src/Unix/sigsegv.cpp

/*
 *  sigsegv.cpp - SIGSEGV signals support
 *
 *  Derived from Bruno Haible's work on his SIGSEGV library for clisp
 *  <http://clisp.sourceforge.net/>
 *
 *  Basilisk II (C) 1997-2002 Christian Bauer
 *
 *  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
 */

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <signal.h>
#include "sigsegv.h"

// Return value type of a signal handler (standard type if not defined)
#ifndef RETSIGTYPE
#define RETSIGTYPE void
#endif

// Type of the system signal handler
typedef RETSIGTYPE (*signal_handler)(int);

// Is the fault to be ignored?
static bool sigsegv_ignore_fault = false;

// User's SIGSEGV handler
static sigsegv_fault_handler_t sigsegv_fault_handler = 0;

// Function called to dump state if we can't handle the fault
static sigsegv_state_dumper_t sigsegv_state_dumper = 0;

// Actual SIGSEGV handler installer
static bool sigsegv_do_install_handler(int sig);


/*
 *  Instruction decoding aids
 */

// Transfer type
enum transfer_type_t {
        TYPE_UNKNOWN,
        TYPE_LOAD,
        TYPE_STORE
};

// Transfer size
enum transfer_size_t {
        SIZE_UNKNOWN,
        SIZE_BYTE,
        SIZE_WORD,
        SIZE_LONG
};

#if (defined(powerpc) || defined(__powerpc__) || defined(__ppc__))
// Addressing mode
enum addressing_mode_t {
        MODE_UNKNOWN,
        MODE_NORM,
        MODE_U,
        MODE_X,
        MODE_UX
};

// Decoded instruction
struct instruction_t {
        transfer_type_t         transfer_type;
        transfer_size_t         transfer_size;
        addressing_mode_t       addr_mode;
        unsigned int            addr;
        char                            ra, rd;
};

static void powerpc_decode_instruction(instruction_t *instruction, unsigned int nip, unsigned int * gpr)
{
        // Get opcode and divide into fields
        unsigned int opcode = *((unsigned int *)nip);
        unsigned int primop = opcode >> 26;
        unsigned int exop = (opcode >> 1) & 0x3ff;
        unsigned int ra = (opcode >> 16) & 0x1f;
        unsigned int rb = (opcode >> 11) & 0x1f;
        unsigned int rd = (opcode >> 21) & 0x1f;
        signed int imm = (signed short)(opcode & 0xffff);
        
        // Analyze opcode
        transfer_type_t transfer_type = TYPE_UNKNOWN;
        transfer_size_t transfer_size = SIZE_UNKNOWN;
        addressing_mode_t addr_mode = MODE_UNKNOWN;
        switch (primop) {
        case 31:
                switch (exop) {
                case 23:        // lwzx
                        transfer_type = TYPE_LOAD; transfer_size = SIZE_LONG; addr_mode = MODE_X; break;
                case 55:        // lwzux
                        transfer_type = TYPE_LOAD; transfer_size = SIZE_LONG; addr_mode = MODE_UX; break;
                case 87:        // lbzx
                        transfer_type = TYPE_LOAD; transfer_size = SIZE_BYTE; addr_mode = MODE_X; break;
                case 119:       // lbzux
                        transfer_type = TYPE_LOAD; transfer_size = SIZE_BYTE; addr_mode = MODE_UX; break;
                case 151:       // stwx
                        transfer_type = TYPE_STORE; transfer_size = SIZE_LONG; addr_mode = MODE_X; break;
                case 183:       // stwux
                        transfer_type = TYPE_STORE; transfer_size = SIZE_LONG; addr_mode = MODE_UX; break;
                case 215:       // stbx
                        transfer_type = TYPE_STORE; transfer_size = SIZE_BYTE; addr_mode = MODE_X; break;
                case 247:       // stbux
                        transfer_type = TYPE_STORE; transfer_size = SIZE_BYTE; addr_mode = MODE_UX; break;
                case 279:       // lhzx
                        transfer_type = TYPE_LOAD; transfer_size = SIZE_WORD; addr_mode = MODE_X; break;
                case 311:       // lhzux
                        transfer_type = TYPE_LOAD; transfer_size = SIZE_WORD; addr_mode = MODE_UX; break;
                case 343:       // lhax
                        transfer_type = TYPE_LOAD; transfer_size = SIZE_WORD; addr_mode = MODE_X; break;
                case 375:       // lhaux
                        transfer_type = TYPE_LOAD; transfer_size = SIZE_WORD; addr_mode = MODE_UX; break;
                case 407:       // sthx
                        transfer_type = TYPE_STORE; transfer_size = SIZE_WORD; addr_mode = MODE_X; break;
                case 439:       // sthux
                        transfer_type = TYPE_STORE; transfer_size = SIZE_WORD; addr_mode = MODE_UX; break;
                }
                break;
        
        case 32:        // lwz
                transfer_type = TYPE_LOAD; transfer_size = SIZE_LONG; addr_mode = MODE_NORM; break;
        case 33:        // lwzu
                transfer_type = TYPE_LOAD; transfer_size = SIZE_LONG; addr_mode = MODE_U; break;
        case 34:        // lbz
                transfer_type = TYPE_LOAD; transfer_size = SIZE_BYTE; addr_mode = MODE_NORM; break;
        case 35:        // lbzu
                transfer_type = TYPE_LOAD; transfer_size = SIZE_BYTE; addr_mode = MODE_U; break;
        case 36:        // stw
                transfer_type = TYPE_STORE; transfer_size = SIZE_LONG; addr_mode = MODE_NORM; break;
        case 37:        // stwu
                transfer_type = TYPE_STORE; transfer_size = SIZE_LONG; addr_mode = MODE_U; break;
        case 38:        // stb
                transfer_type = TYPE_STORE; transfer_size = SIZE_BYTE; addr_mode = MODE_NORM; break;
        case 39:        // stbu
                transfer_type = TYPE_STORE; transfer_size = SIZE_BYTE; addr_mode = MODE_U; break;
        case 40:        // lhz
                transfer_type = TYPE_LOAD; transfer_size = SIZE_WORD; addr_mode = MODE_NORM; break;
        case 41:        // lhzu
                transfer_type = TYPE_LOAD; transfer_size = SIZE_WORD; addr_mode = MODE_U; break;
        case 42:        // lha
                transfer_type = TYPE_LOAD; transfer_size = SIZE_WORD; addr_mode = MODE_NORM; break;
        case 43:        // lhau
                transfer_type = TYPE_LOAD; transfer_size = SIZE_WORD; addr_mode = MODE_U; break;
        case 44:        // sth
                transfer_type = TYPE_STORE; transfer_size = SIZE_WORD; addr_mode = MODE_NORM; break;
        case 45:        // sthu
                transfer_type = TYPE_STORE; transfer_size = SIZE_WORD; addr_mode = MODE_U; break;
        }
        
        // Calculate effective address
        unsigned int addr = 0;
        switch (addr_mode) {
        case MODE_X:
        case MODE_UX:
                if (ra == 0)
                        addr = gpr[rb];
                else
                        addr = gpr[ra] + gpr[rb];
                break;
        case MODE_NORM:
        case MODE_U:
                if (ra == 0)
                        addr = (signed int)(signed short)imm;
                else
                        addr = gpr[ra] + (signed int)(signed short)imm;
                break;
        default:
                break;
        }
        
        // Commit decoded instruction
        instruction->addr = addr;
        instruction->addr_mode = addr_mode;
        instruction->transfer_type = transfer_type;
        instruction->transfer_size = transfer_size;
        instruction->ra = ra;
        instruction->rd = rd;
}
#endif


