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. > > -- > Catalin -- Thomas -- 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
