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backtrace: Refactor ast_bt_get_symbols so it doesn't crash

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We've been seeing crashes in libbfd when we attempt to generate
a stack trace from multiple threads.  It turns out that libbfd
is NOT thread-safe.  It can cache the bfd structure and give it to
multiple threads without protecting itself.  To get around this,
we've added a global mutex around the bfd functions and also have
refactored the use of those functions to be more efficient and
to provide more information about inlined functions.

Also added a few more tests to test_pbx.c.  One just calls
ast_assert() and the other calls ast_log_backtrace().  Neither are
run by default.

WARNING:  This change necessitated changing the return value of
ast_bt_get_symbols() from an array of strings to a VECTOR of
strings.  However, the use of this function outside Asterisk is not
likely.

ASTERISK-28140

Change-Id: I79d02862ddaa2423a0809caa4b3b85c128131621
This commit is contained in:
George Joseph
2018-11-08 08:53:44 -07:00
parent fa048183aa
commit ece5f8015f
10 changed files with 318 additions and 183 deletions
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19
include/asterisk/backtrace.h
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@@ -33,11 +33,13 @@
#define ast_bt_create() __ast_bt_create()
#define ast_bt_destroy(bt) __ast_bt_destroy((bt))
#define ast_bt_get_symbols(addresses, num_frames) __ast_bt_get_symbols((addresses), (num_frames))
#define ast_bt_free_symbols(string_vector) __ast_bt_free_symbols((string_vector))
#else
#define ast_bt_get_addresses(bt) 0
#define ast_bt_create() NULL
#define ast_bt_destroy(bt) NULL
#define ast_bt_get_symbols(addresses, num_frames) NULL
#define ast_bt_free_symbols(string_vector) NULL
#endif
/* \brief
@@ -86,11 +88,24 @@ void *__ast_bt_destroy(struct ast_bt *bt);
*
* \param addresses A list of addresses, such as the ->addresses structure element of struct ast_bt.
* \param num_frames Number of addresses in the addresses list
*
* \retval NULL Unable to allocate memory
* \return List of strings. Free the entire list with a single ast_std_free call.
* \return Vector of strings. Free with ast_bt_free_symbols
*
* \note The first frame in the addresses array will usually point to __ast_bt_create
* so when printing the symbols you may wish to start at position 1 rather than 0.
*
* \since 1.6.2.16
*/
char **__ast_bt_get_symbols(void **addresses, size_t num_frames);
struct ast_vector_string *__ast_bt_get_symbols(void **addresses, size_t num_frames);
/* \brief Free symbols returned from ast_bt_get_symbols
*
* \param symbols The symbol string vector
*
* \since 13.24.0
*/
void __ast_bt_free_symbols(struct ast_vector_string *symbols);
#endif /* HAVE_BKTR */