | 23 +++++++-
> arch/powerpc/include/asm/jump_label.h | 23 +++++++-
> arch/s390/include/asm/jump_label.h | 23 +++++++-
> arch/sparc/include/asm/jump_label.h | 38 ++++++++++---
> arch/x86/include/asm/jump_label.h | 24 +++++++-
> include/linux/jump_label.h | 101 +++++++++++++++++++++++++++++++++-
> kernel/jump_label.c | 89 +++++++++++++++---------------
> 9 files changed, 297 insertions(+), 68 deletions(-)
>
> diff --git a/arch/arm/include/asm/jump_label.h b/arch/arm/include/asm/jump_label.h
> index 5f337dc5c108..6c9789b33497 100644
> --- a/arch/arm/include/asm/jump_label.h
> +++ b/arch/arm/include/asm/jump_label.h
> @@ -13,14 +13,32 @@
> #define JUMP_LABEL_NOP "nop"
> #endif
>
> -static __always_inline bool arch_static_branch(struct static_key *key)
> +static __always_inline bool arch_static_branch(struct static_key *key, bool inv)
> {
> + unsigned long kval = (unsigned long)key + inv;
> +
> asm_volatile_goto("1:\n\t"
> JUMP_LABEL_NOP "\n\t"
> ".pushsection __jump_table, \"aw\"\n\t"
> ".word 1b, %l[l_yes], %c0\n\t"
> ".popsection\n\t"
> - : : "i" (key) : : l_yes);
> + : : "i" (kval) : : l_yes);
> +
> + return false;
> +l_yes:
> + return true;
> +}
> +
> +static __always_inline bool arch_static_branch_jump(struct static_key *key, bool inv)
> +{
> + unsigned long kval = (unsigned long)key + inv;
> +
> + asm_volatile_goto("1:\n\t"
> + "b %l[l_yes]\n\t"
> + ".pushsection __jump_table, \"aw\"\n\t"
> + ".word 1b, %l[l_yes], %c0\n\t"
> + ".popsection\n\t"
> + : : "i" (kval) : : l_yes);
>
> return false;
> l_yes:
> diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h
> index c0e5165c2f76..e5cda5d75c62 100644
> --- a/arch/arm64/include/asm/jump_label.h
> +++ b/arch/arm64/include/asm/jump_label.h
> @@ -26,14 +26,32 @@
>
> #define JUMP_LABEL_NOP_SIZE AARCH64_INSN_SIZE
>
> -static __always_inline bool arch_static_branch(struct static_key *key)
> +static __always_inline bool arch_static_branch(struct static_key *key, bool inv)
> {
> + unsigned long kval = (unsigned long)key + inv;
> +
> asm goto("1: nop\n\t"
> ".pushsection __jump_table, \"aw\"\n\t"
> ".align 3\n\t"
> ".quad 1b, %l[l_yes], %c0\n\t"
> ".popsection\n\t"
> - : : "i"(key) : : l_yes);
> + : : "i"(kval) : : l_yes);
> +
> + return false;
> +l_yes:
> + return true;
> +}
> +
> +static __always_inline bool arch_static_branch_jump(struct static_key *key, bool inv)
> +{
> + unsigned long kval = (unsigned long)key + inv;
> +
> + asm goto("1: b %l[l_yes]\n\t"
> + ".pushsection __jump_table, \"aw\"\n\t"
> + ".align 3\n\t"
> + ".quad 1b, %l[l_yes], %c0\n\t"
> + ".popsection\n\t"
> + : : "i"(kval) : : l_yes);
>
> return false;
> l_yes:
> diff --git a/arch/mips/include/asm/jump_label.h b/arch/mips/include/asm/jump_label.h
> index 608aa57799c8..d9fca6f52a93 100644
> --- a/arch/mips/include/asm/jump_label.h
> +++ b/arch/mips/include/asm/jump_label.h
> @@ -26,14 +26,33 @@
> #define NOP_INSN "nop"
> #endif
>
> -static __always_inline bool arch_static_branch(struct static_key *key)
> +static __always_inline bool arch_static_branch(struct static_key *key, bool inv)
> {
> + unsigned long kval = (unsigned long)key + inv;
> +
> asm_volatile_goto("1:\t" NOP_INSN "\n\t"
> "nop\n\t"
> ".pushsection __jump_table, \"aw\"\n\t"
> WORD_INSN " 1b, %l[l_yes], %0\n\t"
> ".popsection\n\t"
> - : : "i" (key) : : l_yes);
> + : : "i" (kval) : : l_yes);
> +
> + return false;
> +l_yes:
> + return true;
> +}
> +
> +static __always_inline bool arch_static_branch_jump(struct static_key *key, bool inv)
> +{
> + unsigned long kval = (unsigned long)key + inv;
> +
> + asm_volatile_goto("1:\tj %l[l_yes]\n\t"
> + "nop\n\t"
> + ".pushsection __jump_table, \"aw\"\n\t"
