[binutils-gdb] [gdb/breakpoints] Fix longjmp master breakpoint with separate debug info
Tom de Vries
vries@sourceware.org
Thu Jan 28 09:59:45 GMT 2021
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2a7f6487d0a2f9a5f16d0f67904ac35100313eb1
commit 2a7f6487d0a2f9a5f16d0f67904ac35100313eb1
Author: Tom de Vries <tdevries@suse.de>
Date: Thu Jan 28 10:59:42 2021 +0100
[gdb/breakpoints] Fix longjmp master breakpoint with separate debug info
When running test-case gdb.base/longjmp.exp with target board unix/-m32, we
run into:
...
(gdb) next^M
Warning:^M
Cannot insert breakpoint 0.^M
Cannot access memory at address 0x7dbf7353^M
^M
__libc_siglongjmp (env=0x804a040 <env>, val=1) at longjmp.c:28^M
28 longjmps++;^M
(gdb) FAIL: gdb.base/longjmp.exp: next over longjmp(1)
...
The failure to access memory happens in i386_get_longjmp_target and is due to
glibc having pointer encryption (aka "pointer mangling" or "pointer guard") of
the long jump buffer. This is a known problem.
In create_longjmp_master_breakpoint (which attempts to install a master
longjmp breakpoint) a preference scheme is present, which installs a
probe breakpoint if a libc:longjmp probe is present, and otherwise falls back
to setting breakpoints at the names in the longjmp_names array.
But in fact, both the probe breakpoint and the longjmp_names breakpoints are
set. The latter ones are set when processing libc.so.debug, and the former
one when processing libc.so. In other words, this is the longjmp variant of
PR26881, which describes the same problem for master exception breakpoints.
This problem only triggers when the glibc debug info package is installed,
which is not due to the debug info itself in libc.so.debug, but due to the
minimal symbols (because create_longjmp_master_breakpoint uses minimal symbols
to translate the longjmp_names to addresses).
The problem doesn't trigger for -m64, because there tdep->jb_pc_offset is not
set.
Fix this similar to commit 1940319c0ef (the fix for PR26881): only install
longjmp_names breakpoints in libc.so/libc.so.debug if installing the
libc:longjmp probe in libc.so failed.
Tested on x86_64-linux.
gdb/ChangeLog:
2021-01-28 Tom de Vries <tdevries@suse.de>
PR breakpoints/27205
* breakpoint.c (create_longjmp_master_breakpoint_probe)
(create_longjmp_master_breakpoint_names): New function, factored out
of ...
(create_longjmp_master_breakpoint): ... here. Only try to install
longjmp_names breakpoints in libc.so/libc.so.debug if installing probe
breakpoint in libc.so failed.
Diff:
---
gdb/ChangeLog | 10 +++
gdb/breakpoint.c | 182 +++++++++++++++++++++++++++++++++----------------------
2 files changed, 118 insertions(+), 74 deletions(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 6cf6d40a247..f16a4d61be2 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,13 @@
+2021-01-28 Tom de Vries <tdevries@suse.de>
+
+ PR breakpoints/27205
+ * breakpoint.c (create_longjmp_master_breakpoint_probe)
+ (create_longjmp_master_breakpoint_names): New function, factored out
+ of ...
+ (create_longjmp_master_breakpoint): ... here. Only try to install
+ longjmp_names breakpoints in libc.so/libc.so.debug if installing probe
+ breakpoint in libc.so failed.
+
2021-01-27 Lancelot SIX <lsix@lancelotsix.com>
PR gdb/27133
diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 70a4d0e1690..70b0d88cb45 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -3327,100 +3327,134 @@ create_overlay_event_breakpoint (void)
}
}
-static void
-create_longjmp_master_breakpoint (void)
+/* Install a master longjmp breakpoint for OBJFILE using a probe. Return
+ true if a breakpoint was installed. */
+
+static bool
+create_longjmp_master_breakpoint_probe (objfile *objfile)
{
- scoped_restore_current_program_space restore_pspace;
+ struct gdbarch *gdbarch = objfile->arch ();
+ struct breakpoint_objfile_data *bp_objfile_data
+ = get_breakpoint_objfile_data (objfile);
- for (struct program_space *pspace : program_spaces)
+ if (!bp_objfile_data->longjmp_searched)
{
- set_current_program_space (pspace);
+ std::vector<probe *> ret
+ = find_probes_in_objfile (objfile, "libc", "longjmp");
- for (objfile *objfile : current_program_space->objfiles ())
+ if (!ret.empty ())
{
- int i;
- struct gdbarch *gdbarch;
- struct breakpoint_objfile_data *bp_objfile_data;
+ /* We are only interested in checking one element. */
+ probe *p = ret[0];
- gdbarch = objfile->arch ();
+ if (!p->can_evaluate_arguments ())
+ {
+ /* We cannot use the probe interface here,
+ because it does not know how to evaluate
+ arguments. */
+ ret.clear ();
+ }
+ }
+ bp_objfile_data->longjmp_probes = ret;
+ bp_objfile_data->longjmp_searched = 1;
+ }
- bp_objfile_data = get_breakpoint_objfile_data (objfile);
+ if (bp_objfile_data->longjmp_probes.empty ())
+ return false;
- if (!bp_objfile_data->longjmp_searched)
- {
- std::vector<probe *> ret
- = find_probes_in_objfile (objfile, "libc", "longjmp");
+ for (probe *p : bp_objfile_data->longjmp_probes)
+ {
+ struct breakpoint *b;
- if (!ret.empty ())
- {
- /* We are only interested in checking one element. */
- probe *p = ret[0];
+ b = create_internal_breakpoint (gdbarch,
+ p->get_relocated_address (objfile),
+ bp_longjmp_master,
+ &internal_breakpoint_ops);
+ b->location = new_probe_location ("-probe-stap libc:longjmp");
+ b->enable_state = bp_disabled;
+ }
- if (!p->can_evaluate_arguments ())
- {
- /* We cannot use the probe interface here,
- because it does not know how to evaluate
- arguments. */
- ret.clear ();
- }
- }
- bp_objfile_data->longjmp_probes = ret;
- bp_objfile_data->longjmp_searched = 1;
- }
+ return true;
+}
- if (!bp_objfile_data->longjmp_probes.empty ())
- {
- for (probe *p : bp_objfile_data->longjmp_probes)
- {
- struct breakpoint *b;
-
- b = create_internal_breakpoint (gdbarch,
- p->get_relocated_address (objfile),
- bp_longjmp_master,
- &internal_breakpoint_ops);
- b->location = new_probe_location ("-probe-stap libc:longjmp");
- b->enable_state = bp_disabled;
- }
+/* Install master longjmp breakpoints for OBJFILE using longjmp_names.
