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SubjectRe: [v5 17/20] x86/umip: Force a page fault when unable to copy emulated result to user
On Fri, Mar 3, 2017 at 1:41 PM, Ricardo Neri
<ricardo.neri-calderon@linux.intel.com> wrote:
> fixup_umip_exception will be called from do_general_protection. If the
> former returns false, the latter will issue a SIGSEGV with SEND_SIG_PRIV.
> However, when emulation is successful but the emulated result cannot be
> copied to user space memory, it is more accurate to issue a SIGSEGV with
> SEGV_MAPERR with the offending address. A new function is inspired in
> force_sig_info_fault is introduced to model the page fault.
>
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> ---
> arch/x86/kernel/umip.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 43 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
> index e932f40..5b6a7cf 100644
> --- a/arch/x86/kernel/umip.c
> +++ b/arch/x86/kernel/umip.c
> @@ -170,6 +170,41 @@ static int __emulate_umip_insn(struct insn *insn, enum umip_insn umip_inst,
> }
>
> /**
> + * __force_sig_info_umip_fault - Force a SIGSEGV with SEGV_MAPERR
> + * @address: Address that caused the signal
> + * @regs: Register set containing the instruction pointer
> + *
> + * Force a SIGSEGV signal with SEGV_MAPERR as the error code. This function is
> + * intended to be used to provide a segmentation fault when the result of the
> + * UMIP emulation could not be copied to the user space memory.
> + *
> + * Return: none
> + */
> +static void __force_sig_info_umip_fault(void __user *address,
> + struct pt_regs *regs)
> +{
> + siginfo_t info;
> + struct task_struct *tsk = current;
> +
> + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV)) {
> + printk_ratelimited("%s[%d] umip emulation segfault ip:%lx sp:%lx error:%lx in %lx\n",
> + tsk->comm, task_pid_nr(tsk), regs->ip,
> + regs->sp, UMIP_PF_USER | UMIP_PF_WRITE,
> + regs->ip);
> + }
> +
> + tsk->thread.cr2 = (unsigned long)address;
> + tsk->thread.error_code = UMIP_PF_USER | UMIP_PF_WRITE;

Please just move enum x86_pf_error_code into a header and rename the
fields X86_PF_USER, etc rather than duplicating it.

--Andy

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