Unix/Linux/paranoia.cpp

/*
 *  paranoia.cpp - Check undocumented features of the Linux kernel that
 *                 SheepShaver relies upon
 *
 *  SheepShaver (C) 1997-2005 Christian Bauer and Marc Hellwig
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <errno.h>

#include "sysdeps.h"
#include "main.h"
#include "user_strings.h"

typedef struct {
        uint32 u[4];
} __attribute((aligned(16))) vector128;
#include <linux/elf.h>

#define DEBUG 1
#include "debug.h"


// Constants
const uint32 SIG_STACK_SIZE = 0x10000;          // Size of signal stack

// Prototypes
extern "C" void *get_sp(void);
extern "C" void set_r2(uint32 val);
extern void paranoia_check(void);
static void sigusr2_handler(int sig, sigcontext_struct *sc);

// Global variables
static void *sig_stack = NULL;

static int err = 0;
static void *sig_sp = NULL;
static void *sig_r4 = NULL;
static int sig_sc_signal = 0;
static void *sig_sc_regs = NULL;
static uint32 sig_r2 = 0;


void paranoia_check(void)
{
        char str[256];

        D(bug("Paranoia checks...\n"));

        // Create and install stack for signal handler
        sig_stack = malloc(SIG_STACK_SIZE);
        if (sig_stack == NULL) {
                ErrorAlert(GetString(STR_NOT_ENOUGH_MEMORY_ERR));
                exit(1);
        }

        struct sigaltstack old_stack;
        struct sigaltstack new_stack;
        new_stack.ss_sp = sig_stack;
        new_stack.ss_flags = 0;
        new_stack.ss_size = SIG_STACK_SIZE;
        if (sigaltstack(&new_stack, &old_stack) < 0) {
                sprintf(str, GetString(STR_SIGALTSTACK_ERR), strerror(errno));
                ErrorAlert(str);
                exit(1);
        }

        // Install SIGUSR2 signal handler
        static struct sigaction old_action;
        static struct sigaction sigusr2_action;
        sigemptyset(&sigusr2_action.sa_mask);
        sigusr2_action.sa_handler = (__sighandler_t)sigusr2_handler;
        sigusr2_action.sa_flags = SA_ONSTACK | SA_RESTART;
        sigusr2_action.sa_restorer = NULL;
        if (sigaction(SIGUSR2, &sigusr2_action, &old_action) < 0) {
                sprintf(str, GetString(STR_SIGUSR2_INSTALL_ERR), strerror(errno));
                ErrorAlert(str);
                exit(1);
        }

        // Raise SIGUSR2
        set_r2(0xaffebad5);
        raise(SIGUSR2);

        // Check error code
        switch (err) {
                case 1:
                        printf("FATAL: sigaltstack() doesn't seem to work (sp in signal handler was %08lx, expected %08lx..%08lx)\n", (uint32)sig_sp, (uint32)sig_stack, (uint32)sig_stack + SIG_STACK_SIZE);
                        break;
                case 2:
                        printf("FATAL: r4 in signal handler (%08lx) doesn't point to stack\n", (uint32)sig_r4);
                        break;
                case 3:
                        printf("FATAL: r4 in signal handler doesn't seem to point to a sigcontext_struct (signal number was %d, expected %d)", sig_sc_signal, SIGUSR2);
                        break;
                case 4:
                        printf("FATAL: sc->regs in signal handler (%08lx) doesn't point to stack\n", (uint32)sig_sc_regs);
                        break;
                case 5:
                        printf("FATAL: sc->regs->gpr[2] in signal handler (%08lx) doesn't have expected value (%08x)\n", (uint32)sig_r2, 0xaffebad5);
                        break;
        }
        if (err) {
                printf("Maybe you need a different kernel?\n");
                exit(1);
        }

