Re: [Qemu-devel] [PATCH RFC 2/6] posix: add linux-only memfd fallback

[Paolo Bonzini]

On 23/07/2015 17:25, Michael S. Tsirkin wrote:
> > +#ifdef CONFIG_LINUX
> > +
> > +#ifndef F_LINUX_SPECIFIC_BASE
> > +#define F_LINUX_SPECIFIC_BASE 1024
> > +#endif
> > +
> > +#ifndef F_ADD_SEALS
> > +#define F_ADD_SEALS (F_LINUX_SPECIFIC_BASE + 9)
> > +#define F_GET_SEALS (F_LINUX_SPECIFIC_BASE + 10)
> > +
> > +#define F_SEAL_SEAL     0x0001  /* prevent further seals from being set */
> > +#define F_SEAL_SHRINK   0x0002  /* prevent file from shrinking */
> > +#define F_SEAL_GROW     0x0004  /* prevent file from growing */
> > +#define F_SEAL_WRITE    0x0008  /* prevent writes */
> > +#endif
>
> These are from include/uapi/linux/fcntl.h,
> they should be imported into linux-headers I think.

linux-headers is usually used for virt-related features that we want in
QEMU a few weeks before they are distributed upstream.

Here, I think just including linux/fcntl.h is enough.

>> +#ifndef __NR_memfd_create
>> +#  if defined __x86_64__
>> +#    define __NR_memfd_create 319
>> +#  elif defined __arm__
>> +#    define __NR_memfd_create 385
>> +#  elif defined __aarch64__
>> +#    define __NR_memfd_create 279
>> +#  elif defined _MIPS_SIM
>> +#    if _MIPS_SIM == _MIPS_SIM_ABI32
>> +#      define __NR_memfd_create 4354
>> +#    endif
>> +#    if _MIPS_SIM == _MIPS_SIM_NABI32
>> +#      define __NR_memfd_create 6318
>> +#    endif
>> +#    if _MIPS_SIM == _MIPS_SIM_ABI64
>> +#      define __NR_memfd_create 5314
>> +#    endif
> 
> What's defining all these macros?

They're in asm/unistd.h.

I think that, instead of making qemu/osdep.h the new qemu-common.h, the
wrappers added by patch 3 should be declared in a new header
qemu/memfd.h.  The implementation in util/memfd.c can include both
linux/fcntl.h and asm/unistd.h.

Paolo