Re: [PATCH v3 1/5] [PATCH 1/5] gdb/aarch64: Add POR_EL0 register support for FEAT_S1POE

[Srinath Parvathaneni <Srinath.Parvathaneni@arm.com>]

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Hi,

>On 25/07/2026 07:13, Thiago Jung Bauermann wrote:
>> Srinath Parvathaneni <Srinath.Parvathaneni@arm.com> writes:
>>
>>>>> *  p/x $por_el0
>>>>> *  set $por_el0 = <value>
>>>>>
>>>>> Example:
>>>>> (gdb) info register por_el0
>>>>> por_el0 0x7 [ P15=--- P14=--- P13=--- P12=--- P11=--- P10=--- P9=--- P8=--- P7=---
>>> P6=--- P5=--- P4=--- P3=--- P2=--- P1=--- P0=rwx ]
>>>>> (gdb) set $por_el0=0xffffffff77777777
>>>>> (gdb) info register por_el0
>>>>> por_el0 0xffffffff77777777 [ P15=??? P14=??? P13=??? P12=??? P11=??? P10=??? P9=???
>>> P8=??? P7=rwx P6=rwx P5=rwx P4=rwx P3=rwx P2=rwx P1=rwx P0=rwx ]
>>>>> (gdb) p $por_el0
>>>>> $1 = [ P15=??? P14=??? P13=??? P12=??? P11=??? P10=??? P9=??? P8=??? P7=rwx P6=rwx
>>> P5=rwx P4=rwx P3=rwx P2=rwx P1=rwx P0=rwx ]
>>>>> (gdb) p/x $por_el0
>>>>> $2 = 0xffffffff77777777
>>>>> (gdb) set $por_el0=0x57
>>>>> (gdb) info register por_el0
>>>>> por_el0 0x57 [ P15=--- P14=--- P13=--- P12=--- P11=--- P10=--- P9=--- P8=--- P7=---
>>> P6=--- P5=--- P4=--- P3=--- P2=--- P1=rw- P0=rwx ]
>>>>> (gdb) set $por_el0=0xf7f7f7f7f7f7f7f7
>>>>> (gdb) info register por_el0
>>>>> por_el0 0xf7f7f7f7f7f7f7f7 [ P15=??? P14=rwx P13=??? P12=rwx P11=??? P10=rwx P9=???
>>> P8=rwx P7=??? P6=rwx P5=??? P4=rwx P3=??? P2=rwx P1=??? P0=rwx ]
>>>>> (gdb)
>>>>
>>>> Looking at the output above I think it is a bit hard to read.
>>
>> I think part of the reason for it being hard to read is that the output
>> is very wide.
>
>Indeed. I mean, as an overview it's fine. But it really depends on the
>most common use case for this register.
>
>What I want to steer clear from is something like we have for SVE
>registers. It is a barrage of text that isn´t very easy to use.
>
>>
>> One way to address this is Srinath's suggestion below to not print
>> zeroed keys. Another would be to improve the output of the flag type to
>> add line breaks when the terminal's width is reached, as is done when
>> printing array values.
>>
>> Another option would be to use a struct rather than a flags type. Then
>> there would be one type per field, and it would be possible to display
>> (and set) only one key.
>>
>> Not sure which of them I prefer. The struct idea has the advantage of
>> letting the user easily set protection keys individually. OTOH it's
>> not printed isn a very compact way.
>>
>> If easily displaying/setting individual keys isn't that important, I
>> think I slightly prefer not printing zeroed keys as Srinath suggests,
>> possibly coupled with adding line breaks when the line is too long, to
>> address the case of having many keys set in the register.
>>
>
>Good suggestions. I'd say if users want...
>
>- An overview with permissions, then print what we have above
>- To use it as a mask, we should have the raw value
>- To read/write individual P<x> entries within the register, then we
>should have pseudo-registers that map back to por_el0.
>
>The pseudo registers would leave the interpretation of the raw values
>out of the XML, therefore remote stubs wouldn´t need to pass that sort
>of information.
>
>Stretching it a little bit, remote stubs could even send a modified
>version of these fields in the XML and gdb would start printing
>something else.
>

Hi Luis/Thiago,

After looking at the suggestions in the thread, I made a few changes to the
POR_EL0 interface. The custom display for por_el0 has been updated, and I've
also added support for pseudo registers for the individual permission fields.

Could you please have a look at the output below? If this looks ok, I'll re-spin
the series, address the remaining review comments and send it out for another
review.

Also added a new group (por) for por_el0 register along with poe pseduo registers.

