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Use signal information to determine SIGTRAP type for FreeBSD. 

Use the signal code from siginfo_t to distinguish SIGTRAP events due
to trace traps (TRAP_TRACE) and software breakpoints (TRAP_BRKPT).
For software breakpoints, adjust the PC when the event is reported as
part of the API when supplying "stopped_by_sw_breakpoint".  Currently
FreeBSD only supports hardware watchpoints and breakpoints on x86
which are reported as trace traps.  Signal information is not used on
MIPS and sparc64 kernels which do not reliably report TRAP_BRKPT for
software breakpoints.

gdb/ChangeLog:

	* fbsd-nat.c: Include "inf-ptrace.h".
	(USE_SIGTRAP_SIGINFO): Conditionally define.
	[USE_SIGTRAP_SIGINFO] (fbsd_handle_debug_trap): New function.
	(fbsd_wait) [USE_SIGTRAP_SIGINFO]: Call "fbsd_handle_debug_trap".
	[USE_SIGTRAP_SIGINFO] (fbsd_stopped_by_sw_breakpoint): New
	function.
	[USE_SIGTRAP_SIGINFO] (fbsd_supports_stopped_by_sw_breakpoint):
	Likewise.
	[USE_SIGTRAP_SIGINFO] (fbsd_supports_stopped_by_hw_breakpoint):
	Likewise.
	(fbsd_nat_add_target) [USE_SIGTRAP_SIGINFO]: Set
	"stopped_by_sw_breakpoint", "supports_stopped_by_sw_breakpoint",
	"supports_stopped_by_hw_breakpoint" target methods.
This commit is contained in:
John Baldwin 2018-03-03 21:25:33 -08:00
parent 386a867618
commit 7efba073e2
2 changed files with 123 additions and 0 deletions
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16
gdb/ChangeLog
View File

@ -1,3 +1,19 @@
2018-03-04 John Baldwin <jhb@FreeBSD.org>
* fbsd-nat.c: Include "inf-ptrace.h".
(USE_SIGTRAP_SIGINFO): Conditionally define.
[USE_SIGTRAP_SIGINFO] (fbsd_handle_debug_trap): New function.
(fbsd_wait) [USE_SIGTRAP_SIGINFO]: Call "fbsd_handle_debug_trap".
[USE_SIGTRAP_SIGINFO] (fbsd_stopped_by_sw_breakpoint): New
function.
[USE_SIGTRAP_SIGINFO] (fbsd_supports_stopped_by_sw_breakpoint):
Likewise.
[USE_SIGTRAP_SIGINFO] (fbsd_supports_stopped_by_hw_breakpoint):
Likewise.
(fbsd_nat_add_target) [USE_SIGTRAP_SIGINFO]: Set
"stopped_by_sw_breakpoint", "supports_stopped_by_sw_breakpoint",
"supports_stopped_by_hw_breakpoint" target methods.
2018-03-04 John Baldwin <jhb@FreeBSD.org>
* NEWS (Changes since GDB 8.1): Add "set/show debug fbsd-nat".

107
gdb/fbsd-nat.c
View File

@ -26,6 +26,7 @@
#include "gdbcmd.h"
#include "gdbthread.h"
#include "gdb_wait.h"
#include "inf-ptrace.h"
#include <sys/types.h>
#include <sys/procfs.h>
#include <sys/ptrace.h>
@ -45,6 +46,14 @@
#include <list>
#ifdef TRAP_BRKPT
/* MIPS does not set si_code for SIGTRAP. sparc64 reports
non-standard values in si_code for SIGTRAP. */
# if !defined(__mips__) && !defined(__sparc64__)
# define USE_SIGTRAP_SIGINFO
# endif
#endif
/* Return the name of a file that can be opened to get the symbols for
the child process identified by PID. */
@ -1187,6 +1196,56 @@ fbsd_resume (struct target_ops *ops,
super_resume (ops, ptid, step, signo);
}
#ifdef USE_SIGTRAP_SIGINFO
/* Handle breakpoint and trace traps reported via SIGTRAP. If the
trap was a breakpoint or trace trap that should be reported to the
core, return true. */
static bool
fbsd_handle_debug_trap (struct target_ops *ops, ptid_t ptid,
const struct ptrace_lwpinfo &pl)
{
/* Ignore traps without valid siginfo or for signals other than
SIGTRAP. */
if (! (pl.pl_flags & PL_FLAG_SI) || pl.pl_siginfo.si_signo != SIGTRAP)
return false;
/* Trace traps are either a single step or a hardware watchpoint or
breakpoint. */
if (pl.pl_siginfo.si_code == TRAP_TRACE)
{
if (debug_fbsd_nat)
fprintf_unfiltered (gdb_stdlog,
"FNAT: trace trap for LWP %ld\n", ptid.lwp ());
return true;
}
if (pl.pl_siginfo.si_code == TRAP_BRKPT)
{
/* Fixup PC for the software breakpoint. */
struct regcache *regcache = get_thread_regcache (ptid);
struct gdbarch *gdbarch = regcache->arch ();
int decr_pc = gdbarch_decr_pc_after_break (gdbarch);
if (debug_fbsd_nat)
fprintf_unfiltered (gdb_stdlog,
"FNAT: sw breakpoint trap for LWP %ld\n",
ptid.lwp ());
if (decr_pc != 0)
{
CORE_ADDR pc;
pc = regcache_read_pc (regcache);
regcache_write_pc (regcache, pc - decr_pc);
}
return true;
}
return false;
}
#endif
/* Wait for the child specified by PTID to do something. Return the
process ID of the child, or MINUS_ONE_PTID in case of error; store
the status in *OURSTATUS. */
@ -1372,6 +1431,11 @@ fbsd_wait (struct target_ops *ops,
}
#endif
#ifdef USE_SIGTRAP_SIGINFO
if (fbsd_handle_debug_trap (ops, wptid, pl))
return wptid;
#endif
/* Note that PL_FLAG_SCE is set for any event reported while
a thread is executing a system call in the kernel. In
particular, signals that interrupt a sleep in a system
@ -1410,6 +1474,42 @@ fbsd_wait (struct target_ops *ops,
}
}
#ifdef USE_SIGTRAP_SIGINFO
/* Implement the "to_stopped_by_sw_breakpoint" target_ops method. */
static int
fbsd_stopped_by_sw_breakpoint (struct target_ops *ops)
{
struct ptrace_lwpinfo pl;
if (ptrace (PT_LWPINFO, get_ptrace_pid (inferior_ptid), (caddr_t) &pl,
sizeof pl) == -1)
return 0;
return ((pl.pl_flags & PL_FLAG_SI)
&& pl.pl_siginfo.si_signo == SIGTRAP
&& pl.pl_siginfo.si_code == TRAP_BRKPT);
}
/* Implement the "to_supports_stopped_by_sw_breakpoint" target_ops
method. */
static int
fbsd_supports_stopped_by_sw_breakpoint (struct target_ops *ops)
{
return 1;
}
/* Implement the "to_supports_stopped_by_hw_breakpoint" target_ops
method. */
static int
fbsd_supports_stopped_by_hw_breakpoint (struct target_ops *ops)
{
return ops->to_stopped_by_hw_breakpoint != NULL;
}
#endif
#ifdef TDP_RFPPWAIT
/* Target hook for follow_fork. On entry and at return inferior_ptid is
the ptid of the followed inferior. */
@ -1560,6 +1660,13 @@ fbsd_nat_add_target (struct target_ops *t)
t->to_wait = fbsd_wait;
t->to_post_startup_inferior = fbsd_post_startup_inferior;
t->to_post_attach = fbsd_post_attach;
#ifdef USE_SIGTRAP_SIGINFO
t->to_stopped_by_sw_breakpoint = fbsd_stopped_by_sw_breakpoint;
t->to_supports_stopped_by_sw_breakpoint
= fbsd_supports_stopped_by_sw_breakpoint;
t->to_supports_stopped_by_hw_breakpoint
= fbsd_supports_stopped_by_hw_breakpoint;
#endif
#ifdef TDP_RFPPWAIT
t->to_follow_fork = fbsd_follow_fork;
t->to_insert_fork_catchpoint = fbsd_insert_fork_catchpoint;