A fast, lightweight and minimalistic Wayland terminal emulator
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#include "shm.h"
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <unistd.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/time.h>
#include <linux/mman.h>
#include <linux/memfd.h>
#include <fcntl.h>
#include <pixman.h>
#include <fcft/stride.h>
#include <tllist.h>
#define LOG_MODULE "shm"
#define LOG_ENABLE_DBG 0
#include "log.h"
#include "macros.h"
#include "xmalloc.h"
#if !defined(MAP_UNINITIALIZED)
#define MAP_UNINITIALIZED 0
#endif
#define TIME_SCROLL 0
/*
* Maximum memfd size allowed.
*
* On 64-bit, we could in theory use up to 2GB (wk_shm_create_pool()
* is limited to int32_t), since we never mmap() the entire region.
*
* The compositor is different matter - it needs to mmap() the entire
* range, and *keep* the mapping for as long as is has buffers
* referencing it (thus - always). And if we open multiple terminals,
* then the required address space multiples...
*
* That said, 128TB (the total amount of available user address space
* on 64-bit) is *a lot*; we can fit 67108864 2GB memfds into
* that. But, let's be conservative for now.
*
* On 32-bit the available address space is too small and SHM
* scrolling is disabled.
*
* Note: this is the _default_ size. It can be overridden by calling
* shm_set_max_pool_size();
*/
static off_t max_pool_size = 512 * 1024 * 1024;
static tll(struct buffer) buffers;
static bool can_punch_hole = false;
static bool can_punch_hole_initialized = false;
#undef MEASURE_SHM_ALLOCS
#if defined(MEASURE_SHM_ALLOCS)
static size_t max_alloced = 0;
#endif
void
shm_set_max_pool_size(off_t _max_pool_size)
{
max_pool_size = _max_pool_size;
}
static void
buffer_destroy_dont_close(struct buffer *buf)
{
if (buf->pix != NULL) {
for (size_t i = 0; i < buf->pix_instances; i++)
if (buf->pix[i] != NULL)
pixman_image_unref(buf->pix[i]);
}
if (buf->wl_buf != NULL)
wl_buffer_destroy(buf->wl_buf);
free(buf->pix);
buf->pix = NULL;
buf->wl_buf = NULL;
buf->mmapped = NULL;
}
static void
buffer_destroy(struct buffer *buf)
{
buffer_destroy_dont_close(buf);
if (buf->real_mmapped != MAP_FAILED)
munmap(buf->real_mmapped, buf->mmap_size);
if (buf->pool != NULL)
wl_shm_pool_destroy(buf->pool);
if (buf->fd >= 0)
close(buf->fd);
buf->real_mmapped = MAP_FAILED;
buf->pool = NULL;
buf->fd = -1;
}
void
shm_fini(void)
{
tll_foreach(buffers, it) {
buffer_destroy(&it->item);
tll_remove(buffers, it);
}
#if defined(MEASURE_SHM_ALLOCS) && MEASURE_SHM_ALLOCS
LOG_INFO("max total allocations was: %zu MB", max_alloced / 1024 / 1024);
#endif
}
static void
buffer_release(void *data, struct wl_buffer *wl_buffer)
{
struct buffer *buffer = data;
LOG_DBG("release: cookie=%lx (buf=%p)", buffer->cookie, (void *)buffer);
assert(buffer->wl_buf == wl_buffer);
assert(buffer->busy);
buffer->busy = false;
}
static const struct wl_buffer_listener buffer_listener = {
.release = &buffer_release,
};
static size_t
page_size(void)
{
static size_t size = 0;
if (size == 0) {
long n = sysconf(_SC_PAGE_SIZE);
if (n <= 0) {
LOG_ERRNO("failed to get page size");
size = 4096;
} else {
size = (size_t)n;
}
}
assert(size > 0);
return size;
}
static bool
instantiate_offset(struct wl_shm *shm, struct buffer *buf, off_t new_offset)
{
assert(buf->fd >= 0);
assert(buf->mmapped == NULL);
assert(buf->wl_buf == NULL);
assert(buf->pix == NULL);
void *mmapped = MAP_FAILED;
struct wl_buffer *wl_buf = NULL;
pixman_image_t **pix = xcalloc(buf->pix_instances, sizeof(*pix));
mmapped = (uint8_t *)buf->real_mmapped + new_offset;
wl_buf = wl_shm_pool_create_buffer(
