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1/*
2 * syscall_arg_fault.c - tests faults 32-bit fast syscall stack args
3 * Copyright (c) 2015 Andrew Lutomirski
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms and conditions of the GNU General Public License,
7 * version 2, as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
13 */
14
15#define _GNU_SOURCE
16
17#include <stdlib.h>
18#include <stdio.h>
19#include <string.h>
20#include <sys/signal.h>
21#include <sys/ucontext.h>
22#include <err.h>
23#include <setjmp.h>
24#include <errno.h>
25
26/* Our sigaltstack scratch space. */
27static unsigned char altstack_data[SIGSTKSZ];
28
29static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
30 int flags)
31{
32 struct sigaction sa;
33 memset(&sa, 0, sizeof(sa));
34 sa.sa_sigaction = handler;
35 sa.sa_flags = SA_SIGINFO | flags;
36 sigemptyset(&sa.sa_mask);
37 if (sigaction(sig, &sa, 0))
38 err(1, "sigaction");
39}
40
41static volatile sig_atomic_t sig_traps;
42static sigjmp_buf jmpbuf;
43
44static volatile sig_atomic_t n_errs;
45
46static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
47{
48 ucontext_t *ctx = (ucontext_t*)ctx_void;
49
50 if (ctx->uc_mcontext.gregs[REG_EAX] != -EFAULT) {
51 printf("[FAIL]\tAX had the wrong value: 0x%x\n",
52 ctx->uc_mcontext.gregs[REG_EAX]);
53 n_errs++;
54 } else {
55 printf("[OK]\tSeems okay\n");
56 }
57
58 siglongjmp(jmpbuf, 1);
59}
60
61static void sigill(int sig, siginfo_t *info, void *ctx_void)
62{
63 printf("[SKIP]\tIllegal instruction\n");
64 siglongjmp(jmpbuf, 1);
65}
66
67int main()
68{
69 stack_t stack = {
70 .ss_sp = altstack_data,
71 .ss_size = SIGSTKSZ,
72 };
73 if (sigaltstack(&stack, NULL) != 0)
74 err(1, "sigaltstack");
75
76 sethandler(SIGSEGV, sigsegv, SA_ONSTACK);
77 sethandler(SIGILL, sigill, SA_ONSTACK);
78
79 /*
80 * Exercise another nasty special case. The 32-bit SYSCALL
81 * and SYSENTER instructions (even in compat mode) each
82 * clobber one register. A Linux system call has a syscall
83 * number and six arguments, and the user stack pointer
84 * needs to live in some register on return. That means
85 * that we need eight registers, but SYSCALL and SYSENTER
86 * only preserve seven registers. As a result, one argument
87 * ends up on the stack. The stack is user memory, which
88 * means that the kernel can fail to read it.
89 *
90 * The 32-bit fast system calls don't have a defined ABI:
91 * we're supposed to invoke them through the vDSO. So we'll
92 * fudge it: we set all regs to invalid pointer values and
93 * invoke the entry instruction. The return will fail no
94 * matter what, and we completely lose our program state,
95 * but we can fix it up with a signal handler.
96 */
97
98 printf("[RUN]\tSYSENTER with invalid state\n");
99 if (sigsetjmp(jmpbuf, 1) == 0) {
100 asm volatile (
101 "movl $-1, %%eax\n\t"
102 "movl $-1, %%ebx\n\t"
103 "movl $-1, %%ecx\n\t"
104 "movl $-1, %%edx\n\t"
105 "movl $-1, %%esi\n\t"
106 "movl $-1, %%edi\n\t"
107 "movl $-1, %%ebp\n\t"
108 "movl $-1, %%esp\n\t"
109 "sysenter"
110 : : : "memory", "flags");
111 }
112
113 printf("[RUN]\tSYSCALL with invalid state\n");
114 if (sigsetjmp(jmpbuf, 1) == 0) {
115 asm volatile (
116 "movl $-1, %%eax\n\t"
117 "movl $-1, %%ebx\n\t"
118 "movl $-1, %%ecx\n\t"
119 "movl $-1, %%edx\n\t"
120 "movl $-1, %%esi\n\t"
121 "movl $-1, %%edi\n\t"
122 "movl $-1, %%ebp\n\t"
123 "movl $-1, %%esp\n\t"
124 "syscall\n\t"
125 "pushl $0" /* make sure we segfault cleanly */
126 : : : "memory", "flags");
