PowerPC optimization of the immediate values which uses a li instruction, patched with an immediate value. Signed-off-by: Mathieu Desnoyers --- arch/powerpc/kernel/Makefile | 1 arch/powerpc/kernel/immediate.c | 98 ++++++++++++++++++++++++++++++++++++ include/asm-powerpc/immediate.h | 107 +++++++++++++++++++++++++++++++++++++++- 3 files changed, 205 insertions(+), 1 deletion(-) Index: linux-2.6-lttng/include/asm-powerpc/immediate.h =================================================================== --- linux-2.6-lttng.orig/include/asm-powerpc/immediate.h 2007-07-13 19:26:18.000000000 -0400 +++ linux-2.6-lttng/include/asm-powerpc/immediate.h 2007-07-13 19:28:49.000000000 -0400 @@ -1 +1,106 @@ -#include +#ifndef _ASM_POWERPC_IMMEDIATE_H +#define _ASM_POWERPC_IMMEDIATE_H + +/* + * Immediate values. PowerPC architecture optimizations. + * + * (C) Copyright 2006 Mathieu Desnoyers + * + * This file is released under the GPLv2. + * See the file COPYING for more details. + */ + +#include + +struct module; + +struct __immediate { + long var; /* Identifier variable of the immediate value */ + long immediate; /* + * Pointer to the memory location that holds + * the immediate value within the load immediate + * instruction. + */ + long size; /* Type size. */ +}; + +/* + * Optimized version of the immediate. + * Make sure the 2 bytes update will be atomic by aligning the immediate + * value. + * Use a normal memory read for the 4 bytes immediate because there is no way to + * atomically update it without using a seqlock read side, which would cost more + * in term of total i-cache and d-cache space than a simple memory read. + * Do not use in __init and __exit functions. Use _immediate_read() instead. + */ +#define immediate_read(var) \ + ({ \ + __typeof__((var)->value) value; \ + switch (sizeof(value)) { \ + case 1: \ + asm ( ".section __immediate, \"a\", @progbits;\n\t" \ + PPC_LONG "%1, ((0f)+3), 1;\n\t" \ + ".previous;\n\t" \ + "0:\n\t" \ + "li %0,%2;\n\t" \ + : "=r" (value) \ + : "i" (&(var)->value), \ + "i" (0)); \ + break; \ + case 2: \ + asm ( ".section __immediate, \"a\", @progbits;\n\t" \ + PPC_LONG "%1, ((0f)+2), 2;\n\t" \ + ".previous;\n\t" \ + ".align 2\n\t" \ + "0:\n\t" \ + "li %0,%2;\n\t" \ + : "=r" (value) \ + : "i" (&(var)->value), \ + "i" (0)); \ + break; \ + default: \ + value = (var)->value; \ + break; \ + }; \ + value; \ + }) + +/* + * Update immediate value, can take module mutex. + */ +#define immediate_set(var, i) \ + (var)->value = (i); \ + immediate_update(1); + +/* + * Update immediate value. Module mutex must already be taken. + */ +#define _immediate_set(var, i) \ + (var)->value = (i); \ + immediate_update(0); + +/* + * Update immediate value at early boot. + */ +#define immediate_set_early(var, i) \ + (var)->value = (i); \ + immediate_update_early(); + +/* + * Branch depending on an immediate value. Could eventually be optimized further + * by improving gcc to give the ability to patch a jump instruction instead of + * the value it depends on. + * Do not use in __init and __exit functions. Use _immediate_if() instead. + */ +#define immediate_if(var) if (unlikely(immediate_read(var))) + +/* + * Used internally. + */ +extern void immediate_update(int lock); +extern void module_immediate_setup(struct module *mod); +extern void immediate_update_early(void); +extern int arch_immediate_update(const struct __immediate *immediate); +extern void arch_immediate_update_early(const struct __immediate *immediate); + +#endif /* _ASM_POWERPC_IMMEDIATE_H */ Index: linux-2.6-lttng/arch/powerpc/kernel/Makefile =================================================================== --- linux-2.6-lttng.orig/arch/powerpc/kernel/Makefile 2007-07-13 19:26:18.000000000 -0400 +++ linux-2.6-lttng/arch/powerpc/kernel/Makefile 2007-07-13 19:28:29.000000000 -0400 @@ -103,3 +103,4 @@ extra-$(CONFIG_PPC_FPU) += fpu.o extra-$(CONFIG_PPC64) += entry_64.o +obj-$(CONFIG_IMMEDIATE) += immediate.o Index: linux-2.6-lttng/arch/powerpc/kernel/immediate.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6-lttng/arch/powerpc/kernel/immediate.c 2007-07-13 19:28:29.000000000 -0400 @@ -0,0 +1,98 @@ +/* + * Powerpc optimized immediate values enabling/disabling. + * + * Mathieu Desnoyers + */ + +#include +#include +#include +#include +#include +#include + +#define LI_OPCODE_LEN 2 + +/* + * The immediate value are aligned. + */ +int arch_immediate_update(const struct __immediate *immediate) +{ +#ifdef CONFIG_KPROBES + kprobe_opcode_t *insn; + /* + * Fail if a kprobe has been set on this instruction. + * (TODO: we could eventually do better and modify all the (possibly + * nested) kprobes for this site if kprobes had an API for this. + */ + switch (immediate->size) { + case 1: /* The uint8_t points to the 3rd byte of the + * instruction */ + insn = (void*)(immediate->immediate - 1 - LI_OPCODE_LEN); + break; + case 2: insn = (void*)(immediate->immediate - LI_OPCODE_LEN); + break; + default: + return -EINVAL; + } + + if (unlikely(*insn == BREAKPOINT_INSTRUCTION)) { + printk(KERN_WARNING "Immediate value in conflict with kprobe. " + "Variable at %p, " + "instruction at %p, size %lu\n", + (void*)immediate->immediate, + (void*)immediate->var, immediate->size); + return -EBUSY; + } +#endif + + /* + * If the variable and the instruction have the same value, there is + * nothing to do. + */ + switch (immediate->size) { + case 1: if (*(uint8_t*)immediate->immediate + == *(uint8_t*)immediate->var) + return 0; + break; + case 2: if (*(uint16_t*)immediate->immediate + == *(uint16_t*)immediate->var) + return 0; + break; + default:return -EINVAL; + } + memcpy((void*)immediate->immediate, (void*)immediate->var, + immediate->size); + flush_icache_range((unsigned long)immediate->immediate, + immediate->size); + return 0; +} + +/* + * Very early initialization of the in-core immediate values. + * We can use flush_icache_range, since the cpu identification has been done in + * the early_init stage. + */ +void __init arch_immediate_update_early(const struct __immediate *immediate) +{ + /* + * If the variable and the instruction have the same value, there is + * nothing to do. + */ + switch (immediate->size) { + case 1: if (*(uint8_t*)immediate->immediate + == *(uint8_t*)immediate->var) + return; + break; + case 2: if (*(uint16_t*)immediate->immediate + == *(uint16_t*)immediate->var) + return; + break; + default:return; + } + memcpy((void*)immediate->immediate, (void*)immediate->var, + immediate->size); + flush_icache_range((unsigned long)immediate->immediate, + immediate->size); +} + -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/