#include "Rts.h"

#include "sm/OSMem.h"
#include "linker/MMap.h"
#include "Trace.h"
#include "ReportMemoryMap.h"

#if RTS_LINKER_USE_MMAP
#include <sys/mman.h>
#endif

/* Link objects into the lower 2Gb on x86_64 and AArch64.  GHC assumes the
 * small memory model on this architecture (see gcc docs,
 * -mcmodel=small).
 *
 * MAP_32BIT not available on OpenBSD/amd64
 */
#if defined(MAP_32BIT) && (defined(x86_64_HOST_ARCH) || (defined(aarch64_TARGET_ARCH) || defined(aarch64_HOST_ARCH)))
#define MAP_LOW_MEM
#define TRY_MAP_32BIT MAP_32BIT
#else
#define TRY_MAP_32BIT 0
#endif

/* MAP_ANONYMOUS is MAP_ANON on some systems,
   e.g. OS X (before Sierra), OpenBSD etc */
#if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
#define MAP_ANONYMOUS MAP_ANON
#endif

/* In order to simplify control flow a bit, some references to mmap-related
   definitions are blocked off by a C-level if statement rather than a CPP-level
   #if statement. Since those are dead branches when !RTS_LINKER_USE_MMAP, we
   just stub out the relevant symbols here
*/
#if !RTS_LINKER_USE_MMAP
#define munmap(x,y) /* nothing */
#define MAP_ANONYMOUS 0
#endif

void *mmap_32bit_base = LINKER_LOAD_BASE;

static const char *memoryAccessDescription(MemoryAccess mode)
{
  switch (mode) {
  case MEM_NO_ACCESS:    return "no-access";
  case MEM_READ_ONLY:    return "read-only";
  case MEM_READ_WRITE:   return "read-write";
  case MEM_READ_EXECUTE: return "read-execute";
  case MEM_READ_WRITE_EXECUTE:
                         return "read-write-execute";
  default: barf("invalid MemoryAccess");
  }
}

/* A region of memory that we might map into. */
struct MemoryRegion {
    void *start;
    void *end;
    void *last;
      /* the end of the last mapping which we made into this region.
       * this is where we will start searching next time we need to allocate.
       */
};

#define LOW_ADDR 0x01000000
static struct MemoryRegion allMemory = {
    .start = (void *) LOW_ADDR,
    .end = (void *) -1,
    .last = (void *) LOW_ADDR
};

#if defined(mingw32_HOST_OS)

static DWORD
memoryAccessToProt(MemoryAccess access)
{
  switch (access) {
  case MEM_NO_ACCESS:    return PAGE_NOACCESS;
  case MEM_READ_ONLY:    return PAGE_READONLY;
  case MEM_READ_WRITE:   return PAGE_READWRITE;
  case MEM_READ_EXECUTE: return PAGE_EXECUTE_READ;
  case MEM_READ_WRITE_EXECUTE:
                         return PAGE_EXECUTE_READWRITE;
  default: barf("invalid MemoryAccess");
  }
}

//
// Returns NULL on failure.
//
void *
mmapAnonForLinker (size_t bytes)
{
  return VirtualAlloc(NULL, bytes, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
}

void
munmapForLinker (void *addr, size_t bytes, const char *caller)
{
  if (VirtualFree(addr, 0, MEM_RELEASE) == 0) {
    sysErrorBelch("munmapForLinker: %s: Failed to unmap %zd bytes at %p",
                  caller, bytes, addr);
  }
}

/**
 * Change the allowed access modes of a region of memory previously allocated
 * with mmapAnonForLinker.
 */
void
mprotectForLinker(void *start, size_t len, MemoryAccess mode)
{
  DWORD old;
  if (len == 0) {
    return;
  }
  DWORD prot = memoryAccessToProt(mode);

  if (VirtualProtect(start, len, prot, &old) == 0) {
    sysErrorBelch("mprotectForLinker: failed to protect %zd bytes at %p as %s",
                  len, start, memoryAccessDescription(mode));
    ASSERT(false);
  }
}

#elif RTS_LINKER_USE_MMAP

static int
memoryAccessToProt(MemoryAccess access)
{
    switch (access) {
    case MEM_NO_ACCESS:    return 0;
    case MEM_READ_ONLY:    return PROT_READ;
    case MEM_READ_WRITE:   return PROT_READ | PROT_WRITE;
    case MEM_READ_EXECUTE: return PROT_READ | PROT_EXEC;
    case MEM_READ_WRITE_EXECUTE:
                           return PROT_READ | PROT_WRITE | PROT_EXEC;
    default: barf("invalid MemoryAccess");
    }
}

static void *
doMmap(void *map_addr, size_t bytes, int prot, uint32_t flags, int fd, int offset)
{
    flags |= MAP_PRIVATE;

    IF_DEBUG(linker_verbose,
             debugBelch("mmapForLinker: \tprotection %#0x\n", prot));
    IF_DEBUG(linker_verbose,
             debugBelch("mmapForLinker: \tflags      %#0x\n", flags));
    IF_DEBUG(linker_verbose,
             debugBelch("mmapForLinker: \tsize       %#0zx\n", bytes));
    IF_DEBUG(linker_verbose,
             debugBelch("mmapForLinker: \tmap_addr   %p\n", map_addr));

    void * result = mmap(map_addr, bytes, prot, flags, fd, offset);
    if (result == MAP_FAILED) {
        sysErrorBelch("mmap %zx bytes at %p", bytes, map_addr);
        reportMemoryMap();
        errorBelch("Try specifying an address with +RTS -xm<addr> -RTS");
        return NULL;
    }
    return result;
}


static struct MemoryRegion *
nearImage(void) {
    static struct MemoryRegion region = { NULL, NULL, NULL };
    if (region.end == NULL) {
        region.start = mmap_32bit_base;
        region.end = (uint8_t *) region.start + 0x80000000;
        region.last = region.start;
    }
    return &region;
}

static void *
mmapInRegion (
        struct MemoryRegion *region,
        size_t bytes,
        MemoryAccess access,
        uint32_t flags,
        int fd,
        int offset)
{
    bool wrapped = false;
    int prot = memoryAccessToProt(access);
    void *p = region->last;
    while (1) {
        void *result = doMmap(p, bytes, prot, flags, fd, offset);
        if (result == NULL) {
            // The mapping failed
            return NULL;
        } else if (result < region->start) {
            // Uh oh, we assume that mmap() will only give us a
            // an address at or after the requested address.
            // Try again.
            p = (uint8_t *) result + bytes;
        } else if (result < region->end) {
            // Success!
            region->last = (uint8_t *) result + bytes;
            return result;
        } else if (wrapped) {
            // We failed to find a suitable mapping
            munmap(result, bytes);
            reportMemoryMap();
            errorBelch("mmapForLinker: failed to mmap() memory below 2Gb; "
                       "asked for %zu bytes at %p. "
                       "Try specifying an address with +RTS -xm<addr> -RTS",
                       bytes, p);
            return NULL;
        }

        // mmap() gave us too high an address; wrap around and try again
        munmap(result, bytes);
        wrapped = true;
        p = region->start;
    }
}

/*
 * Map memory for code.
 * Returns NULL on failure.
 */
void *
mmapForLinker (size_t bytes, MemoryAccess access, uint32_t flags, int fd, int offset)
{
    bytes = roundUpToPage(bytes);
    struct MemoryRegion *region;

    IF_DEBUG(linker_verbose, debugBelch("mmapForLinker: start\n"));
    if (RtsFlags.MiscFlags.linkerAlwaysPic) {
        /* make no attempt at mapping low memory if we are assuming PIC */
        region = &allMemory;
    } else {
        region = nearImage();
    }

    /* Use MAP_32BIT if appropriate */
    if (region->end <= (void *) 0xffffffff) {
        flags |= TRY_MAP_32BIT;
    }

    void *result = mmapInRegion(region, bytes, access, flags, fd, offset);
    IF_DEBUG(linker_verbose,
             debugBelch("mmapForLinker: mapped %zd bytes starting at %p\n",
                        bytes, result));
    IF_DEBUG(linker_verbose,
             debugBelch("mmapForLinker: done\n"));
    return result;
}

/*
 * Map read/write pages in low memory. Returns NULL on failure.
 */
void *
mmapAnonForLinker (size_t bytes)
{
    return mmapForLinker (bytes, MEM_READ_WRITE, MAP_ANONYMOUS, -1, 0);
}

void munmapForLinker (void *addr, size_t bytes, const char *caller)
{
    int r = munmap(addr, bytes);
    if (r == -1) {
        // Should we abort here?
        sysErrorBelch("munmap: %s", caller);
    }
}

/* Note [Memory protection in the linker]
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * For many years the linker would simply map all of its memory
 * with PROT_READ|PROT_WRITE|PROT_EXEC. However operating systems have been
 * becoming increasingly reluctant to accept this practice (e.g. #17353,
 * #12657) and for good reason: writable code is ripe for exploitation.
 *
 * Consequently mmapForLinker now maps its memory with PROT_READ|PROT_WRITE.
 * After the linker has finished filling/relocating the mapping it must then
 * call mprotectForLinker on the sections of the mapping which
 * contain executable code.
 *
 * Note that the m32 allocator handles protection of its allocations. For this
 * reason the caller to m32_alloc() must tell the allocator whether the
 * allocation needs to be executable. The caller must then ensure that they
 * call m32_allocator_flush() after they are finished filling the region, which
 * will cause the allocator to change the protection bits to
 * PROT_READ|PROT_EXEC.
 *
 */

/*
 * Mark an portion of a mapping previously reserved by mmapForLinker
 * as executable (but not writable).
 */
void mprotectForLinker(void *start, size_t len, MemoryAccess mode)
{
    if (len == 0) {
        return;
    }
    IF_DEBUG(linker_verbose,
             debugBelch("mprotectForLinker: protecting %" FMT_Word
                        " bytes starting at %p as %s\n",
                        (W_)len, start, memoryAccessDescription(mode)));

    int prot = memoryAccessToProt(mode);

    if (mprotect(start, len, prot) == -1) {
        sysErrorBelch("mprotectForLinker: failed to protect %zd bytes at %p as %s",
                      len, start, memoryAccessDescription(mode));
    }
}
#endif