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x86/static_call: Add out-of-line static call implementation

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Add the x86 out-of-line static call implementation.  For each key, a
permanent trampoline is created which is the destination for all static
calls for the given key.  The trampoline has a direct jump which gets
patched by static_call_update() when the destination function changes.

[peterz: fixed trampoline, rewrote patching code]

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20200818135804.804315175@infradead.org
This commit is contained in:
Josh Poimboeuf 2020-08-18 15:57:44 +02:00 committed by Ingo Molnar
parent 6333e8f73b
commit e6d6c071f2
4 changed files with 56 additions and 0 deletions
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1
arch/x86/Kconfig
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@ -215,6 +215,7 @@ config X86
select HAVE_FUNCTION_ARG_ACCESS_API
select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
select HAVE_STACK_VALIDATION if X86_64
select HAVE_STATIC_CALL
select HAVE_RSEQ
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UNSTABLE_SCHED_CLOCK

23
arch/x86/include/asm/static_call.h Normal file
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@ -0,0 +1,23 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_STATIC_CALL_H
#define _ASM_STATIC_CALL_H
#include <asm/text-patching.h>
/*
* For CONFIG_HAVE_STATIC_CALL, this is a permanent trampoline which
* does a direct jump to the function. The direct jump gets patched by
* static_call_update().
*/
#define ARCH_DEFINE_STATIC_CALL_TRAMP(name, func) \
asm(".pushsection .text, \"ax\" \n" \
".align 4 \n" \
".globl " STATIC_CALL_TRAMP_STR(name) " \n" \
STATIC_CALL_TRAMP_STR(name) ": \n" \
" .byte 0xe9 # jmp.d32 \n" \
" .long " #func " - (. + 4) \n" \
".type " STATIC_CALL_TRAMP_STR(name) ", @function \n" \
".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \
".popsection \n")
#endif /* _ASM_STATIC_CALL_H */

1
arch/x86/kernel/Makefile
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@ -68,6 +68,7 @@ obj-y += tsc.o tsc_msr.o io_delay.o rtc.o
obj-y += pci-iommu_table.o
obj-y += resource.o
obj-y += irqflags.o
obj-y += static_call.o
obj-y += process.o
obj-y += fpu/

31
arch/x86/kernel/static_call.c Normal file
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@ -0,0 +1,31 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/static_call.h>
#include <linux/memory.h>
#include <linux/bug.h>
#include <asm/text-patching.h>
static void __static_call_transform(void *insn, u8 opcode, void *func)
{
const void *code = text_gen_insn(opcode, insn, func);
if (WARN_ONCE(*(u8 *)insn != opcode,
"unexpected static call insn opcode 0x%x at %pS\n",
opcode, insn))
return;
if (memcmp(insn, code, CALL_INSN_SIZE) == 0)
return;
text_poke_bp(insn, code, CALL_INSN_SIZE, NULL);
}
void arch_static_call_transform(void *site, void *tramp, void *func)
{
mutex_lock(&text_mutex);
if (tramp)
__static_call_transform(tramp, JMP32_INSN_OPCODE, func);
mutex_unlock(&text_mutex);
}
EXPORT_SYMBOL_GPL(arch_static_call_transform);