Re: [PATCH v2] linux-user: Use memfd for open syscall emulation

[Richard Henderson <richard.henderson@linaro.org>]

On 7/29/22 14:19, Rainer Müller wrote:
> On 29/07/2022 18.01, Richard Henderson wrote:
>> On 7/29/22 08:49, Rainer Müller wrote:
>>> +            /* create temporary file to map stat to */
>>> +            tmpdir = getenv("TMPDIR");
>>> +            if (!tmpdir)
>>> +                tmpdir = "/tmp";
>>> +            snprintf(filename, sizeof(filename),
>>> "%s/qemu-open.XXXXXX", tmpdir);
>>> +            fd = mkstemp(filename);
>>> +            if (fd < 0) {
>>> +                return fd;
>>> +            }
>>
>> We've been using g_file_open_tmp elsewhere; probably good to follow suit
>> here.
> 
> That seemed reasonable at first, but with regards to error handling it
> gets a bit complicated.
> 
> The suggested g_file_open_tmp() would leave us with a GError only, but
> to return something meaningful to the caller we must set errno in this
> context. As far as I can see, there is no way to convert back to an
> errno from GError.
> 
> With g_file_open_tmp() we could always set the same generic errno, but
> that would hide the real cause completely. I debugged this problem with
> this message that was confusing, but at least it gave away a hint:
>    cat: can't open '/proc/self/stat': Read-only file system

That's a good reason.  Let's leave this alone then.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~