1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* Copyright (C) 2019 ARM Limited */ 3 4 #include <asm/unistd.h> 5 6 .section .rodata, "a" 7 call_fmt: 8 .asciz "Calling sigreturn with fake sigframe sized:%zd at SP @%08lX\n" 9 10 .text 11 12 .globl fake_sigreturn 13 14 /* fake_sigreturn x0:&sigframe, x1:sigframe_size, x2:misalign_bytes */ 15 fake_sigreturn: 16 stp x29, x30, [sp, #-16]! 17 mov x29, sp 18 19 mov x20, x0 20 mov x21, x1 21 mov x22, x2 22 23 /* create space on the stack for fake sigframe 16 bytes-aligned */ 24 add x0, x21, x22 25 add x0, x0, #15 26 bic x0, x0, #15 /* round_up(sigframe_size + misalign_bytes, 16) */ 27 sub sp, sp, x0 28 add x23, sp, x22 /* new sigframe base with misaligment if any */ 29 30 ldr x0, =call_fmt 31 mov x1, x21 32 mov x2, x23 33 bl printf 34 35 /* memcpy the provided content, while still keeping SP aligned */ 36 mov x0, x23 37 mov x1, x20 38 mov x2, x21 39 bl memcpy 40 41 /* 42 * Here saving a last minute SP to current->token acts as a marker: 43 * if we got here, we are successfully faking a sigreturn; in other 44 * words we are sure no bad fatal signal has been raised till now 45 * for unrelated reasons, so we should consider the possibly observed 46 * fatal signal like SEGV coming from Kernel restore_sigframe() and 47 * triggered as expected from our test-case. 48 * For simplicity this assumes that current field 'token' is laid out 49 * as first in struct tdescr 50 */ 51 ldr x0, current 52 str x23, [x0] 53 /* finally move SP to misaligned address...if any requested */ 54 mov sp, x23 55 56 mov x8, #__NR_rt_sigreturn 57 svc #0 58 59 /* 60 * Above sigreturn should not return...looping here leads to a timeout 61 * and ensure proper and clean test failure, instead of jumping around 62 * on a potentially corrupted stack. 63 */ 64 b . 65