----- On Feb 26, 2021, at 11:04 AM, emmir em...@google.com wrote:
> On Fri, 26 Feb 2021 at 16:32, Mathieu Desnoyers
> <mathieu.desnoy...@efficios.com> wrote:
>>
>> ----- On Feb 26, 2021, at 8:51 AM, Piotr Figiel fig...@google.com wrote:
>> [...]
>> > ---
>> > v2:
>> > Applied review comments:
>> > - changed return value from the ptrace request to the size of the
>> > configuration structure
>> > - expanded configuration structure with the flags field and
>> > the rseq abi structure size
>> >
>> [...]
>> > +#define PTRACE_GET_RSEQ_CONFIGURATION 0x420f
>> > +
>> > +struct ptrace_rseq_configuration {
>> > + __u64 rseq_abi_pointer;
>> > + __u32 rseq_abi_size;
>> > + __u32 signature;
>> > + __u32 flags;
>> > + __u32 pad;
>> > +};
>> > +
>> [...]
>> > +#ifdef CONFIG_RSEQ
>> > +static long ptrace_get_rseq_configuration(struct task_struct *task,
>> > + unsigned long size, void __user
>> > *data)
>> > +{
>> > + struct ptrace_rseq_configuration conf = {
>> > + .rseq_abi_pointer = (u64)(uintptr_t)task->rseq,
>> > + .rseq_abi_size = sizeof(*task->rseq),
>> > + .signature = task->rseq_sig,
>> > + .flags = 0,
>> > + };
>> > +
>> > + size = min_t(unsigned long, size, sizeof(conf));
>> > + if (copy_to_user(data, &conf, size))
>> > + return -EFAULT;
>> > + return sizeof(conf);
>> > +}
>>
>> I think what Florian was after would be:
>>
>> struct ptrace_rseq_configuration {
>> __u32 size; /* size of struct ptrace_rseq_configuration */
>> __u32 flags;
>> __u64 rseq_abi_pointer;
>> __u32 signature;
>> __u32 pad;
>> };
>>
>> where:
>>
>> .size = sizeof(struct ptrace_rseq_configuration),
>>
>> This way, the configuration structure can be expanded in the future. The
>> rseq ABI structure is by definition fixed-size, so there is no point in
>> having its size here.
>>
>> Florian, did I understand your request correctly, or am I missing your point
>> ?
>
> In this case returning sizeof(conf) would serve the same purpose, wouldn't it?
If the size is received as input from user-space as well, this can be used to
make sure the kernel detects what size is expected by user-space and act
accordingly.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