Set 1:
(gdb) info register por_el0
por_el0        0x0000000000000077 [ P1=rwx P0=rwx ]
(gdb) info register por
por_el0        0x0000000000000077 [ P1=rwx P0=rwx ]
por_el0_p0     0x7                rwx
por_el0_p1     0x7                rwx
por_el0_p2     0x0                ---
por_el0_p3     0x0                ---
por_el0_p4     0x0                ---
por_el0_p5     0x0                ---
por_el0_p6     0x0                ---
por_el0_p7     0x0                ---
por_el0_p8     0x0                ---
por_el0_p9     0x0                ---
por_el0_p10    0x0                ---
por_el0_p11    0x0                ---
por_el0_p12    0x0                ---
por_el0_p13    0x0                ---
por_el0_p14    0x0                ---
por_el0_p15    0x0                ---

Set 2:
(gdb) set $por_el0=0xf7f7f7f7f7f7f7f7
(gdb) info register por_el0
por_el0        0xf7f7f7f7f7f7f7f7 [ P15=??? P14=rwx P13=??? P12=rwx
                                                           P11=??? P10=rwx P9=??? P8=rwx
                                                                 P7=??? P6=rwx P5=??? P4=rwx
                                                                 P3=??? P2=rwx P1=??? P0=rwx ]
(gdb) info register por
por_el0        0xf7f7f7f7f7f7f7f7 [ P15=??? P14=rwx P13=??? P12=rwx
                                                                 P11=??? P10=rwx P9=??? P8=rwx
                                                                 P7=??? P6=rwx P5=??? P4=rwx
                                                                 P3=??? P2=rwx P1=??? P0=rwx ]
por_el0_p0     0x7                       rwx
por_el0_p1     0xf                        ???
por_el0_p2     0x7                       rwx
por_el0_p3     0xf                        ???
por_el0_p4     0x7                       rwx
por_el0_p5     0xf                      ???
por_el0_p6     0x7                      rwx
por_el0_p7     0xf                      ???
por_el0_p8     0x7                            rwx
por_el0_p9     0xf                             ???
por_el0_p10    0x7                           rwx
por_el0_p11    0xf                            ???
por_el0_p12    0x7                           rwx
por_el0_p13    0xf                            ???
por_el0_p14    0x7                           rwx
por_el0_p15    0xf                            ???

Set 3:
(gdb) set $por_el0=0x0123456789abcdef
(gdb) info register por_el0
por_el0        0x0123456789abcdef [ P14=r-- P13=--x P12=r-x P11=-w-
                                                  P10=rw- P9=-wx P8=rwx P7=???
                                                   P6=??? P5=??? P4=??? P3=???
                                                   P2=??? P1=??? P0=??? ]
(gdb) info register por
por_el0        0x0123456789abcdef [ P14=r-- P13=--x P12=r-x P11=-w-
                                                  P10=rw- P9=-wx P8=rwx P7=???
                                                  P6=??? P5=??? P4=??? P3=???
                                                  P2=??? P1=??? P0=??? ]
por_el0_p0     0xf                     ???
por_el0_p1     0xe                    ???
por_el0_p2     0xd                    ???
por_el0_p3     0xc                    ???
por_el0_p4     0xb                         ???
por_el0_p5     0xa                         ???
por_el0_p6     0x9                         ???
por_el0_p7     0x8                         ???
por_el0_p8     0x7                         rwx
por_el0_p9     0x6                         -wx
por_el0_p10    0x5                         rw-
por_el0_p11    0x4                        -w-
por_el0_p12    0x3                        r-x
por_el0_p13    0x2                        --x
por_el0_p14    0x1                        r--
por_el0_p15    0x0                        ---
(gdb)

Set 4:
(gdb) set $por_el0=0x7
(gdb) info register por
por_el0        0x0000000000000007 [ P0=rwx ]
por_el0_p0     0x7                        rwx
por_el0_p1     0x0                        ---
por_el0_p2     0x0                       ---
por_el0_p3     0x0                        ---
por_el0_p4     0x0                        ---
por_el0_p5     0x0                        ---
por_el0_p6     0x0                        ---
por_el0_p7     0x0                        ---
por_el0_p8     0x0                        ---
por_el0_p9     0x0                        ---
por_el0_p10    0x0                        ---
por_el0_p11    0x0                        ---
por_el0_p12    0x0                        ---
por_el0_p13    0x0                        ---
por_el0_p14    0x0                        ---
por_el0_p15    0x0                        ---
(gdb) set $por_el0_p1=0x7
(gdb) set $por_el0_p3=0x5
(gdb) set $por_el0_p4=0x3
(gdb) set $por_el0_p5=0x1
(gdb) set $por_el0_p6=0xf
(gdb) info register por
por_el0        0x000000000f135077 [ P6=??? P5=r-- P4=r-x P3=rw-
                                                  P1=rwx P0=rwx ]
por_el0_p0     0x7                     rwx
por_el0_p1     0x7                   rwx
por_el0_p2     0x0                         ---
por_el0_p3     0x5                        rw-
por_el0_p4     0x3                        r-x
por_el0_p5     0x1                        r--
por_el0_p6     0xf                        ???
por_el0_p7     0x0                        ---
por_el0_p8     0x0                        ---
por_el0_p9     0x0                        ---
por_el0_p10    0x0                        ---
por_el0_p11    0x0                        ---
por_el0_p12    0x0                        ---
por_el0_p13    0x0                        ---
por_el0_p14    0x0                        ---
por_el0_p15    0x0                        ---
(gdb)

Please let me know your comments, thanks.

Regards,
Sri.

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