Fix regression on aarch64-linux gdbserver

Commit 9a03f218 ("Fix gdb.base/watchpoint-unaligned.exp on aarch64")
fixed a watchpoint bug in gdb -- but did not touch the corresponding
code in gdbserver.

This patch moves the gdb code into gdb/nat, so that it can be shared
with gdbserver, and then changes gdbserver to use it, fixing the bug.

This is yet another case where having a single back end would prevent
bugs.

I tested this using the AdaCore internal gdb testsuite.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29423
Approved-By: Luis Machado <luis.machado@arm.com>

5 files changed, 126 insertions, 158 deletions

diff --git a/gdb/aarch64-nat.c b/gdb/aarch64-nat.c
index 894fb73095b..1ba9c4c19a7 100644
--- a/gdb/aarch64-nat.c
+++ b/gdb/aarch64-nat.c
@@ -224,121 +224,6 @@ aarch64_remove_watchpoint (CORE_ADDR addr, int len, enum target_hw_bp_type type,
   return ret;
 }
 
-/* See aarch64-nat.h.  */
-
-bool
-aarch64_stopped_data_address (const struct aarch64_debug_reg_state *state,
-			      CORE_ADDR addr_trap, CORE_ADDR *addr_p)
-{
-  bool found = false;
-  for (int phase = 0; phase <= 1; ++phase)
-    for (int i = aarch64_num_wp_regs - 1; i >= 0; --i)
-      {
-	if (!(state->dr_ref_count_wp[i]
-	      && DR_CONTROL_ENABLED (state->dr_ctrl_wp[i])))
-	  {
-	    /* Watchpoint disabled.  */
-	    continue;
-	  }
-
-	const enum target_hw_bp_type type
-	  = aarch64_watchpoint_type (state->dr_ctrl_wp[i]);
-	if (type == hw_execute)
-	  {
-	    /* Watchpoint disabled.  */
-	    continue;
-	  }
-
-	if (phase == 0)
-	  {
-	    /* Phase 0: No hw_write.  */
-	    if (type == hw_write)
-	      continue;
-	  }
-	else
-	  {
-	    /* Phase 1: Only hw_write.  */
-	    if (type != hw_write)
-	      continue;
-	  }
-
-	const unsigned int offset
-	  = aarch64_watchpoint_offset (state->dr_ctrl_wp[i]);
-	const unsigned int len
-	  = aarch64_watchpoint_length (state->dr_ctrl_wp[i]);
-	const CORE_ADDR addr_watch = state->dr_addr_wp[i] + offset;
-	const CORE_ADDR addr_watch_aligned
-	  = align_down (state->dr_addr_wp[i], AARCH64_HWP_MAX_LEN_PER_REG);
-	const CORE_ADDR addr_orig = state->dr_addr_orig_wp[i];
-
-	/* ADDR_TRAP reports the first address of the memory range
-	   accessed by the CPU, regardless of what was the memory
-	   range watched.  Thus, a large CPU access that straddles
-	   the ADDR_WATCH..ADDR_WATCH+LEN range may result in an
-	   ADDR_TRAP that is lower than the
-	   ADDR_WATCH..ADDR_WATCH+LEN range.  E.g.:
-
-	   addr: |   4	 |   5	 |   6	 |   7	 |   8	 |
-				 |---- range watched ----|
-		 |----------- range accessed ------------|
-
-	   In this case, ADDR_TRAP will be 4.
-
-	   The access size also can be larger than that of the watchpoint
-	   itself.  For instance, the access size of an stp instruction is 16.
-	   So, if we use stp to store to address p, and set a watchpoint on
-	   address p + 8, the reported ADDR_TRAP can be p + 8 (observed on
-	   RK3399 SOC). But it also can be p (observed on M1 SOC).  Checking
-	   for this situation introduces the possibility of false positives,
-	   so we only do this for hw_write watchpoints.  */
-	const CORE_ADDR max_access_size = type == hw_write ? 16 : 8;
-	const CORE_ADDR addr_watch_base = addr_watch_aligned -
-	  (max_access_size - AARCH64_HWP_MAX_LEN_PER_REG);
-	if (!(addr_trap >= addr_watch_base
-	      && addr_trap < addr_watch + len))
-	  {
-	    /* Not a match.  */
-	    continue;
-	  }
-
-	/* To match a watchpoint known to GDB core, we must never
-	   report *ADDR_P outside of any ADDR_WATCH..ADDR_WATCH+LEN
-	   range.  ADDR_WATCH <= ADDR_TRAP < ADDR_ORIG is a false
-	   positive on kernels older than 4.10.  See PR
-	   external/20207.  */
-	if (addr_p != nullptr)
-	  *addr_p = addr_orig;
-
-	if (phase == 0)
-	  {
-	    /* Phase 0: Return first match.  */
-	    return true;
-	  }
-
-	/* Phase 1.  */
-	if (addr_p == nullptr)
-	  {
-	    /* First match, and we don't need to report an address.  No need
-	       to look for other matches.  */
-	    return true;
-	  }
-
-	if (!found)
-	  {
-	    /* First match, and we need to report an address.  Look for other
-	       matches.  */
-	    found = true;
-	    continue;
-	  }
-
-	/* More than one match, and we need to return an address.  No need to
-	   look for further matches.  */
-	return false;
-      }
-
-  return found;
-}
-
 /* Define AArch64 maintenance commands.  */
 
 static void
diff --git a/gdb/aarch64-nat.h b/gdb/aarch64-nat.h
index 947d2805602..ec85524b2d4 100644
--- a/gdb/aarch64-nat.h
+++ b/gdb/aarch64-nat.h
@@ -45,14 +45,6 @@ struct aarch64_debug_reg_state *aarch64_get_debug_reg_state (pid_t pid);
 
 void aarch64_remove_debug_reg_state (pid_t pid);
 
-/* Helper for the "stopped_data_address" target method.  Returns TRUE
-   if a hardware watchpoint trap at ADDR_TRAP matches a set
-   watchpoint.  The address of the matched watchpoint is returned in
-   *ADDR_P.  */
-
-bool aarch64_stopped_data_address (const struct aarch64_debug_reg_state *state,
-				   CORE_ADDR addr_trap, CORE_ADDR *addr_p);
-
 /* Helper functions used by aarch64_nat_target below.  See their
    definitions.  */
 
diff --git a/gdb/nat/aarch64-hw-point.c b/gdb/nat/aarch64-hw-point.c
index b62c4627d96..6acee0fb814 100644
--- a/gdb/nat/aarch64-hw-point.c
+++ b/gdb/nat/aarch64-hw-point.c
@@ -645,3 +645,118 @@ aarch64_region_ok_for_watchpoint (CORE_ADDR addr, int len)
      the checking is costly.  */
   return 1;
 }
+
+/* See nat/aarch64-hw-point.h.  */
+
+bool
+aarch64_stopped_data_address (const struct aarch64_debug_reg_state *state,
+			      CORE_ADDR addr_trap, CORE_ADDR *addr_p)
+{
+  bool found = false;
+  for (int phase = 0; phase <= 1; ++phase)
+    for (int i = aarch64_num_wp_regs - 1; i >= 0; --i)
+      {
+	if (!(state->dr_ref_count_wp[i]
+	      && DR_CONTROL_ENABLED (state->dr_ctrl_wp[i])))
+	  {
+	    /* Watchpoint disabled.  */
+	    continue;
+	  }
+
+	const enum target_hw_bp_type type
+	  = aarch64_watchpoint_type (state->dr_ctrl_wp[i]);
+	if (type == hw_execute)
+	  {
+	    /* Watchpoint disabled.  */
+	    continue;
+	  }
+
+	if (phase == 0)
+	  {
+	    /* Phase 0: No hw_write.  */
+	    if (type == hw_write)
+	      continue;
+	  }
+	else
+	  {
+	    /* Phase 1: Only hw_write.  */
+	    if (type != hw_write)
+	      continue;
+	  }
+
+	const unsigned int offset
+	  = aarch64_watchpoint_offset (state->dr_ctrl_wp[i]);
+	const unsigned int len
+	  = aarch64_watchpoint_length (state->dr_ctrl_wp[i]);
+	const CORE_ADDR addr_watch = state->dr_addr_wp[i] + offset;
+	const CORE_ADDR addr_watch_aligned
+	  = align_down (state->dr_addr_wp[i], AARCH64_HWP_MAX_LEN_PER_REG);
+	const CORE_ADDR addr_orig = state->dr_addr_orig_wp[i];
+
+	/* ADDR_TRAP reports the first address of the memory range
+	   accessed by the CPU, regardless of what was the memory
+	   range watched.  Thus, a large CPU access that straddles
+	   the ADDR_WATCH..ADDR_WATCH+LEN range may result in an
+	   ADDR_TRAP that is lower than the
+	   ADDR_WATCH..ADDR_WATCH+LEN range.  E.g.:
+
+	   addr: |   4	 |   5	 |   6	 |   7	 |   8	 |
+				 |---- range watched ----|
+		 |----------- range accessed ------------|
+
+	   In this case, ADDR_TRAP will be 4.
+
+	   The access size also can be larger than that of the watchpoint
+	   itself.  For instance, the access size of an stp instruction is 16.
+	   So, if we use stp to store to address p, and set a watchpoint on
+	   address p + 8, the reported ADDR_TRAP can be p + 8 (observed on
+	   RK3399 SOC). But it also can be p (observed on M1 SOC).  Checking
+	   for this situation introduces the possibility of false positives,
+	   so we only do this for hw_write watchpoints.  */
+	const CORE_ADDR max_access_size = type == hw_write ? 16 : 8;
+	const CORE_ADDR addr_watch_base = addr_watch_aligned -
+	  (max_access_size - AARCH64_HWP_MAX_LEN_PER_REG);
+	if (!(addr_trap >= addr_watch_base
+	      && addr_trap < addr_watch + len))
+	  {
+	    /* Not a match.  */
+	    continue;
+	  }
+
+	/* To match a watchpoint known to GDB core, we must never
+	   report *ADDR_P outside of any ADDR_WATCH..ADDR_WATCH+LEN
+	   range.  ADDR_WATCH <= ADDR_TRAP < ADDR_ORIG is a false
+	   positive on kernels older than 4.10.  See PR
+	   external/20207.  */
+	if (addr_p != nullptr)
+	  *addr_p = addr_orig;
+
+	if (phase == 0)
+	  {
+	    /* Phase 0: Return first match.  */
+	    return true;
+	  }
+
+	/* Phase 1.  */
+	if (addr_p == nullptr)
+	  {
+	    /* First match, and we don't need to report an address.  No need
+	       to look for other matches.  */
+	    return true;
+	  }
+
+	if (!found)
+	  {
+	    /* First match, and we need to report an address.  Look for other
+	       matches.  */
+	    found = true;
+	    continue;
+	  }
+
+	/* More than one match, and we need to return an address.  No need to
+	   look for further matches.  */
+	return false;
+      }
+
+  return found;
+}
diff --git a/gdb/nat/aarch64-hw-point.h b/gdb/nat/aarch64-hw-point.h
index bdcca932e57..0d50eaab0de 100644
--- a/gdb/nat/aarch64-hw-point.h
+++ b/gdb/nat/aarch64-hw-point.h
@@ -110,6 +110,14 @@ unsigned int aarch64_watchpoint_offset (unsigned int ctrl);
 unsigned int aarch64_watchpoint_length (unsigned int ctrl);
 enum target_hw_bp_type aarch64_watchpoint_type (unsigned int ctrl);
 
