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authorNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>2017-09-15 15:38:21 +0530
committerMichael Ellerman <mpe@ellerman.id.au>2017-09-20 20:21:24 +1000
commit8afafa6fba7809c0785018b77c95b19e58b35b94 (patch)
tree81d6e4a689023221cfa7cdcc5c94e85e67e14fc9 /arch/powerpc/kernel
parentb134165eadd6dd07c49f8db40b218185ca3130b0 (diff)
powerpc/kprobes: Update optprobes to use emulate_update_regs()
Optprobes depended on an updated regs->nip from analyse_instr() to identify the location to branch back from the optprobes trampoline. However, since commit 3cdfcbfd32b9d ("powerpc: Change analyse_instr so it doesn't modify *regs"), analyse_instr() doesn't update the registers anymore. Due to this, we end up branching back from the optprobes trampoline to the same branch into the trampoline resulting in a loop. Fix this by calling out to emulate_update_regs() before using the nip. Additionally, explicitly compare the return value from analyse_instr() to 1, rather than just checking for !0 so as to guard against any future changes to analyse_instr() that may result in -1 being returned in more scenarios. Fixes: 3cdfcbfd32b9d ("powerpc: Change analyse_instr so it doesn't modify *regs") Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel')
-rw-r--r--arch/powerpc/kernel/optprobes.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
index 6f8273f5e988..91e037ab20a1 100644
--- a/arch/powerpc/kernel/optprobes.c
+++ b/arch/powerpc/kernel/optprobes.c
@@ -104,8 +104,10 @@ static unsigned long can_optimize(struct kprobe *p)
* and that can be emulated.
*/
if (!is_conditional_branch(*p->ainsn.insn) &&
- analyse_instr(&op, &regs, *p->ainsn.insn))
+ analyse_instr(&op, &regs, *p->ainsn.insn) == 1) {
+ emulate_update_regs(&regs, &op);
nip = regs.nip;
+ }
return nip;
}