        // Clean up
        D(bug("...passed\n"));
        sigaction(SIGUSR2, &old_action, NULL);
        sigaltstack(&old_stack, NULL);
        free(sig_stack);
}


static void sigusr2_handler(int sig, sigcontext_struct *sc)
{
        // Check whether sigaltstack works
        sig_sp = get_sp();
        if (sig_sp < sig_stack || sig_sp >= ((uint8 *)sig_stack + SIG_STACK_SIZE)) {
                err = 1;
                return;
        }

        // Check whether r4 points to info on the stack
        sig_r4 = sc;
        if (sig_r4 < sig_stack || sig_r4 >= ((uint8 *)sig_stack + SIG_STACK_SIZE)) {
                err = 2;
                return;
        }

        // Check whether r4 looks like a sigcontext
        sig_sc_signal = sc->signal;
        if (sig_sc_signal != SIGUSR2) {
                err = 3;
                return;
        }

        // Check whether sc->regs points to info on the stack
        sig_sc_regs = sc->regs;
        if (sig_sc_regs < sig_stack || sig_sc_regs >= ((uint8 *)sig_stack + SIG_STACK_SIZE)) {
                err = 4;
                return;
        }

        // Check whether r2 still holds the value we set it to
        sig_r2 = sc->regs->gpr[2];
        if (sig_r2 != 0xaffebad5) {
                err = 5;
                return;
        }
}
Revision:	1.3
Committed:	2005-01-30T21:48:20Z (19 years, 9 months ago) by gbeauche
Branch:	MAIN
Changes since 1.2:	+1 -1 lines
Log Message:	Happy New Year 2005!
#	User	Rev	Content
1	cebix	1.1	/*
2			* paranoia.cpp - Check undocumented features of the Linux kernel that
3			* SheepShaver relies upon
4			*
5	gbeauche	1.3	* SheepShaver (C) 1997-2005 Christian Bauer and Marc Hellwig
6	cebix	1.1	*
7			* This program is free software; you can redistribute it and/or modify
8			* it under the terms of the GNU General Public License as published by
9			* the Free Software Foundation; either version 2 of the License, or
10			* (at your option) any later version.
11			*
12			* This program is distributed in the hope that it will be useful,
13			* but WITHOUT ANY WARRANTY; without even the implied warranty of
14			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15			* GNU General Public License for more details.
16			*
17			* You should have received a copy of the GNU General Public License
18			* along with this program; if not, write to the Free Software
19			* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20			*/
21
22			#include <unistd.h>
23			#include <stdio.h>
24			#include <signal.h>
25			#include <errno.h>
26
27			#include "sysdeps.h"
28			#include "main.h"
29			#include "user_strings.h"
30
31			typedef struct {
32			uint32 u[4];
33			} __attribute((aligned(16))) vector128;
34			#include <linux/elf.h>
35
36			#define DEBUG 1
37			#include "debug.h"
38
39
40			// Constants
41			const uint32 SIG_STACK_SIZE = 0x10000; // Size of signal stack
42
43			// Prototypes
44			extern "C" void *get_sp(void);
45			extern "C" void set_r2(uint32 val);
46			extern void paranoia_check(void);
47			static void sigusr2_handler(int sig, sigcontext_struct *sc);
48
49			// Global variables
50			static void *sig_stack = NULL;
51
52			static int err = 0;
53			static void *sig_sp = NULL;
54			static void *sig_r4 = NULL;
55			static int sig_sc_signal = 0;
56			static void *sig_sc_regs = NULL;
57			static uint32 sig_r2 = 0;
58
59
60			void paranoia_check(void)
