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The x86 architecture has a set of page fault error codes. These indicate things like whether the fault occurred from a write, or whether it originated in userspace. The SGX hardware architecture has its own per-page memory management metadata (EPCM) [*] and hardware which is separate from the normal x86 MMU. The architecture has a new page fault error code: PF_SGX. This new error code bit is set whenever a page fault occurs as the result of the SGX MMU. These faults occur for a variety of reasons. For instance, an access attempt to enclave memory from outside the enclave causes a PF_SGX fault. PF_SGX would also be set for permission conflicts, such as if a write to an enclave page occurs and the page is marked read-write in the x86 page tables but is read-only in the EPCM. These faults do not always indicate errors, though. SGX pages are encrypted with a key that is destroyed at hardware reset, including suspend. Throwing a SIGSEGV allows user space software to react and recover when these events occur. Include PF_SGX in the PF error codes list and throw SIGSEGV when it is encountered. [*] Intel SDM: 36.5.1 Enclave Page Cache Map (EPCM) [ bp: Add bit 15 to the comment above enum x86_pf_error_code too. ] Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Jethro Beekman <jethro@fortanix.com> Link: https://lkml.kernel.org/r/20201112220135.165028-7-jarkko@kernel.org
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.