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452cddbff7
Extend the static_call infrastructure to optimize the following common
pattern:
if (func_ptr)
func_ptr(args...)
For the trampoline (which is in effect a tail-call), we patch the
JMP.d32 into a RET, which then directly consumes the trampoline call.
For the in-line sites we replace the CALL with a NOP5.
NOTE: this is 'obviously' limited to functions with a 'void' return type.
NOTE: DEFINE_STATIC_COND_CALL() only requires a typename, as opposed
to a full function.
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/20200818135805.042977182@infradead.org
56 lines
1.2 KiB
C
56 lines
1.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/static_call.h>
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#include <linux/memory.h>
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#include <linux/bug.h>
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#include <asm/text-patching.h>
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enum insn_type {
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CALL = 0, /* site call */
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NOP = 1, /* site cond-call */
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JMP = 2, /* tramp / site tail-call */
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RET = 3, /* tramp / site cond-tail-call */
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};
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static void __static_call_transform(void *insn, enum insn_type type, void *func)
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{
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int size = CALL_INSN_SIZE;
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const void *code;
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switch (type) {
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case CALL:
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code = text_gen_insn(CALL_INSN_OPCODE, insn, func);
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break;
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case NOP:
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code = ideal_nops[NOP_ATOMIC5];
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break;
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case JMP:
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code = text_gen_insn(JMP32_INSN_OPCODE, insn, func);
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break;
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case RET:
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code = text_gen_insn(RET_INSN_OPCODE, insn, func);
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size = RET_INSN_SIZE;
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break;
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}
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if (memcmp(insn, code, size) == 0)
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return;
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text_poke_bp(insn, code, size, NULL);
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}
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void arch_static_call_transform(void *site, void *tramp, void *func)
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{
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mutex_lock(&text_mutex);
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if (tramp)
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__static_call_transform(tramp, func ? JMP : RET, func);
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if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site)
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__static_call_transform(site, func ? CALL : NOP, func);
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mutex_unlock(&text_mutex);
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}
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EXPORT_SYMBOL_GPL(arch_static_call_transform);
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