[Pdbg] [PATCH 13/19] pdbg/gdbserver: Add in basic skeleton for a gdbserver on p8

[Rashmica]

On 04/09/18 16:23, Rashmica wrote:

> On 30/08/18 21:25, Nicholas Piggin wrote:
>
>> On Thu, 30 Aug 2018 10:18:30 +1000
>> Rashmica <rashmica.g at gmail.com> wrote:
>>> On 29/08/18 18:36, Nicholas Piggin wrote:
>>>> On Wed, 29 Aug 2018 11:50:41 +1000
>>>> Rashmica Gupta <rashmica.g at gmail.com> wrote:
>>>>> From: Alistair Popple <alistair at popple.id.au>
>>>>>
>>>>> I have changed a few bits here and there but this patch is largely
>>>>> authored by Alistair Popple.  
>>>> So what's missing for P9? enable_attn? Anything else?  
>>> There's a couple of things that I'm trying to work out regarding P9.
>>>
>>> - we can't mtnia from an arbitrary register in ramming mode (can only do it
>>>  from the link register).
>> There's a few bits that seem to make P9 work. No guarantee I didn't
>> break P8 MTNIA because I haven't tested it.
>>
>> As we can see, the need for target specific .ram_spr function is
>> increasing. P9 still isn't quite right with all its MTSPRs either.
> When I tried doing value -> LR -> NIA like below, the last two bits of NIA on p9
> were always set to 0. I'll try on some other machines to see if it happens there.

derp that's what should happen! Ignore me :)

>> --
>>
>> P9 MTNIA and MTMSR fixes
>>
>> ---
>>  libpdbg/chip.c   | 19 +++++++++++++++----
>>  libpdbg/p9chip.c |  6 +++---
>>  src/reg.c        |  2 +-
>>  3 files changed, 19 insertions(+), 8 deletions(-)
>>
>> diff --git a/libpdbg/chip.c b/libpdbg/chip.c
>> index 80a2261..1d41d87 100644
>> --- a/libpdbg/chip.c
>> +++ b/libpdbg/chip.c
>> @@ -145,8 +145,8 @@ int ram_sreset_thread(struct pdbg_target *thread_target)
>>   * into *results. *results must point to an array the same size as
>>   * *opcodes. Each entry from *results is put into SCR0 prior to
>>   * executing an opcode so that it may also be used to pass in
>> - * data. Note that only register r0 is saved and restored so opcodes
>> - * must not touch other registers.
>> + * data. Note that only registers r0 and r1 are saved and restored so
>> + * opcode sequences must preserve other registers.
>>   */
>>  static int ram_instructions(struct pdbg_target *thread_target, uint64_t *opcodes,
>>  			    uint64_t *results, int len, unsigned int lpar)
>> @@ -242,10 +242,21 @@ int ram_getnia(struct pdbg_target *thread, uint64_t *value)
>>  	return 0;
>>  }
>>  
>> +/*
>> + * P9 must MTNIA from LR, P8 can MTNIA from R0. So we set both LR and R0
>> + * to value. LR must be saved and restored.
>> + *
>> + * This is a hack and should be made much cleaner once we have target
>> + * specific putspr commands.
>> + */
>>  int ram_putnia(struct pdbg_target *thread, uint64_t value)
>>  {
>> -	uint64_t opcodes[] = {mfspr(0, 277), mtnia(0)};
>> -	uint64_t results[] = {value, 0};
>> +	uint64_t opcodes[] = {	mfspr(1, 8),	/* mflr r1 */
>> +				mfspr(0, 277),	/* value -> r0 */
>> +				mtspr(8, 0),	/* mtlr r0 */
>> +				mtnia(0),
>> +				mtspr(8, 1), };	/* mtlr r1 */
>> +	uint64_t results[] = {0, value, 0, 0, 0};
>>  
>>  	CHECK_ERR(ram_instructions(thread, opcodes, results, ARRAY_SIZE(opcodes), 0));
>>  	return 0;
>> diff --git a/libpdbg/p9chip.c b/libpdbg/p9chip.c
>> index 189d80a..9094c24 100644
>> --- a/libpdbg/p9chip.c
>> +++ b/libpdbg/p9chip.c
>> @@ -291,10 +291,9 @@ static int __p9_ram_instruction(struct thread *thread, uint64_t opcode, uint64_t
>>  
>>  	switch(opcode & OPCODE_MASK) {
>>  	case MTNIA_OPCODE:
>> +		opcode = 0x4c0000a4;
>> +		opcode |= 0x001E0000;
>>  		predecode = 8;
>> -
>> -		/* Not currently supported as we can only MTNIA from LR */
>> -		PR_ERROR("MTNIA is not currently supported\n");
>>  		break;
>>  
>>  	case MFNIA_OPCODE:
>> @@ -304,6 +303,7 @@ static int __p9_ram_instruction(struct thread *thread, uint64_t opcode, uint64_t
>>  
>>  	case MTMSR_OPCODE:
>>  		predecode = 8;
>> +		opcode |= 0x001E0000;
>>  		break;
>>  
>>  	case MFSPR_OPCODE:
>> diff --git a/src/reg.c b/src/reg.c
>> index aa77a8a..c63f6da 100644
>> --- a/src/reg.c
>> +++ b/src/reg.c
>> @@ -116,7 +116,7 @@ OPTCMD_DEFINE_CMD(getnia, getnia);
>>  static int putnia(uint64_t nia)
>>  {
>>  	uint64_t reg = REG_NIA;
>> -	return for_each_target("thread", getprocreg, &reg, &nia);
>> +	return for_each_target("thread", putprocreg, &reg, &nia);
>>  }
>>  OPTCMD_DEFINE_CMD_WITH_ARGS(putnia, putnia, (DATA));
>>  
>>
>>