/*
 *  OS-dependant SIGSEGV signals support section
 */

#if HAVE_SIGINFO_T
// Generic extended signal handler
#if defined(__NetBSD__) || defined(__FreeBSD__)
#define SIGSEGV_ALL_SIGNALS                             FAULT_HANDLER(SIGBUS)
#else
#define SIGSEGV_ALL_SIGNALS                             FAULT_HANDLER(SIGSEGV)
#endif
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, siginfo_t *sip, void *scp
#define SIGSEGV_FAULT_ADDRESS                   sip->si_addr
#if (defined(i386) || defined(__i386__))
#define SIGSEGV_FAULT_INSTRUCTION               (((struct sigcontext *)scp)->sc_eip)
#define SIGSEGV_REGISTER_FILE                   ((unsigned int *)&(((struct sigcontext *)scp)->sc_edi))
#define SIGSEGV_SKIP_INSTRUCTION                ix86_skip_instruction
#endif
#if defined(__linux__)
#if (defined(i386) || defined(__i386__))
#include <sys/ucontext.h>
#define SIGSEGV_CONTEXT_REGS                    (((ucontext_t *)scp)->uc_mcontext.gregs)
#define SIGSEGV_FAULT_INSTRUCTION               SIGSEGV_CONTEXT_REGS[14] /* should use REG_EIP instead */
#define SIGSEGV_REGISTER_FILE                   (unsigned int *)SIGSEGV_CONTEXT_REGS
#define SIGSEGV_SKIP_INSTRUCTION                ix86_skip_instruction
#endif
#if (defined(ia64) || defined(__ia64__))
#define SIGSEGV_FAULT_INSTRUCTION               (((struct sigcontext *)scp)->sc_ip & ~0x3ULL) /* slot number is in bits 0 and 1 */
#endif
#if (defined(powerpc) || defined(__powerpc__))
#include <sys/ucontext.h>
#define SIGSEGV_CONTEXT_REGS                    (((ucontext_t *)scp)->uc_mcontext.regs)
#define SIGSEGV_FAULT_INSTRUCTION               (SIGSEGV_CONTEXT_REGS->nip)
#define SIGSEGV_REGISTER_FILE                   (unsigned int *)&SIGSEGV_CONTEXT_REGS->nip, (unsigned int *)(SIGSEGV_CONTEXT_REGS->gpr)
#define SIGSEGV_SKIP_INSTRUCTION                powerpc_skip_instruction
#endif
#endif
#endif

#if HAVE_SIGCONTEXT_SUBTERFUGE
// Linux kernels prior to 2.4 ?
#if defined(__linux__)
#define SIGSEGV_ALL_SIGNALS                             FAULT_HANDLER(SIGSEGV)
#if (defined(i386) || defined(__i386__))
#include <asm/sigcontext.h>
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, struct sigcontext scs
#define SIGSEGV_FAULT_ADDRESS                   scs.cr2
#define SIGSEGV_FAULT_INSTRUCTION               scs.eip
#define SIGSEGV_REGISTER_FILE                   (unsigned int *)(&scs)
#define SIGSEGV_SKIP_INSTRUCTION                ix86_skip_instruction
#endif
#if (defined(sparc) || defined(__sparc__))
#include <asm/sigcontext.h>
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, int code, struct sigcontext *scp, char *addr
#define SIGSEGV_FAULT_ADDRESS                   addr
#endif
#if (defined(powerpc) || defined(__powerpc__))
#include <asm/sigcontext.h>
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, struct sigcontext *scp
#define SIGSEGV_FAULT_ADDRESS                   scp->regs->dar
#define SIGSEGV_FAULT_INSTRUCTION               scp->regs->nip
#define SIGSEGV_REGISTER_FILE                   (unsigned int *)&scp->regs->nip, (unsigned int *)(scp->regs->gpr)
#define SIGSEGV_SKIP_INSTRUCTION                powerpc_skip_instruction
#endif
#if (defined(alpha) || defined(__alpha__))
#include <asm/sigcontext.h>
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, int code, struct sigcontext *scp
#define SIGSEGV_FAULT_ADDRESS                   get_fault_address(scp)
#define SIGSEGV_FAULT_INSTRUCTION               scp->sc_pc

