[PATCH v2] gdb/csky support .reg2 for kernel 4.x and later

[jiangshuai_li via Gdb-patches <gdb-patches@sourceware.org>]

>> When kernel's version >= 4.x, the size of .reg2 section will be 400.
>> Contents of .reg2 are {
>>     unsigned long vr[96]; // vr0~vr15 & fr16~fr31
>>     unsigned long fcr;
>>     unsigned long fesr;
>>     unsigned long fid;
>>     unsigned long reserved;
>> };
>>
>> ---
>>  gdb/csky-linux-tdep.c | 150 +++++++++++++++++++++++++++++++++++++-----
>>  1 file changed, 134 insertions(+), 16 deletions(-)
>> 
>> diff --git a/gdb/csky-linux-tdep.c b/gdb/csky-linux-tdep.c
>> index 440045e7713..aa85a299922 100644
>> --- a/gdb/csky-linux-tdep.c
>> +++ b/gdb/csky-linux-tdep.c
>> @@ -36,6 +36,8 @@
>>  #define SIZEOF_CSKY_GREGSET 34*4
>>  /* Float regset fesr fsr fr0-fr31 for CK810.  */
>>  #define SIZEOF_CSKY_FREGSET 34*4
>> +/* Float regset vr0~vr15 fr15~fr31, reserved for CK810 when kernel 4.x.  */
>
>You might want to expand the comment above indicating that the struct
>layout can be found in a comment within csky_supply_fregset.
>
>> +#define SIZEOF_CSKY_FREGSET_K4X  400
>>  
>>  /* Offset mapping table from core_section to regcache of general
>>     registers for ck810.  */
>> @@ -118,15 +120,76 @@ csky_supply_fregset (const struct regset
>> *regset, int fregset_num = ARRAY_SIZE (csky_fregset_offset);
>>  
>>    gdb_assert (len >= SIZEOF_CSKY_FREGSET);
>> -  for (i = 0; i < fregset_num; i++)
>> +  if (len == SIZEOF_CSKY_FREGSET)
>>      {
>> -      if ((regnum == csky_fregset_offset[i] || regnum == -1)
>> -   && csky_fregset_offset[i] != -1)
>> - {
>> -   int num = csky_fregset_offset[i];
>> -   offset += register_size (gdbarch, num);
>> -   regcache->raw_supply (csky_fregset_offset[i], fregs +
>> offset);
>> - }
>> +      for (i = 0; i < fregset_num; i++)
>> +        {
>> +          if ((regnum == csky_fregset_offset[i] || regnum == -1)
>> +              && csky_fregset_offset[i] != -1)
>> +            {
>> +              int num = csky_fregset_offset[i];
>> +              offset += register_size (gdbarch, num);
>> +              regcache->raw_supply (csky_fregset_offset[i], fregs +
>> offset);
>> +            }
>> +        }
>> +    }
>> +  else if (len == SIZEOF_CSKY_FREGSET_K4X)
>> +    {
>> +      /* When kernel version >= 4.x, .reg2 size will be 400.
>> +         Contents is {
>> +           unsigned long vr[96]; // vr0~vr15 + fr16~fr31
>> +           unsigned long fcr;
>> +           unsigned long fesr;
>> +           unsigned long fid;
>> +           unsigned long reserved;
>> +         }  */
>> +      int fcr_regno[] = {122, 123, 121}; /* fcr, fesr, fid.  */
>> +
>> +      /* Supply vr0~vr15.  */
>> +      for (i = 0; i < 16; i ++)
>> +        {
>> +          if (gdbarch_register_name (gdbarch, (CSKY_VR0_REGNUM + i)))
>> +            {
>> +              offset = 16 * i;
>> +              regcache->raw_supply (CSKY_VR0_REGNUM + i,
>> +                                    fregs + offset);
>> +            }
>> +        }
>> +      /* Supply fr0~fr15.  */
>> +      for (i = 0; i < 16; i ++)
>> +        {
>> +          if (gdbarch_register_name (gdbarch, (CSKY_FR0_REGNUM + i)))
>> +            {
>> +              offset = 16 * i;
>
>Are these offsets correct?  I.e. do the fr0~fr15 registers use
>the same offsets as vr0~vr15?

Yes. The bit width of floating-point register is 64bits, and the bit width of vector
register is 128bit. In fr0~fr15 and vr0~vr15, each FRx is the lower 64 bits of
the corresponding VRx.

>
>Also, not related to this patch, but while trying to figure this out,
>I found this line in csky-tdep.h - it looks fishy to me since it's
>way bigger than CSKY_MAX_REGS:
>
>  CSKY_FR16_REGNUM = 1172,

Actually, the max regs number should be 1187, but if the gdb stub does not send a
tdesc-xml file to gdb, 253 works.