buf->pool, new_offset, buf->width, buf->height, buf->stride, WL_SHM_FORMAT_ARGB8888);
if (wl_buf == NULL) {
LOG_ERR("failed to create SHM buffer");
goto err;
}
/* One pixman image for each worker thread (do we really need multiple?) */
for (size_t i = 0; i < buf->pix_instances; i++) {
pix[i] = pixman_image_create_bits_no_clear(
PIXMAN_a8r8g8b8, buf->width, buf->height, (uint32_t *)mmapped, buf->stride);
if (pix[i] == NULL) {
LOG_ERR("failed to create pixman image");
goto err;
}
}
buf->offset = new_offset;
buf->mmapped = mmapped;
buf->wl_buf = wl_buf;
buf->pix = pix;
wl_buffer_add_listener(wl_buf, &buffer_listener, buf);
return true;
err:
if (pix != NULL) {
for (size_t i = 0; i < buf->pix_instances; i++)
if (pix[i] != NULL)
pixman_image_unref(pix[i]);
}
free(pix);
if (wl_buf != NULL)
wl_buffer_destroy(wl_buf);
abort();
return false;
}
struct buffer *
shm_get_buffer(struct wl_shm *shm, int width, int height, unsigned long cookie, bool scrollable, size_t pix_instances)
{
/* Purge buffers marked for purging */
tll_foreach(buffers, it) {
if (it->item.cookie != cookie)
continue;
if (!it->item.purge)
continue;
assert(!it->item.busy);
LOG_DBG("cookie=%lx: purging buffer %p (width=%d, height=%d): %zu KB",
cookie, (void *)&it->item, it->item.width, it->item.height,
it->item.size / 1024);
buffer_destroy(&it->item);
tll_remove(buffers, it);
}
tll_foreach(buffers, it) {
if (it->item.width != width)
continue;
if (it->item.height != height)
continue;
if (it->item.cookie != cookie)
continue;
if (!it->item.busy) {
LOG_DBG("cookie=%lx: re-using buffer from cache (buf=%p)",
cookie, (void *)&it->item);
it->item.busy = true;
it->item.purge = false;
assert(it->item.pix_instances == pix_instances);
return &it->item;
}
}
/* Purge old buffers associated with this cookie */
tll_foreach(buffers, it) {
if (it->item.cookie != cookie)
continue;
if (it->item.busy)
continue;
if (it->item.width == width && it->item.height == height)
continue;
LOG_DBG("cookie=%lx: marking buffer %p for purging", cookie, (void *)&it->item);
it->item.purge = true;
}
/*
* No existing buffer available. Create a new one by:
*
* 1. open a memory backed "file" with memfd_create()
* 2. mmap() the memory file, to be used by the pixman image
* 3. create a wayland shm buffer for the same memory file
*
* The pixman image and the wayland buffer are now sharing memory.
*/
int pool_fd = -1;
const int stride = stride_for_format_and_width(PIXMAN_a8r8g8b8, width);
const size_t size = stride * height;
void *real_mmapped = MAP_FAILED;
struct wl_shm_pool *pool = NULL;
LOG_DBG("cookie=%lx: allocating new buffer: %zu KB", cookie, size / 1024);
/* Backing memory for SHM */
pool_fd = memfd_create("foot-wayland-shm-buffer-pool", MFD_CLOEXEC | MFD_ALLOW_SEALING);
if (pool_fd == -1) {
LOG_ERRNO("failed to create SHM backing memory file");
goto err;
}
#if defined(__i386__)
off_t initial_offset = 0;
off_t memfd_size = size;
#else
off_t initial_offset = scrollable && max_pool_size > 0 ? (max_pool_size / 4) & ~(page_size() - 1) : 0;
off_t memfd_size = scrollable && max_pool_size > 0 ? max_pool_size : size;
#endif
LOG_DBG("memfd-size: %lu, initial offset: %lu", memfd_size, initial_offset);
if (ftruncate(pool_fd, memfd_size) == -1) {
LOG_ERRNO("failed to set size of SHM backing memory file");
goto err;
}
if (!can_punch_hole_initialized) {
can_punch_hole_initialized = true;
#if defined(__x86_64__)
can_punch_hole = fallocate(
pool_fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0, 1) == 0;
if (!can_punch_hole) {
LOG_WARN(
"fallocate(FALLOC_FL_PUNCH_HOLE) not "
"supported (%s): expect lower performance", strerror(errno));
}
#else
/* This is mostly to make sure we skip the warning issued
