From 5c6b76fc7d8220e8f00e7a49fb56ca852d7fb661 Mon Sep 17 00:00:00 2001 From: Jon Medhurst Date: Fri, 8 Apr 2011 15:32:56 +0100 Subject: [PATCH] ARM: kprobes: Fix emulation of LDRD and STRD instructions The decoding of these instructions got the register indexed and immediate indexed forms the wrong way around, causing incorrect emulation. Instructions like "LDRD Rx, [Rx]" were corrupting Rx because the base register writeback was being performed unconditionally, overwriting the value just loaded from memory. The fix is to only writeback the base register when that form of the instruction is used. Note, now that we reject probing writeback with PC the emulation code doesn't need the check rn!=15. Signed-off-by: Jon Medhurst Signed-off-by: Nicolas Pitre --- arch/arm/kernel/kprobes-decode.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/arm/kernel/kprobes-decode.c b/arch/arm/kernel/kprobes-decode.c index a4dba1f7c87b..826abc16e670 100644 --- a/arch/arm/kernel/kprobes-decode.c +++ b/arch/arm/kernel/kprobes-decode.c @@ -560,8 +560,8 @@ static void __kprobes emulate_ldrd(struct kprobe *p, struct pt_regs *regs) [i_fn] "r" (i_fn) : "r0", "r1", "r2", "r3", "lr", "cc" ); - if (rn != 15) - regs->uregs[rn] = rnv; /* Save Rn in case of writeback. */ + if (is_writeback(insn)) + regs->uregs[rn] = rnv; } static void __kprobes emulate_strd(struct kprobe *p, struct pt_regs *regs) @@ -580,8 +580,8 @@ static void __kprobes emulate_strd(struct kprobe *p, struct pt_regs *regs) rnv_wb = insnslot_4arg_rflags(rnv, rmv, regs->uregs[rd], regs->uregs[rd+1], regs->ARM_cpsr, i_fn); - if (rn != 15) - regs->uregs[rn] = rnv_wb; /* Save Rn in case of writeback. */ + if (is_writeback(insn)) + regs->uregs[rn] = rnv_wb; } static void __kprobes emulate_ldr(struct kprobe *p, struct pt_regs *regs) @@ -1183,8 +1183,8 @@ space_cccc_000x(kprobe_opcode_t insn, struct arch_specific_insn *asi) insn &= 0xfff00fff; insn |= 0x00002000; /* Rn = r0, Rd = r2 */ - if (insn & (1 << 22)) { - /* I bit */ + if (!(insn & (1 << 22))) { + /* Register index */ insn &= ~0xf; insn |= 1; /* Rm = r1 */ } -- 2.30.2