> + WORD_INSN " 1b, %l[l_yes], %0\n\t"
> + ".popsection\n\t"
> + : : "i" (kval) : : l_yes);
> +
> return false;
> l_yes:
> return true;
> diff --git a/arch/powerpc/include/asm/jump_label.h b/arch/powerpc/include/asm/jump_label.h
> index efbf9a322a23..c7cffedb1801 100644
> --- a/arch/powerpc/include/asm/jump_label.h
> +++ b/arch/powerpc/include/asm/jump_label.h
> @@ -18,14 +18,33 @@
> #define JUMP_ENTRY_TYPE stringify_in_c(FTR_ENTRY_LONG)
> #define JUMP_LABEL_NOP_SIZE 4
>
> -static __always_inline bool arch_static_branch(struct static_key *key)
> +static __always_inline bool arch_static_branch(struct static_key *key, bool inv)
> {
> + unsigned long kval = (unsigned long)key + inv;
> +
> asm_volatile_goto("1:\n\t"
> "nop\n\t"
> ".pushsection __jump_table, \"aw\"\n\t"
> JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t"
> ".popsection \n\t"
> - : : "i" (key) : : l_yes);
> + : : "i" (kval) : : l_yes);
> +
> + return false;
> +l_yes:
> + return true;
> +}
> +
> +static __always_inline bool arch_static_branch_jump(struct static_key *key, bool inv)
> +{
> + unsigned long kval = (unsigned long)key + inv;
> +
> + asm_volatile_goto("1:\n\t"
> + "b %l[l_yes]\n\t"
> + ".pushsection __jump_table, \"aw\"\n\t"
> + JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t"
> + ".popsection \n\t"
> + : : "i" (kval) : : l_yes);
> +
> return false;
> l_yes:
> return true;
> diff --git a/arch/s390/include/asm/jump_label.h b/arch/s390/include/asm/jump_label.h
> index 69972b7957ee..4734b09b9fce 100644
> --- a/arch/s390/include/asm/jump_label.h
> +++ b/arch/s390/include/asm/jump_label.h
> @@ -12,14 +12,33 @@
> * We use a brcl 0,2 instruction for jump labels at compile time so it
> * can be easily distinguished from a hotpatch generated instruction.
> */
> -static __always_inline bool arch_static_branch(struct static_key *key)
> +static __always_inline bool arch_static_branch(struct static_key *key, bool inv)
> {
> + unsigned long kval = (unsigned long)key + inv;
> +
> asm_volatile_goto("0: brcl 0,"__stringify(JUMP_LABEL_NOP_OFFSET)"\n"
> ".pushsection __jump_table, \"aw\"\n"
> ".balign 8\n"
> ".quad 0b, %l[label], %0\n"
> ".popsection\n"
> - : : "X" (key) : : label);
> + : : "X" (kval) : : label);
> +
> + return false;
> +label:
> + return true;
> +}
> +
> +static __always_inline bool arch_static_branch_jump(struct static_key *key, bool inv)
> +{
> + unsigned long kval = (unsigned long)key + inv;
> +
> + asm_volatile_goto("0: j %l[l_yes]\n"
> + ".pushsection __jump_table, \"aw\"\n"
> + ".balign 8\n"
> + ".quad 0b, %l[label], %0\n"
> + ".popsection\n"
> + : : "X" (kval) : : label);
> +
> return false;
> label:
> return true;
> diff --git a/arch/sparc/include/asm/jump_label.h b/arch/sparc/include/asm/jump_label.h
> index cc9b04a2b11b..764f3c21da21 100644
> --- a/arch/sparc/include/asm/jump_label.h
> +++ b/arch/sparc/include/asm/jump_label.h
> @@ -7,16 +7,36 @@
>
> #define JUMP_LABEL_NOP_SIZE 4
>
> -static __always_inline bool arch_static_branch(struct static_key *key)
> +static __always_inline bool arch_static_branch(struct static_key *key, bool inv)
> {
> - asm_volatile_goto("1:\n\t"
> - "nop\n\t"
> - "nop\n\t"
> - ".pushsection __jump_table, \"aw\"\n\t"
> - ".align 4\n\t"
> - ".word 1b, %l[l_yes], %c0\n\t"
> - ".popsection \n\t"
> - : : "i" (key) : : l_yes);
> + unsigned long kval = (unsigned long)key + inv;
> +
> + asm_volatile_goto("1:\n\t"
> + "nop\n\t"
> + "nop\n\t"
> + ".pushsection __jump_table, \"aw\"\n\t"
> + ".align 4\n\t"
> + ".word 1b, %l[l_yes], %c0\n\t"
> + ".popsection \n\t"
> + : : "i" (kval) : : l_yes);
> +
> + return false;
> +l_yes:
> + return true;
> +}
> +
