mirror of
https://github.com/torvalds/linux.git
synced 2024-12-30 14:52:05 +00:00
cc1adb5f32
hcall tracepoints add quite a few instructions to our hcall path: plpar_hcall: mr r2,r2 mfcr r0 stw r0,8(r1) b 164 <---- start ld r12,0(r2) std r12,32(r1) cmpdi r12,0 beq 164 <---- end ... We have an unconditional branch that gets noped out during boot and a load/compare/branch. We also store the tracepoint value to the stack for the hcall_exit path to use. By using jump labels we can simplify this to just a single nop that gets replaced with a branch when the tracepoint is enabled: plpar_hcall: mr r2,r2 mfcr r0 stw r0,8(r1) nop <---- ... If jump labels are not enabled, we fall back to the old method. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
55 lines
1.2 KiB
C
55 lines
1.2 KiB
C
#ifndef _ASM_POWERPC_JUMP_LABEL_H
|
|
#define _ASM_POWERPC_JUMP_LABEL_H
|
|
|
|
/*
|
|
* Copyright 2010 Michael Ellerman, IBM Corp.
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License
|
|
* as published by the Free Software Foundation; either version
|
|
* 2 of the License, or (at your option) any later version.
|
|
*/
|
|
|
|
#ifndef __ASSEMBLY__
|
|
#include <linux/types.h>
|
|
|
|
#include <asm/feature-fixups.h>
|
|
|
|
#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)
|
|
{
|
|
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);
|
|
return false;
|
|
l_yes:
|
|
return true;
|
|
}
|
|
|
|
#ifdef CONFIG_PPC64
|
|
typedef u64 jump_label_t;
|
|
#else
|
|
typedef u32 jump_label_t;
|
|
#endif
|
|
|
|
struct jump_entry {
|
|
jump_label_t code;
|
|
jump_label_t target;
|
|
jump_label_t key;
|
|
};
|
|
|
|
#else
|
|
#define ARCH_STATIC_BRANCH(LABEL, KEY) \
|
|
1098: nop; \
|
|
.pushsection __jump_table, "aw"; \
|
|
FTR_ENTRY_LONG 1098b, LABEL, KEY; \
|
|
.popsection
|
|
#endif
|
|
|
|
#endif /* _ASM_POWERPC_JUMP_LABEL_H */
|