// From Boehm's GC 6.0alpha8
static sigsegv_address_t get_fault_address(struct sigcontext *scp)
{
        unsigned int instruction = *((unsigned int *)(scp->sc_pc));
        unsigned long fault_address = scp->sc_regs[(instruction >> 16) & 0x1f];
        fault_address += (signed long)(signed short)(instruction & 0xffff);
        return (sigsegv_address_t)fault_address;
}
#endif
#endif

// Irix 5 or 6 on MIPS
#if (defined(sgi) || defined(__sgi)) && (defined(SYSTYPE_SVR4) || defined(__SYSTYPE_SVR4))
#include <ucontext.h>
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, int code, struct sigcontext *scp
#define SIGSEGV_FAULT_ADDRESS                   scp->sc_badvaddr
#define SIGSEGV_ALL_SIGNALS                             FAULT_HANDLER(SIGSEGV)
#endif

// HP-UX
#if (defined(hpux) || defined(__hpux__))
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, int code, struct sigcontext *scp
#define SIGSEGV_FAULT_ADDRESS                   scp->sc_sl.sl_ss.ss_narrow.ss_cr21
#define SIGSEGV_ALL_SIGNALS                             FAULT_HANDLER(SIGSEGV) FAULT_HANDLER(SIGBUS)
#endif

// OSF/1 on Alpha
#if defined(__osf__)
#include <ucontext.h>
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, int code, struct sigcontext *scp
#define SIGSEGV_FAULT_ADDRESS                   scp->sc_traparg_a0
#define SIGSEGV_ALL_SIGNALS                             FAULT_HANDLER(SIGSEGV)
#endif

// AIX
#if defined(_AIX)
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, int code, struct sigcontext *scp
#define SIGSEGV_FAULT_ADDRESS                   scp->sc_jmpbuf.jmp_context.o_vaddr
#define SIGSEGV_ALL_SIGNALS                             FAULT_HANDLER(SIGSEGV)
#endif

// NetBSD or FreeBSD
#if defined(__NetBSD__) || defined(__FreeBSD__)
#if (defined(m68k) || defined(__m68k__))
#include <m68k/frame.h>
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, int code, struct sigcontext *scp
#define SIGSEGV_FAULT_ADDRESS                   get_fault_address(scp)
#define SIGSEGV_ALL_SIGNALS                             FAULT_HANDLER(SIGSEGV)

// Use decoding scheme from BasiliskII/m68k native
static sigsegv_address_t get_fault_address(struct sigcontext *scp)
{
        struct sigstate {
                int ss_flags;
                struct frame ss_frame;
        };
        struct sigstate *state = (struct sigstate *)scp->sc_ap;
        char *fault_addr;
        switch (state->ss_frame.f_format) {
        case 7:         /* 68040 access error */
                /* "code" is sometimes unreliable (i.e. contains NULL or a bogus address), reason unknown */
                fault_addr = state->ss_frame.f_fmt7.f_fa;
                break;
        default:
                fault_addr = (char *)code;
                break;
        }
        return (sigsegv_address_t)fault_addr;
}
#else
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, int code, void *scp, char *addr
#define SIGSEGV_FAULT_ADDRESS                   addr
#define SIGSEGV_ALL_SIGNALS                             FAULT_HANDLER(SIGBUS)
#endif
#endif

// MacOS X
#if defined(__APPLE__) && defined(__MACH__)
#if (defined(ppc) || defined(__ppc__))
#define SIGSEGV_FAULT_HANDLER_ARGLIST   int sig, int code, struct sigcontext *scp
#define SIGSEGV_FAULT_ADDRESS                   get_fault_address(scp)
#define SIGSEGV_FAULT_INSTRUCTION               scp->sc_ir
#define SIGSEGV_ALL_SIGNALS                             FAULT_HANDLER(SIGBUS)
#define SIGSEGV_REGISTER_FILE                   (unsigned int *)&scp->sc_ir, &((unsigned int *) scp->sc_regs)[2]
#define SIGSEGV_SKIP_INSTRUCTION                powerpc_skip_instruction

