From: "tip-bot2 for Peter Zijlstra" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>,
Frederic Weisbecker <frederic@kernel.org>,
Ingo Molnar <mingo@kernel.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: sched/core] static_call/x86: Add __static_call_return0()
Date: Wed, 17 Feb 2021 13:17:35 -0000 [thread overview]
Message-ID: <161356785556.20312.8835577071462298948.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210118141223.123667-2-frederic@kernel.org>
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 3f2a8fc4b15de18644e8a80a09edda168676e22c
Gitweb: https://git.kernel.org/tip/3f2a8fc4b15de18644e8a80a09edda168676e22c
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Mon, 18 Jan 2021 15:12:16 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 17 Feb 2021 14:08:43 +01:00
static_call/x86: Add __static_call_return0()
Provide a stub function that return 0 and wire up the static call site
patching to replace the CALL with a single 5 byte instruction that
clears %RAX, the return value register.
The function can be cast to any function pointer type that has a
single %RAX return (including pointers). Also provide a version that
returns an int for convenience. We are clearing the entire %RAX register
in any case, whether the return value is 32 or 64 bits, since %RAX is
always a scratch register anyway.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210118141223.123667-2-frederic@kernel.org
---
arch/x86/kernel/static_call.c | 17 +++++++++++++++--
include/linux/static_call.h | 12 ++++++++++++
kernel/static_call.c | 5 +++++
3 files changed, 32 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c
index ca9a380..9442c41 100644
--- a/arch/x86/kernel/static_call.c
+++ b/arch/x86/kernel/static_call.c
@@ -11,14 +11,26 @@ enum insn_type {
RET = 3, /* tramp / site cond-tail-call */
};
+/*
+ * data16 data16 xorq %rax, %rax - a single 5 byte instruction that clears %rax
+ * The REX.W cancels the effect of any data16.
+ */
+static const u8 xor5rax[] = { 0x66, 0x66, 0x48, 0x31, 0xc0 };
+
static void __ref __static_call_transform(void *insn, enum insn_type type, void *func)
{
+ const void *emulate = NULL;
int size = CALL_INSN_SIZE;
const void *code;
switch (type) {
case CALL:
code = text_gen_insn(CALL_INSN_OPCODE, insn, func);
+ if (func == &__static_call_return0) {
+ emulate = code;
+ code = &xor5rax;
+ }
+
break;
case NOP:
@@ -41,7 +53,7 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, void
if (unlikely(system_state == SYSTEM_BOOTING))
return text_poke_early(insn, code, size);
- text_poke_bp(insn, code, size, NULL);
+ text_poke_bp(insn, code, size, emulate);
}
static void __static_call_validate(void *insn, bool tail)
@@ -54,7 +66,8 @@ static void __static_call_validate(void *insn, bool tail)
return;
} else {
if (opcode == CALL_INSN_OPCODE ||
- !memcmp(insn, ideal_nops[NOP_ATOMIC5], 5))
+ !memcmp(insn, ideal_nops[NOP_ATOMIC5], 5) ||
+ !memcmp(insn, xor5rax, 5))
return;
}
diff --git a/include/linux/static_call.h b/include/linux/static_call.h
index a2c0645..bd6735d 100644
--- a/include/linux/static_call.h
+++ b/include/linux/static_call.h
@@ -142,6 +142,8 @@ extern void __static_call_update(struct static_call_key *key, void *tramp, void
extern int static_call_mod_init(struct module *mod);
extern int static_call_text_reserved(void *start, void *end);
+extern long __static_call_return0(void);
+
#define DEFINE_STATIC_CALL(name, _func) \
DECLARE_STATIC_CALL(name, _func); \
struct static_call_key STATIC_CALL_KEY(name) = { \
@@ -206,6 +208,11 @@ static inline int static_call_text_reserved(void *start, void *end)
return 0;
}
+static inline long __static_call_return0(void)
+{
+ return 0;
+}
+
#define EXPORT_STATIC_CALL(name) \
EXPORT_SYMBOL(STATIC_CALL_KEY(name)); \
EXPORT_SYMBOL(STATIC_CALL_TRAMP(name))
@@ -222,6 +229,11 @@ struct static_call_key {
void *func;
};
+static inline long __static_call_return0(void)
+{
+ return 0;
+}
+
#define DEFINE_STATIC_CALL(name, _func) \
DECLARE_STATIC_CALL(name, _func); \
struct static_call_key STATIC_CALL_KEY(name) = { \
