pumpitupdev_pumptools/src/main/hook/patch/mounts.c

#define LOG_MODULE "patch-mounts"

#include <assert.h>
#include <stdbool.h>
#include <stdint.h>
#include <string.h>

#include "capnhook/hook/filehook.h"

#include "util/log.h"

/* looks odd but hddd is intentional */
static const char *patch_mount_proc_mount_file = "/dev/hddd /mnt/hd";

static FILE *patch_mount_file = NULL;
static bool patch_mount_eof;

static enum cnh_result patch_hdd_check_filehook(struct cnh_filehook_irp *irp)
{
  enum cnh_result result;

  result = CNH_RESULT_SUCCESS;

  assert(irp);

  if (irp->op != CNH_FILEHOOK_IRP_OP_OPEN && irp->file != patch_mount_file) {
    return cnh_filehook_invoke_next(irp);
  }

  switch (irp->op) {
    case CNH_FILEHOOK_IRP_OP_OPEN: {
      if (!strcmp(irp->open_filename, "/proc/mounts")) {
        patch_mount_file = cnh_filehook_open_dummy_file_handle();
        irp->file = patch_mount_file;

        patch_mount_eof = false;

        log_debug("/proc/mounts opened: %p", irp->file);
      } else {
        return cnh_filehook_invoke_next(irp);
      }

      break;
    }

    case CNH_FILEHOOK_IRP_OP_FGETS: {
      size_t size;

      log_info("/proc/mounts fake read");

      size = strlen(patch_mount_proc_mount_file) + 1;

      /* +1: copy the null terminator, too */
      memcpy(
          &irp->read.bytes[irp->read.pos], patch_mount_proc_mount_file, size);
      irp->read.pos += size;

      patch_mount_eof = true;

      break;
    }

    case CNH_FILEHOOK_IRP_OP_SEEK: {
      /* Ignore seeking */

      break;
    }

    case CNH_FILEHOOK_IRP_OP_TELL: {
      /* Return size */
      irp->tell_offset = strlen(patch_mount_proc_mount_file) + 1;

      break;
    }

    case CNH_FILEHOOK_IRP_OP_EOF: {
      irp->eof = patch_mount_eof;
      break;
    }

    case CNH_FILEHOOK_IRP_OP_CLOSE: {
      patch_mount_file = NULL;

      /* Actually close dummy handle */
      return cnh_filehook_invoke_next(irp);
    }

    default:
      log_warn("Unhandled file op: %d", irp->op);
      break;
  }

  return result;
}

void patch_mounts_init(void)
{
  cnh_filehook_push_handler(patch_hdd_check_filehook);
  log_info("Initialized");
}