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[PATCH] [AArch64] Only check breakpoint alignment on inserting


This patch fixes the GDB internal error on AArch64 when running
watchpoint-fork.exp

top?bt 15
    at ../../binutils-gdb/gdb/common/errors.c:51
...
...
    at ../../binutils-gdb/gdb/nat/aarch64-linux-hw-point.c:465
    at ../../binutils-gdb/gdb/aarch64-linux-nat.c:657
    at ../../binutils-gdb/gdb/target-delegates.c:492

After the fork, GDB will physically remove the breakpoints from the child
process (in frame #14), but at that time, GDB doesn't create an inferior
yet for child, but inferior_ptid is set to child's ptid (in frame #13).
In aarch64_point_is_aligned, we'll get the regcache of current_lwp_ptid
to determine if the current process is 32-bit or 64-bit, so the inferior
can't be found, and the internal error is caused.

I don't find a better fix other than not checking alignment on removing
breakpoint.

gdb:

2015-11-23  Yao Qi  <yao.qi@linaro.org>

	* nat/aarch64-linux-hw-point.c (aarch64_dr_state_remove_one_point):
	Don't assert on alignment.
	(aarch64_handle_breakpoint): Only check alignment when IS_INSERT
	is true.
---
 gdb/nat/aarch64-linux-hw-point.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/gdb/nat/aarch64-linux-hw-point.c b/gdb/nat/aarch64-linux-hw-point.c
index dcbfa98..466823a 100644
--- a/gdb/nat/aarch64-linux-hw-point.c
+++ b/gdb/nat/aarch64-linux-hw-point.c
@@ -411,7 +411,6 @@ aarch64_dr_state_remove_one_point (struct aarch64_debug_reg_state *state,
 
   /* Set up state pointers.  */
   is_watchpoint = (type != hw_execute);
-  gdb_assert (aarch64_point_is_aligned (is_watchpoint, addr, len));
   if (is_watchpoint)
     {
       num_regs = aarch64_num_wp_regs;
@@ -460,13 +459,21 @@ aarch64_handle_breakpoint (enum target_hw_bp_type type, CORE_ADDR addr,
 			   int len, int is_insert,
 			   struct aarch64_debug_reg_state *state)
 {
-  /* The hardware breakpoint on AArch64 should always be 4-byte
-     aligned, but on AArch32, it can be 2-byte aligned.  */
-  if (!aarch64_point_is_aligned (0 /* is_watchpoint */ , addr, len))
-    return -1;
-
   if (is_insert)
-    return aarch64_dr_state_insert_one_point (state, type, addr, len);
+    {
+      /* The hardware breakpoint on AArch64 should always be 4-byte
+	 aligned, but on AArch32, it can be 2-byte aligned.  Note that
+	 we only check the alignment on inserting breakpoint because
+	 aarch64_point_is_aligned needs the inferior_ptid inferior's
+	 regcache to decide whether the inferior is 32-bit or 64-bit.
+	 However when GDB follows the parent process and detach breakpoints
+	 from child process, inferior_ptid is the child ptid, but the
+	 child inferior doesn't exist in GDB's view yet.  */
+      if (!aarch64_point_is_aligned (0 /* is_watchpoint */ , addr, len))
+	return -1;
+
+      return aarch64_dr_state_insert_one_point (state, type, addr, len);
+    }
   else
     return aarch64_dr_state_remove_one_point (state, type, addr, len);
 }
-- 
1.9.1


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