From: Masami Hiramatsu <mhiramat@redhat.com> Date: Mon, 10 Sep 2007 12:36:45 -0400 Subject: [ia64] enable kprobe's trap code on slot 1 Message-id: 46E5729D.5060903@redhat.com O-Subject: Re: [RHEL5 PATCH] enable kprobe's trap code on slot 1 on ia64 Bugzilla: 207107 This patch enables kprobe to insert trap code on slot 1 on ia64. Since slot 1 of one instruction bundle crosses border of two consecutive 8-byte (this means it can not be written atomically), kprobe on slot 1 is disabled. This patch only replaces higher 8-bytes of the instruction bundle and changes the exception code to ignore the low 12 bits of the break number (which is across the border in the lower 8-bytes of the bundle). The original patch was merged into upstream kernel. Commit: 08ed38b68099f2a492196414b08a7f5dd8dc3537 http://www.mail-archive.com/git-commits-head@vger.kernel.org/msg02626.html This patch can be applied for 2.6.18-44.el5. Since the original patch broke the kABI (add a slot member to the arch_specific_insn data structure which is a part of the kprobe data structure), I modified the patch to calculate the slot number from other parameters instead of reading it from the slot member. This patch resolves bz #207107. Testing: I built a test kernel and tested the patch by the command below: $ stap -e 'probe kernel.function("page_get_cache").inline {printf("%s\n", pp()); exit()}' "page_get_cache" is an inline function, and it is expanded in slot 1. When I tested it without this patch, the command failed to execute as below. --(result)-- ERROR: probe kernel.function("page_get_cache@mm/slab.c:591").inline registration error (rc -22) diff --git a/arch/ia64/kernel/jprobes.S b/arch/ia64/kernel/jprobes.S index 5cd6226..f69389c 100644 --- a/arch/ia64/kernel/jprobes.S +++ b/arch/ia64/kernel/jprobes.S @@ -45,13 +45,14 @@ * to the correct location. */ #include <asm/asmmacro.h> +#include <asm/break.h> /* * void jprobe_break(void) */ .section .kprobes.text, "ax" ENTRY(jprobe_break) - break.m 0x80300 + break.m __IA64_BREAK_JPROBE END(jprobe_break) /* diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c index 3092f33..5fcfc6c 100644 --- a/arch/ia64/kernel/kprobes.c +++ b/arch/ia64/kernel/kprobes.c @@ -296,12 +296,6 @@ static int __kprobes valid_kprobe_addr(int template, int slot, return -EINVAL; } - if (slot == 1 && bundle_encoding[template][1] != L) { - printk(KERN_WARNING "Inserting kprobes on slot #1 " - "is not supported\n"); - return -EINVAL; - } - return 0; } @@ -451,25 +445,66 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) return 0; } +static inline unsigned int get_kprobe_slot(struct kprobe *p) +{ + unsigned int slot = ((unsigned long)p->addr) & 0xf; + /* p->ainsn.insn contains the original unaltered kprobe_opcode_t */ + unsigned int template = p->ainsn.insn->bundle.quad0.template; + + /* Move to slot 2, if bundle is MLX type and kprobe slot is 1 */ + if (slot == 1 && bundle_encoding[template][1] == L) + slot = 2; + + return slot; +} + void __kprobes arch_arm_kprobe(struct kprobe *p) { - unsigned long addr = (unsigned long)p->addr; - unsigned long arm_addr = addr & ~0xFULL; + unsigned long arm_addr; + bundle_t *src, *dest; + unsigned int slot = get_kprobe_slot(p); + + arm_addr = ((unsigned long)p->addr) & ~0xFUL; + dest = &((kprobe_opcode_t *)arm_addr)->bundle; + src = &p->opcode.bundle; flush_icache_range((unsigned long)p->ainsn.insn, (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t)); - memcpy((char *)arm_addr, &p->opcode, sizeof(kprobe_opcode_t)); + switch (slot) { + case 0: + dest->quad0.slot0 = src->quad0.slot0; + break; + case 1: + dest->quad1.slot1_p1 = src->quad1.slot1_p1; + break; + case 2: + dest->quad1.slot2 = src->quad1.slot2; + break; + } flush_icache_range(arm_addr, arm_addr + sizeof(kprobe_opcode_t)); } void __kprobes arch_disarm_kprobe(struct kprobe *p) { - unsigned long addr = (unsigned long)p->addr; - unsigned long arm_addr = addr & ~0xFULL; + unsigned long arm_addr; + bundle_t *src, *dest; + unsigned int slot = get_kprobe_slot(p); + arm_addr = ((unsigned long)p->addr) & ~0xFUL; + dest = &((kprobe_opcode_t *)arm_addr)->bundle; /* p->ainsn.insn contains the original unaltered kprobe_opcode_t */ - memcpy((char *) arm_addr, (char *) p->ainsn.insn, - sizeof(kprobe_opcode_t)); + src = &p->ainsn.insn->bundle; + switch (slot) { + case 0: + dest->quad0.slot0 = src->quad0.slot0; + break; + case 1: + dest->quad1.slot1_p1 = src->quad1.slot1_p1; + break; + case 2: + dest->quad1.slot2 = src->quad1.slot2; + break; + } flush_icache_range(arm_addr, arm_addr + sizeof(kprobe_opcode_t)); } @@ -802,7 +837,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, switch(val) { case DIE_BREAK: /* err is break number from ia64_bad_break() */ - if (args->err == 0x80200 || args->err == 0x80300 || args->err == 0) + if ((args->err >> 12) == (__IA64_BREAK_KPROBE >> 12) + || args->err == __IA64_BREAK_JPROBE + || args->err == 0) if (pre_kprobes_handler(args)) ret = NOTIFY_STOP; break; diff --git a/include/asm-ia64/break.h b/include/asm-ia64/break.h index 8167828..f034020 100644 --- a/include/asm-ia64/break.h +++ b/include/asm-ia64/break.h @@ -12,8 +12,8 @@ * OS-specific debug break numbers: */ #define __IA64_BREAK_KDB 0x80100 -#define __IA64_BREAK_KPROBE 0x80200 -#define __IA64_BREAK_JPROBE 0x80300 +#define __IA64_BREAK_KPROBE 0x81000 /* .. 0x81fff */ +#define __IA64_BREAK_JPROBE 0x82000 /* * OS-specific break numbers: