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authorPedro Alves <palves@redhat.com>2014-10-15 20:18:31 +0100
committerPedro Alves <palves@redhat.com>2014-10-15 20:18:31 +0100
commit7c16b83e0521a007e4d86fc30e334b41b01668b4 (patch)
tree4b2b8fbdaf92625694dfa3b894e7b74665dd718a /gdb/breakpoint.h
parent0cbcdb96eaba80fe8e94ccc2b6f1f382a467a04e (diff)
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Put single-step breakpoints on the bp_location chain
This patch makes single-step breakpoints "real" breakpoints on the global location list. There are several benefits to this: - It removes the currently limitation that only 2 single-step breakpoints can be inserted. See an example here of a discussion around a case that wants more than 2, possibly unbounded: https://sourceware.org/ml/gdb-patches/2014-03/msg00663.html - makes software single-step work on read-only code regions. The logic to convert a software breakpoint to a hardware breakpoint if the memory map says the breakpoint address is in read only memory is in insert_bp_location. Because software single-step breakpoints bypass all that go and straight to target_insert_breakpoint, we can't software single-step over read only memory. This patch removes that limitation, and adds a test that makes sure that works, by forcing a code region to read-only with "mem LOW HIGH ro" and then stepping through that. - Fixes PR breakpoints/9649 This is an assertion failure in insert_single_step_breakpoint in breakpoint.c, because we may leave stale single-step breakpoints behind on error. The tests for stepping through read-only regions exercise the root cause of the bug, which is that we leave single-step breakpoints behind if we fail to insert any single-step breakpoint. Deleting the single-step breakpoints in resume_cleanups, delete_just_stopped_threads_infrun_breakpoints, and fetch_inferior_event fixes this. Without that, we'd no longer hit the assertion, as that code is deleted, but we'd instead run into errors/warnings trying to insert/remove the stale breakpoints on next resume. - Paves the way to have multiple threads software single-stepping at the same time, leaving update_global_location_list to worry about duplicate locations. - Makes the moribund location machinery aware of software single-step breakpoints, paving the way to enable software single-step on non-stop, instead of forcing serialized displaced stepping for all single steps. - It's generaly cleaner. We no longer have to play games with single-step breakpoints inserted at the same address as regular breakpoints, like we recently had to do for 7.8. See this discussion: https://sourceware.org/ml/gdb-patches/2014-06/msg00052.html. Tested on x86_64 Fedora 20, on top of my 'single-step breakpoints on x86' series. gdb/ 2014-10-15 Pedro Alves <palves@redhat.com> PR breakpoints/9649 * breakpoint.c (single_step_breakpoints, single_step_gdbarch): Delete array globals. (single_step_breakpoints): New global. (breakpoint_xfer_memory): Remove special handling for single-step breakpoints. (update_breakpoints_after_exec): Delete bp_single_step breakpoints. (detach_breakpoints): Remove special handling for single-step breakpoints. (breakpoint_init_inferior): Delete bp_single_step breakpoints. (bpstat_stop_status): Add comment. (bpstat_what, bptype_string, print_one_breakpoint_location) (adjust_breakpoint_address, init_bp_location): Handle bp_single_step. (new_single_step_breakpoint): New function. (set_momentary_breakpoint, bkpt_remove_location): Remove special handling for single-step breakpoints. (insert_single_step_breakpoint, single_step_breakpoints_inserted) (remove_single_step_breakpoints, cancel_single_step_breakpoints): Rewrite. (detach_single_step_breakpoints, find_single_step_breakpoint): Delete functions. (breakpoint_has_location_inserted_here): New function. (single_step_breakpoint_inserted_here_p): Rewrite. * breakpoint.h: Remove FIXME. (enum bptype) <bp_single_step>: New enum value. (insert_single_step_breakpoint): Update comment. * infrun.c (resume_cleanups) (delete_step_thread_step_resume_breakpoint): Remove single-step breakpoints. (fetch_inferior_event): Install a cleanup that removes infrun breakpoints. (switch_back_to_stepped_thread) <expect thread advanced also>: Clear step-over info. gdb/testsuite/ 2014-10-15 Pedro Alves <palves@redhat.com> PR breakpoints/9649 * gdb.base/breakpoint-in-ro-region.c (main): Add more instructions. * gdb.base/breakpoint-in-ro-region.exp (probe_target_hardware_step): New procedure. (top level): Probe hardware stepping and hardware breakpoint support. Test stepping through a read-only region, with both "breakpoint auto-hw" on and off and both "always-inserted" on and off.
Diffstat (limited to 'gdb/breakpoint.h')
-rw-r--r--gdb/breakpoint.h13
1 files changed, 5 insertions, 8 deletions
diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
index b611057..7c563c1 100644
--- a/gdb/breakpoint.h
+++ b/gdb/breakpoint.h
@@ -47,18 +47,13 @@ struct linespec_sals;
/* Type of breakpoint. */
-/* FIXME In the future, we should fold all other breakpoint-like
- things into here. This includes:
-
- * single-step (for machines where we have to simulate single
- stepping) (probably, though perhaps it is better for it to look as
- much as possible like a single-step to wait_for_inferior). */
enum bptype
{
bp_none = 0, /* Eventpoint has been deleted */
bp_breakpoint, /* Normal breakpoint */
bp_hardware_breakpoint, /* Hardware assisted breakpoint */
+ bp_single_step, /* Software single-step */
bp_until, /* used by until command */
bp_finish, /* used by finish command */
bp_watchpoint, /* Watchpoint */
@@ -1461,8 +1456,10 @@ extern void add_solib_catchpoint (char *arg, int is_load, int is_temp,
deletes all breakpoints. */
extern void delete_command (char *arg, int from_tty);
-/* Manage a software single step breakpoint (or two). Insert may be
- called twice before remove is called. */
+/* Create and insert a new software single step breakpoint for the
+ current thread. May be called multiple times; each time will add a
+ new location to the set of potential addresses the next instruction
+ is at. */
extern void insert_single_step_breakpoint (struct gdbarch *,
struct address_space *,
CORE_ADDR);