[Crash-utility] [PATCH] crash extension: trace

[Wengang Wang]

>From a UEK5 vmcore, I see that

crash> p &__start___trace_bprintk_fmt
$1 = (const char *(*)[]) 0xffffffffa163f1d0
crash> p &__stop___trace_bprintk_fmt
$2 = (const char *(*)[]) 0xffffffffa163f1f0

so (0xffffffffa163f1f0 - 0xffffffffa163f1d0)/8 = 4.

there are two zero addresses at index 2 and 3.
crash> rd __start___trace_bprintk_fmt 4
ffffffffa163f1d0:  ffffffffa11ccdca ffffffffa11ccdca   ................
ffffffffa163f1e0:  0000000000000000 0000000000000000   ................

current implementation will fail (no output for trace show command)
on seeing the zero addresses.

fix: ignore zero addresses in add_print_address.

tested to be good (compared the ftrace log from vmcore and that from live system).

Signed-off-by: Wengang Wang <wen.gang.wang at oracle.com>
---
 extensions/trace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/extensions/trace.c b/extensions/trace.c
index c26b6c7..491e4eb 100644
--- a/extensions/trace.c
+++ b/extensions/trace.c
@@ -2226,6 +2226,8 @@ static int add_print_address(long address)
 	size_t len;
 	int i;
 
+	if (!address)
+		return 0;
 	len = read_string(address, string, sizeof(string));
 	if (!len)
 		return -1;
-- 
1.8.3.1