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http://sourceware.org/ml/gdb-patches/2015-02/msg00734.html
Subject: [PATCH 7/8] gdbserver/Linux: Use TRAP_BRKPT/TRAP_HWBPT
This patch adjusts gdbserver's Linux backend to tell gdbserver core
(and ultimately GDB) whether a trap was caused by a breakpoint.
It teaches the backend to get that information out of the si_code of
the SIGTRAP siginfo.
gdb/gdbserver/ChangeLog:
2015-02-25 Pedro Alves <palves@redhat.com>
* linux-low.c (check_stopped_by_breakpoint) [USE_SIGTRAP_SIGINFO]:
Decide whether a breakpoint triggered based on the SIGTRAP's
siginfo.si_code.
(thread_still_has_status_pending_p) [USE_SIGTRAP_SIGINFO]: Don't check whether a
breakpoint is inserted if relying on SIGTRAP's siginfo.si_code.
(linux_low_filter_event): Check for breakpoints before checking
watchpoints.
(linux_wait_1): Don't re-increment the PC if relying on SIGTRAP's
siginfo.si_code.
(linux_stopped_by_sw_breakpoint)
(linux_supports_stopped_by_sw_breakpoint)
(linux_stopped_by_hw_breakpoint)
(linux_supports_stopped_by_hw_breakpoint): New functions.
(linux_target_ops): Install new target methods.
---
gdb/gdbserver/linux-low.c | 122 +++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 116 insertions(+), 6 deletions(-)
Index: gdb-7.6.1/gdb/gdbserver/linux-low.c
===================================================================
--- gdb-7.6.1.orig/gdb/gdbserver/linux-low.c 2016-03-13 21:42:34.115589901 +0100
+++ gdb-7.6.1/gdb/gdbserver/linux-low.c 2016-03-13 21:45:00.625644976 +0100
@@ -1360,6 +1360,8 @@
return (struct lwp_info*) find_inferior (&all_lwps, same_lwp, &ptid);
}
+static void save_stop_reason (struct lwp_info *lwp);
+
static struct lwp_info *
linux_wait_for_lwp (ptid_t ptid, int *wstatp, int options)
{
@@ -1465,6 +1467,10 @@
current_inferior = saved_inferior;
}
+
+ /* RHEL */
+ if (!child->stopped_by_watchpoint)
+ save_stop_reason (child);
}
/* Store the STOP_PC, with adjustment applied. This depends on the
@@ -1847,6 +1853,47 @@
being stepped. */
ptid_t step_over_bkpt;
+// gdb/nat/linux-ptrace.h
+#if defined __i386__ || defined __x86_64__
+# define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == SI_KERNEL)
+# define GDB_ARCH_IS_TRAP_HWBKPT(X) ((X) == TRAP_HWBKPT)
+#elif defined __powerpc__
+# define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == SI_KERNEL || (X) == TRAP_BRKPT)
+# define GDB_ARCH_IS_TRAP_HWBKPT(X) ((X) == TRAP_HWBKPT)
+#elif defined __mips__
+# define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == SI_KERNEL)
+# define GDB_ARCH_IS_TRAP_HWBKPT(X) ((X) == SI_KERNEL)
+#else
+# define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == TRAP_BRKPT)
+# define GDB_ARCH_IS_TRAP_HWBKPT(X) ((X) == TRAP_HWBKPT)
+#endif
+
+// gdb/nat/linux-ptrace.h
+#ifndef TRAP_HWBKPT
+# define TRAP_HWBKPT 4
+#endif
+
+static void
+save_stop_reason (struct lwp_info *lwp)
+{
+ siginfo_t siginfo;
+
+ if (ptrace (PTRACE_GETSIGINFO, lwpid_of (lwp),
+ (PTRACE_ARG3_TYPE) 0, &siginfo) == 0)
+ {
+ if (siginfo.si_signo == SIGTRAP)
+ {
+ if (GDB_ARCH_IS_TRAP_HWBKPT (siginfo.si_code))
+ {
+ /* This can indicate either a hardware breakpoint or
+ hardware watchpoint. Check debug registers. */
+// if (!check_stopped_by_watchpoint (lwp))
+ lwp->stopped_by_hw_breakpoint = 1;
+ }
+ }
+ }
+}
+
/* Wait for an event from child PID. If PID is -1, wait for any
child. Store the stop status through the status pointer WSTAT.
OPTIONS is passed to the waitpid call. Return 0 if no child stop
@@ -3332,6 +3396,7 @@
errno = 0;
lwp->stopped = 0;
lwp->stopped_by_watchpoint = 0;
+ lwp->stopped_by_hw_breakpoint = 0;
lwp->stepping = step;
ptrace (step ? PTRACE_SINGLESTEP : PTRACE_CONT, lwpid_of (lwp),
(PTRACE_ARG3_TYPE) 0,
@@ -4856,6 +4921,26 @@
return 1;
}
+/* Implement the to_stopped_by_hw_breakpoint target_ops
+ method. */
+
+static int
+linux_stopped_by_hw_breakpoint (void)
+{
+ struct lwp_info *lwp = get_thread_lwp (current_inferior);
+
+ return lwp->stopped_by_hw_breakpoint;
+}
+
+/* Implement the to_supports_stopped_by_hw_breakpoint target_ops
+ method. */
+
+static int
+linux_supports_stopped_by_hw_breakpoint (void)
+{
+ return 1; // RHEL
+}
+
static int
linux_stopped_by_watchpoint (void)
{
@@ -5946,6 +6031,8 @@
linux_read_auxv,
linux_insert_point,
linux_remove_point,
+ linux_stopped_by_hw_breakpoint,
+ linux_supports_stopped_by_hw_breakpoint,
linux_stopped_by_watchpoint,
linux_stopped_data_address,
#if defined(__UCLIBC__) && defined(HAS_NOMMU)
Index: gdb-7.6.1/gdb/gdbserver/linux-low.h
===================================================================
--- gdb-7.6.1.orig/gdb/gdbserver/linux-low.h 2016-03-13 21:45:52.861021138 +0100
+++ gdb-7.6.1/gdb/gdbserver/linux-low.h 2016-03-13 21:46:00.668077363 +0100
@@ -223,6 +223,9 @@
watchpoint trap. */
int stopped_by_watchpoint;
+ /* RHEL: TARGET_STOPPED_BY_HW_BREAKPOINT */
+ int stopped_by_hw_breakpoint;
+
/* On architectures where it is possible to know the data address of
a triggered watchpoint, STOPPED_DATA_ADDRESS is non-zero, and
contains such data address. Only valid if STOPPED_BY_WATCHPOINT