1/* Copyright (C) 2001-2020 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