Re: [PATCH v2] ptrace: add PTRACE_GET_RSEQ_CONFIGURATION request
From: Michał Mirosław
Date: Fri Feb 26 2021 - 11:05:29 EST
On 2021年2月26日 at 16:32, Mathieu Desnoyers
<mathieu.desnoyers@xxxxxxxxxxxx> wrote:
>
>
----- On Feb 26, 2021, at 8:51 AM, Piotr Figiel figiel@xxxxxxxxxx wrote:
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[...]
>
> ---
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> v2:
>
> Applied review comments:
>
> - changed return value from the ptrace request to the size of the
>
> configuration structure
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> - expanded configuration structure with the flags field and
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> the rseq abi structure size
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>
>
[...]
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> +#define PTRACE_GET_RSEQ_CONFIGURATION 0x420f
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> +
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> +struct ptrace_rseq_configuration {
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> + __u64 rseq_abi_pointer;
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> + __u32 rseq_abi_size;
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> + __u32 signature;
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> + __u32 flags;
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> + __u32 pad;
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> +};
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> +
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[...]
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> +#ifdef CONFIG_RSEQ
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> +static long ptrace_get_rseq_configuration(struct task_struct *task,
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> + unsigned long size, void __user *data)
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> +{
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> + struct ptrace_rseq_configuration conf = {
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> + .rseq_abi_pointer = (u64)(uintptr_t)task->rseq,
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> + .rseq_abi_size = sizeof(*task->rseq),
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> + .signature = task->rseq_sig,
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> + .flags = 0,
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> + };
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> +
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> + size = min_t(unsigned long, size, sizeof(conf));
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> + if (copy_to_user(data, &conf, size))
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> + return -EFAULT;
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> + return sizeof(conf);
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> +}
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>
I think what Florian was after would be:
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>
struct ptrace_rseq_configuration {
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__u32 size; /* size of struct ptrace_rseq_configuration */
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__u32 flags;
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__u64 rseq_abi_pointer;
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__u32 signature;
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__u32 pad;
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};
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>
where:
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>
.size = sizeof(struct ptrace_rseq_configuration),
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>
This way, the configuration structure can be expanded in the future. The
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rseq ABI structure is by definition fixed-size, so there is no point in
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having its size here.
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>
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?
Best Regards
Michał Mirosław
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