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powerpc: Add jump label support

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This patch adds support for the new "jump label" feature.

Unlike x86 and sparc we just merrily patch the code with no locks etc,
as far as I know this is safe, but I'm not really sure what the x86/sparc
code is protecting against so maybe it's not.

I also don't see any reason for us to implement the poke_early() routine,
even though sparc does.

[BenH: Updated the patch to upstream generic changes]

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Michael Ellerman 2011-06-29 19:16:59 +00:00 committed by Benjamin Herrenschmidt
parent 87fa35dd88
commit ac5f89c7d8
4 changed files with 72 additions and 0 deletions
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1
arch/powerpc/Kconfig
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@ -134,6 +134,7 @@ config PPC
select GENERIC_IRQ_SHOW_LEVEL
select HAVE_RCU_TABLE_FREE if SMP
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_ARCH_JUMP_LABEL
config EARLY_PRINTK
bool

47
arch/powerpc/include/asm/jump_label.h Normal file
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@ -0,0 +1,47 @@
#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.
*/
#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 jump_label_key *key)
{
asm goto("1:\n\t"
"nop\n\t"
".pushsection __jump_table, \"aw\"\n\t"
".align 4\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;
jump_label_t pad;
};
#endif /* _ASM_POWERPC_JUMP_LABEL_H */

1
arch/powerpc/kernel/Makefile
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@ -76,6 +76,7 @@ obj-$(CONFIG_MODULES) += module.o module_$(CONFIG_WORD_SIZE).o
obj-$(CONFIG_44x) += cpu_setup_44x.o
obj-$(CONFIG_PPC_FSL_BOOK3E) += cpu_setup_fsl_booke.o dbell.o
obj-$(CONFIG_PPC_BOOK3E_64) += dbell.o
obj-$(CONFIG_JUMP_LABEL) += jump_label.o
extra-y := head_$(CONFIG_WORD_SIZE).o
extra-$(CONFIG_40x) := head_40x.o

23
arch/powerpc/kernel/jump_label.c Normal file
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@ -0,0 +1,23 @@
/*
* 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.
*/
#include <linux/kernel.h>
#include <linux/jump_label.h>
#include <asm/code-patching.h>
void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type)
{
u32 *addr = (u32 *)(unsigned long)entry->code;
if (type == JUMP_LABEL_ENABLE)
patch_branch(addr, entry->target, 0);
else
patch_instruction(addr, PPC_INST_NOP);
}