Fix: incorrect urcu git URL in README

[lttng-ust.git] / liblttng-ust-libc-wrapper / lttng-ust-malloc.c

diff --git a/liblttng-ust-libc-wrapper/lttng-ust-malloc.c b/liblttng-ust-libc-wrapper/lttng-ust-malloc.c
index 3212ff0bacca50f7e8511977ce66b708113f3c81..33ed18be09d5ea48eb5f0cabd73ce27ca151da46 100644 (file)
--- a/liblttng-ust-libc-wrapper/lttng-ust-malloc.c
+++ b/liblttng-ust-libc-wrapper/lttng-ust-malloc.c
@@ -21,14 +21,42 @@
 #include <dlfcn.h>
 #include <sys/types.h>
 #include <stdio.h>
+#include <urcu/system.h>
+#include <urcu/uatomic.h>
 
 #define TRACEPOINT_DEFINE
 #define TRACEPOINT_CREATE_PROBES
 #include "ust_libc.h"
 
+#define STATIC_CALLOC_LEN 4096
+static char static_calloc_buf[STATIC_CALLOC_LEN];
+static unsigned long static_calloc_buf_offset;
+
+static void *static_calloc(size_t nmemb, size_t size)
+{
+       unsigned long prev_offset, new_offset, res_offset;
+
+       /*
+        * Protect static_calloc_buf_offset from concurrent updates
+        * using a cmpxchg loop rather than a mutex to remove a
+        * dependency on pthread. This will minimize the risk of bad
+        * interaction between mutex and malloc instrumentation.
+        */
+       res_offset = CMM_LOAD_SHARED(static_calloc_buf_offset);
+       do {
+               prev_offset = res_offset;
+               if (nmemb * size > sizeof(static_calloc_buf) - prev_offset) {
+                       return NULL;
+               }
+               new_offset = prev_offset + nmemb * size;
+       } while ((res_offset = uatomic_cmpxchg(&static_calloc_buf_offset,
+                       prev_offset, new_offset)) != prev_offset);
+       return &static_calloc_buf[prev_offset];
+}
+
 void *malloc(size_t size)
 {
-       static void *(*plibc_malloc)(size_t size) = NULL;
+       static void *(*plibc_malloc)(size_t size);
        void *retval;
 
        if (plibc_malloc == NULL) {
@@ -45,7 +73,16 @@ void *malloc(size_t size)
 
 void free(void *ptr)
 {
-       static void *(*plibc_free)(void *ptr) = NULL;
+       static void (*plibc_free)(void *ptr);
+
+       /* Check whether the memory was allocated with
+        * static_calloc, in which case there is nothing
+        * to free.
+        */
+       if ((char *)ptr >= static_calloc_buf &&
+           (char *)ptr < static_calloc_buf + STATIC_CALLOC_LEN) {
+               return;
+       }
 
        if (plibc_free == NULL) {
                plibc_free = dlsym(RTLD_NEXT, "free");
@@ -57,3 +94,76 @@ void free(void *ptr)
        tracepoint(ust_libc, free, ptr);
        plibc_free(ptr);
 }
+
+void *calloc(size_t nmemb, size_t size)
+{
+       static void *(*volatile plibc_calloc)(size_t nmemb, size_t size);
+       void *retval;
+
+       if (plibc_calloc == NULL) {
+               /*
+                * Temporarily redirect to static_calloc,
+                * until the dlsym lookup has completed.
+                */
+               plibc_calloc = static_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);
+       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;
+}
+
+void *memalign(size_t alignment, size_t size)
+{
+       static void *(*plibc_memalign)(size_t alignment, size_t size);
+       void *retval;
+
+       if (plibc_memalign == NULL) {
+               plibc_memalign = dlsym(RTLD_NEXT, "memalign");
+               if (plibc_memalign == NULL) {
+                       fprintf(stderr, "memalignwrap: unable to find memalign\n");
+                       return NULL;
+               }
+       }
+       retval = plibc_memalign(alignment, size);
+       tracepoint(ust_libc, memalign, alignment, size, retval);
+       return retval;
+}
+
+int posix_memalign(void **memptr, size_t alignment, size_t size)
+{
+       static int(*plibc_posix_memalign)(void **memptr, size_t alignment, size_t size);
+       int retval;
+
+       if (plibc_posix_memalign == NULL) {
+               plibc_posix_memalign = dlsym(RTLD_NEXT, "posix_memalign");
+               if (plibc_posix_memalign == NULL) {
+                       fprintf(stderr, "posix_memalignwrap: unable to find posix_memalign\n");
+                       return ENOMEM;
+               }
+       }
+       retval = plibc_posix_memalign(memptr, alignment, size);
+       tracepoint(ust_libc, posix_memalign, *memptr, alignment, size, retval);
+       return retval;
+}