__ftrace_make_nop() needs to detect either the two instruction or
the three instruction versions of the _mcount() sequence.
But if we're running a kernel with the two instruction sequence, we need
to be careful not to read from ip - 8, or we'll fault and (possibly)
incorrectly declare the sequence doesn't match.
To keep the code simpler just look at ip - 4, and if it is either of the
expected instructions declare it good. We've already passed a lot of
other checks.
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
---
arch/powerpc/kernel/ftrace.c | 23 +++++++----------------
1 file changed, 7 insertions(+), 16 deletions(-)
Squash.
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index f190528e3781..fe7486f9849e 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -174,28 +174,19 @@ __ftrace_make_nop(struct module *mod,
return -EFAULT;
}
- if (op != PPC_INST_LD_TOC)
- {
- unsigned int op0, op1;
+ if (op != PPC_INST_LD_TOC) {
+ unsigned int inst;
- if (probe_kernel_read(&op0, (void *)(ip-8), MCOUNT_INSN_SIZE)) {
- pr_err("Fetching op0 failed.\n");
+ if (probe_kernel_read(&inst, (void *)(ip - 4), 4)) {
+ pr_err("Fetching instruction at %lx failed.\n", ip - 4);
return -EFAULT;
}
- if (probe_kernel_read(&op1, (void *)(ip-4), MCOUNT_INSN_SIZE)) {
- pr_err("Fetching op1 failed.\n");
- return -EFAULT;
- }
-
- /* mflr r0 ; [ std r0,LRSAVE(r1) ]? */
- if ( (op0 != PPC_INST_MFLR ||
- op1 != PPC_INST_STD_LR)
- && op1 != PPC_INST_MFLR )
- {
+ /* We expect either a mlfr r0, or a std r0, LRSAVE(r1) */
+ if (inst != PPC_INST_MFLR && inst != PPC_INST_STD_LR) {
pr_err("Unexpected instructions around bl _mcount\n"
"when enabling dynamic ftrace!\t"
- "(%08x,%08x,bl,%08x)\n", op0, op1, op);
+ "(%08x,bl,%08x)\n", inst, op);
return -EINVAL;
}
--
2.5.0
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