Re: [PATCH v2 1/7] powerpc: properly negate error in syscall_set_return_value()

Christophe Leroy
2025-01-27T12:20:03Z

Le 27/01/2025 à 12:44, Dmitry V. Levin a écrit :
> On Mon, Jan 27, 2025 at 12:36:53PM +0100, Christophe Leroy wrote:
>> Le 27/01/2025 à 12:20, Dmitry V. Levin a écrit :
>>> On Thu, Jan 23, 2025 at 11:07:21PM +0100, Christophe Leroy wrote:
>>> [...]
>>>> To add a bit more to the confusion,
>>>
>>> Looks like there is no end to it:
>>>
>>> static inline long regs_return_value(struct pt_regs *regs)
>>> {
>>> if (trap_is_scv(regs))
>>> return regs->gpr[3];
>>>
>>> if (is_syscall_success(regs))
>>> return regs->gpr[3];
>>> else
>>> return -regs->gpr[3];
>>> }
>>>
>>> static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
>>> {
>>> regs->gpr[3] = rc;
>>> }
>>>
>>> This doesn't look consistent, does it?
>>>
>>>
>>
>> That regs_set_return_value() looks pretty similar to
>> syscall_get_return_value().
>
> Yes, but here similarities end, and differences begin.
>
>> regs_set_return_value() documentation in asm-generic/syscall.h
>> explicitely says: This value is meaningless if syscall_get_error()
>> returned nonzero
>>
>> Is it the same with regs_set_return_value(), only meaningfull where
>> there is no error ?
>
> Did you mean syscall_set_return_value? No, it explicitly has two
> arguments, "int error" and "long val", so it can be used to either
> clear or set the error condition as specified by the caller.

Sorry, I mean syscall_get_return_value() here.

static inline long syscall_get_return_value(struct task_struct *task,
struct pt_regs *regs)
{
return regs->gpr[3];
}

Versus

static inline void regs_set_return_value(struct pt_regs *regs, unsigned
long rc)
{
regs->gpr[3] = rc;
}

>
>> By the way, why have two very similar APIs, one in syscall.h one in
>> ptrace.h ?
>
> I have no polite answer to this, sorry.
>
>