127 }
128
129 return 0;
130}
1/*
2 * syscall_arg_fault.c - tests faults 32-bit fast syscall stack args
3 * Copyright (c) 2015 Andrew Lutomirski
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms and conditions of the GNU General Public License,
7 * version 2, as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
13 */
14
15#define _GNU_SOURCE
16
17#include <stdlib.h>
18#include <stdio.h>
19#include <string.h>
20#include <sys/signal.h>
21#include <sys/ucontext.h>
22#include <err.h>
23#include <setjmp.h>
24#include <errno.h>
25
26/* Our sigaltstack scratch space. */
27static unsigned char altstack_data[SIGSTKSZ];
28
29static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
30 int flags)
31{
32 struct sigaction sa;
33 memset(&sa, 0, sizeof(sa));
34 sa.sa_sigaction = handler;
35 sa.sa_flags = SA_SIGINFO | flags;
36 sigemptyset(&sa.sa_mask);
37 if (sigaction(sig, &sa, 0))
38 err(1, "sigaction");
39}
40
41static volatile sig_atomic_t sig_traps;
42static sigjmp_buf jmpbuf;
43
44static volatile sig_atomic_t n_errs;
45
46static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
47{
48 ucontext_t *ctx = (ucontext_t*)ctx_void;
49
50 if (ctx->uc_mcontext.gregs[REG_EAX] != -EFAULT) {
51 printf("[FAIL]\tAX had the wrong value: 0x%x\n",
52 ctx->uc_mcontext.gregs[REG_EAX]);
53 n_errs++;
54 } else {
55 printf("[OK]\tSeems okay\n");
56 }
57
58 siglongjmp(jmpbuf, 1);
59}
60
61static void sigill(int sig, siginfo_t *info, void *ctx_void)
62{
63 printf("[SKIP]\tIllegal instruction\n");
64 siglongjmp(jmpbuf, 1);
65}
66
67int main()
68{
69 stack_t stack = {
70 .ss_sp = altstack_data,
71 .ss_size = SIGSTKSZ,
72 };
73 if (sigaltstack(&stack, NULL) != 0)
74 err(1, "sigaltstack");
75
76 sethandler(SIGSEGV, sigsegv, SA_ONSTACK);
77 sethandler(SIGILL, sigill, SA_ONSTACK);
78
79 /*
80 * Exercise another nasty special case. The 32-bit SYSCALL
81 * and SYSENTER instructions (even in compat mode) each
82 * clobber one register. A Linux system call has a syscall
83 * number and six arguments, and the user stack pointer
84 * needs to live in some register on return. That means
85 * that we need eight registers, but SYSCALL and SYSENTER
86 * only preserve seven registers. As a result, one argument
87 * ends up on the stack. The stack is user memory, which
88 * means that the kernel can fail to read it.
89 *
90 * The 32-bit fast system calls don't have a defined ABI:
91 * we're supposed to invoke them through the vDSO. So we'll
92 * fudge it: we set all regs to invalid pointer values and
93 * invoke the entry instruction. The return will fail no
94 * matter what, and we completely lose our program state,
95 * but we can fix it up with a signal handler.
96 */
97
98 printf("[RUN]\tSYSENTER with invalid state\n");
99 if (sigsetjmp(jmpbuf, 1) == 0) {
100 asm volatile (
101 "movl $-1, %%eax\n\t"
102 "movl $-1, %%ebx\n\t"
103 "movl $-1, %%ecx\n\t"
104 "movl $-1, %%edx\n\t"
105 "movl $-1, %%esi\n\t"
106 "movl $-1, %%edi\n\t"
107 "movl $-1, %%ebp\n\t"
108 "movl $-1, %%esp\n\t"
109 "sysenter"
110 : : : "memory", "flags");
111 }
112
113 printf("[RUN]\tSYSCALL with invalid state\n");
114 if (sigsetjmp(jmpbuf, 1) == 0) {
115 asm volatile (
116 "movl $-1, %%eax\n\t"
117 "movl $-1, %%ebx\n\t"
118 "movl $-1, %%ecx\n\t"
119 "movl $-1, %%edx\n\t"
120 "movl $-1, %%esi\n\t"
121 "movl $-1, %%edi\n\t"
122 "movl $-1, %%ebp\n\t"
123 "movl $-1, %%esp\n\t"
124 "syscall\n\t"
125 "pushl $0" /* make sure we segfault cleanly */
126 : : : "memory", "flags");
127 }
128
129 return 0;
130}