>
>It definitely matters since you refer to CSKY_FR16_REGNUM below.
>
>> +              regcache->raw_supply (CSKY_FR0_REGNUM + i,
>> +                                    fregs + offset);
>> +            }
>> +        }
>> +      /* Supply fr16~fr31.  */
>> +      for (i = 0; i < 16; i ++)
>> +        {
>> +          if (gdbarch_register_name (gdbarch, (CSKY_FR16_REGNUM +
>> i)))
>> +            {
>> +              offset = (16 * 16) + (8 * i);
>> +              regcache->raw_supply (CSKY_FR16_REGNUM + i,
>> +                                    fregs + offset);
>> +            }
>> +        }
>> +     /* Supply fcr, fesr, fid.  */
>> +      for (i = 0; i < 3; i ++)
>> +        {
>> +          if (gdbarch_register_name (gdbarch, fcr_regno[i]))
>> +            {
>> +              offset = (16 * 16) + (16 * 8) + (4 * i);
>> +              regcache->raw_supply (fcr_regno[i],
>> +                                    fregs + offset);
>> +            }
>> +        }
>> +    }
>> +  else
>> +    {
>> +      warning (_("Unknow size %ld of section .reg2, can not get
>> value"
>> +                 " of float registers."), len);
>>      }
>>  }
>>  
>> @@ -144,14 +207,66 @@ csky_collect_fregset (const struct regset
>> *regset, int offset = 0;
>>  
>>    gdb_assert (len >= SIZEOF_CSKY_FREGSET);
>> -  for (regno = 0; regno < fregset_num; regno++)
>> +  if (len == SIZEOF_CSKY_FREGSET)
>> +    {
>> +      for (regno = 0; regno < fregset_num; regno++)
>> +        {
>> +          if ((regnum == csky_fregset_offset[regno] || regnum == -1)
>> +               && csky_fregset_offset[regno] != -1)
>> +            {
>> +              offset += register_size (gdbarch,
>> csky_fregset_offset[regno]);
>> +              regcache->raw_collect (regno, fregs + offset);
>> +            }
>> +        }
>> +    }
>> +  else if (len == SIZEOF_CSKY_FREGSET_K4X)
>> +    {
>> +      /* When kernel version >= 4.x, .reg2 size will be 400.
>> +         Contents is {
>> +           unsigned long vr[96]; // vr0~vr15 + fr16~fr31
>> +           unsigned long fcr;
>> +           unsigned long fesr;
>> +           unsigned long fid;
>> +           unsigned long reserved;
>> +         }  */
>> +      int i = 0;
>> +      int fcr_regno[] = {122, 123, 121}; /* fcr, fesr, fid.  */
>> +
>> +      /* Supply vr0~vr15.  */
>> +      for (i = 0; i < 16; i ++)
>> +        {
>> +          if (gdbarch_register_name (gdbarch, (CSKY_VR0_REGNUM + i)))
>> +            {
>> +              offset = 16 * i;
>> +              regcache ->raw_collect (CSKY_VR0_REGNUM + i,
>> +                                      fregs + offset);
>> +            }
>> +        }
>> +      /* Supply fr16~fr31.  */
>> +      for (i = 0; i < 16; i ++)
>> +        {
>> +          if (gdbarch_register_name (gdbarch, (CSKY_FR16_REGNUM +
>> i)))
>> +            {
>> +              offset = (16 * 16) + (8 * i);
>> +              regcache ->raw_collect (CSKY_FR16_REGNUM + i,
>> +                                      fregs + offset);
>> +            }
>> +        }
>> +      /* Supply fcr, fesr, fid.  */
>> +      for (i = 0; i < 3; i ++)
>> +        {
>> +          if (gdbarch_register_name (gdbarch, fcr_regno[i]))
>> +            {
>> +              offset = (16 * 16) + (16 * 8) + (4 * i);
>> +              regcache ->raw_collect (fcr_regno[i],
>> +                                      fregs + offset);
>> +            }
>> +        }
>> +    }
>> +  else
>>      {
>> -      if ((regnum == csky_fregset_offset[regno] || regnum == -1)
>> -   && csky_fregset_offset[regno] != -1)
>> - {
>> -   offset += register_size (gdbarch,
>> csky_fregset_offset[regno]);
>> -   regcache->raw_collect (regno, fregs + offset);
>> - }
>> +      warning (_("Unknow size %ld of section .reg2, will not set
>> value"
>> +                 " of float registers."), len);
>>      }
>>  }
>>  
>> @@ -166,7 +281,10 @@ static const struct regset csky_regset_float =
>>  {
>>    NULL,
>>    csky_supply_fregset,
>> -  csky_collect_fregset
>> +  csky_collect_fregset,
>> +  /* Allow .reg2 has different size, buf size of .reg2 should
>> +     always is or bigger than SIZEOF_CSKY_FREGSET.  */
>
>I recommend a slightly different wording for the above comment:
>
>     /* Allow .reg2 to have a different size, but the size of .reg2 should
>       always be bigger than SIZEOF_CSKY_FREGSET.  */

Get.

>
>> +  1
>>  };
>>  
>>  /* Iterate over core file register note sections.  */
>> -- 
>> 2.25.1
>> 

Thanks Kevin Buettner.