[PATCH] MIPS/Linux: Also recognize TRAP_BRKPT and TRAP_HWBKPT

[Pedro Alves <palves@redhat.com>]

Ref: https://sourceware.org/ml/gdb-patches/2016-02/msg00756.html

This makes the MIPS Linux backends recognize TRAP_BRKPT and
TRAP_HWBKPT in siginfo.si_code too, in addition to SI_KERNEL.  This is
in anticipation of a future kernel change.

On kernels that reports SI_KERNEL, we'll enter the "ambiguous" path of
save_stop_reason:

	  if (GDB_ARCH_IS_TRAP_BRKPT (siginfo.si_code)
	      && GDB_ARCH_IS_TRAP_HWBKPT (siginfo.si_code))
	    {
	      /* The si_code is ambiguous on this arch -- check debug
		 registers.  */
	      if (!check_stopped_by_watchpoint (lp))
		lp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
	    }

while on kernels that report the finer-grained si_code values, we'll
enter the corresponding branches:

	  else if (GDB_ARCH_IS_TRAP_BRKPT (siginfo.si_code))
	    {
	    }
	  else if (GDB_ARCH_IS_TRAP_HWBKPT (siginfo.si_code))
	    {
	      ...

gdb/ChangeLog:
2016-02-24  Pedro Alves  <palves@redhat.com>

	* nat/linux-ptrace.h [__mips__] (GDB_ARCH_IS_TRAP_BRKPT): Also
	accept TRAP_BRKPT.
	 [__mips__] (GDB_ARCH_IS_TRAP_HWBKPT): Also accept TRAP_HWBKPT.
---
 gdb/nat/linux-ptrace.h | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/gdb/nat/linux-ptrace.h b/gdb/nat/linux-ptrace.h
index b9123c9..86b1f29 100644
--- a/gdb/nat/linux-ptrace.h
+++ b/gdb/nat/linux-ptrace.h
@@ -140,8 +140,8 @@ struct buffer;
    in SPU code on a Cell/B.E.  However, SI_KERNEL is never seen
    on a SIGTRAP for any other reason.
 
-   The MIPS kernel uses SI_KERNEL for all kernel generated traps.
-   Since:
+   The MIPS kernel (up until 4.5 at least) uses SI_KERNEL for all
+   kernel generated traps.  Since:
 
      - MIPS doesn't do hardware single-step.
      - We don't need to care about exec SIGTRAPs --- we assume
@@ -152,6 +152,9 @@ struct buffer;
    software breakpoints and hardware watchpoints, which can be done by
    peeking the debug registers.
 
+   However, it is anticipated that later MIPS kernels will report
+   proper TRAP_BRKPT and TRAP_HWBKPT codes, so we also match them.
+
    The generic Linux target code should use GDB_ARCH_IS_TRAP_* instead
    of TRAP_* to abstract out these peculiarities.  */
 #if defined __i386__ || defined __x86_64__
@@ -161,8 +164,8 @@ struct buffer;
 # 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)
+# define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == SI_KERNEL || (X) == TRAP_BRKPT)
+# define GDB_ARCH_IS_TRAP_HWBKPT(X) ((X) == SI_KERNEL || (X) == TRAP_HWBKPT)
 #else
 # define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == TRAP_BRKPT)
 # define GDB_ARCH_IS_TRAP_HWBKPT(X) ((X) == TRAP_HWBKPT)
-- 
1.9.3