+ Return true if at least one breakpoint was installed. */
+
+static bool
+create_longjmp_master_breakpoint_names (objfile *objfile)
+{
+ struct gdbarch *gdbarch = objfile->arch ();
+ if (!gdbarch_get_longjmp_target_p (gdbarch))
+ return false;
+ struct breakpoint_objfile_data *bp_objfile_data
+ = get_breakpoint_objfile_data (objfile);
+ unsigned int installed_bp = 0;
+
+ for (int i = 0; i < NUM_LONGJMP_NAMES; i++)
+ {
+ struct breakpoint *b;
+ const char *func_name;
+ CORE_ADDR addr;
+ struct explicit_location explicit_loc;
+
+ if (msym_not_found_p (bp_objfile_data->longjmp_msym[i].minsym))
+ continue;
+
+ func_name = longjmp_names[i];
+ if (bp_objfile_data->longjmp_msym[i].minsym == NULL)
+ {
+ struct bound_minimal_symbol m;
+
+ m = lookup_minimal_symbol_text (func_name, objfile);
+ if (m.minsym == NULL)
+ {
+ /* Prevent future lookups in this objfile. */
+ bp_objfile_data->longjmp_msym[i].minsym = &msym_not_found;
continue;
}
+ bp_objfile_data->longjmp_msym[i] = m;
+ }
- if (!gdbarch_get_longjmp_target_p (gdbarch))
- continue;
+ addr = BMSYMBOL_VALUE_ADDRESS (bp_objfile_data->longjmp_msym[i]);
+ b = create_internal_breakpoint (gdbarch, addr, bp_longjmp_master,
+ &internal_breakpoint_ops);
+ initialize_explicit_location (&explicit_loc);
+ explicit_loc.function_name = ASTRDUP (func_name);
+ b->location = new_explicit_location (&explicit_loc);
+ b->enable_state = bp_disabled;
+ installed_bp++;
+ }
- for (i = 0; i < NUM_LONGJMP_NAMES; i++)
- {
- struct breakpoint *b;
- const char *func_name;
- CORE_ADDR addr;
- struct explicit_location explicit_loc;
+ return installed_bp > 0;
+}
- if (msym_not_found_p (bp_objfile_data->longjmp_msym[i].minsym))
- continue;
+/* Create a master longjmp breakpoint. */
- func_name = longjmp_names[i];
- if (bp_objfile_data->longjmp_msym[i].minsym == NULL)
- {
- struct bound_minimal_symbol m;
+static void
+create_longjmp_master_breakpoint (void)
+{
+ scoped_restore_current_program_space restore_pspace;
- m = lookup_minimal_symbol_text (func_name, objfile);
- if (m.minsym == NULL)
- {
- /* Prevent future lookups in this objfile. */
- bp_objfile_data->longjmp_msym[i].minsym = &msym_not_found;
- continue;
- }
- bp_objfile_data->longjmp_msym[i] = m;
- }
+ for (struct program_space *pspace : program_spaces)
+ {
+ set_current_program_space (pspace);
- addr = BMSYMBOL_VALUE_ADDRESS (bp_objfile_data->longjmp_msym[i]);
- b = create_internal_breakpoint (gdbarch, addr, bp_longjmp_master,
- &internal_breakpoint_ops);
- initialize_explicit_location (&explicit_loc);
- explicit_loc.function_name = ASTRDUP (func_name);
- b->location = new_explicit_location (&explicit_loc);
- b->enable_state = bp_disabled;
- }
+ for (objfile *obj : current_program_space->objfiles ())
+ {
+ /* Skip separate debug object, it's handled in the loop below. */
+ if (obj->separate_debug_objfile_backlink != nullptr)
+ continue;
+
+ /* Try a probe kind breakpoint on main objfile. */
+ if (create_longjmp_master_breakpoint_probe (obj))
+ continue;
+
+ /* Try longjmp_names kind breakpoints on main and separate_debug
+ objfiles. */
+ for (objfile *debug_objfile : obj->separate_debug_objfiles ())
+ if (create_longjmp_master_breakpoint_names (debug_objfile))
+ break;
}
}
}
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