+/* Helper for the "stopped_data_address" target method.  Returns TRUE
+   if a hardware watchpoint trap at ADDR_TRAP matches a set
+   watchpoint.  The address of the matched watchpoint is returned in
+   *ADDR_P.  */
+
+bool aarch64_stopped_data_address (const struct aarch64_debug_reg_state *state,
+				   CORE_ADDR addr_trap, CORE_ADDR *addr_p);
+
 int aarch64_handle_breakpoint (enum target_hw_bp_type type, CORE_ADDR addr,
 			       int len, int is_insert, ptid_t ptid,
 			       struct aarch64_debug_reg_state *state);
diff --git a/gdbserver/linux-aarch64-low.cc b/gdbserver/linux-aarch64-low.cc
index 5df67fccd08..da5c1fd0629 100644
--- a/gdbserver/linux-aarch64-low.cc
+++ b/gdbserver/linux-aarch64-low.cc
@@ -576,41 +576,9 @@ aarch64_target::low_stopped_data_address ()
 
   /* Check if the address matches any watched address.  */
   state = aarch64_get_debug_reg_state (pid_of (current_thread));
-  for (i = aarch64_num_wp_regs - 1; i >= 0; --i)
-    {
-      const unsigned int offset
-	= aarch64_watchpoint_offset (state->dr_ctrl_wp[i]);
-      const unsigned int len = aarch64_watchpoint_length (state->dr_ctrl_wp[i]);
-      const CORE_ADDR addr_watch = state->dr_addr_wp[i] + offset;
-      const CORE_ADDR addr_watch_aligned = align_down (state->dr_addr_wp[i], 8);
-      const CORE_ADDR addr_orig = state->dr_addr_orig_wp[i];
-
-      if (state->dr_ref_count_wp[i]
-	  && DR_CONTROL_ENABLED (state->dr_ctrl_wp[i])
-	  && addr_trap >= addr_watch_aligned
-	  && addr_trap < addr_watch + len)
-	{
-	  /* ADDR_TRAP reports the first address of the memory range
-	     accessed by the CPU, regardless of what was the memory
-	     range watched.  Thus, a large CPU access that straddles
-	     the ADDR_WATCH..ADDR_WATCH+LEN range may result in an
-	     ADDR_TRAP that is lower than the
-	     ADDR_WATCH..ADDR_WATCH+LEN range.  E.g.:
-
-	     addr: |   4   |   5   |   6   |   7   |   8   |
-				   |---- range watched ----|
-		   |----------- range accessed ------------|
-
-	     In this case, ADDR_TRAP will be 4.
-
-	     To match a watchpoint known to GDB core, we must never
-	     report *ADDR_P outside of any ADDR_WATCH..ADDR_WATCH+LEN
-	     range.  ADDR_WATCH <= ADDR_TRAP < ADDR_ORIG is a false
-	     positive on kernels older than 4.10.  See PR
-	     external/20207.  */
-	  return addr_orig;
-	}
-    }
+  CORE_ADDR result;
+  if (aarch64_stopped_data_address (state, addr_trap, &result))
+    return result;
 
   return (CORE_ADDR) 0;
 }