gdbstub: update aarch64-core.xml

[PATCH] gdbstub: update aarch64-core.xml

Posted by Manos Pitsidianakis 7 months ago

Update aarch64-core.xml to include field definitions for PSTATE, which
in gdb is modelled in the cpsr (current program status register)
pseudo-register, named after the actual cpsr register in armv7.

Defining the fields layout of the register allows easy inspection of for
example, the current exception level (EL):

For example. Before booting a Linux guest, EL=2, but after booting and
Ctrl-C'ing in gdb, we get EL=0:

  (gdb) info registers $cpsr
  cpsr           0x20402009          [ SP EL=2 BTYPE=0 PAN C ]
  (gdb) cont
  Continuing.
  ^C
  Thread 2 received signal SIGINT, Interrupt.
  0x0000ffffaaff286c in ?? ()
  (gdb) info registers $cpsr
  cpsr           0x20001000          [ EL=0 BTYPE=0 SSBS C ]

The aarch64-core.xml has been updated to match exactly the version
retrieved from upstream gdb, retrieved in 2025-05-19 from HEAD commit
9f4dc0b137c86f6ff2098cb1ab69442c69d6023d.

https://sourceware.org/git/?p=binutils-gdb.git;a=tree;h=9f4dc0b137c86f6ff2098cb1ab69442c69d6023d

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
---
 gdb-xml/aarch64-core.xml | 52 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 2 deletions(-)

diff --git a/gdb-xml/aarch64-core.xml b/gdb-xml/aarch64-core.xml
index e1e9dc3f91370111eae36380449cddabc31265a4..b8046510b9a085d30463d37b3ecc8d435f5fb7a4 100644
--- a/gdb-xml/aarch64-core.xml
+++ b/gdb-xml/aarch64-core.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<!-- Copyright (C) 2009-2012 Free Software Foundation, Inc.
+<!-- Copyright (C) 2009-2025 Free Software Foundation, Inc.
      Contributed by ARM Ltd.
 
      Copying and distribution of this file, with or without modification,
@@ -42,5 +42,53 @@
   <reg name="sp" bitsize="64" type="data_ptr"/>
 
   <reg name="pc" bitsize="64" type="code_ptr"/>
-  <reg name="cpsr" bitsize="32"/>
+
+  <flags id="cpsr_flags" size="4">
+    <!-- Stack Pointer.  -->
+    <field name="SP" start="0" end="0"/>
+
+    <!-- Exception Level.  -->
+    <field name="EL" start="2" end="3"/>
+    <!-- Execution state.  -->
+    <field name="nRW" start="4" end="4"/>
+
+    <!-- FIQ interrupt mask.  -->
+    <field name="F" start="6" end="6"/>
+    <!-- IRQ interrupt mask.  -->
+    <field name="I" start="7" end="7"/>
+    <!-- SError interrupt mask.  -->
+    <field name="A" start="8" end="8"/>
+    <!-- Debug exception mask.  -->
+    <field name="D" start="9" end="9"/>
+
+    <!-- ARMv8.5-A: Branch Target Identification BTYPE.  -->
+    <field name="BTYPE" start="10" end="11"/>
+
+    <!-- ARMv8.0-A: Speculative Store Bypass.  -->
+    <field name="SSBS" start="12" end="12"/>
+
+    <!-- Illegal Execution state.  -->
+    <field name="IL" start="20" end="20"/>
+    <!-- Software Step.  -->
+    <field name="SS" start="21" end="21"/>
+    <!-- ARMv8.1-A: Privileged Access Never.  -->
+    <field name="PAN" start="22" end="22"/>
+    <!-- ARMv8.2-A: User Access Override.  -->
+    <field name="UAO" start="23" end="23"/>
+    <!-- ARMv8.4-A: Data Independent Timing.  -->
+    <field name="DIT" start="24" end="24"/>
+    <!-- ARMv8.5-A: Tag Check Override.  -->
+    <field name="TCO" start="25" end="25"/>
+
+    <!-- Overflow Condition flag.  -->
+    <field name="V" start="28" end="28"/>
+    <!-- Carry Condition flag.  -->
+    <field name="C" start="29" end="29"/>
+    <!-- Zero Condition flag.  -->
+    <field name="Z" start="30" end="30"/>
+    <!-- Negative Condition flag.  -->
+    <field name="N" start="31" end="31"/>
+  </flags>
+  <reg name="cpsr" bitsize="32" type="cpsr_flags"/>
+
 </feature>

---
base-commit: 757a34115e7491744a63dfc3d291fd1de5297ee2
change-id: 20250519-gdbstub-aarch64-pstate-xml-d90bac349712

--
γαῖα πυρί μιχθήτω

Re: [PATCH] gdbstub: update aarch64-core.xml

Posted by Alex Bennée 7 months ago

Manos Pitsidianakis <manos.pitsidianakis@linaro.org> writes:

> Update aarch64-core.xml to include field definitions for PSTATE, which
> in gdb is modelled in the cpsr (current program status register)
> pseudo-register, named after the actual cpsr register in armv7.
>
> Defining the fields layout of the register allows easy inspection of for
> example, the current exception level (EL):
>
> For example. Before booting a Linux guest, EL=2, but after booting and
> Ctrl-C'ing in gdb, we get EL=0:
>
>   (gdb) info registers $cpsr
>   cpsr           0x20402009          [ SP EL=2 BTYPE=0 PAN C ]
>   (gdb) cont
>   Continuing.
>   ^C
>   Thread 2 received signal SIGINT, Interrupt.
>   0x0000ffffaaff286c in ?? ()
>   (gdb) info registers $cpsr
>   cpsr           0x20001000          [ EL=0 BTYPE=0 SSBS C ]
>
> The aarch64-core.xml has been updated to match exactly the version
> retrieved from upstream gdb, retrieved in 2025-05-19 from HEAD commit
> 9f4dc0b137c86f6ff2098cb1ab69442c69d6023d.
>
> https://sourceware.org/git/?p=binutils-gdb.git;a=tree;h=9f4dc0b137c86f6ff2098cb1ab69442c69d6023d
>
> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>

Queued to gdbstub/next, thanks.

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro

Re: [PATCH] gdbstub: update aarch64-core.xml

Posted by Manos Pitsidianakis 7 months ago

On Mon, 19 May 2025 15:55, Alex Bennée <alex.bennee@linaro.org> wrote:
>Manos Pitsidianakis <manos.pitsidianakis@linaro.org> writes:
>
>> Update aarch64-core.xml to include field definitions for PSTATE, which
>> in gdb is modelled in the cpsr (current program status register)
>> pseudo-register, named after the actual cpsr register in armv7.
>>
>> Defining the fields layout of the register allows easy inspection of for
>> example, the current exception level (EL):
>>
>> For example. Before booting a Linux guest, EL=2, but after booting and
>> Ctrl-C'ing in gdb, we get EL=0:
>>
>>   (gdb) info registers $cpsr
>>   cpsr           0x20402009          [ SP EL=2 BTYPE=0 PAN C ]
>>   (gdb) cont
>>   Continuing.
>>   ^C
>>   Thread 2 received signal SIGINT, Interrupt.
>>   0x0000ffffaaff286c in ?? ()
>>   (gdb) info registers $cpsr
>>   cpsr           0x20001000          [ EL=0 BTYPE=0 SSBS C ]
>>
>> The aarch64-core.xml has been updated to match exactly the version
>> retrieved from upstream gdb, retrieved in 2025-05-19 from HEAD commit
>> 9f4dc0b137c86f6ff2098cb1ab69442c69d6023d.
>>
>> https://sourceware.org/git/?p=binutils-gdb.git;a=tree;h=9f4dc0b137c86f6ff2098cb1ab69442c69d6023d
>>
>> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
>
>Queued to gdbstub/next, thanks.
>

Would patches for the field system registers (NZCV, CurrentEL, DAIF, 
SPSel) be acceptable?

If yes, I think defining them in the static core xml is cleaner than 
generating them dynamically in "system-registers.xml" like we do with 
arm_gen_dynamic_sysreg_feature() but both can work. The drawback would 
be that we wouldn't match upstream gdb's core xml schema anymore. (Maybe 
we  can add a new xml include "pstate.xml" instead)

Re: [PATCH] gdbstub: update aarch64-core.xml

Posted by Alex Bennée 6 months, 4 weeks ago

Manos Pitsidianakis <manos.pitsidianakis@linaro.org> writes:

> On Mon, 19 May 2025 15:55, Alex Bennée <alex.bennee@linaro.org> wrote:
>>Manos Pitsidianakis <manos.pitsidianakis@linaro.org> writes:
>>
>>> Update aarch64-core.xml to include field definitions for PSTATE, which
>>> in gdb is modelled in the cpsr (current program status register)
>>> pseudo-register, named after the actual cpsr register in armv7.
>>>
>>> Defining the fields layout of the register allows easy inspection of for
>>> example, the current exception level (EL):
>>>
>>> For example. Before booting a Linux guest, EL=2, but after booting and
>>> Ctrl-C'ing in gdb, we get EL=0:
>>>
>>>   (gdb) info registers $cpsr
>>>   cpsr           0x20402009          [ SP EL=2 BTYPE=0 PAN C ]
>>>   (gdb) cont
>>>   Continuing.
>>>   ^C
>>>   Thread 2 received signal SIGINT, Interrupt.
>>>   0x0000ffffaaff286c in ?? ()
>>>   (gdb) info registers $cpsr
>>>   cpsr           0x20001000          [ EL=0 BTYPE=0 SSBS C ]
>>>
>>> The aarch64-core.xml has been updated to match exactly the version
>>> retrieved from upstream gdb, retrieved in 2025-05-19 from HEAD commit
>>> 9f4dc0b137c86f6ff2098cb1ab69442c69d6023d.
>>>
>>> https://sourceware.org/git/?p=binutils-gdb.git;a=tree;h=9f4dc0b137c86f6ff2098cb1ab69442c69d6023d
>>>
>>> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
>>
>>Queued to gdbstub/next, thanks.
>>
>
> Would patches for the field system registers (NZCV, CurrentEL, DAIF, 
> SPSel) be acceptable?
>
> If yes, I think defining them in the static core xml is cleaner than 
> generating them dynamically in "system-registers.xml" like we do with 
> arm_gen_dynamic_sysreg_feature() but both can work. The drawback would 
> be that we wouldn't match upstream gdb's core xml schema anymore. (Maybe 
> we  can add a new xml include "pstate.xml" instead)

You could submit to the gdb core schema first (surely they would also
benefit from the patch?).


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro