/*
 * This software is part of the SBCL system. See the README file for
 * more information.
 *
 * This software is derived from the CMU CL system, which was
 * written at Carnegie Mellon University and released into the
 * public domain. The software is in the public domain and is
 * provided with absolutely no warranty. See the COPYING and CREDITS
 * files for more information.
 */

#include <stdio.h>

#include "sbcl.h"
#include "runtime.h"
#include "globals.h"
#include "validate.h"
#include "os.h"
#include "arch.h"
#include "lispregs.h"
#include "alloc.h"
#include "interrupt.h"
#include "interr.h"
#include "breakpoint.h"
#include "thread.h"
#include "pseudo-atomic.h"

#include "genesis/static-symbols.h"
#include "genesis/symbol.h"

#define BREAKPOINT_INST 0xcc    /* INT3 */
#define UD2_INST 0x0b0f         /* UD2 */

#ifndef LISP_FEATURE_UD2_BREAKPOINTS
#define BREAKPOINT_WIDTH 1
#else
#define BREAKPOINT_WIDTH 2
#endif

void arch_init(void)
{}

#ifndef LISP_FEATURE_WIN32
os_vm_address_t
arch_get_bad_addr(int sig, siginfo_t *code, os_context_t *context)
{
    return (os_vm_address_t)code->si_addr;
}
#endif


/*
 * hacking signal contexts
 *
 * (This depends both on architecture, which determines what we might
 * want to get to, and on OS, which determines how we get to it.)
 */

int *
context_eflags_addr(os_context_t *context)
{
#if defined __linux__ || defined __sun
    /* KLUDGE: As of kernel 2.2.14 on Red Hat 6.2, there's code in the
     * <sys/ucontext.h> file to define symbolic names for offsets into
     * gregs[], but it's conditional on __USE_GNU and not defined, so
     * we need to do this nasty absolute index magic number thing
     * instead. */
    return &context->uc_mcontext.gregs[16];
#elif defined __FreeBSD__
    return &context->uc_mcontext.mc_eflags;
#elif defined __OpenBSD__
    return &context->sc_eflags;
#elif defined LISP_FEATURE_DARWIN
    return (int *)(&context->uc_mcontext->SS.EFLAGS);
#elif defined __NetBSD__
    return &(context->uc_mcontext.__gregs[_REG_EFL]);
#elif defined LISP_FEATURE_WIN32
    return (int *)&context->win32_context->EFlags;
#else
#error unsupported OS
#endif
}

void arch_skip_instruction(os_context_t *context)
{
    /* Assuming we get here via an INT3 xxx instruction, the PC now
     * points to the interrupt code (a Lisp value) so we just move
     * past it. Skip the code; after that, if the code is an
     * error-trap or cerror-trap then skip the data bytes that follow. */

    int vlen;
    int code;


    /* Get and skip the Lisp interrupt code. */
    code = *(char*)(*os_context_pc_addr(context))++;
    switch (code)
        {
        case trap_Error:
        case trap_Cerror:
            /* Lisp error arg vector length */
            vlen = *(char*)(*os_context_pc_addr(context))++;
            /* Skip Lisp error arg data bytes. */
            while (vlen-- > 0) {
                ++*os_context_pc_addr(context);
            }
            break;

        case trap_Breakpoint:           /* not tested */
        case trap_FunEndBreakpoint: /* not tested */
            break;

#ifdef LISP_FEATURE_SB_SAFEPOINT
        case trap_GlobalSafepoint:
        case trap_CspSafepoint:
#endif
        case trap_PendingInterrupt:
        case trap_Halt:
        case trap_SingleStepAround:
        case trap_SingleStepBefore:
            /* only needed to skip the Code */
            break;

        default:
            fprintf(stderr,"[arch_skip_inst invalid code %d\n]\n",code);
            break;
        }

    FSHOW((stderr,
           "/[arch_skip_inst resuming at %x]\n",
           *os_context_pc_addr(context)));
}

unsigned char *
arch_internal_error_arguments(os_context_t *context)
{
    return 1 + (unsigned char *)(*os_context_pc_addr(context));
}

boolean
arch_pseudo_atomic_atomic(os_context_t *context)
{
    return get_pseudo_atomic_atomic(arch_os_get_current_thread());
}

void
arch_set_pseudo_atomic_interrupted(os_context_t *context)
{
    struct thread *thread = arch_os_get_current_thread();
    set_pseudo_atomic_interrupted(thread);
}

void
arch_clear_pseudo_atomic_interrupted(os_context_t *context)
{
    struct thread *thread = arch_os_get_current_thread();
    clear_pseudo_atomic_interrupted(thread);
}

/*
 * This stuff seems to get called for TRACE and debug activity.
 */

unsigned int
arch_install_breakpoint(void *pc)
{
    unsigned int result = *(unsigned int*)pc;

#ifndef LISP_FEATURE_UD2_BREAKPOINTS
    *(char*)pc = BREAKPOINT_INST;               /* x86 INT3       */
    *((char*)pc+1) = trap_Breakpoint;           /* Lisp trap code */
#else
    *(char*)pc = UD2_INST & 0xff;
    *((char*)pc+1) = UD2_INST >> 8;
    *((char*)pc+2) = trap_Breakpoint;
#endif

    return result;
}

void
arch_remove_breakpoint(void *pc, unsigned int orig_inst)
{
    *((char *)pc) = orig_inst & 0xff;
    *((char *)pc + 1) = (orig_inst & 0xff00) >> 8;
#if BREAKPOINT_WIDTH > 1
    *((char *)pc + 2) = (orig_inst & 0xff0000) >> 16;
#endif
}

/* When single stepping, single_stepping holds the original instruction
 * PC location. */
unsigned int *single_stepping = NULL;
#ifdef CANNOT_GET_TO_SINGLE_STEP_FLAG
unsigned int  single_step_save1;
unsigned int  single_step_save2;
unsigned int  single_step_save3;
#endif

void
arch_do_displaced_inst(os_context_t *context, unsigned int orig_inst)
{
    unsigned int *pc = (unsigned int*)(*os_context_pc_addr(context));

    /* Put the original instruction back. */
    arch_remove_breakpoint(pc, orig_inst);

#ifdef CANNOT_GET_TO_SINGLE_STEP_FLAG
    /* Install helper instructions for the single step:
     * pushf; or [esp],0x100; popf. */
    single_step_save1 = *(pc-3);
    single_step_save2 = *(pc-2);
    single_step_save3 = *(pc-1);
    *(pc-3) = 0x9c909090;
    *(pc-2) = 0x00240c81;
    *(pc-1) = 0x9d000001;
#else
    *context_eflags_addr(context) |= 0x100;
#endif

    single_stepping = pc;

#ifdef CANNOT_GET_TO_SINGLE_STEP_FLAG
    *os_context_pc_addr(context) = (os_context_register_t)((char *)pc - 9);
#endif
}

void
restore_breakpoint_from_single_step(os_context_t * context)
{
    /* fprintf(stderr,"* single step trap %x\n", single_stepping); */
#ifdef CANNOT_GET_TO_SINGLE_STEP_FLAG
    /* Un-install single step helper instructions. */
    *(single_stepping-3) = single_step_save1;
    *(single_stepping-2) = single_step_save2;
    *(single_stepping-1) = single_step_save3;
#else
    *context_eflags_addr(context) &= ~0x100;
#endif
    /* Re-install the breakpoint if possible. */
    if (((char *)*os_context_pc_addr(context) >
         (char *)single_stepping) &&
        ((char *)*os_context_pc_addr(context) <=
         (char *)single_stepping + BREAKPOINT_WIDTH)) {
        fprintf(stderr, "warning: couldn't reinstall breakpoint\n");
    } else {
        arch_install_breakpoint(single_stepping);
    }

    single_stepping = NULL;
    return;
}

void
arch_handle_breakpoint(os_context_t *context)
{
    *os_context_pc_addr(context) -= BREAKPOINT_WIDTH;
    handle_breakpoint(context);
}

void
arch_handle_fun_end_breakpoint(os_context_t *context)
{
    *os_context_pc_addr(context) -= BREAKPOINT_WIDTH;
    *os_context_pc_addr(context) =
        (int)handle_fun_end_breakpoint(context);
}

void
arch_handle_single_step_trap(os_context_t *context, int trap)
{
    arch_skip_instruction(context);
    /* On x86 the fdefn / function is always in EAX, so we pass 0
     * as the register_offset. */
    handle_single_step_trap(context, trap, 0);
}

#ifndef LISP_FEATURE_WIN32
void
sigtrap_handler(int signal, siginfo_t *info, os_context_t *context)
{
    unsigned int trap;

    if (single_stepping) {
        restore_breakpoint_from_single_step(context);
        return;
    }

    /* This is just for info in case the monitor wants to print an
     * approximation. */
    access_control_stack_pointer(arch_os_get_current_thread()) =
        (lispobj *)*os_context_sp_addr(context);

#ifdef LISP_FEATURE_SUNOS
    /* For some reason the breakpoints that :ENCAPSULATE NIL tracing sets up
     * cause a trace trap (i.e. processor single-stepping trap) on the following
     * instruction on Solaris 10/x86. -- JES, 2006-04-07
     */
    if (info->si_code == TRAP_TRACE) {
        lose("foo");
        return;
    }
#endif

    /* On entry %eip points just after the INT3 byte and aims at the
     * 'kind' value (eg trap_Cerror). For error-trap and Cerror-trap a
     * number of bytes will follow, the first is the length of the byte
     * arguments to follow. */
    trap = *(unsigned char *)(*os_context_pc_addr(context));
    handle_trap(context, trap);
}

void
sigill_handler(int signal, siginfo_t *siginfo, os_context_t *context) {
    /* Triggering SIGTRAP using int3 is unreliable on OS X/x86, so
     * we need to use illegal instructions for traps.
     */
#if defined(LISP_FEATURE_UD2_BREAKPOINTS) && !defined(LISP_FEATURE_MACH_EXCEPTION_HANDLER)
    if (*((unsigned short *)*os_context_pc_addr(context)) == UD2_INST) {
        *os_context_pc_addr(context) += 2;
        return sigtrap_handler(signal, siginfo, context);
    }
#endif
    fake_foreign_function_call(context);
    lose("Unhandled SIGILL");
}
#endif /* not LISP_FEATURE_WIN32 */

void
arch_install_interrupt_handlers()
{
    SHOW("entering arch_install_interrupt_handlers()");

    /* Note: The old CMU CL code here used sigtrap_handler() to handle
     * SIGILL as well as SIGTRAP. I couldn't see any reason to do
     * things that way. So, I changed to separate handlers when
     * debugging a problem on OpenBSD, where SBCL wasn't catching
     * SIGILL properly, but was instead letting the process be
     * terminated with an "Illegal instruction" output. If this change
     * turns out to break something (maybe breakpoint handling on some
     * OS I haven't tested on?) and we have to go back to the old CMU
     * CL way, I hope there will at least be a comment to explain
     * why.. -- WHN 2001-06-07 */
#if !defined(LISP_FEATURE_WIN32) && !defined(LISP_FEATURE_MACH_EXCEPTION_HANDLER)
    undoably_install_low_level_interrupt_handler(SIGILL , sigill_handler);
    undoably_install_low_level_interrupt_handler(SIGTRAP, sigtrap_handler);
#endif
    SHOW("returning from arch_install_interrupt_handlers()");
}

#ifdef LISP_FEATURE_LINKAGE_TABLE
/* FIXME: It might be cleaner to generate these from the lisp side of
 * things.
 */

void
arch_write_linkage_table_jmp(char * reloc, void * fun)
{
    /* Make JMP to function entry. JMP offset is calculated from next
     * instruction.
     */
    long offset = (char *)fun - (reloc + 5);
    int i;

    *reloc++ = 0xe9;            /* opcode for JMP rel32 */
    for (i = 0; i < 4; i++) {
        *reloc++ = offset & 0xff;
        offset >>= 8;
    }

    /* write a nop for good measure. */
    *reloc = 0x90;
}

void
arch_write_linkage_table_ref(void * reloc, void * data)
{
    *(unsigned long *)reloc = (unsigned long)data;
}

#endif
