1/* Copyright (C) 2001-2021 Free Software Foundation, Inc.
2   This file is part of the GNU C Library.
3
4   The GNU C Library is free software; you can redistribute it and/or
5   modify it under the terms of the GNU Lesser General Public
6   License as published by the Free Software Foundation; either
7   version 2.1 of the License, or (at your option) any later version.
8
9   The GNU C Library is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   Lesser General Public License for more details.
13
14   You should have received a copy of the GNU Lesser General Public
15   License along with the GNU C Library; if not, see
16   <https://www.gnu.org/licenses/>.  */
17
18#include <sysdep.h>
19#include <jmpbuf-offsets.h>
20#include <jmp_buf-ssp.h>
21#include <asm-syntax.h>
22#include <stap-probe.h>
23
24/* Don't restore shadow stack register if
25   1. Shadow stack isn't enabled.  Or
26   2. __longjmp is defined for __longjmp_cancel.
27 */
28#if !SHSTK_ENABLED || defined __longjmp
29# undef SHADOW_STACK_POINTER_OFFSET
30#endif
31
32/* Jump to the position specified by ENV, causing the
33   setjmp call there to return VAL, or 1 if VAL is 0.
34   void __longjmp (__jmp_buf env, int val).  */
35	.text
36ENTRY(__longjmp)
37	/* Restore registers.  */
38	mov (JB_RSP*8)(%rdi),%R8_LP
39	mov (JB_RBP*8)(%rdi),%R9_LP
40	mov (JB_PC*8)(%rdi),%RDX_LP
41#ifdef PTR_DEMANGLE
42	PTR_DEMANGLE (%R8_LP)
43	PTR_DEMANGLE (%R9_LP)
44	PTR_DEMANGLE (%RDX_LP)
45# ifdef __ILP32__
46	/* We ignored the high bits of the %rbp value because only the low
47	   bits are mangled.  But we cannot presume that %rbp is being used
48	   as a pointer and truncate it, so recover the high bits.  */
49	movl (JB_RBP*8 + 4)(%rdi), %eax
50	shlq $32, %rax
51	orq %rax, %r9
52# endif
53#endif
54#ifdef SHADOW_STACK_POINTER_OFFSET
55# if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
56	/* Check if Shadow Stack is enabled.  */
57	testl $X86_FEATURE_1_SHSTK, %fs:FEATURE_1_OFFSET
58	jz L(skip_ssp)
59# else
60	xorl %eax, %eax
61# endif
62	/* Check and adjust the Shadow-Stack-Pointer.  */
63	/* Get the current ssp.  */
64	rdsspq %rax
65	/* And compare it with the saved ssp value.  */
66	subq SHADOW_STACK_POINTER_OFFSET(%rdi), %rax
67	je L(skip_ssp)
68	/* Count the number of frames to adjust and adjust it
69	   with incssp instruction.  The instruction can adjust
70	   the ssp by [0..255] value only thus use a loop if
71	   the number of frames is bigger than 255.  */
72	negq %rax
73	shrq $3, %rax
74	/* NB: We saved Shadow-Stack-Pointer of setjmp.  Since we are
75	       restoring Shadow-Stack-Pointer of setjmp's caller, we
76	       need to unwind shadow stack by one more frame.  */
77	addq $1, %rax
78
79	movl $255, %ebx
80L(loop):
81	cmpq %rbx, %rax
82	cmovb %rax, %rbx
83	incsspq %rbx
84	subq %rbx, %rax
85	ja L(loop)
86
87L(skip_ssp):
88#endif
89	LIBC_PROBE (longjmp, 3, LP_SIZE@%RDI_LP, -4@%esi, LP_SIZE@%RDX_LP)
90	/* We add unwind information for the target here.  */
91	cfi_def_cfa(%rdi, 0)
92	cfi_register(%rsp,%r8)
93	cfi_register(%rbp,%r9)
94	cfi_register(%rip,%rdx)
95	cfi_offset(%rbx,JB_RBX*8)
96	cfi_offset(%r12,JB_R12*8)
97	cfi_offset(%r13,JB_R13*8)
98	cfi_offset(%r14,JB_R14*8)
99	cfi_offset(%r15,JB_R15*8)
100	movq (JB_RBX*8)(%rdi),%rbx
101	movq (JB_R12*8)(%rdi),%r12
102	movq (JB_R13*8)(%rdi),%r13
103	movq (JB_R14*8)(%rdi),%r14
104	movq (JB_R15*8)(%rdi),%r15
105	/* Set return value for setjmp.  */
106	mov %esi, %eax
107	mov %R8_LP,%RSP_LP
108	movq %r9,%rbp
109	LIBC_PROBE (longjmp_target, 3,
110		    LP_SIZE@%RDI_LP, -4@%eax, LP_SIZE@%RDX_LP)
111	jmpq *%rdx
112END (__longjmp)
113