> +static __always_inline bool arch_static_branch_jump(struct static_key *key, bool inv)
> +{
> + unsigned long kval = (unsigned long)key + inv;
> +
> + asm_volatile_goto("1:\n\t"
> + "b %l[l_yes]\n\t"
> + ".pushsection __jump_table, \"aw\"\n\t"
> + ".align 4\n\t"
> + ".word 1b, %l[l_yes], %c0\n\t"
> + ".popsection \n\t"
> + : : "i" (kval) : : l_yes);
> +
> return false;
> l_yes:
> return true;
> diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
> index a4c1cf7e93f8..43531baaee38 100644
> --- a/arch/x86/include/asm/jump_label.h
> +++ b/arch/x86/include/asm/jump_label.h
> @@ -16,15 +16,35 @@
> # define STATIC_KEY_INIT_NOP GENERIC_NOP5_ATOMIC
> #endif
>
> -static __always_inline bool arch_static_branch(struct static_key *key)
> +static __always_inline bool arch_static_branch(struct static_key *key, bool inv)
> {
> + unsigned long kval = (unsigned long)key + inv;
> +
> asm_volatile_goto("1:"
> ".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t"
> ".pushsection __jump_table, \"aw\" \n\t"
> _ASM_ALIGN "\n\t"
> _ASM_PTR "1b, %l[l_yes], %c0 \n\t"
> ".popsection \n\t"
> - : : "i" (key) : : l_yes);
> + : : "i" (kval) : : l_yes);
> +
> + return false;
> +l_yes:
> + return true;
> +}
> +
> +static __always_inline bool arch_static_branch_jump(struct static_key *key, bool inv)
> +{
> + unsigned long kval = (unsigned long)key + inv;
> +
> + asm_volatile_goto("1:"
> + "jmp %l[l_yes]\n\t"
> + ".pushsection __jump_table, \"aw\" \n\t"
> + _ASM_ALIGN "\n\t"
> + _ASM_PTR "1b, %l[l_yes], %c0 \n\t"
> + ".popsection \n\t"
> + : : "i" (kval) : : l_yes);
> +
> return false;
> l_yes:
> return true;
> diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
> index f4de473f226b..4c97fed7acea 100644
> --- a/include/linux/jump_label.h
> +++ b/include/linux/jump_label.h
> @@ -122,7 +122,7 @@ static inline bool jump_label_get_branch_default(struct static_key *key)
>
> static __always_inline bool static_key_false(struct static_key *key)
> {
> - return arch_static_branch(key);
> + return arch_static_branch(key, false);
> }
>
> static __always_inline bool static_key_true(struct static_key *key)
> @@ -213,6 +213,105 @@ static inline bool static_key_enabled(struct static_key *key)
> return static_key_count(key) > 0;
> }
>
> +static inline void static_key_enable(struct static_key *key)
> +{
> + int count = static_key_count(key);
> +
> + WARN_ON_ONCE(count < 0 || count > 1);
> +
> + if (!count)
> + static_key_slow_inc(key);
> +}
> +
> +static inline void static_key_disable(struct static_key *key)
> +{
> + int count = static_key_count(key);
> +
> + WARN_ON_ONCE(count < 0 || count > 1);
> +
> + if (count)
> + static_key_slow_dec(key);
> +}
> +
> +
> +/* -------------------------------------------------------------------------- */
> +
> +/*
> + * Two type wrappers around static_key, such that we can use compile time
> + * type differentiation to emit the right code.
> + *
> + * All the below code is macros in order to play type games.
> + */
> +
> +struct static_key_true {
> + struct static_key key;
> +};
> +
> +struct static_key_false {
> + struct static_key key;
> +};
> +
> +#define STATIC_KEY_TRUE_INIT (struct static_key_true) { .key = STATIC_KEY_INIT_TRUE, }
> +#define STATIC_KEY_FALSE_INIT (struct static_key_false){ .key = STATIC_KEY_INIT_FALSE, }
> +
> +#define DEFINE_STATIC_KEY_TRUE(name) \
> + struct static_key_true name = STATIC_KEY_TRUE_INIT
> +
> +#define DEFINE_STATIC_KEY_FALSE(name) \
> + struct static_key_false name = STATIC_KEY_FALSE_INIT
> +
> +#ifdef HAVE_JUMP_LABEL
> +
> +/*
> + * Combine the right initial value (type) with the right branch order and section
> + * to generate the desired result.
