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tracing: Just use strcmp() for testing __string() and __assign_str() match

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As __assign_str() no longer uses its "src" parameter, there's a check to
make sure nothing depends on it being different than what was passed to
__string(). It originally just compared the pointer passed to __string()
with the pointer passed into __assign_str() via the "src" parameter. But
there's a couple of outliers that just pass in a quoted string constant,
where comparing the pointers is UB to the compiler, as the compiler is
free to create multiple copies of the same string constant.

Instead, just use strcmp(). It may slow down the trace event, but this
will eventually be removed.

Also, fix the issue of passing NULL to strcmp() by adding a WARN_ON() to
make sure that both "src" and the pointer saved in __string() are either
both NULL or have content, and then checking if "src" is not NULL before
performing the strcmp().

Link: https://lore.kernel.org/all/CAHk-=wjxX16kWd=uxG5wzqt=aXoYDf1BgWOKk+qVmAO0zh7sjA@mail.gmail.com/

Fixes: b1afefa62c ("tracing: Use strcmp() in __assign_str() WARN_ON() check")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Steven Rostedt (Google) 2024-03-19 13:39:59 -04:00 committed by Linus Torvalds
parent fbd88dd057
commit 24f5bb9f24
1 changed files with 2 additions and 3 deletions
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5
include/trace/stages/stage6_event_callback.h
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@ -35,9 +35,8 @@
do { \
char *__str__ = __get_str(dst); \
int __len__ = __get_dynamic_array_len(dst) - 1; \
WARN_ON_ONCE(__builtin_constant_p(src) ? \
strcmp((src), __data_offsets.dst##_ptr_) : \
(src) != __data_offsets.dst##_ptr_); \
WARN_ON_ONCE(!(void *)(src) != !(void *)__data_offsets.dst##_ptr_); \
WARN_ON_ONCE((src) && strcmp((src), __data_offsets.dst##_ptr_)); \
memcpy(__str__, __data_offsets.dst##_ptr_ ? : \
EVENT_NULL_STR, __len__); \
__str__[__len__] = '\0'; \