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authorJon Medhurst <tixy@yxit.co.uk>2011-04-06 14:17:09 +0400
committerNicolas Pitre <nicolas.pitre@linaro.org>2011-04-29 07:40:54 +0400
commit073090cb701148396b1130be81f8ac84a41f196d (patch)
tree033428a02241173a7645e8f84f8382d0fb8eaab8 /arch
parentcf3cc1aa9b6d0bf1750143af65829f4368d77492 (diff)
downloadlinux-073090cb701148396b1130be81f8ac84a41f196d.tar.xz
ARM: kprobes: Fix probing of conditionally executed instructions
When a kprobe is placed onto conditionally executed ARM instructions, many of the emulation routines used to single step them produce corrupt register results. Rather than fix all of these cases we modify the framework which calls them to test the relevant condition flags and, if the test fails, skip calling the emulation code. Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/include/asm/kprobes.h3
-rw-r--r--arch/arm/kernel/kprobes-decode.c91
-rw-r--r--arch/arm/kernel/kprobes.c3
3 files changed, 96 insertions, 1 deletions
diff --git a/arch/arm/include/asm/kprobes.h b/arch/arm/include/asm/kprobes.h
index bb8a19bd5822..e46bdd0097eb 100644
--- a/arch/arm/include/asm/kprobes.h
+++ b/arch/arm/include/asm/kprobes.h
@@ -39,10 +39,13 @@ typedef u32 kprobe_opcode_t;
struct kprobe;
typedef void (kprobe_insn_handler_t)(struct kprobe *, struct pt_regs *);
+typedef unsigned long (kprobe_check_cc)(unsigned long);
+
/* Architecture specific copy of original instruction. */
struct arch_specific_insn {
kprobe_opcode_t *insn;
kprobe_insn_handler_t *insn_handler;
+ kprobe_check_cc *insn_check_cc;
};
struct prev_kprobe {
diff --git a/arch/arm/kernel/kprobes-decode.c b/arch/arm/kernel/kprobes-decode.c
index 3b0cf90cb449..2e84169b9e91 100644
--- a/arch/arm/kernel/kprobes-decode.c
+++ b/arch/arm/kernel/kprobes-decode.c
@@ -1396,6 +1396,96 @@ space_cccc_111x(kprobe_opcode_t insn, struct arch_specific_insn *asi)
return INSN_GOOD;
}
+static unsigned long __kprobes __check_eq(unsigned long cpsr)
+{
+ return cpsr & PSR_Z_BIT;
+}
+
+static unsigned long __kprobes __check_ne(unsigned long cpsr)
+{
+ return (~cpsr) & PSR_Z_BIT;
+}
+
+static unsigned long __kprobes __check_cs(unsigned long cpsr)
+{
+ return cpsr & PSR_C_BIT;
+}
+
+static unsigned long __kprobes __check_cc(unsigned long cpsr)
+{
+ return (~cpsr) & PSR_C_BIT;
+}
+
+static unsigned long __kprobes __check_mi(unsigned long cpsr)
+{
+ return cpsr & PSR_N_BIT;
+}
+
+static unsigned long __kprobes __check_pl(unsigned long cpsr)
+{
+ return (~cpsr) & PSR_N_BIT;
+}
+
+static unsigned long __kprobes __check_vs(unsigned long cpsr)
+{
+ return cpsr & PSR_V_BIT;
+}
+
+static unsigned long __kprobes __check_vc(unsigned long cpsr)
+{
+ return (~cpsr) & PSR_V_BIT;
+}
+
+static unsigned long __kprobes __check_hi(unsigned long cpsr)
+{
+ cpsr &= ~(cpsr >> 1); /* PSR_C_BIT &= ~PSR_Z_BIT */
+ return cpsr & PSR_C_BIT;
+}
+
+static unsigned long __kprobes __check_ls(unsigned long cpsr)
+{
+ cpsr &= ~(cpsr >> 1); /* PSR_C_BIT &= ~PSR_Z_BIT */
+ return (~cpsr) & PSR_C_BIT;
+}
+
+static unsigned long __kprobes __check_ge(unsigned long cpsr)
+{
+ cpsr ^= (cpsr << 3); /* PSR_N_BIT ^= PSR_V_BIT */
+ return (~cpsr) & PSR_N_BIT;
+}
+
+static unsigned long __kprobes __check_lt(unsigned long cpsr)
+{
+ cpsr ^= (cpsr << 3); /* PSR_N_BIT ^= PSR_V_BIT */
+ return cpsr & PSR_N_BIT;
+}
+
+static unsigned long __kprobes __check_gt(unsigned long cpsr)
+{
+ unsigned long temp = cpsr ^ (cpsr << 3); /* PSR_N_BIT ^= PSR_V_BIT */
+ temp |= (cpsr << 1); /* PSR_N_BIT |= PSR_Z_BIT */
+ return (~temp) & PSR_N_BIT;
+}
+
+static unsigned long __kprobes __check_le(unsigned long cpsr)
+{
+ unsigned long temp = cpsr ^ (cpsr << 3); /* PSR_N_BIT ^= PSR_V_BIT */
+ temp |= (cpsr << 1); /* PSR_N_BIT |= PSR_Z_BIT */
+ return temp & PSR_N_BIT;
+}
+
+static unsigned long __kprobes __check_al(unsigned long cpsr)
+{
+ return true;
+}
+
+static kprobe_check_cc * const condition_checks[16] = {
+ &__check_eq, &__check_ne, &__check_cs, &__check_cc,
+ &__check_mi, &__check_pl, &__check_vs, &__check_vc,
+ &__check_hi, &__check_ls, &__check_ge, &__check_lt,
+ &__check_gt, &__check_le, &__check_al, &__check_al
+};
+
/* Return:
* INSN_REJECTED If instruction is one not allowed to kprobe,
* INSN_GOOD If instruction is supported and uses instruction slot,
@@ -1411,6 +1501,7 @@ space_cccc_111x(kprobe_opcode_t insn, struct arch_specific_insn *asi)
enum kprobe_insn __kprobes
arm_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
+ asi->insn_check_cc = condition_checks[insn>>28];
asi->insn[1] = KPROBE_RETURN_INSTRUCTION;
if ((insn & 0xf0000000) == 0xf0000000) {
diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
index 2ba7deb3072e..1656c87501c0 100644
--- a/arch/arm/kernel/kprobes.c
+++ b/arch/arm/kernel/kprobes.c
@@ -134,7 +134,8 @@ static void __kprobes singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
regs->ARM_pc += 4;
- p->ainsn.insn_handler(p, regs);
+ if (p->ainsn.insn_check_cc(regs->ARM_cpsr))
+ p->ainsn.insn_handler(p, regs);
}
/*