61			{
62			char str[256];
63
64			D(bug("Paranoia checks...\n"));
65
66			// Create and install stack for signal handler
67			sig_stack = malloc(SIG_STACK_SIZE);
68			if (sig_stack == NULL) {
69			ErrorAlert(GetString(STR_NOT_ENOUGH_MEMORY_ERR));
70			exit(1);
71			}
72
73			struct sigaltstack old_stack;
74			struct sigaltstack new_stack;
75			new_stack.ss_sp = sig_stack;
76			new_stack.ss_flags = 0;
77			new_stack.ss_size = SIG_STACK_SIZE;
78			if (sigaltstack(&new_stack, &old_stack) < 0) {
79			sprintf(str, GetString(STR_SIGALTSTACK_ERR), strerror(errno));
80			ErrorAlert(str);
81			exit(1);
82			}
83
84			// Install SIGUSR2 signal handler
85			static struct sigaction old_action;
86			static struct sigaction sigusr2_action;
87			sigemptyset(&sigusr2_action.sa_mask);
88			sigusr2_action.sa_handler = (__sighandler_t)sigusr2_handler;
89			sigusr2_action.sa_flags = SA_ONSTACK \| SA_RESTART;
90			sigusr2_action.sa_restorer = NULL;
91			if (sigaction(SIGUSR2, &sigusr2_action, &old_action) < 0) {
92			sprintf(str, GetString(STR_SIGUSR2_INSTALL_ERR), strerror(errno));
93			ErrorAlert(str);
94			exit(1);
95			}
96
97			// Raise SIGUSR2
98			set_r2(0xaffebad5);
99			raise(SIGUSR2);
100
101			// Check error code
102			switch (err) {
103			case 1:
104			printf("FATAL: sigaltstack() doesn't seem to work (sp in signal handler was %08lx, expected %08lx..%08lx)\n", (uint32)sig_sp, (uint32)sig_stack, (uint32)sig_stack + SIG_STACK_SIZE);
105			break;
106			case 2:
107			printf("FATAL: r4 in signal handler (%08lx) doesn't point to stack\n", (uint32)sig_r4);
108			break;
109			case 3:
110			printf("FATAL: r4 in signal handler doesn't seem to point to a sigcontext_struct (signal number was %d, expected %d)", sig_sc_signal, SIGUSR2);
111			break;
112			case 4:
113			printf("FATAL: sc->regs in signal handler (%08lx) doesn't point to stack\n", (uint32)sig_sc_regs);
114			break;
115			case 5:
116			printf("FATAL: sc->regs->gpr[2] in signal handler (%08lx) doesn't have expected value (%08x)\n", (uint32)sig_r2, 0xaffebad5);
117			break;
118			}
119			if (err) {
120			printf("Maybe you need a different kernel?\n");
121			exit(1);
122			}
123
124			// Clean up
125			D(bug("...passed\n"));
126			sigaction(SIGUSR2, &old_action, NULL);
127			sigaltstack(&old_stack, NULL);
128			free(sig_stack);
129			}
130
131
132			static void sigusr2_handler(int sig, sigcontext_struct *sc)
133			{
134			// Check whether sigaltstack works
135			sig_sp = get_sp();
136			if (sig_sp < sig_stack \|\| sig_sp >= ((uint8 *)sig_stack + SIG_STACK_SIZE)) {
137			err = 1;
138			return;
139			}
140
141			// Check whether r4 points to info on the stack
142			sig_r4 = sc;
143			if (sig_r4 < sig_stack \|\| sig_r4 >= ((uint8 *)sig_stack + SIG_STACK_SIZE)) {
144			err = 2;
145			return;
146			}
147
148			// Check whether r4 looks like a sigcontext
149			sig_sc_signal = sc->signal;
150			if (sig_sc_signal != SIGUSR2) {
151			err = 3;
152			return;
153			}
154
155			// Check whether sc->regs points to info on the stack
156			sig_sc_regs = sc->regs;
157			if (sig_sc_regs < sig_stack \|\| sig_sc_regs >= ((uint8 *)sig_stack + SIG_STACK_SIZE)) {
158			err = 4;
159			return;
160			}
161
162			// Check whether r2 still holds the value we set it to
163			sig_r2 = sc->regs->gpr[2];
164			if (sig_r2 != 0xaffebad5) {
165			err = 5;
166			return;
167			}
168			}