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authorJon Medhurst <tixy@yxit.co.uk>2011-07-02 15:46:05 +0100
committerTixy <tixy@medhuaa1.miniserver.com>2011-07-13 17:32:43 +0000
commit02d194f64772aee91e7319ca033905b0bafee04c (patch)
tree67071bb76ec91b1df072bc8eaa889f8c62cbb5d7 /arch/arm/kernel/kprobes-thumb.c
parent7460bce42323df6570c7ba5091cb5201c7af1944 (diff)
ARM: kprobes: Decode 16-bit Thumb data-processing instructions
These instructions only operate on the low registers R0-R7, therefore it is possible to emulate them by executing the original instruction unaltered if we restore and save these registers. This is what t16_emulate_loregs does. Some of these instructions don't update the PSR when they execute in an IT block, so there are two flavours of emulation functions: t16_emulate_loregs_{noit}rwflags Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Diffstat (limited to 'arch/arm/kernel/kprobes-thumb.c')
-rw-r--r--arch/arm/kernel/kprobes-thumb.c81
1 files changed, 81 insertions, 0 deletions
diff --git a/arch/arm/kernel/kprobes-thumb.c b/arch/arm/kernel/kprobes-thumb.c
index 7dcf6df4a85..e1cef827312 100644
--- a/arch/arm/kernel/kprobes-thumb.c
+++ b/arch/arm/kernel/kprobes-thumb.c
@@ -26,6 +26,42 @@
*/
#define current_cond(cpsr) ((cpsr >> 12) & 0xf)
+static unsigned long __kprobes
+t16_emulate_loregs(struct kprobe *p, struct pt_regs *regs)
+{
+ unsigned long oldcpsr = regs->ARM_cpsr;
+ unsigned long newcpsr;
+
+ __asm__ __volatile__ (
+ "msr cpsr_fs, %[oldcpsr] \n\t"
+ "ldmia %[regs], {r0-r7} \n\t"
+ "blx %[fn] \n\t"
+ "stmia %[regs], {r0-r7} \n\t"
+ "mrs %[newcpsr], cpsr \n\t"
+ : [newcpsr] "=r" (newcpsr)
+ : [oldcpsr] "r" (oldcpsr), [regs] "r" (regs),
+ [fn] "r" (p->ainsn.insn_fn)
+ : "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
+ "lr", "memory", "cc"
+ );
+
+ return (oldcpsr & ~APSR_MASK) | (newcpsr & APSR_MASK);
+}
+
+static void __kprobes
+t16_emulate_loregs_rwflags(struct kprobe *p, struct pt_regs *regs)
+{
+ regs->ARM_cpsr = t16_emulate_loregs(p, regs);
+}
+
+static void __kprobes
+t16_emulate_loregs_noitrwflags(struct kprobe *p, struct pt_regs *regs)
+{
+ unsigned long cpsr = t16_emulate_loregs(p, regs);
+ if (!in_it_block(cpsr))
+ regs->ARM_cpsr = cpsr;
+}
+
static const union decode_item t16_table_1011[] = {
/* Miscellaneous 16-bit instructions */
@@ -51,6 +87,51 @@ static const union decode_item t16_table_1011[] = {
const union decode_item kprobe_decode_thumb16_table[] = {
/*
+ * Shift (immediate), add, subtract, move, and compare
+ * 00xx xxxx xxxx xxxx
+ */
+
+ /* CMP (immediate) 0010 1xxx xxxx xxxx */
+ DECODE_EMULATE (0xf800, 0x2800, t16_emulate_loregs_rwflags),
+
+ /* ADD (register) 0001 100x xxxx xxxx */
+ /* SUB (register) 0001 101x xxxx xxxx */
+ /* LSL (immediate) 0000 0xxx xxxx xxxx */
+ /* LSR (immediate) 0000 1xxx xxxx xxxx */
+ /* ASR (immediate) 0001 0xxx xxxx xxxx */
+ /* ADD (immediate, Thumb) 0001 110x xxxx xxxx */
+ /* SUB (immediate, Thumb) 0001 111x xxxx xxxx */
+ /* MOV (immediate) 0010 0xxx xxxx xxxx */
+ /* ADD (immediate, Thumb) 0011 0xxx xxxx xxxx */
+ /* SUB (immediate, Thumb) 0011 1xxx xxxx xxxx */
+ DECODE_EMULATE (0xc000, 0x0000, t16_emulate_loregs_noitrwflags),
+
+ /*
+ * 16-bit Thumb data-processing instructions
+ * 0100 00xx xxxx xxxx
+ */
+
+ /* TST (register) 0100 0010 00xx xxxx */
+ DECODE_EMULATE (0xffc0, 0x4200, t16_emulate_loregs_rwflags),
+ /* CMP (register) 0100 0010 10xx xxxx */
+ /* CMN (register) 0100 0010 11xx xxxx */
+ DECODE_EMULATE (0xff80, 0x4280, t16_emulate_loregs_rwflags),
+ /* AND (register) 0100 0000 00xx xxxx */
+ /* EOR (register) 0100 0000 01xx xxxx */
+ /* LSL (register) 0100 0000 10xx xxxx */
+ /* LSR (register) 0100 0000 11xx xxxx */
+ /* ASR (register) 0100 0001 00xx xxxx */
+ /* ADC (register) 0100 0001 01xx xxxx */
+ /* SBC (register) 0100 0001 10xx xxxx */
+ /* ROR (register) 0100 0001 11xx xxxx */
+ /* RSB (immediate) 0100 0010 01xx xxxx */
+ /* ORR (register) 0100 0011 00xx xxxx */
+ /* MUL 0100 0011 00xx xxxx */
+ /* BIC (register) 0100 0011 10xx xxxx */
+ /* MVN (register) 0100 0011 10xx xxxx */
+ DECODE_EMULATE (0xfc00, 0x4000, t16_emulate_loregs_noitrwflags),
+
+ /*
* Miscellaneous 16-bit instructions
* 1011 xxxx xxxx xxxx
*/