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    SubjectRe: [PATCH 3/6] intel_sgx: driver for Intel Secure Guard eXtensions
    On Tue, Apr 26, 2016 at 11:49:38PM -0700, Jethro Beekman wrote:
    > On 25-04-16 10:34, Jarkko Sakkinen wrote:
    > > diff --git a/drivers/staging/intel_sgx/isgx_ioctl.c
    > b/drivers/staging/intel_sgx/isgx_ioctl.c
    > > new file mode 100644
    > > index 0000000..9d8b36b
    > > --- /dev/null
    > > +++ b/drivers/staging/intel_sgx/isgx_ioctl.c
    > >
    > > +static long isgx_ioctl_enclave_create(struct file *filep, unsigned int cmd,
    > > + unsigned long arg)
    > >
    > > + secs->base = vm_mmap(filep, 0, secs->size,
    > > + PROT_READ | PROT_WRITE | PROT_EXEC,
    > > + MAP_SHARED, 0);
    >
    > Why does the ioctl interface map userspace memory for an open device?
    > There's already a perfectly good syscall for that: mmap.

    You didn't explain what would be the value in doing this but after
    thinking for a short while I found out two good reasons:

    * The current API is ugly in a way that you can anyway call mmap
    directly too and have a useless zombie enclave. This would make
    the API less ambiguous.
    * SGX_IOC_ENCLAVE_CREATE could be removed. SECS could be passed
    through SGX_IOC_ENCLAVE_ADD_PAGE thus simplifying the API a lot.

    Given these circumstances I think this does make sense.

    > > diff --git a/drivers/staging/intel_sgx/isgx_user.h b/drivers/staging/intel_sgx/isgx_user.h
    > > new file mode 100644
    > > index 0000000..672d19c
    > > --- /dev/null
    > > +++ b/drivers/staging/intel_sgx/isgx_user.h
    > >
    > > +#define SGX_ADD_SKIP_EEXTEND 0x1
    > > +
    > > +struct sgx_add_param {
    > > + unsigned long addr;
    > > + unsigned long user_addr;
    > > + struct isgx_secinfo *secinfo;
    > > + unsigned int flags;
    > > +};
    >
    > The hardware supports calling EEXTEND on only a part of a page, I think the
    > driver should also support that.

    Why would you want to do that?

    > Jethro

    /Jarkko

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