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 e64d8e5..bd06e26 100644 --- a/arch/x86/kernel/umip.c +++ b/arch/x86/kernel/umip.c @@ -163,6 +163,41 @@ 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:%x in %lx\n", + tsk->comm, task_pid_nr(tsk), regs->ip, + regs->sp, X86_PF_USER | X86_PF_WRITE, + regs->ip); + } + + tsk->thread.cr2 = (unsigned long)address; + tsk->thread.error_code = X86_PF_USER | X86_PF_WRITE; + tsk->thread.trap_nr = X86_TRAP_PF; + + info.si_signo = SIGSEGV; + info.si_errno = 0; + info.si_code = SEGV_MAPERR; + info.si_addr = address; + force_sig_info(SIGSEGV, &info, tsk); +} + +/** * fixup_umip_exception - Fixup #GP faults caused by UMIP * @regs: Registers as saved when entering the #GP trap * @@ -247,8 +282,14 @@ bool fixup_umip_exception(struct pt_regs *regs) } else { uaddr = insn_get_addr_ref(&insn, regs); nr_copied = copy_to_user(uaddr, dummy_data, dummy_data_size); - if (nr_copied > 0) - return false; + if (nr_copied > 0) { + /* + * If copy fails, send a signal and tell caller that + * fault was fixed up + */ + __force_sig_info_umip_fault(uaddr, regs); + return true; + } }
/* increase IP to let the program keep going */