Fix PR30369 regression on aarch64/arm (PR30506)

The gdb.dwarf2/dw2-prologue-end-2.exp test was failing for both AArch64 and
Arm.

As Tom pointed out here (https://inbox.sourceware.org/gdb-patches/6663707c-4297-c2f2-a0bd-f3e84fc62aad@suse.de/),
there are issues with both the prologue skipper for AArch64 and Arm and an
incorrect assumption by the testcase.

This patch fixes both of AArch64's and Arm's prologue skippers to not skip past
the end of a function.  It also incorporates a fix to the testcase so it
doesn't assume the prologue skipper will stop at the first instruction of the
functions/labels.

Regression-tested on aarch64-linux/arm-linux Ubuntu 20.04/22.04 and
x86_64-linux Ubuntu 20.04.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30506

Co-Authored-By: Tom de Vries <tdevries@suse.de>
Co-Authored-By: Luis Machado <luis.machado@arm.com>

3 files changed, 32 insertions, 11 deletions

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index d8603c4..84a90b6 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -917,12 +917,15 @@ aarch64_analyze_prologue_test (void)
 static CORE_ADDR
 aarch64_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
 {
-  CORE_ADDR func_addr, limit_pc;
+  CORE_ADDR func_addr, func_end_addr, limit_pc;
 
   /* See if we can determine the end of the prologue via the symbol
      table.  If so, then return either PC, or the PC after the
      prologue, whichever is greater.  */
-  if (find_pc_partial_function (pc, NULL, &func_addr, NULL))
+  bool func_addr_found
+    = find_pc_partial_function (pc, NULL, &func_addr, &func_end_addr);
+
+  if (func_addr_found)
     {
       CORE_ADDR post_prologue_pc
 	= skip_prologue_using_sal (gdbarch, func_addr);
@@ -942,6 +945,9 @@ aarch64_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
   if (limit_pc == 0)
     limit_pc = pc + 128;	/* Magic.  */
 
+  limit_pc
+    = func_end_addr == 0? limit_pc : std::min (limit_pc, func_end_addr - 4);
+
   /* Try disassembling prologue.  */
   return aarch64_analyze_prologue (gdbarch, pc, limit_pc, NULL);
 }
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index d512875..a0f5955 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -1769,12 +1769,18 @@ arm_skip_stack_protector(CORE_ADDR pc, struct gdbarch *gdbarch)
 static CORE_ADDR
 arm_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
 {
-  CORE_ADDR func_addr, limit_pc;
+  CORE_ADDR func_addr, func_end_addr, limit_pc;
 
   /* See if we can determine the end of the prologue via the symbol table.
      If so, then return either PC, or the PC after the prologue, whichever
      is greater.  */
-  if (find_pc_partial_function (pc, NULL, &func_addr, NULL))
+  bool func_addr_found
+    = find_pc_partial_function (pc, NULL, &func_addr, &func_end_addr);
+
+  /* Whether the function is thumb mode or not.  */
+  bool func_is_thumb = false;
+
+  if (func_addr_found)
     {
       CORE_ADDR post_prologue_pc
 	= skip_prologue_using_sal (gdbarch, func_addr);
@@ -1811,7 +1817,8 @@ arm_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
 	     associate prologue code with the opening brace; so this
 	     lets us skip the first line if we think it is the opening
 	     brace.  */
-	  if (arm_pc_is_thumb (gdbarch, func_addr))
+	  func_is_thumb = arm_pc_is_thumb (gdbarch, func_addr);
+	  if (func_is_thumb)
 	    analyzed_limit = thumb_analyze_prologue (gdbarch, func_addr,
 						     post_prologue_pc, NULL);
 	  else
@@ -1837,6 +1844,14 @@ arm_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
   if (limit_pc == 0)
     limit_pc = pc + 64;          /* Magic.  */
 
+  /* Set the correct adjustment based on whether the function is thumb mode or
+     not.  We use it to get the address of the last instruction in the
+     function (as opposed to the first address of the next function).  */
+  CORE_ADDR adjustment = func_is_thumb? 2 : 4;
+
+  limit_pc
+    = func_end_addr == 0? limit_pc : std::min (limit_pc,
+					       func_end_addr - adjustment);
 
   /* Check if this is Thumb code.  */
   if (arm_pc_is_thumb (gdbarch, pc))
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-prologue-end-2.exp b/gdb/testsuite/gdb.dwarf2/dw2-prologue-end-2.exp
index 488f85f..e1872eb 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-prologue-end-2.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-prologue-end-2.exp
@@ -93,17 +93,17 @@ if { $break_addr == "" } {
     return
 }
 
-# Get the "foo_label" address.
+# Get the "bar_label" address.
 
-set foo_label_addr ""
-gdb_test_multiple "print /x &foo_label" "" {
+set bar_label_addr ""
+gdb_test_multiple "print /x &bar_label" "" {
     -re -wrap "= ($hex)" {
-	set foo_label_addr $expect_out(1,string)
+	set bar_label_addr $expect_out(1,string)
 	pass $gdb_test_name
     }
 }
 
-if { $foo_label_addr == "" } {
+if { $bar_label_addr == "" } {
     return
 }
 
@@ -115,4 +115,4 @@ gdb_test "print &foo_end == &bar_label" " = 1"
 # Check that the breakpoint is set at the expected address.  Regression test
 # for PR30369.
 
-gdb_assert { $break_addr == $foo_label_addr }
+gdb_assert { $break_addr < $bar_label_addr }