[patch v6 12/21] frame, backtrace: allow targets to supply a frame unwinder

Markus Metzger
2013-09-20T11:30:53Z

Allow targets to supply their own target-specific frame unwinders; one for
normal frames and one for tailcall frames. If a target-specific unwinder
is supplied, it will be chosen before any other unwinder.

gdb/
2013-02-11 Jan Kratochvil <jan.kratochvil@redhat.com>

* dwarf2-frame.c (dwarf2_frame_cfa): Move UNWIND_UNAVAILABLE check
earlier.
* frame-unwind.c: Include target.h.
(frame_unwind_try_unwinder): New function with code from ...
(frame_unwind_find_by_frame): ... here. New variable
unwinder_from_target, call also target_get_unwinder,
target_get_tailcall_unwinder, and frame_unwind_try_unwinder for it.
* frame.c (get_frame_unwind_stop_reason): Unconditionally call
get_prev_frame_1.
* target.c (target_get_unwinder, target_get_tailcall_unwinder): New.
* target.h (struct target_ops): New fields to_get_unwinder and
to_get_tailcall_unwinder.
(target_get_unwinder, target_get_tailcall_unwinder): New declarations.

---
gdb/dwarf2-frame.c | 8 ++--
gdb/frame-unwind.c | 86 +++++++++++++++++++++++++++++++++++-----------------
gdb/frame.c | 9 ++----
gdb/target.c | 28 +++++++++++++++++
gdb/target.h | 11 +++++++
5 files changed, 104 insertions(+), 38 deletions(-)

diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c
index 5c88b03..2aff23e 100644
--- a/gdb/dwarf2-frame.c
+++ b/gdb/dwarf2-frame.c
@@ -1497,16 +1497,16 @@ dwarf2_frame_cfa (struct frame_info *this_frame)
{
while (get_frame_type (this_frame) == INLINE_FRAME)
this_frame = get_prev_frame (this_frame);
+ if (get_frame_unwind_stop_reason (this_frame) == UNWIND_UNAVAILABLE)
+ throw_error (NOT_AVAILABLE_ERROR,
+ _("can't compute CFA for this frame: "
+ "required registers or memory are unavailable"));
/* This restriction could be lifted if other unwinders are known to
compute the frame base in a way compatible with the DWARF
unwinder. */
if (!frame_unwinder_is (this_frame, &dwarf2_frame_unwind)
&& !frame_unwinder_is (this_frame, &dwarf2_tailcall_frame_unwind))
error (_("can't compute CFA for this frame"));
- if (get_frame_unwind_stop_reason (this_frame) == UNWIND_UNAVAILABLE)
- throw_error (NOT_AVAILABLE_ERROR,
- _("can't compute CFA for this frame: "
- "required registers or memory are unavailable"));
return get_frame_base (this_frame);
}
\f
diff --git a/gdb/frame-unwind.c b/gdb/frame-unwind.c
index ce2f6da..e163e73 100644
--- a/gdb/frame-unwind.c
+++ b/gdb/frame-unwind.c
@@ -27,6 +27,7 @@
#include "exceptions.h"
#include "gdb_assert.h"
#include "gdb_obstack.h"
+#include "target.h"

static struct gdbarch_data *frame_unwind_data;

@@ -88,6 +89,48 @@ frame_unwind_append_unwinder (struct gdbarch *gdbarch,
(*ip)->unwinder = unwinder;
}

+/* Call SNIFFER from UNWINDER. If it succeeded set UNWINDER for
+ THIS_FRAME and return 1. Otherwise the function keeps THIS_FRAME
+ unchanged and returns 0. */
+
+static int
+frame_unwind_try_unwinder (struct frame_info *this_frame, void **this_cache,
+ const struct frame_unwind *unwinder)
+{
+ struct cleanup *old_cleanup;
+ volatile struct gdb_exception ex;
+ int res = 0;
+
+ old_cleanup = frame_prepare_for_sniffer (this_frame, unwinder);
+
+ TRY_CATCH (ex, RETURN_MASK_ERROR)
+ {
+ res = unwinder->sniffer (unwinder, this_frame, this_cache);
+ }
+ if (ex.reason < 0 && ex.error == NOT_AVAILABLE_ERROR)
+ {
+ /* This usually means that not even the PC is available,
+ thus most unwinders aren't able to determine if they're
+ the best fit. Keep trying. Fallback prologue unwinders
+ should always accept the frame. */
+ do_cleanups (old_cleanup);
+ return 0;
+ }
+ else if (ex.reason < 0)
+ throw_exception (ex);
+ else if (res)
+ {
+ discard_cleanups (old_cleanup);
+ return 1;
+ }
+ else
+ {
+ do_cleanups (old_cleanup);
+ return 0;
+ }
+ gdb_assert_not_reached ("frame_unwind_try_unwinder");
+}
+
/* Iterate through sniffers for THIS_FRAME frame until one returns with an
unwinder implementation. THIS_FRAME->UNWIND must be NULL, it will get set
by this function. Possibly initialize THIS_CACHE. */
@@ -98,37 +141,24 @@ frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
struct gdbarch *gdbarch = get_frame_arch (this_frame);
struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
struct frame_unwind_table_entry *entry;
+ const struct frame_unwind *unwinder_from_target;
+
+ unwinder_from_target = target_get_unwinder ();
+ if (unwinder_from_target != NULL
+ && frame_unwind_try_unwinder (this_frame, this_cache,
+ unwinder_from_target))
+ return;
+
+ unwinder_from_target = target_get_tailcall_unwinder ();
+ if (unwinder_from_target != NULL
+ && frame_unwind_try_unwinder (this_frame, this_cache,
+ unwinder_from_target))
+ return;

