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authorCheng Jian <cj.chengjian@huawei.com>2020-05-15 10:08:28 +0000
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2020-05-19 21:08:01 -0400
commitc143b7753b308d5f7d03b165a7fdff1dda1f271d (patch)
treed711efa0801557d5b217391bd711503ce8161db1 /kernel/trace
parentb9bbe6ed63b2b9f2c9ee5cbd0f2c946a2723f4ce (diff)
ftrace: show debugging information when panic_on_warn set
When an anomaly is detected in the function call modification code, ftrace_bug() is called to disable function tracing as well as give some warn and information that may help debug the problem. But currently, we call FTRACE_WARN_ON_ONCE() first in ftrace_bug(), so when panic_on_warn is set, we can't see the debugging information here. Call FTRACE_WARN_ON_ONCE() at the end of ftrace_bug() to ensure that the debugging information is displayed first. after this patch, the dmesg looks like: ------------[ ftrace bug ]------------ ftrace failed to modify [<ffff800010081004>] bcm2835_handle_irq+0x4/0x58 actual: 1f:20:03:d5 Setting ftrace call site to call ftrace function ftrace record flags: 80000001 (1) expected tramp: ffff80001009d6f0 ------------[ cut here ]------------ WARNING: CPU: 2 PID: 1635 at kernel/trace/ftrace.c:2078 ftrace_bug+0x204/0x238 Kernel panic - not syncing: panic_on_warn set ... CPU: 2 PID: 1635 Comm: sh Not tainted 5.7.0-rc5-00033-gb922183867f5 #14 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x0/0x1b0 show_stack+0x20/0x30 dump_stack+0xc0/0x10c panic+0x16c/0x368 __warn+0x120/0x160 report_bug+0xc8/0x160 bug_handler+0x28/0x98 brk_handler+0x70/0xd0 do_debug_exception+0xcc/0x1ac el1_sync_handler+0xe4/0x120 el1_sync+0x7c/0x100 ftrace_bug+0x204/0x238 Link: https://lkml.kernel.org/r/20200515100828.7091-1-cj.chengjian@huawei.com Signed-off-by: Cheng Jian <cj.chengjian@huawei.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/ftrace.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index bd030b1b9514..cd39cbf3631a 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2027,14 +2027,14 @@ void ftrace_bug(int failed, struct dyn_ftrace *rec)
{
unsigned long ip = rec ? rec->ip : 0;
+ pr_info("------------[ ftrace bug ]------------\n");
+
switch (failed) {
case -EFAULT:
- FTRACE_WARN_ON_ONCE(1);
pr_info("ftrace faulted on modifying ");
print_ip_sym(ip);
break;
case -EINVAL:
- FTRACE_WARN_ON_ONCE(1);
pr_info("ftrace failed to modify ");
print_ip_sym(ip);
print_ip_ins(" actual: ", (unsigned char *)ip);
@@ -2045,12 +2045,10 @@ void ftrace_bug(int failed, struct dyn_ftrace *rec)
}
break;
case -EPERM:
- FTRACE_WARN_ON_ONCE(1);
pr_info("ftrace faulted on writing ");
print_ip_sym(ip);
break;
default:
- FTRACE_WARN_ON_ONCE(1);
pr_info("ftrace faulted on unknown error ");
print_ip_sym(ip);
}
@@ -2077,6 +2075,8 @@ void ftrace_bug(int failed, struct dyn_ftrace *rec)
ip = ftrace_get_addr_curr(rec);
pr_cont("\n expected tramp: %lx\n", ip);
}
+
+ FTRACE_WARN_ON_ONCE(1);
}
static int ftrace_check_record(struct dyn_ftrace *rec, bool enable, bool update)