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libsysprof-capture: use signed int for backtrace return

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This allows us to more safely subtract 1 from the unw_backtrace() to get
the proper number of frames (and detect it in the collector).
This commit is contained in:
Christian Hergert
2020-02-18 14:03:19 -08:00
parent 9f43bf2813
commit 7490a774ab
3 changed files with 16 additions and 12 deletions
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6
src/libsysprof-capture/sysprof-capture-writer.h
View File

@ -72,9 +72,9 @@ typedef struct _SysprofCaptureWriter SysprofCaptureWriter;
*
* Returns: the number of addresses filled in @addrs
*/
typedef guint (*SysprofBacktraceFunc) (SysprofCaptureAddress *addrs,
guint n_addrs,
gpointer user_data);
typedef gint (*SysprofBacktraceFunc) (SysprofCaptureAddress *addrs,
guint n_addrs,
gpointer user_data);
SYSPROF_AVAILABLE_IN_ALL
SysprofCaptureWriter *sysprof_capture_writer_new_from_env (gsize buffer_size);

7
src/libsysprof-capture/sysprof-collector.c
View File

@ -383,6 +383,8 @@ sysprof_collector_allocate (SysprofCaptureAddress alloc_addr,
if ((ev = mapped_ring_buffer_allocate (collector->buffer, len)))
{
gint n_addrs;
/* First take a backtrace, so that backtrace_func() can overwrite
* a little bit of data *BEFORE* ev->addrs as stratch space. This
* is useful to allow using unw_backtrace() or backtrace() to skip
@ -392,9 +394,9 @@ sysprof_collector_allocate (SysprofCaptureAddress alloc_addr,
* scratch space anyway.
*/
if (backtrace_func)
ev->n_addrs = backtrace_func (ev->addrs, MAX_UNWIND_DEPTH, backtrace_data);
n_addrs = backtrace_func (ev->addrs, MAX_UNWIND_DEPTH, backtrace_data);
else
ev->n_addrs = 0;
n_addrs = 0;
ev->frame.len = sizeof *ev + sizeof (SysprofCaptureAddress) * ev->n_addrs;
ev->frame.type = SYSPROF_CAPTURE_FRAME_ALLOCATION;
@ -404,6 +406,7 @@ sysprof_collector_allocate (SysprofCaptureAddress alloc_addr,
ev->tid = collector->tid;
ev->alloc_addr = alloc_addr;
ev->alloc_size = alloc_size;
ev->n_addrs = CLAMP (n_addrs, 0, MAX_UNWIND_DEPTH);
mapped_ring_buffer_advance (collector->buffer, ev->frame.len);
}

15
src/libsysprof/preload/sysprof-memory-collector.c
View File

@ -70,7 +70,7 @@ collector_init_ctor (void)
collector_ready = TRUE;
}
static guint
static gint
backtrace_func (SysprofCaptureAddress *addrs,
guint n_addrs,
gpointer user_data)
@ -82,7 +82,7 @@ backtrace_func (SysprofCaptureAddress *addrs,
* and subtract an offset from addrs to avoid having to
* copy frame pointers around.
*/
return unw_backtrace ((void **)addrs - 1, n_addrs);
return unw_backtrace ((void **)addrs - 1, n_addrs) - 1;
# else
static const gint skip = 1;
void **stack = alloca (n_addrs * sizeof (gpointer));
@ -94,13 +94,14 @@ backtrace_func (SysprofCaptureAddress *addrs,
#elif defined(HAVE_EXECINFO_H)
# if GLIB_SIZEOF_VOID_P == 8
/* See note on unw_backtrace() */
return backtrace ((void **)addrs - 1, n_addrs);
return backtrace ((void **)addrs - 1, n_addrs) - 1;
# else /* GLIB_SIZEOF_VOID_P != 8 */
static const gint skip = 1;
void **stack = alloca (n_addrs * sizeof (gpointer));
guint n = backtrace (stack, n_addrs);
for (guint i = 0; i < n; i++)
addrs[i] = GPOINTER_TO_SIZE (stack[i]);
return n;
gint n = backtrace (stack, n_addrs);
for (guint i = skip; i < n; i++)
addrs[i-skip] = GPOINTER_TO_SIZE (stack[i]);
return MAX (0, n - skip);
# endif /* GLIB_SIZEOF_VOID_P */
#else
return 0;