The attached patch adds support for calloc and realloc to the lttng-ust-libc-wrapper library.
The implementation for calloc is slightly tricky, as dlsym calls calloc internally, so the library needs to provide a 'dummy' implementation for calloc to avoid an endless recursion. Testing has shown however that the object(s) allocated at that point are small, so a dummy static 'heap' suffices as a workaround. -- Stefan Seefeld CodeSourcery / Mentor Graphics http://www.mentor.com/embedded-software/
>From 78696689a46c13cdd2625c59348cbb1c03a32b0e Mon Sep 17 00:00:00 2001 From: Stefan Seefeld <[email protected]> Date: Sat, 27 Jul 2013 01:10:23 -0400 Subject: [PATCH] Add trace support for calloc and realloc. Signed-off-by: Stefan Seefeld <[email protected]> --- liblttng-ust-libc-wrapper/lttng-ust-malloc.c | 68 ++++++++++++++++++++++++++++ liblttng-ust-libc-wrapper/ust_libc.h | 18 ++++++++ 2 files changed, 86 insertions(+) diff --git a/liblttng-ust-libc-wrapper/lttng-ust-malloc.c b/liblttng-ust-libc-wrapper/lttng-ust-malloc.c index 3212ff0..772663a 100644 --- a/liblttng-ust-libc-wrapper/lttng-ust-malloc.c +++ b/liblttng-ust-libc-wrapper/lttng-ust-malloc.c @@ -57,3 +57,71 @@ void free(void *ptr) tracepoint(ust_libc, free, ptr); plibc_free(ptr); } + +/* + The following 'dummy' variables and functions are needed + to break out of an endless recursion: + dlsym itself appears to call calloc, so we need to provide + an implementation for the very first call to calloc to use. +*/ + +#define DUMMY_HEAP_SIZE 1024 +static char dummy_heap[DUMMY_HEAP_SIZE] = {0}; +static int dummy_end_of_heap = 0; + +static void *dummy_malloc(size_t size) +{ + if(size == 0) + return NULL; + + size_t dummy_end_of_heap_reserved = dummy_end_of_heap + size; + if(dummy_end_of_heap_reserved >= DUMMY_HEAP_SIZE) + return NULL; + + void *loc = (void*) &dummy_heap[dummy_end_of_heap]; + dummy_end_of_heap = dummy_end_of_heap_reserved; + return loc; +}; + +static void *dummy_calloc(size_t nmemb, size_t size) +{ + return dummy_malloc(nmemb * size); +} + +void *calloc(size_t nmemb, size_t size) +{ + static void *(* volatile plibc_calloc)(size_t nmemb, size_t size) = NULL; + void *retval; + + if (plibc_calloc == NULL) { + /* Temporarily redirect to dummy_calloc, + until the dlsym lookup has completed. */ + plibc_calloc = dummy_calloc; + plibc_calloc = dlsym(RTLD_NEXT, "calloc"); + if (plibc_calloc == NULL) { + fprintf(stderr, "callocwrap: unable to find calloc\n"); + return NULL; + } + } + retval = plibc_calloc(nmemb, size); + tracepoint(ust_libc, calloc, nmemb, size, retval); + return retval; +} + +void *realloc(void *ptr, size_t size) +{ + static void *(*plibc_realloc)(void *ptr, size_t size) = NULL; + void *retval; + + if (plibc_realloc == NULL) { + plibc_realloc = dlsym(RTLD_NEXT, "realloc"); + if (plibc_realloc == NULL) { + fprintf(stderr, "reallocwrap: unable to find realloc\n"); + return NULL; + } + } + retval = plibc_realloc(ptr, size); + tracepoint(ust_libc, realloc, ptr, size, retval); + return retval; +} + diff --git a/liblttng-ust-libc-wrapper/ust_libc.h b/liblttng-ust-libc-wrapper/ust_libc.h index af705aa..6b03a4d 100644 --- a/liblttng-ust-libc-wrapper/ust_libc.h +++ b/liblttng-ust-libc-wrapper/ust_libc.h @@ -47,6 +47,24 @@ TRACEPOINT_EVENT(ust_libc, free, ) ) +TRACEPOINT_EVENT(ust_libc, calloc, + TP_ARGS(size_t, nmemb, size_t, size, void *, ptr), + TP_FIELDS( + ctf_integer(size_t, nmemb, nmemb) + ctf_integer(size_t, size, size) + ctf_integer_hex(unsigned long, ptr, (unsigned long) ptr) + ) +) + +TRACEPOINT_EVENT(ust_libc, realloc, + TP_ARGS(void *, in_ptr, size_t, size, void *, ptr), + TP_FIELDS( + ctf_integer_hex(unsigned long, in_ptr, (unsigned long) in_ptr) + ctf_integer(size_t, size, size) + ctf_integer_hex(unsigned long, ptr, (unsigned long) ptr) + ) +) + #endif /* _TRACEPOINT_UST_LIBC_H */ #undef TRACEPOINT_INCLUDE -- 1.8.3.1
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