[PATCH v4 06/10] riscv: Allow ptrace control of the tagged address ABI

[Samuel Holland]

Hi Charlie,

On 2024-09-12 9:51 PM, Charlie Jenkins wrote:
> On Wed, Aug 28, 2024 at 06:01:28PM -0700, Samuel Holland wrote:
>> This allows a tracer to control the ABI of the tracee, as on arm64.
>>
>> Signed-off-by: Samuel Holland <samuel.holland at sifive.com>
>> ---
> 
> Since this code is identical to the arm64 port, could it be extracted
> out into the generic ptrace.c and ifdef on either CONFIG_RISCV_ISA_SUPM
> or CONFIG_ARM64_TAGGED_ADDR_ABI by adding some generic flag like
> CONFIG_HAVE_ARCH_TAGGED_ADDR_ABI?

Yes, it could be factored out, though I don't know if it is worth the overhead
for these two trivial functions. I don't see any other code like this outside of
arch/.

Regards,
Samuel

>>
>> (no changes since v1)
>>
>>  arch/riscv/kernel/ptrace.c | 42 ++++++++++++++++++++++++++++++++++++++
>>  include/uapi/linux/elf.h   |  1 +
>>  2 files changed, 43 insertions(+)
>>
>> diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
>> index 92731ff8c79a..ea67e9fb7a58 100644
>> --- a/arch/riscv/kernel/ptrace.c
>> +++ b/arch/riscv/kernel/ptrace.c
>> @@ -28,6 +28,9 @@ enum riscv_regset {
>>  #ifdef CONFIG_RISCV_ISA_V
>>  	REGSET_V,
>>  #endif
>> +#ifdef CONFIG_RISCV_ISA_SUPM
>> +	REGSET_TAGGED_ADDR_CTRL,
>> +#endif
>>  };
>>  
>>  static int riscv_gpr_get(struct task_struct *target,
>> @@ -152,6 +155,35 @@ static int riscv_vr_set(struct task_struct *target,
>>  }
>>  #endif
>>  
>> +#ifdef CONFIG_RISCV_ISA_SUPM
>> +static int tagged_addr_ctrl_get(struct task_struct *target,
>> +				const struct user_regset *regset,
>> +				struct membuf to)
>> +{
>> +	long ctrl = get_tagged_addr_ctrl(target);
>> +
>> +	if (IS_ERR_VALUE(ctrl))
>> +		return ctrl;
>> +
>> +	return membuf_write(&to, &ctrl, sizeof(ctrl));
>> +}
>> +
>> +static int tagged_addr_ctrl_set(struct task_struct *target,
>> +				const struct user_regset *regset,
>> +				unsigned int pos, unsigned int count,
>> +				const void *kbuf, const void __user *ubuf)
>> +{
>> +	int ret;
>> +	long ctrl;
>> +
>> +	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &ctrl, 0, -1);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return set_tagged_addr_ctrl(target, ctrl);
>> +}
>> +#endif
>> +
>>  static const struct user_regset riscv_user_regset[] = {
>>  	[REGSET_X] = {
>>  		.core_note_type = NT_PRSTATUS,
>> @@ -182,6 +214,16 @@ static const struct user_regset riscv_user_regset[] = {
>>  		.set = riscv_vr_set,
>>  	},
>>  #endif
>> +#ifdef CONFIG_RISCV_ISA_SUPM
>> +	[REGSET_TAGGED_ADDR_CTRL] = {
>> +		.core_note_type = NT_RISCV_TAGGED_ADDR_CTRL,
>> +		.n = 1,
>> +		.size = sizeof(long),
>> +		.align = sizeof(long),
>> +		.regset_get = tagged_addr_ctrl_get,
>> +		.set = tagged_addr_ctrl_set,
>> +	},
>> +#endif
>>  };
>>  
>>  static const struct user_regset_view riscv_user_native_view = {
>> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
>> index b54b313bcf07..9a32532d7264 100644
>> --- a/include/uapi/linux/elf.h
>> +++ b/include/uapi/linux/elf.h
>> @@ -448,6 +448,7 @@ typedef struct elf64_shdr {
>>  #define NT_MIPS_MSA	0x802		/* MIPS SIMD registers */
>>  #define NT_RISCV_CSR	0x900		/* RISC-V Control and Status Registers */
>>  #define NT_RISCV_VECTOR	0x901		/* RISC-V vector registers */
>> +#define NT_RISCV_TAGGED_ADDR_CTRL 0x902	/* RISC-V tagged address control (prctl()) */
>>  #define NT_LOONGARCH_CPUCFG	0xa00	/* LoongArch CPU config registers */
>>  #define NT_LOONGARCH_CSR	0xa01	/* LoongArch control and status registers */
>>  #define NT_LOONGARCH_LSX	0xa02	/* LoongArch Loongson SIMD Extension registers */
>> -- 
>> 2.45.1
>>
>>
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