Ftrace modifies function calls using Int3 breakpoints on x86.
The breakpoints are handled only when the patching is in progress.
If something goes wrong, there is a recovery code that removes
the breakpoints. If this fails, the system might get silently
rebooted when a remaining break is not handled or an invalid
instruction is proceed.
A better solution is to BUG() when the recovery fails. It helps
to point to the sinner responsible for the reboot.
Signed-off-by: Petr Mladek <pmla...@suse.cz>
---
arch/x86/kernel/ftrace.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 30d63c4a4195..525a9f954c8b 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -424,7 +424,7 @@ static int remove_breakpoint(struct dyn_ftrace *rec)
/* If this does not have a breakpoint, we are done */
if (ins[0] != BREAKPOINT_INSTRUCTION)
- return -1;
+ return 0;
/* Check if it is nop instruction */
valid_ins = ftrace_nop_replace();
@@ -625,8 +625,15 @@ void ftrace_replace_code(int enable)
ftrace_bug(ret, rec ? rec->ip : 0);
printk(KERN_WARNING "Failed on %s (%d):\n", report, count);
for_ftrace_rec_iter(iter) {
+ int err;
+
rec = ftrace_rec_iter_record(iter);
- remove_breakpoint(rec);
+ err = remove_breakpoint(rec);
+ /*
+ * The breakpoints will not be handled after this function
+ * finishes. Let's stop on a well defined point.
+ */
+ BUG_ON(err);
}
}
--
1.8.4
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