diff --git a/kernel/static_call.c b/kernel/static_call.c
index 84565c2..0bc11b5 100644
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -438,6 +438,11 @@ int __init static_call_init(void)
}
early_initcall(static_call_init);
+long __static_call_return0(void)
+{
+ return 0;
+}
+
#ifdef CONFIG_STATIC_CALL_SELFTEST
static int func_a(int x)
next prev parent reply other threads:[~2021-02-17 13:28 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-18 14:12 [RFC PATCH 0/7] preempt: Tune preemption flavour on boot v4 Frederic Weisbecker
2021-01-18 14:12 ` [RFC PATCH 1/8] static_call/x86: Add __static_call_return0() Frederic Weisbecker
2021-02-08 12:00 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-02-17 13:17 ` tip-bot2 for Peter Zijlstra [this message]
2021-01-18 14:12 ` [RFC PATCH 2/8] static_call: Provide DEFINE_STATIC_CALL_RET0() Frederic Weisbecker
2021-02-08 12:00 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker
2021-01-18 14:12 ` [RFC PATCH 3/8] static_call: Pull some static_call declarations to the type headers Frederic Weisbecker
2021-01-19 10:46 ` Jürgen Groß
2021-02-08 12:00 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-02-17 13:17 ` tip-bot2 for Peter Zijlstra
2021-01-18 14:12 ` [RFC PATCH 4/8] preempt: Introduce CONFIG_PREEMPT_DYNAMIC Frederic Weisbecker
2021-01-22 16:53 ` Peter Zijlstra
2021-01-28 12:17 ` Frederic Weisbecker
2021-02-08 12:00 ` [tip: sched/core] " tip-bot2 for Michal Hocko
2021-02-17 13:17 ` tip-bot2 for Michal Hocko
2021-01-18 14:12 ` [RFC PATCH 5/8] preempt/dynamic: Provide cond_resched() and might_resched() static calls Frederic Weisbecker
2021-02-08 12:00 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra (Intel)
2021-02-17 13:17 ` tip-bot2 for Peter Zijlstra (Intel)
2021-01-18 14:12 ` [RFC PATCH 6/8] preempt/dynamic: Provide preempt_schedule[_notrace]() " Frederic Weisbecker
2021-01-21 21:58 ` Peter Zijlstra
2021-01-21 22:25 ` Peter Zijlstra
2021-01-22 16:52 ` Peter Zijlstra
2021-01-22 16:57 ` Ard Biesheuvel
2021-01-22 17:08 ` Peter Zijlstra
2021-02-08 12:00 ` [tip: sched/core] sched: Add /debug/sched_preempt tip-bot2 for Peter Zijlstra
2021-02-09 15:45 ` tip-bot2 for Peter Zijlstra
2021-02-17 13:17 ` tip-bot2 for Peter Zijlstra
2021-01-25 23:40 ` [RFC PATCH 6/8] preempt/dynamic: Provide preempt_schedule[_notrace]() static calls Josh Poimboeuf
2021-01-26 9:24 ` Peter Zijlstra
2021-01-26 23:57 ` Josh Poimboeuf
2021-01-27 9:13 ` Peter Zijlstra
2021-01-27 11:27 ` Peter Zijlstra
2021-01-27 15:59 ` Josh Poimboeuf
2021-01-27 16:19 ` Peter Zijlstra
2021-01-27 16:33 ` Josh Poimboeuf
2021-01-27 18:44 ` Peter Zijlstra
2021-01-27 19:00 ` Josh Poimboeuf
2021-01-27 19:02 ` Josh Poimboeuf
2021-01-27 23:18 ` Josh Poimboeuf
2021-02-03 14:04 ` Peter Zijlstra
2021-02-05 15:30 ` Peter Zijlstra
2021-02-06 2:31 ` Josh Poimboeuf
2021-02-06 9:03 ` Peter Zijlstra
2021-02-05 15:22 ` Peter Zijlstra
2021-02-08 12:00 ` [tip: sched/core] static_call: Allow module use without exposing static_call_key tip-bot2 for Josh Poimboeuf
2021-02-09 15:45 ` tip-bot2 for Josh Poimboeuf
2021-02-17 13:17 ` tip-bot2 for Josh Poimboeuf
2021-02-08 12:00 ` [tip: sched/core] preempt/dynamic: Provide preempt_schedule[_notrace]() static calls tip-bot2 for Peter Zijlstra (Intel)
2021-02-17 13:17 ` tip-bot2 for Peter Zijlstra (Intel)
2021-01-18 14:12 ` [RFC PATCH 7/8] preempt/dynamic: Provide irqentry_exit_cond_resched() static call Frederic Weisbecker
2021-02-08 12:00 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra (Intel)
2021-02-17 13:17 ` tip-bot2 for Peter Zijlstra (Intel)
2021-01-18 14:12 ` [RFC PATCH 8/8] preempt/dynamic: Support dynamic preempt with preempt= boot option Frederic Weisbecker
2021-02-08 12:00 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra (Intel)
2021-02-09 15:45 ` tip-bot2 for Peter Zijlstra (Intel)
2021-02-17 13:17 ` tip-bot2 for Peter Zijlstra (Intel)
2021-01-21 21:22 ` [RFC PATCH 0/7] preempt: Tune preemption flavour on boot v4 Peter Zijlstra
2021-01-22 15:02 ` Paul E. McKenney
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