// Use decoding scheme from SheepShaver
static sigsegv_address_t get_fault_address(struct sigcontext *scp)
{
        unsigned int   nip = (unsigned int) scp->sc_ir;
        unsigned int * gpr = &((unsigned int *) scp->sc_regs)[2];
        instruction_t  instr;

        powerpc_decode_instruction(&instr, nip, gpr);
        return (sigsegv_address_t)instr.addr;
}
#endif
#endif
#endif


/*
 *  Instruction skipping
 */

#ifdef HAVE_SIGSEGV_SKIP_INSTRUCTION
// Decode and skip X86 instruction
#if (defined(i386) || defined(__i386__))
#if defined(__linux__)
enum {
        X86_REG_EIP = 14,
        X86_REG_EAX = 11,
        X86_REG_ECX = 10,
        X86_REG_EDX = 9,
        X86_REG_EBX = 8,
        X86_REG_ESP = 7,
        X86_REG_EBP = 6,
        X86_REG_ESI = 5,
        X86_REG_EDI = 4
};
#endif
#if defined(__NetBSD__) || defined(__FreeBSD__)
enum {
        X86_REG_EIP = 10,
        X86_REG_EAX = 7,
        X86_REG_ECX = 6,
        X86_REG_EDX = 5,
        X86_REG_EBX = 4,
        X86_REG_ESP = 13,
        X86_REG_EBP = 2,
        X86_REG_ESI = 1,
        X86_REG_EDI = 0
};
#endif
// FIXME: this is partly redundant with the instruction decoding phase
// to discover transfer type and register number
static inline int ix86_step_over_modrm(unsigned char * p)
{
        int mod = (p[0] >> 6) & 3;
        int rm = p[0] & 7;
        int offset = 0;

        // ModR/M Byte
        switch (mod) {
        case 0: // [reg]
                if (rm == 5) return 4; // disp32
                break;
        case 1: // disp8[reg]
                offset = 1;
                break;
        case 2: // disp32[reg]
                offset = 4;
                break;
        case 3: // register
                return 0;
        }
        
        // SIB Byte
        if (rm == 4) {
                if (mod == 0 && (p[1] & 7) == 5)
                        offset = 5; // disp32[index]
                else
                        offset++;
        }

        return offset;
}

static bool ix86_skip_instruction(unsigned int * regs)
{
        unsigned char * eip = (unsigned char *)regs[X86_REG_EIP];

        if (eip == 0)
                return false;
        
        transfer_type_t transfer_type = TYPE_UNKNOWN;
        transfer_size_t transfer_size = SIZE_LONG;
        
        int reg = -1;
        int len = 0;
        
        // Operand size prefix
        if (*eip == 0x66) {
                eip++;
                len++;
                transfer_size = SIZE_WORD;
        }

        // Decode instruction
        switch (eip[0]) {
        case 0x0f:
            if (eip[1] == 0xb7) { // MOVZX r32, r/m16
                switch (eip[2] & 0xc0) {
                case 0x80:
                    reg = (eip[2] >> 3) & 7;
                    transfer_type = TYPE_LOAD;
                    break;
                case 0x40:
                    reg = (eip[2] >> 3) & 7;
                    transfer_type = TYPE_LOAD;
                    break;
                case 0x00:
                    reg = (eip[2] >> 3) & 7;
                    transfer_type = TYPE_LOAD;
                    break;
                }
                len += 3 + ix86_step_over_modrm(eip + 2);
            }
          break;
        case 0x8a: // MOV r8, r/m8
                transfer_size = SIZE_BYTE;
        case 0x8b: // MOV r32, r/m32 (or 16-bit operation)
                switch (eip[1] & 0xc0) {
                case 0x80:
                        reg = (eip[1] >> 3) & 7;
                        transfer_type = TYPE_LOAD;
                        break;
                case 0x40:
                        reg = (eip[1] >> 3) & 7;
                        transfer_type = TYPE_LOAD;
                        break;
                case 0x00:
                        reg = (eip[1] >> 3) & 7;
                        transfer_type = TYPE_LOAD;
                        break;
                }
                len += 2 + ix86_step_over_modrm(eip + 1);
                break;
        case 0x88: // MOV r/m8, r8
                transfer_size = SIZE_BYTE;
        case 0x89: // MOV r/m32, r32 (or 16-bit operation)
                switch (eip[1] & 0xc0) {
                case 0x80:
                        reg = (eip[1] >> 3) & 7;
                        transfer_type = TYPE_STORE;
                        break;
                case 0x40:
                        reg = (eip[1] >> 3) & 7;
                        transfer_type = TYPE_STORE;
                        break;
                case 0x00:
                        reg = (eip[1] >> 3) & 7;
                        transfer_type = TYPE_STORE;
                        break;
                }
                len += 2 + ix86_step_over_modrm(eip + 1);
                break;
        }

        if (transfer_type == TYPE_UNKNOWN) {
                // Unknown machine code, let it crash. Then patch the decoder
                return false;
        }

        if (transfer_type == TYPE_LOAD && reg != -1) {
                static const int x86_reg_map[8] = {
                        X86_REG_EAX, X86_REG_ECX, X86_REG_EDX, X86_REG_EBX,
                        X86_REG_ESP, X86_REG_EBP, X86_REG_ESI, X86_REG_EDI
                };
                
                if (reg < 0 || reg >= 8)
                        return false;

                int rloc = x86_reg_map[reg];
                switch (transfer_size) {
                case SIZE_BYTE:
                        regs[rloc] = (regs[rloc] & ~0xff);
                        break;
                case SIZE_WORD:
                        regs[rloc] = (regs[rloc] & ~0xffff);
                        break;
                case SIZE_LONG:
                        regs[rloc] = 0;
                        break;
                }
        }

#if DEBUG
        printf("%08x: %s %s access", regs[X86_REG_EIP],
                   transfer_size == SIZE_BYTE ? "byte" : transfer_size == SIZE_WORD ? "word" : "long",
                   transfer_type == TYPE_LOAD ? "read" : "write");
        
        if (reg != -1) {
                static const char * x86_reg_str_map[8] = {
                        "eax", "ecx", "edx", "ebx",
                        "esp", "ebp", "esi", "edi"
                };
                printf(" %s register %%%s", transfer_type == TYPE_LOAD ? "to" : "from", x86_reg_str_map[reg]);
        }
        printf(", %d bytes instruction\n", len);
#endif
        
        regs[X86_REG_EIP] += len;
        return true;
}
#endif

// Decode and skip PPC instruction
#if (defined(powerpc) || defined(__powerpc__) || defined(__ppc__))
static bool powerpc_skip_instruction(unsigned int * nip_p, unsigned int * regs)
{
        instruction_t instr;
        powerpc_decode_instruction(&instr, *nip_p, regs);
        
        if (instr.transfer_type == TYPE_UNKNOWN) {
                // Unknown machine code, let it crash. Then patch the decoder
                return false;
        }

#if DEBUG
        printf("%08x: %s %s access", *nip_p,
                   instr.transfer_size == SIZE_BYTE ? "byte" : instr.transfer_size == SIZE_WORD ? "word" : "long",
                   instr.transfer_type == TYPE_LOAD ? "read" : "write");
        
        if (instr.addr_mode == MODE_U || instr.addr_mode == MODE_UX)
                printf(" r%d (ra = %08x)\n", instr.ra, instr.addr);
        if (instr.transfer_type == TYPE_LOAD)
                printf(" r%d (rd = 0)\n", instr.rd);
#endif
        
        if (instr.addr_mode == MODE_U || instr.addr_mode == MODE_UX)
                regs[instr.ra] = instr.addr;
        if (instr.transfer_type == TYPE_LOAD)
                regs[instr.rd] = 0;
        
