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

On Mar 16, 2021, at 2:22 PM, Wengang Wang <wen.gang.wang(a)oracle.com&gt; wrote: 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(a)oracle.com&gt; --- 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