// Copyright 2016 The Fuchsia Authors
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#include <err.h>
#include <inttypes.h>
#include <lib/crypto/global_prng.h>
#include <lib/user_copy/user_ptr.h>
#include <platform.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <trace.h>
#include <zircon/syscalls/log.h>
#include <zircon/syscalls/policy.h>
#include <zircon/types.h>

#include <explicit-memory/bytes.h>
#include <fbl/alloc_checker.h>
#include <fbl/ref_ptr.h>
#include <kernel/auto_lock.h>
#include <kernel/thread.h>
#include <ktl/atomic.h>
#include <object/event_dispatcher.h>
#include <object/event_pair_dispatcher.h>
#include <object/handle.h>
#include <object/log_dispatcher.h>
#include <object/process_dispatcher.h>
#include <object/resource.h>
#include <object/thread_dispatcher.h>

#include "priv.h"

#define LOCAL_TRACE 0

constexpr size_t kMaxCPRNGDraw = ZX_CPRNG_DRAW_MAX_LEN;
constexpr size_t kMaxCPRNGSeed = ZX_CPRNG_ADD_ENTROPY_MAX_LEN;

// zx_status_t zx_nanosleep
zx_status_t sys_nanosleep(zx_time_t deadline) {
  LTRACEF("nseconds %" PRIi64 "\n", deadline);

  if (deadline <= 0) {
    thread_yield();
    return ZX_OK;
  }

  const auto up = ProcessDispatcher::GetCurrent();
  const Deadline slackDeadline(deadline, up->GetTimerSlackPolicy());
  const zx_time_t now = current_time();

  ThreadDispatcher::AutoBlocked by(ThreadDispatcher::Blocked::SLEEPING);

  // This syscall is declared as "blocking" in syscalls.abigen, so a higher
  // layer will automatically retry if we return ZX_ERR_INTERNAL_INTR_RETRY.
  return thread_sleep_etc(slackDeadline, /* interruptable */ true, now);
}

// This must be accessed atomically from any given thread.
//
// NOTE(abdulla): This is used by pvclock. If logic here is changed, please
// update pvclock too.
ktl::atomic<int64_t> utc_offset;

zx_status_t sys_clock_get(zx_clock_t clock_id, user_out_ptr<zx_time_t> out_time) {
  zx_time_t time;
  switch (clock_id) {
    case ZX_CLOCK_MONOTONIC:
      time = current_time();
      break;
    case ZX_CLOCK_UTC:
      time = current_time() + utc_offset.load();
      break;
    case ZX_CLOCK_THREAD:
      time = ThreadDispatcher::GetCurrent()->runtime_ns();
      break;
    default:
      return ZX_ERR_INVALID_ARGS;
  }

  return out_time.copy_to_user(time);
}

zx_time_t sys_clock_get_monotonic() { return current_time(); }

// zx_status_t zx_clock_adjust
zx_status_t sys_clock_adjust(zx_handle_t hrsrc, zx_clock_t clock_id, int64_t offset) {
  // TODO(ZX-971): finer grained validation
  zx_status_t status;
  if ((status = validate_resource(hrsrc, ZX_RSRC_KIND_ROOT)) < 0) {
    return status;
  }

  switch (clock_id) {
    case ZX_CLOCK_MONOTONIC:
      return ZX_ERR_ACCESS_DENIED;
    case ZX_CLOCK_UTC:
      utc_offset.store(offset);
      return ZX_OK;
    default:
      return ZX_ERR_INVALID_ARGS;
  }
}

// zx_status_t zx_event_create
zx_status_t sys_event_create(uint32_t options, user_out_handle* event_out) {
  LTRACEF("options 0x%x\n", options);

  if (options != 0u)
    return ZX_ERR_INVALID_ARGS;

  auto up = ProcessDispatcher::GetCurrent();
  zx_status_t res = up->EnforceBasicPolicy(ZX_POL_NEW_EVENT);
  if (res != ZX_OK)
    return res;

  KernelHandle<EventDispatcher> handle;
  zx_rights_t rights;

  zx_status_t result = EventDispatcher::Create(options, &handle, &rights);
  if (result == ZX_OK)
    result = event_out->make(ktl::move(handle), rights);
  return result;
}

// zx_status_t zx_eventpair_create
zx_status_t sys_eventpair_create(uint32_t options, user_out_handle* out0, user_out_handle* out1) {
  if (options != 0u)  // No options defined/supported yet.
    return ZX_ERR_NOT_SUPPORTED;

  auto up = ProcessDispatcher::GetCurrent();
  zx_status_t res = up->EnforceBasicPolicy(ZX_POL_NEW_EVENTPAIR);
  if (res != ZX_OK)
    return res;

  KernelHandle<EventPairDispatcher> handle0, handle1;
  zx_rights_t rights;
  zx_status_t result = EventPairDispatcher::Create(&handle0, &handle1, &rights);

  if (result == ZX_OK)
    result = out0->make(ktl::move(handle0), rights);
  if (result == ZX_OK)
    result = out1->make(ktl::move(handle1), rights);

  return result;
}

// zx_status_t zx_debuglog_create
zx_status_t sys_debuglog_create(zx_handle_t rsrc, uint32_t options, user_out_handle* out) {
  LTRACEF("options 0x%x\n", options);

  // TODO(ZX-2184) Require a non-INVALID handle.
  if (rsrc != ZX_HANDLE_INVALID) {
    // TODO(ZX-971): finer grained validation
    zx_status_t status = validate_resource(rsrc, ZX_RSRC_KIND_ROOT);
    if (status != ZX_OK)
      return status;
  }

  // create a Log dispatcher
  KernelHandle<LogDispatcher> handle;
  zx_rights_t rights;
  zx_status_t result = LogDispatcher::Create(options, &handle, &rights);
  if (result != ZX_OK)
    return result;

  // by default log objects are write-only
  // as readable logs are more expensive
  if (options & ZX_LOG_FLAG_READABLE) {
    rights |= ZX_RIGHT_READ;
  }

  // create a handle and attach the dispatcher to it
  return out->make(ktl::move(handle), rights);
}

// zx_status_t zx_debuglog_write
zx_status_t sys_debuglog_write(zx_handle_t log_handle, uint32_t options,
                               user_in_ptr<const void> ptr, size_t len) {
  LTRACEF("log handle %x, opt %x, ptr 0x%p, len %zu\n", log_handle, options, ptr.get(), len);

  len = len > DLOG_MAX_DATA ? DLOG_MAX_DATA : len;

  if (options & (~ZX_LOG_FLAGS_MASK))
    return ZX_ERR_INVALID_ARGS;

  auto up = ProcessDispatcher::GetCurrent();

  fbl::RefPtr<LogDispatcher> log;
  zx_status_t status = up->GetDispatcherWithRights(log_handle, ZX_RIGHT_WRITE, &log);
  if (status != ZX_OK)
    return status;

  char buf[DLOG_MAX_RECORD];
  if (ptr.reinterpret<const char>().copy_array_from_user(buf, len) != ZX_OK)
    return ZX_ERR_INVALID_ARGS;

  return log->Write(options, buf, len);
}

// zx_status_t zx_debuglog_read
zx_status_t sys_debuglog_read(zx_handle_t log_handle, uint32_t options, user_out_ptr<void> ptr,
                              size_t len) {
  LTRACEF("log handle %x, opt %x, ptr 0x%p, len %zu\n", log_handle, options, ptr.get(), len);

  if (options != 0)
    return ZX_ERR_INVALID_ARGS;

  auto up = ProcessDispatcher::GetCurrent();

  fbl::RefPtr<LogDispatcher> log;
  zx_status_t status = up->GetDispatcherWithRights(log_handle, ZX_RIGHT_READ, &log);
  if (status != ZX_OK)
    return status;

  char buf[DLOG_MAX_RECORD];
  size_t actual;
  if ((status = log->Read(options, buf, DLOG_MAX_RECORD, &actual)) < 0)
    return status;

  const size_t to_copy = fbl::min(actual, len);
  if (ptr.copy_array_to_user(buf, to_copy) != ZX_OK)
    return ZX_ERR_INVALID_ARGS;

  return static_cast<zx_status_t>(to_copy);
}

// zx_status_t zx_cprng_draw_once
zx_status_t sys_cprng_draw_once(user_out_ptr<void> buffer, size_t len) {
  if (len > kMaxCPRNGDraw)
    return ZX_ERR_INVALID_ARGS;

  uint8_t kernel_buf[kMaxCPRNGDraw];
  // Ensure we get rid of the stack copy of the random data as this function returns.
  explicit_memory::ZeroDtor<uint8_t> zero_guard(kernel_buf, sizeof(kernel_buf));

  auto prng = crypto::GlobalPRNG::GetInstance();
  ASSERT(prng->is_thread_safe());
  prng->Draw(kernel_buf, len);

  if (buffer.copy_array_to_user(kernel_buf, len) != ZX_OK)
    return ZX_ERR_INVALID_ARGS;
  return ZX_OK;
}

// zx_status_t zx_cprng_add_entropy
zx_status_t sys_cprng_add_entropy(user_in_ptr<const void> buffer, size_t buffer_size) {
  if (buffer_size > kMaxCPRNGSeed)
    return ZX_ERR_INVALID_ARGS;

  uint8_t kernel_buf[kMaxCPRNGSeed];
  // Ensure we get rid of the stack copy of the entropy as this function
  // returns.
  explicit_memory::ZeroDtor<uint8_t> zero_guard(kernel_buf, sizeof(kernel_buf));

  if (buffer.copy_array_from_user(kernel_buf, buffer_size) != ZX_OK)
    return ZX_ERR_INVALID_ARGS;

  auto prng = crypto::GlobalPRNG::GetInstance();
  ASSERT(prng->is_thread_safe());
  prng->AddEntropy(kernel_buf, buffer_size);

  return ZX_OK;
}