text: #include <sys/ioctl.h>
  #include <stdarg.h>
  #include <errno.h>
  #include <time.h>
  #include <sys/time.h>
  #include <stddef.h>
  #include <stdint.h>
  #include <string.h>
  #include <endian.h>
  #include "syscall.h"
  
  #define alignof(t) offsetof(struct { char c; t x; }, x)
  
  #define W 1
  #define R 2
  #define WR 3
  
  struct ioctl_compat_map {
  	int new_req, old_req;
  	unsigned char old_size, dir, force_align, noffs;
  	unsigned char offsets[8];
  };
  
  #define NINTH(a,b,c,d,e,f,g,h,i,...) i
  #define COUNT(...) NINTH(__VA_ARGS__,8,7,6,5,4,3,2,1,0)
  #define OFFS(...) COUNT(__VA_ARGS__), { __VA_ARGS__ }
  
  /* yields a type for a struct with original size n, with a misaligned
   * timeval/timespec expanded from 32- to 64-bit. for use with ioctl
   * number producing macros; only size of result is meaningful. */
  #define new_misaligned(n) struct { int i; time_t t; char c[(n)-4]; }
  
  struct v4l2_event {
  	uint32_t a;
  	uint64_t b[8];
  	uint32_t c[2], ts[2], d[9];
  };
  
  static const struct ioctl_compat_map compat_map[] = {
  	{ SIOCGSTAMP, SIOCGSTAMP_OLD, 8, R, 0, OFFS(0, 4) },
  	{ SIOCGSTAMPNS, SIOCGSTAMPNS_OLD, 8, R, 0, OFFS(0, 4) },
  
  	/* SNDRV_TIMER_IOCTL_STATUS */
  	{ _IOR('T', 0x14, char[96]), _IOR('T', 0x14, 88), 88, R, 0, OFFS(0,4) },
  
  	/* SNDRV_PCM_IOCTL_STATUS[_EXT] */
  	{ _IOR('A', 0x20, char[128]), _IOR('A', 0x20, char[108]), 108, R, 1, OFFS(4,8,12,16,52,56,60,64) },
  	{ _IOWR('A', 0x24, char[128]), _IOWR('A', 0x24, char[108]), 108, WR, 1, OFFS(4,8,12,16,52,56,60,64) },
  
  	/* SNDRV_RAWMIDI_IOCTL_STATUS */
  	{ _IOWR('W', 0x20, char[48]), _IOWR('W', 0x20, char[36]), 36, WR, 1, OFFS(4,8) },
  
  	/* SNDRV_PCM_IOCTL_SYNC_PTR - with 3 subtables */
  	{ _IOWR('A', 0x23, char[136]), _IOWR('A', 0x23, char[132]), 0, WR, 1, 0 },
  	{ 0, 0, 4, WR, 1, 0 }, /* snd_pcm_sync_ptr (flags only) */
  	{ 0, 0, 32, WR, 1, OFFS(8,12,16,24,28) }, /* snd_pcm_mmap_status */
  	{ 0, 0, 4, WR, 1, 0 }, /* snd_pcm_mmap_control (each member) */
  
  	/* VIDIOC_QUERYBUF, VIDIOC_QBUF, VIDIOC_DQBUF, VIDIOC_PREPARE_BUF */
  	{ _IOWR('V',  9, new_misaligned(68)), _IOWR('V',  9, char[68]), 68, WR, 1, OFFS(20, 24) },
  	{ _IOWR('V', 15, new_misaligned(68)), _IOWR('V', 15, char[68]), 68, WR, 1, OFFS(20, 24) },
  	{ _IOWR('V', 17, new_misaligned(68)), _IOWR('V', 17, char[68]), 68, WR, 1, OFFS(20, 24) },
  	{ _IOWR('V', 93, new_misaligned(68)), _IOWR('V', 93, char[68]), 68, WR, 1, OFFS(20, 24) },
  
  	/* VIDIOC_DQEVENT */
  	{ _IOR('V', 89, new_misaligned(120)), _IOR('V', 89, struct v4l2_event), sizeof(struct v4l2_event),
  	  R, 0, OFFS(offsetof(struct v4l2_event, ts[0]), offsetof(struct v4l2_event, ts[1])) },
  