> + */
> +
> +#define static_branch_likely(x) \
> +({ \
> + bool branch; \
> + if (__builtin_types_compatible_p(typeof(x), struct static_key_true)) \
> + branch = !arch_static_branch(&(x)->key, false); \
> + else if (__builtin_types_compatible_p(typeof(x), struct static_key_false)) \
> + branch = !arch_static_branch_jump(&(x)->key, true); \
> + else \
> + branch = ____wrong_branch_error(); \
> + branch; \
> +})
> +
> +#define static_branch_unlikely(x) \
> +({ \
> + bool branch; \
> + if (__builtin_types_compatible_p(typeof(x), struct static_key_true)) \
> + branch = arch_static_branch(&(x)->key, true); \
> + else if (__builtin_types_compatible_p(typeof(x), struct static_key_false)) \
> + branch = arch_static_branch_jump(&(x)->key, false); \
> + else \
> + branch = ____wrong_branch_error(); \
> + branch; \
> +})
> +
> +#else /* !HAVE_JUMP_LABEL */
> +
> +#define static_branch_likely(x) static_key_true(&(x)->key)
> +#define static_branch_unlikely(x) static_key_false(&(x)->key)
> +
> +#endif /* HAVE_JUMP_LABEL */
> +
> +/*
> + * Advanced usage; refcount, branch is enabled when: count != 0
> + */
> +
> +#define static_branch_inc(x) static_key_slow_inc(&(x)->key)
> +#define static_branch_dec(x) static_key_slow_dec(&(x)->key)
> +
> +/*
> + * Normal usage; boolean enable/disable.
> + */
> +
> +#define static_branch_enable(x) static_key_enable(&(x)->key)
> +#define static_branch_disable(x) static_key_disable(&(x)->key)
> +
> #endif /* _LINUX_JUMP_LABEL_H */
>
> #endif /* __ASSEMBLY__ */
> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> index 52ebaca1b9fc..8d0cb621c5bc 100644
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -54,7 +54,7 @@ jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
> sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
> }
>
> -static void jump_label_update(struct static_key *key, int enable);
> +static void jump_label_update(struct static_key *key);
>
> void static_key_slow_inc(struct static_key *key)
> {
> @@ -63,13 +63,8 @@ void static_key_slow_inc(struct static_key *key)
> return;
>
> jump_label_lock();
> - if (atomic_read(&key->enabled) == 0) {
> - if (!jump_label_get_branch_default(key))
> - jump_label_update(key, JUMP_LABEL_ENABLE);
> - else
> - jump_label_update(key, JUMP_LABEL_DISABLE);
> - }
> - atomic_inc(&key->enabled);
> + if (atomic_inc_and_test(&key->enabled))
> + jump_label_update(key);
> jump_label_unlock();
> }
> EXPORT_SYMBOL_GPL(static_key_slow_inc);
> @@ -87,10 +82,7 @@ static void __static_key_slow_dec(struct static_key *key,
> atomic_inc(&key->enabled);
> schedule_delayed_work(work, rate_limit);
> } else {
> - if (!jump_label_get_branch_default(key))
> - jump_label_update(key, JUMP_LABEL_DISABLE);
> - else
> - jump_label_update(key, JUMP_LABEL_ENABLE);
> + jump_label_update(key);
> }
> jump_label_unlock();
> }
> @@ -149,7 +141,7 @@ static int __jump_label_text_reserved(struct jump_entry *iter_start,
> return 0;
> }
>
> -/*
> +/*
> * Update code which is definitely not currently executing.
> * Architectures which need heavyweight synchronization to modify
> * running code can override this to make the non-live update case
> @@ -158,37 +150,44 @@ static int __jump_label_text_reserved(struct jump_entry *iter_start,
> void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
> enum jump_label_type type)
> {
> - arch_jump_label_transform(entry, type);
> + arch_jump_label_transform(entry, type);
> +}
> +
> +static struct static_key *static_key_cast(jump_label_t key_addr)
> +{
> + return (struct static_key *)(key_addr & ~1UL);
> +}
> +
> +static bool static_key_inv(jump_label_t key_addr)
> +{
> + return key_addr & 1UL;
> +}
> +
> +static enum jump_label_type jump_label_type(struct jump_entry *entry)
> +{
> + struct static_key *key = static_key_cast(iter->key);
> + bool true_branch = jump_label_get_branch_default(key);
> + bool state = static_key_enabled(key);
> + bool inv = static_key_inv(iter->key);
> +
> + return (true_branch ^ state) ^ inv;
iiuc...this allows both the old style keys to co-exist with the
new ones. IE state wouldn't be set for the new ones. And inv
shouldn't be set for the old ones. Is that correct?
Thanks,
-Jason
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