On Fri, 8 Sep 2017 15:45:08 -0700
Ram Pai <linux...@us.ibm.com> wrote:
> Handle Data and Instruction exceptions caused by memory
> protection-key.
>
> The CPU will detect the key fault if the HPTE is already
> programmed with the key.
>
> However if the HPTE is not hashed, a key fault will not
> be detected by the hardware. The software will detect
> pkey violation in such a case.
This bit is not clear.
>
> Signed-off-by: Ram Pai <linux...@us.ibm.com>
> ---
> arch/powerpc/mm/fault.c | 37 ++++++++++++++++++++++++++++++++-----
> 1 files changed, 32 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 4797d08..a16bc43 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -145,6 +145,23 @@ static noinline int bad_area(struct pt_regs *regs,
> unsigned long address)
> return __bad_area(regs, address, SEGV_MAPERR);
> }
>
> +static int bad_page_fault_exception(struct pt_regs *regs, unsigned long
> address,
> + int si_code)
> +{
> + int sig = SIGBUS;
> + int code = BUS_OBJERR;
> +
> +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> + if (si_code & DSISR_KEYFAULT) {
> + sig = SIGSEGV;
> + code = SEGV_PKUERR;
> + }
> +#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
> +
> + _exception(sig, regs, code, address);
> + return 0;
> +}
> +
> static int do_sigbus(struct pt_regs *regs, unsigned long address,
> unsigned int fault)
> {
> @@ -391,11 +408,9 @@ static int __do_page_fault(struct pt_regs *regs,
> unsigned long address,
> return 0;
>
> if (unlikely(page_fault_is_bad(error_code))) {
> - if (is_user) {
> - _exception(SIGBUS, regs, BUS_OBJERR, address);
> - return 0;
> - }
> - return SIGBUS;
> + if (!is_user)
> + return SIGBUS;
> + return bad_page_fault_exception(regs, address, error_code);
> }
>
> /* Additional sanity check(s) */
> @@ -492,6 +507,18 @@ static int __do_page_fault(struct pt_regs *regs,
> unsigned long address,
> if (unlikely(access_error(is_write, is_exec, vma)))
> return bad_area(regs, address);
>
> +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> + if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE,
> + is_exec, 0))
> + return __bad_area(regs, address, SEGV_PKUERR);
Hmm.. this is for the missing entry in the HPT and software detecting the
fault you mentioned above? Why do we need this case?
> +#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
> +
> +
> + /* handle_mm_fault() needs to know if its a instruction access
> + * fault.
> + */
comment style
> + if (is_exec)
> + flags |= FAULT_FLAG_INSTRUCTION;
> /*
> * If for any reason at all we couldn't handle the fault,
> * make sure we exit gracefully rather than endlessly redo
Balbir Singh.