for (entry = table->list; entry != NULL; entry = entry->next)
- {
- struct cleanup *old_cleanup;
- volatile struct gdb_exception ex;
- int res = 0;
-
- old_cleanup = frame_prepare_for_sniffer (this_frame, entry->unwinder);
-
- TRY_CATCH (ex, RETURN_MASK_ERROR)
- {
- res = entry->unwinder->sniffer (entry->unwinder, this_frame,
- this_cache);
- }
- if (ex.reason < 0 && ex.error == NOT_AVAILABLE_ERROR)
- {
- /* This usually means that not even the PC is available,
- thus most unwinders aren't able to determine if they're
- the best fit. Keep trying. Fallback prologue unwinders
- should always accept the frame. */
- }
- else if (ex.reason < 0)
- throw_exception (ex);
- else if (res)
- {
- discard_cleanups (old_cleanup);
- return;
- }
+ if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder))
+ return;

- do_cleanups (old_cleanup);
- }
internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed"));
}

diff --git a/gdb/frame.c b/gdb/frame.c
index d52c26a..5c080eb 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -2426,13 +2426,10 @@ get_frame_sp (struct frame_info *this_frame)
enum unwind_stop_reason
get_frame_unwind_stop_reason (struct frame_info *frame)
{
- /* If we haven't tried to unwind past this point yet, then assume
- that unwinding would succeed. */
- if (frame->prev_p == 0)
- return UNWIND_NO_REASON;
+ /* Fill-in STOP_REASON. */
+ get_prev_frame_1 (frame);
+ gdb_assert (frame->prev_p);

- /* Otherwise, we set a reason when we succeeded (or failed) to
- unwind. */
return frame->stop_reason;
}

diff --git a/gdb/target.c b/gdb/target.c
index 24511b3..c97dcfb 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -4462,6 +4462,34 @@ target_call_history_range (ULONGEST begin, ULONGEST end, int flags)
tcomplain ();
}

+/* See target.h. */
+
+const struct frame_unwind *
+target_get_unwinder (void)
+{
+ struct target_ops *t;
+
+ for (t = current_target.beneath; t != NULL; t = t->beneath)
+ if (t->to_get_unwinder != NULL)
+ return t->to_get_unwinder;
+
+ return NULL;
+}
+
+/* See target.h. */
+
+const struct frame_unwind *
+target_get_tailcall_unwinder (void)
+{
+ struct target_ops *t;
+
+ for (t = current_target.beneath; t != NULL; t = t->beneath)
+ if (t->to_get_tailcall_unwinder != NULL)
+ return t->to_get_tailcall_unwinder;
+
+ return NULL;
+}
+
static int
deprecated_debug_xfer_memory (CORE_ADDR memaddr, bfd_byte *myaddr, int len,
int write, struct mem_attrib *attrib,
diff --git a/gdb/target.h b/gdb/target.h
index 909ddf6..b86ea4e 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -886,6 +886,11 @@ struct target_ops
non-empty annex. */
int (*to_augmented_libraries_svr4_read) (void);

+ /* Those unwinders are tried before any other arch unwinders. Use NULL if
+ it is not used. */
+ const struct frame_unwind *to_get_unwinder;
+ const struct frame_unwind *to_get_tailcall_unwinder;
+
int to_magic;
/* Need sub-structure for target machine related rather than comm related?
*/
@@ -1767,6 +1772,12 @@ extern char *target_fileio_read_stralloc (const char *filename);

extern int target_core_of_thread (ptid_t ptid);

+/* See to_get_unwinder in struct target_ops. */
+extern const struct frame_unwind *target_get_unwinder (void);
+
+/* See to_get_tailcall_unwinder in struct target_ops. */
+extern const struct frame_unwind *target_get_tailcall_unwinder (void);
+
/* Verify that the memory in the [MEMADDR, MEMADDR+SIZE) range matches
the contents of [DATA,DATA+SIZE). Returns 1 if there's a match, 0
if there's a mismatch, and -1 if an error is encountered while
--
1.7.1