        *nip_p += 4;
        return true;
}
#endif
#endif

// Fallbacks
#ifndef SIGSEGV_FAULT_INSTRUCTION
#define SIGSEGV_FAULT_INSTRUCTION               SIGSEGV_INVALID_PC
#endif

// SIGSEGV recovery supported ?
#if defined(SIGSEGV_ALL_SIGNALS) && defined(SIGSEGV_FAULT_HANDLER_ARGLIST) && defined(SIGSEGV_FAULT_ADDRESS)
#define HAVE_SIGSEGV_RECOVERY
#endif


/*
 *  SIGSEGV global handler
 */

#ifdef HAVE_SIGSEGV_RECOVERY
static void sigsegv_handler(SIGSEGV_FAULT_HANDLER_ARGLIST)
{
        sigsegv_address_t fault_address = (sigsegv_address_t)SIGSEGV_FAULT_ADDRESS;
        sigsegv_address_t fault_instruction = (sigsegv_address_t)SIGSEGV_FAULT_INSTRUCTION;
        bool fault_recovered = false;
        
        // Call user's handler and reinstall the global handler, if required
        if (sigsegv_fault_handler(fault_address, fault_instruction)) {
#if (defined(HAVE_SIGACTION) ? defined(SIGACTION_NEED_REINSTALL) : defined(SIGNAL_NEED_REINSTALL))
                sigsegv_do_install_handler(sig);
#endif
                fault_recovered = true;
        }
#if HAVE_SIGSEGV_SKIP_INSTRUCTION
        else if (sigsegv_ignore_fault) {
                // Call the instruction skipper with the register file available
                if (SIGSEGV_SKIP_INSTRUCTION(SIGSEGV_REGISTER_FILE))
                        fault_recovered = true;
        }
#endif

        if (!fault_recovered) {
                // FAIL: reinstall default handler for "safe" crash
#define FAULT_HANDLER(sig) signal(sig, SIG_DFL);
                SIGSEGV_ALL_SIGNALS
#undef FAULT_HANDLER
                
                // We can't do anything with the fault_address, dump state?
                if (sigsegv_state_dumper != 0)
                        sigsegv_state_dumper(fault_address, fault_instruction);
        }
}
#endif


/*
 *  SIGSEGV handler initialization
 */

#if defined(HAVE_SIGINFO_T)
static bool sigsegv_do_install_handler(int sig)
{
        // Setup SIGSEGV handler to process writes to frame buffer
#ifdef HAVE_SIGACTION
        struct sigaction vosf_sa;
        sigemptyset(&vosf_sa.sa_mask);
        vosf_sa.sa_sigaction = sigsegv_handler;
        vosf_sa.sa_flags = SA_SIGINFO;
        return (sigaction(sig, &vosf_sa, 0) == 0);
#else
        return (signal(sig, (signal_handler)sigsegv_handler) != SIG_ERR);
#endif
}
#endif

#if defined(HAVE_SIGCONTEXT_SUBTERFUGE)
static bool sigsegv_do_install_handler(int sig)
{
        // Setup SIGSEGV handler to process writes to frame buffer
#ifdef HAVE_SIGACTION
        struct sigaction vosf_sa;
        sigemptyset(&vosf_sa.sa_mask);
        vosf_sa.sa_handler = (signal_handler)sigsegv_handler;
#if !EMULATED_68K && defined(__NetBSD__)
        sigaddset(&vosf_sa.sa_mask, SIGALRM);
        vosf_sa.sa_flags = SA_ONSTACK;
#else
        vosf_sa.sa_flags = 0;
#endif
        return (sigaction(sig, &vosf_sa, 0) == 0);
#else
        return (signal(sig, (signal_handler)sigsegv_handler) != SIG_ERR);
#endif
}
#endif

bool sigsegv_install_handler(sigsegv_fault_handler_t handler)
{
#ifdef HAVE_SIGSEGV_RECOVERY
        sigsegv_fault_handler = handler;
        bool success = true;
#define FAULT_HANDLER(sig) success = success && sigsegv_do_install_handler(sig);
        SIGSEGV_ALL_SIGNALS
#undef FAULT_HANDLER
        return success;
#else
        // FAIL: no siginfo_t nor sigcontext subterfuge is available
        return false;
#endif
}