  	/* VIDIOC_OMAP3ISP_STAT_REQ */
  	{ _IOWR('V', 192+6, char[32]), _IOWR('V', 192+6, char[24]), 22, WR, 0, OFFS(0,4) },
  
  	/* PPPIOCGIDLE */
  	{ _IOR('t', 63, char[16]), _IOR('t', 63, char[8]), 8, R, 0, OFFS(0,4) },
  
  	/* PPGETTIME, PPSETTIME */
  	{ _IOR('p', 0x95, char[16]), _IOR('p', 0x95, char[8]), 8, R, 0, OFFS(0,4) },
  	{ _IOW('p', 0x96, char[16]), _IOW('p', 0x96, char[8]), 8, W, 0, OFFS(0,4) },
  
  	/* LPSETTIMEOUT */
  	{ _IOW(0x6, 0xf, char[16]), 0x060f, 8, W, 0, OFFS(0,4) },
  };
  
  static void convert_ioctl_struct(const struct ioctl_compat_map *map, char *old, char *new, int dir)
  {
  	int new_offset = 0;
  	int old_offset = 0;
  	int old_size = map->old_size;
  	if (!(dir & map->dir)) return;
  	if (!map->old_size) {
  		/* offsets hard-coded for SNDRV_PCM_IOCTL_SYNC_PTR;
  		 * if another exception appears this needs changing. */
  		convert_ioctl_struct(map+1, old, new, dir);
  		convert_ioctl_struct(map+2, old+4, new+8, dir);
  		/* snd_pcm_mmap_control, special-cased due to kernel
  		 * type definition having been botched. */
  		int adj = BYTE_ORDER==BIG_ENDIAN ? 4 : 0;
  		convert_ioctl_struct(map+3, old+68, new+72+adj, dir);
  		convert_ioctl_struct(map+3, old+72, new+76+3*adj, dir);
  		return;
  	}
  	for (int i=0; i < map->noffs; i++) {
  		int ts_offset = map->offsets[i];
  		int len = ts_offset-old_offset;
  		if (dir==W) memcpy(old+old_offset, new+new_offset, len);
  		else memcpy(new+new_offset, old+old_offset, len);
  		new_offset += len;
  		old_offset += len;
  		long long new_ts;
  		long old_ts;
  		int align = map->force_align ? sizeof(time_t) : alignof(time_t);
  		new_offset += (align-1) & -new_offset;
  		if (dir==W) {
  			memcpy(&new_ts, new+new_offset, sizeof new_ts);
  			old_ts = new_ts;
  			memcpy(old+old_offset, &old_ts, sizeof old_ts);
  		} else {
  			memcpy(&old_ts, old+old_offset, sizeof old_ts);
  			new_ts = old_ts;
  			memcpy(new+new_offset, &new_ts, sizeof new_ts);
  		}
  		new_offset += sizeof new_ts;
  		old_offset += sizeof old_ts;
  	}
  	if (dir==W) memcpy(old+old_offset, new+new_offset, old_size-old_offset);
  	else memcpy(new+new_offset, old+old_offset, old_size-old_offset);
  }
  
  int ioctl(int fd, int req, ...)
  {
  	void *arg;
  	va_list ap;
  	va_start(ap, req);
  	arg = va_arg(ap, void *);
  	va_end(ap);
  	int r = __syscall(SYS_ioctl, fd, req, arg);
  	if (SIOCGSTAMP != SIOCGSTAMP_OLD && req && r==-ENOTTY) {
  		for (int i=0; i<sizeof compat_map/sizeof *compat_map; i++) {
  			if (compat_map[i].new_req != req) continue;
  			union {
  				long long align;
  				char buf[256];
  			} u;
  			convert_ioctl_struct(&compat_map[i], u.buf, arg, W);
  			r = __syscall(SYS_ioctl, fd, compat_map[i].old_req, u.buf);
  			if (r<0) break;
  			convert_ioctl_struct(&compat_map[i], u.buf, arg, R);
  			break;
  		}
  	}
  	return __syscall_ret(r);
  }
  