Re: [PATCH v3] gdb: Fix false match issue in skip_prologue_using_linetable

[Tom de Vries <tdevries@suse.de>]

On 4/24/23 14:53, Luis Machado wrote:
> On 4/22/23 09:01, Tom de Vries via Gdb-patches wrote:
>> On 4/21/23 20:03, Kevin Buettner wrote:
>>> Hi Tom,
>>>
>>> On Tue, 18 Apr 2023 14:15:06 +0200
>>> Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> wrote:
>>>
>>>> On 4/18/23 14:09, Tom de Vries via Gdb-patches wrote:
>>>>> Co-Authored-By: WANG Rui <r@hev.cc> (fix, tiny change [1])
>>>>> Co-Authored-By: Tom de Vries <tdevries@suse.de> (test-case)
>>>>>
>>>>> [1] 
>>>>> https://www.gnu.org/prep/maintain/html_node/Legally-Significant.html
>>>>
>>>> I'm not used to deal with these matters, so I'd appreciate some
>>>> review/approval on this.  Is my copyright status assessment correct, 
>>>> and
>>>> did I write it up correctly?
>>>
>>> I refreshed my memory via the link you provided above.  Based on what
>>> is written there, I conclude that Wang Rui's change is not legally
>>> signficant for copyright purposes.
>>>
>>> Also, I've looked over the Rui's patch as well as your test case, and
>>> it looks good to me.  So...
>>>
>>> Approved-by: Kevin Buettner <kevinb@redhat.com>
>>>
>>
>> Hi Kevin,
>>
>> Thanks for review.
>>
>> Committed and also backported to gdb-13-branch, because it was a 12 -> 
>> 13 regression.
>>
>> Thanks,
>> - Tom
>>
> 
> For some reason aarch64 is grumpy with this test, and it FAIL's the last 
> comparison.
> 
> Maybe aarch64 is broken in this regard?

Hi Luis,

thanks for reporting this.

I could reproduce it on openSUSE Leap 15.4.

I think there are two independent problems:
- the aarch64 prologue analyzer walks past the end of the function
- the test-case assumes that the prologue analyzer will return the first
   insn in foo, rather that some insn in foo.

The WIP patch below addresses both issues, and allows the test-case to 
pass for me.

[ FWIW, alternatively using some "maint set skip-prologue" value from 
this RFC ( 
https://sourceware.org/pipermail/gdb-patches/2022-August/191343.html ) 
could also suffice to ignore the first problem. ]

Thanks,
- Tom

...
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index ec0e51bdaf7..d974595e48f 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -917,12 +917,13 @@ 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);
@@ -941,7 +942,8 @@ aarch64_skip_prologue (struct gdbarch *gdbarch, 
CORE_ADDR pc)
    limit_pc = skip_prologue_using_sal (gdbarch, pc);
    if (limit_pc == 0)
      limit_pc = pc + 128;       /* Magic.  */
-
+  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/testsuite/gdb.dwarf2/dw2-prologue-end-2.exp 
b/gdb/testsuite/gdb.dwarf2/dw2-prologue-end-2.exp
index 488f85f9674..c506cfd55cc 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-prologue-end-2.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-prologue-end-2.exp
@@ -95,15 +95,15 @@ if { $break_addr == "" } {

  # Get the "foo_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 }
...