/*
 *  SIGSEGV handler deinitialization
 */

void sigsegv_deinstall_handler(void)
{
#ifdef HAVE_SIGSEGV_RECOVERY
        sigsegv_fault_handler = 0;
#define FAULT_HANDLER(sig) signal(sig, SIG_DFL);
        SIGSEGV_ALL_SIGNALS
#undef FAULT_HANDLER
#endif
}


/*
 *  SIGSEGV ignore state modifier
 */

void sigsegv_set_ignore_state(bool ignore_fault)
{
        sigsegv_ignore_fault = ignore_fault;
}


/*
 *  Set callback function when we cannot handle the fault
 */

void sigsegv_set_dump_state(sigsegv_state_dumper_t handler)
{
        sigsegv_state_dumper = handler;
}


/*
 *  Test program used for configure/test
 */

#ifdef CONFIGURE_TEST_SIGSEGV_RECOVERY
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mman.h>
#include "vm_alloc.h"

static int page_size;
static volatile char * page = 0;
static volatile int handler_called = 0;

static bool sigsegv_test_handler(sigsegv_address_t fault_address, sigsegv_address_t instruction_address)
{
        handler_called++;
        if ((fault_address - 123) != page)
                exit(1);
        if (vm_protect((char *)((unsigned long)fault_address & -page_size), page_size, VM_PAGE_READ | VM_PAGE_WRITE) != 0)
                exit(1);
        return true;
}

#ifdef HAVE_SIGSEGV_SKIP_INSTRUCTION
static bool sigsegv_insn_handler(sigsegv_address_t fault_address, sigsegv_address_t instruction_address)
{
        return false;
}
#endif

int main(void)
{
        if (vm_init() < 0)
                return 1;

        page_size = getpagesize();
        if ((page = (char *)vm_acquire(page_size)) == VM_MAP_FAILED)
                return 1;
        
        if (vm_protect((char *)page, page_size, VM_PAGE_READ) < 0)
                return 1;
        
        if (!sigsegv_install_handler(sigsegv_test_handler))
                return 1;
        
        page[123] = 45;
        page[123] = 45;
        
        if (handler_called != 1)
                return 1;

#ifdef HAVE_SIGSEGV_SKIP_INSTRUCTION
        if (!sigsegv_install_handler(sigsegv_insn_handler))
                return 1;
        
        if (vm_protect((char *)page, page_size, VM_PAGE_READ | VM_PAGE_WRITE) < 0)
                return 1;
        
        for (int i = 0; i < page_size; i++)
                page[i] = (i + 1) % page_size;
        
        if (vm_protect((char *)page, page_size, VM_PAGE_NOACCESS) < 0)
                return 1;
        
        sigsegv_set_ignore_state(true);

#define TEST_SKIP_INSTRUCTION(TYPE) do {                                \
                const unsigned int TAG = 0x12345678;                    \
                TYPE data = *((TYPE *)(page + sizeof(TYPE)));   \
                volatile unsigned int effect = data + TAG;              \
                if (effect != TAG)                                                              \
                        return 1;                                                                       \
        } while (0)
        
        TEST_SKIP_INSTRUCTION(unsigned char);
        TEST_SKIP_INSTRUCTION(unsigned short);
        TEST_SKIP_INSTRUCTION(unsigned int);
#endif

        vm_exit();
        return 0;
}
#endif
Revision:	1.17
Committed:	2002-05-20T17:49:04Z (22 years, 2 months ago) by gbeauche
Branch:	MAIN
Changes since 1.16:	+38 -1 lines
Log Message:	Implement "ignoresegv" feature on FreeBSD/x86 (tested on FreeBSD 4.5) - sigsegv.cpp (ix86_skip_instruction): Add decoder for movzwl instructions. (main): oddly, FreeBSD doesn't seem to let a write to a page if it is write-only. Aka. make the page readable too.