kprobes/arm: Fix ldrd/strd emulation

Currently emulate_ldrd and emulate_strd don't even have the adjustment
of the PC value, so in case of Rn == PC, it will not update the PC
incorrectly but instead load/store from the wrong address.  Let's add
both the adjustment of the PC value and the check for PC == PC.

Signed-off-by: Viktor Rosendahl <viktor.rosendahl@nokia.com>
Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>

1 files changed, 15 insertions, 5 deletions

diff --git a/arch/arm/kernel/kprobes-decode.c b/arch/arm/kernel/kprobes-decode.c
index 23891317dc4b..3b0cf90cb449 100644
--- a/arch/arm/kernel/kprobes-decode.c
+++ b/arch/arm/kernel/kprobes-decode.c
@@ -540,9 +540,12 @@ static void __kprobes emulate_ldrd(struct kprobe *p, struct pt_regs *regs)
 {
         insn_2arg_fn_t *i_fn = (insn_2arg_fn_t *)&p->ainsn.insn[0];
         kprobe_opcode_t insn = p->opcode;
+        long ppc = (long)p->addr + 8;
         int rd = (insn >> 12) & 0xf;
         int rn = (insn >> 16) & 0xf;
         int rm = insn & 0xf;  /* rm may be invalid, don't care. */
+        long rmv = (rm == 15) ? ppc : regs->uregs[rm];
+        long rnv = (rn == 15) ? ppc : regs->uregs[rn];
 
         /* Not following the C calling convention here, so need asm(). */
         __asm__ __volatile__ (
@@ -554,29 +557,36 @@ static void __kprobes emulate_ldrd(struct kprobe *p, struct pt_regs *regs)
                 "str    r0, %[rn]       \n\t"   /* in case of writeback */
                 "str    r2, %[rd0]      \n\t"
                 "str    r3, %[rd1]      \n\t"
-                : [rn]  "+m" (regs->uregs[rn]),
+                : [rn]  "+m" (rnv),
                   [rd0] "=m" (regs->uregs[rd]),
                   [rd1] "=m" (regs->uregs[rd+1])
-                : [rm]   "m" (regs->uregs[rm]),
+                : [rm]   "m" (rmv),
                   [cpsr] "r" (regs->ARM_cpsr),
                   [i_fn] "r" (i_fn)
                 : "r0", "r1", "r2", "r3", "lr", "cc"
         );
+        if (rn != 15)
+                regs->uregs[rn] = rnv;  /* Save Rn in case of writeback. */
 }
 
 static void __kprobes emulate_strd(struct kprobe *p, struct pt_regs *regs)
 {
         insn_4arg_fn_t *i_fn = (insn_4arg_fn_t *)&p->ainsn.insn[0];
         kprobe_opcode_t insn = p->opcode;
+        long ppc = (long)p->addr + 8;
         int rd = (insn >> 12) & 0xf;
         int rn = (insn >> 16) & 0xf;
         int rm  = insn & 0xf;
-        long rnv = regs->uregs[rn];
-        long rmv = regs->uregs[rm];  /* rm/rmv may be invalid, don't care. */
+        long rnv = (rn == 15) ? ppc : regs->uregs[rn];
+        /* rm/rmv may be invalid, don't care. */
+        long rmv = (rm == 15) ? ppc : regs->uregs[rm];
+        long rnv_wb;
 
-        regs->uregs[rn] = insnslot_4arg_rflags(rnv, rmv, regs->uregs[rd],
+        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. */
 }
 
 static void __kprobes emulate_ldr(struct kprobe *p, struct pt_regs *regs)