tracing: Use a copy of the va_list for __assign_vstr()
If an instance of tracing enables the same trace event as another instance, or the top level instance, or even perf, then the va_list passed into some tracepoints can be used more than once. As va_list can only be traversed once, this can cause issues: # cat /sys/kernel/tracing/instances/qla2xxx/trace cat-56106 [012] ..... 2419873.470098: ql_dbg_log: qla2xxx [0000:05:00.0]-1054:14: Entered (null). cat-56106 [012] ..... 2419873.470101: ql_dbg_log: qla2xxx [0000:05:00.0]-1000:14: Entered ×+<96>²Ü<98>^H. cat-56106 [012] ..... 2419873.470102: ql_dbg_log: qla2xxx [0000:05:00.0]-1006:14: Prepare to issue mbox cmd=0xde589000. # cat /sys/kernel/tracing/trace cat-56106 [012] ..... 2419873.470097: ql_dbg_log: qla2xxx [0000:05:00.0]-1054:14: Entered qla2x00_get_firmware_state. cat-56106 [012] ..... 2419873.470100: ql_dbg_log: qla2xxx [0000:05:00.0]-1000:14: Entered qla2x00_mailbox_command. cat-56106 [012] ..... 2419873.470102: ql_dbg_log: qla2xxx [0000:05:00.0]-1006:14: Prepare to issue mbox cmd=0x69. The instance version is corrupted because the top level instance iterated the va_list first. Use va_copy() in the __assign_vstr() macro to make sure that each trace event for each use case gets a fresh va_list. Link: https://lore.kernel.org/all/259d53a5-958e-6508-4e45-74dba2821242@marvell.com/ Link: https://lkml.kernel.org/r/20220719182004.21daa83e@gandalf.local.home Fixes: 0563231f ("tracing/events: Add __vstring() and __assign_vstr() helper macros") Reported-by: Arun Easi <aeasi@marvell.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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