unwind_vdso.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * unwind_vdso.c - tests unwind info for AT_SYSINFO in the vDSO
  4 * Copyright (c) 2014-2015 Andrew Lutomirski
  5 *
  6 * This tests __kernel_vsyscall's unwind info.
  7 */
  8
  9#define _GNU_SOURCE
 10
 11#include <features.h>
 12#include <stdio.h>
 13
 14#include "helpers.h"
 15
 16#if defined(__GLIBC__) && __GLIBC__ == 2 && __GLIBC_MINOR__ < 16
 17
 18int main()
 19{
 20	/* We need getauxval(). */
 21	printf("[SKIP]\tGLIBC before 2.16 cannot compile this test\n");
 22	return 0;
 23}
 24
 25#else
 26
 27#include <sys/time.h>
 28#include <stdlib.h>
 29#include <syscall.h>
 30#include <unistd.h>
 31#include <string.h>
 32#include <inttypes.h>
 33#include <sys/mman.h>
 34#include <signal.h>
 35#include <sys/ucontext.h>
 36#include <err.h>
 37#include <stddef.h>
 38#include <stdbool.h>
 39#include <sys/ptrace.h>
 40#include <sys/user.h>
 41#include <link.h>
 42#include <sys/auxv.h>
 43#include <dlfcn.h>
 44#include <unwind.h>
 45
 46static volatile sig_atomic_t nerrs;
 47static unsigned long sysinfo;
 48static bool got_sysinfo = false;
 49static unsigned long return_address;
 50
 51struct unwind_state {
 52	unsigned long ip;	/* trap source */
 53	int depth;		/* -1 until we hit the trap source */
 54};
 55
 56_Unwind_Reason_Code trace_fn(struct _Unwind_Context * ctx, void *opaque)
 57{
 58	struct unwind_state *state = opaque;
 59	unsigned long ip = _Unwind_GetIP(ctx);
 60
 61	if (state->depth == -1) {
 62		if (ip == state->ip)
 63			state->depth = 0;
 64		else
 65			return _URC_NO_REASON;	/* Not there yet */
 66	}
 67	printf("\t  0x%lx\n", ip);
 68
 69	if (ip == return_address) {
 70		/* Here we are. */
 71		unsigned long eax = _Unwind_GetGR(ctx, 0);
 72		unsigned long ecx = _Unwind_GetGR(ctx, 1);
 73		unsigned long edx = _Unwind_GetGR(ctx, 2);
 74		unsigned long ebx = _Unwind_GetGR(ctx, 3);
 75		unsigned long ebp = _Unwind_GetGR(ctx, 5);
 76		unsigned long esi = _Unwind_GetGR(ctx, 6);
 77		unsigned long edi = _Unwind_GetGR(ctx, 7);
 78		bool ok = (eax == SYS_getpid || eax == getpid()) &&
 79			ebx == 1 && ecx == 2 && edx == 3 &&
 80			esi == 4 && edi == 5 && ebp == 6;
 81
 82		if (!ok)
 83			nerrs++;
 84		printf("[%s]\t  NR = %ld, args = %ld, %ld, %ld, %ld, %ld, %ld\n",
 85		       (ok ? "OK" : "FAIL"),
 86		       eax, ebx, ecx, edx, esi, edi, ebp);
 87
 88		return _URC_NORMAL_STOP;
 89	} else {
 90		state->depth++;
 91		return _URC_NO_REASON;
 92	}
 93}
 94
 95static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
 96{
 97	ucontext_t *ctx = (ucontext_t *)ctx_void;
 98	struct unwind_state state;
 99	unsigned long ip = ctx->uc_mcontext.gregs[REG_EIP];
100
101	if (!got_sysinfo && ip == sysinfo) {
102		got_sysinfo = true;
103
104		/* Find the return address. */
105		return_address = *(unsigned long *)(unsigned long)ctx->uc_mcontext.gregs[REG_ESP];
106
107		printf("\tIn vsyscall at 0x%lx, returning to 0x%lx\n",
108		       ip, return_address);
109	}
110
111	if (!got_sysinfo)
112		return;		/* Not there yet */
113
114	if (ip == return_address) {
115		ctx->uc_mcontext.gregs[REG_EFL] &= ~X86_EFLAGS_TF;
116		printf("\tVsyscall is done\n");
117		return;
118	}
119
120	printf("\tSIGTRAP at 0x%lx\n", ip);
121
122	state.ip = ip;
123	state.depth = -1;
124	_Unwind_Backtrace(trace_fn, &state);
125}
126
127int main()
128{
129	sysinfo = getauxval(AT_SYSINFO);
130	printf("\tAT_SYSINFO is 0x%lx\n", sysinfo);
131
132	Dl_info info;
133	if (!dladdr((void *)sysinfo, &info)) {
134		printf("[WARN]\tdladdr failed on AT_SYSINFO\n");
135	} else {
136		printf("[OK]\tAT_SYSINFO maps to %s, loaded at 0x%p\n",
137		       info.dli_fname, info.dli_fbase);
138	}
139
140	sethandler(SIGTRAP, sigtrap, 0);
141
142	syscall(SYS_getpid);  /* Force symbol binding without TF set. */
143	printf("[RUN]\tSet TF and check a fast syscall\n");
144	set_eflags(get_eflags() | X86_EFLAGS_TF);
145	syscall(SYS_getpid, 1, 2, 3, 4, 5, 6);
146	if (!got_sysinfo) {
147		set_eflags(get_eflags() & ~X86_EFLAGS_TF);
148
149		/*
150		 * The most likely cause of this is that you're on Debian or
151		 * a Debian-based distro, you're missing libc6-i686, and you're
152		 * affected by libc/19006 (https://sourceware.org/PR19006).
153		 */
154		printf("[WARN]\tsyscall(2) didn't enter AT_SYSINFO\n");
155	}
156
157	if (get_eflags() & X86_EFLAGS_TF) {
158		printf("[FAIL]\tTF is still set\n");
159		nerrs++;
160	}
161
162	if (nerrs) {
163		printf("[FAIL]\tThere were errors\n");
164		return 1;
165	} else {
166		printf("[OK]\tAll is well\n");
167		return 0;
168	}
169}
170
171#endif	/* New enough libc */