On Wed, Apr 05, 2017 at 11:14:34AM -0700, Thomas Garnier wrote: > On Wed, Apr 5, 2017 at 10:49 AM, Catalin Marinas > <catalin.marinas@xxxxxxx> wrote: > > On Wed, Apr 05, 2017 at 07:36:17AM -0700, Thomas Garnier wrote: > >> On Wed, Apr 5, 2017 at 7:22 AM, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > >> > On Tue, Apr 04, 2017 at 10:47:27AM -0700, Thomas Garnier wrote: > >> >> + > >> >> ldr x1, [tsk, #TSK_TI_FLAGS] > >> >> and x2, x1, #_TIF_WORK_MASK > >> >> cbnz x2, work_pending > >> >> @@ -779,6 +788,12 @@ finish_ret_to_user: > >> >> kernel_exit 0 > >> >> ENDPROC(ret_to_user) > >> >> > >> >> +addr_limit_fail: > >> >> + stp x0, lr, [sp,#-16]! > >> >> + bl asm_verify_pre_usermode_state > >> >> + ldp x0, lr, [sp],#16 > >> >> + ret lr > >> > > >> > Where is this supposed to return? What is the value of lr when branching > >> > to addr_limit_fail? > >> > >> It is not supposed to return. Do you think I should remove stp, ldp, > >> ret and jut add a brk 0x100 or jmp/call a break/bug function? > > > > Can you not just make addr_limit_fail a C function which never returns > > (similar to what we to with bad_mode() on arm64)? Since addr_limit_fail > > is only called when the segment is not the right one, I don't really see > > why you need another call to asm_verify_pre_usermode_state() to do a > > similar check again. Just panic in addr_limit_fail (unless I > > misunderstood what you are trying to achieve). > > Calling asm_verify_pre_usermode_state has the advantage of having a > clear BUG_ON for the error (versus a panic description). > > What do you think about replacing asm_verify_pre_usermode_state by a > "address_limit_fail" function that still calls > verify_pre_usermode_state but panic afterwards (because it should > never return)? > > The assembly code would be easier to understand and in case of error > the BUG_ON is clear for the user. It looks fine to me, though I'd have to see the patch. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
