[PATCH] bfd/aarch64-linux: Support reading and writing the GCS core file note

[Jan Beulich]

On 01.07.2025 11:43, Richard Earnshaw (lists) wrote:
> It looks reasonable to me, but this is to a generic bfd file.  Jan?

Looks to be in line with pre-existing similar code, so: Okay.

Jan

> On 08/06/2025 01:59, Thiago Jung Bauermann wrote:
>> ---
>>  bfd/elf.c            | 31 +++++++++++++++++++++++++++++++
>>  include/elf/common.h |  3 +++
>>  2 files changed, 34 insertions(+)
>>
>> Hello,
>>
>> I need this for a GDB patch series adding support for GCS which I will
>> post shortly.
>>
>> diff --git a/bfd/elf.c b/bfd/elf.c
>> index 3073f860621f..6a6b3f1bb9ee 100644
>> --- a/bfd/elf.c
>> +++ b/bfd/elf.c
>> @@ -10629,6 +10629,15 @@ elfcore_grok_aarch_zt (bfd *abfd, Elf_Internal_Note *note)
>>    return elfcore_make_note_pseudosection (abfd, ".reg-aarch-zt", note);
>>  }
>>  
>> +/* Convert NOTE into a bfd_section called ".reg-aarch-gcs".  Return TRUE if
>> +   successful, otherwise return FALSE.  */
>> +
>> +static bool
>> +elfcore_grok_aarch_gcs (bfd *abfd, Elf_Internal_Note *note)
>> +{
>> +  return elfcore_make_note_pseudosection (abfd, ".reg-aarch-gcs", note);
>> +}
>> +
>>  static bool
>>  elfcore_grok_arc_v2 (bfd *abfd, Elf_Internal_Note *note)
>>  {
>> @@ -11372,6 +11381,12 @@ elfcore_grok_note (bfd *abfd, Elf_Internal_Note *note)
>>        else
>>  	return true;
>>  
>> +    case NT_ARM_GCS:
>> +      if (note->namesz == 6 && strcmp (note->namedata, "LINUX") == 0)
>> +	return elfcore_grok_aarch_gcs (abfd, note);
>> +      else
>> +	return true;
>> +
>>      case NT_GDB_TDESC:
>>        if (note->namesz == 4
>>  	  && strcmp (note->namedata, "GDB") == 0)
>> @@ -13042,6 +13057,20 @@ elfcore_write_aarch_zt (bfd *abfd,
>>  			     size);
>>  }
>>  
>> +/* Write the buffer of GCS register values in AARCH_GCS (length SIZE) into
>> +   the note buffer BUF and update *BUFSIZ.  ABFD is the bfd the note is being
>> +   written into.  Return a pointer to the new start of the note buffer, to
>> +   replace BUF which may no longer be valid.  */
>> +
>> +static char *
>> +elfcore_write_aarch_gcs (bfd *abfd, char *buf, int *bufsiz,
>> +			 const void *aarch_gcs, int size)
>> +{
>> +  const char *note_name = "LINUX";
>> +  return elfcore_write_note (abfd, buf, bufsiz, note_name, NT_ARM_GCS,
>> +			     aarch_gcs, size);
>> +}
>> +
>>  char *
>>  elfcore_write_arc_v2 (bfd *abfd,
>>  		      char *buf,
>> @@ -13231,6 +13260,8 @@ elfcore_write_register_note (bfd *abfd,
>>      return elfcore_write_aarch_za (abfd, buf, bufsiz, data, size);
>>    if (strcmp (section, ".reg-aarch-zt") == 0)
>>      return elfcore_write_aarch_zt (abfd, buf, bufsiz, data, size);
>> +  if (strcmp (section, ".reg-aarch-gcs") == 0)
>> +    return elfcore_write_aarch_gcs (abfd, buf, bufsiz, data, size);
>>    if (strcmp (section, ".reg-arc-v2") == 0)
>>      return elfcore_write_arc_v2 (abfd, buf, bufsiz, data, size);
>>    if (strcmp (section, ".gdb-tdesc") == 0)
>> diff --git a/include/elf/common.h b/include/elf/common.h
>> index fd032d1e03ed..f4b543b353ac 100644
>> --- a/include/elf/common.h
>> +++ b/include/elf/common.h
>> @@ -740,6 +740,9 @@
>>  					/*   Note: name must be "LINUX".  */
>>  #define NT_ARM_ZT       0x40d           /* AArch64 SME2 ZT registers.  */
>>  					/*   Note: name must be "LINUX".  */
>> +#define NT_ARM_GCS	0x410		/* AArch64 Guarded Control Stack
>> +					   registers.  */
>> +					/*   Note  name must be "LINUX".  */
>>  #define NT_ARC_V2	0x600		/* ARC HS accumulator/extra registers.  */
>>  					/*   note name must be "LINUX".  */
>>  #define NT_LARCH_CPUCFG 0xa00		/* LoongArch CPU config registers */
>