* above */
can_punch_hole = false;
#endif
}
if (scrollable && !can_punch_hole) {
initial_offset = 0;
memfd_size = size;
scrollable = false;
if (ftruncate(pool_fd, memfd_size) < 0) {
LOG_ERRNO("failed to set size of SHM backing memory file");
goto err;
}
}
real_mmapped = mmap(
NULL, memfd_size, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_UNINITIALIZED, pool_fd, 0);
if (real_mmapped == MAP_FAILED) {
LOG_ERRNO("failed to mmap SHM backing memory file");
goto err;
}
/* Seal file - we no longer allow any kind of resizing */
/* TODO: wayland mmaps(PROT_WRITE), for some unknown reason, hence we cannot use F_SEAL_FUTURE_WRITE */
if (fcntl(pool_fd, F_ADD_SEALS,
F_SEAL_GROW | F_SEAL_SHRINK | /*F_SEAL_FUTURE_WRITE |*/ F_SEAL_SEAL) < 0)
{
LOG_ERRNO("failed to seal SHM backing memory file");
/* This is not a fatal error */
}
pool = wl_shm_create_pool(shm, pool_fd, memfd_size);
if (pool == NULL) {
LOG_ERR("failed to create SHM pool");
goto err;
}
/* Push to list of available buffers, but marked as 'busy' */
tll_push_back(
buffers,
((struct buffer){
.cookie = cookie,
.width = width,
.height = height,
.stride = stride,
.busy = true,
.size = size,
.pix_instances = pix_instances,
.fd = pool_fd,
.pool = pool,
.scrollable = scrollable,
.real_mmapped = real_mmapped,
.mmap_size = memfd_size,
.offset = 0}
)
);
struct buffer *ret = &tll_back(buffers);
if (!instantiate_offset(shm, ret, initial_offset))
goto err;
#if defined(MEASURE_SHM_ALLOCS) && MEASURE_SHM_ALLOCS
{
size_t currently_alloced = 0;
tll_foreach(buffers, it)
currently_alloced += it->item.size;
if (currently_alloced > max_alloced)
max_alloced = currently_alloced;
}
#endif
return ret;
err:
if (pool != NULL)
wl_shm_pool_destroy(pool);
if (real_mmapped != MAP_FAILED)
munmap(real_mmapped, memfd_size);
if (pool_fd != -1)
close(pool_fd);
/* We don't handle this */
abort();
return NULL;
}
bool
shm_can_scroll(const struct buffer *buf)
{
#if defined(__i386__)
/* Not enough virtual address space in 32-bit */
return false;
#else
return can_punch_hole && max_pool_size > 0 && buf->scrollable;
#endif
}
static bool
wrap_buffer(struct wl_shm *shm, struct buffer *buf, off_t new_offset)
{
/* We don't allow overlapping offsets */
off_t UNUSED diff =
new_offset < buf->offset ? buf->offset - new_offset : new_offset - buf->offset;
assert(diff > buf->size);
memcpy((uint8_t *)buf->real_mmapped + new_offset, buf->mmapped, buf->size);
off_t trim_ofs, trim_len;
if (new_offset > buf->offset) {
/* Trim everything *before* the new offset */
trim_ofs = 0;
trim_len = new_offset;
} else {
/* Trim everything *after* the new buffer location */
trim_ofs = new_offset + buf->size;
trim_len = buf->mmap_size - trim_ofs;
}
if (fallocate(
buf->fd,
FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
trim_ofs, trim_len) < 0)
{
LOG_ERRNO("failed to trim SHM backing memory file");
return false;
}
/* Re-instantiate pixman+wl_buffer+raw pointersw */
buffer_destroy_dont_close(buf);
return instantiate_offset(shm, buf, new_offset);
}
static bool
shm_scroll_forward(struct wl_shm *shm, struct buffer *buf, int rows,
int top_margin, int top_keep_rows,
int bottom_margin, int bottom_keep_rows)
{
assert(can_punch_hole);
assert(buf->busy);
assert(buf->pix);
assert(buf->wl_buf);
assert(buf->fd >= 0);
LOG_DBG("scrolling %d rows (%d bytes)", rows, rows * buf->stride);
const off_t diff = rows * buf->stride;
assert(rows > 0);
assert(diff < buf->size);
if (buf->offset + diff + buf->size > max_pool_size) {
LOG_DBG("memfd offset wrap around");
if (!wrap_buffer(shm, buf, 0))
goto err;
}
off_t new_offset = buf->offset + diff;
assert(new_offset > buf->offset);
assert(new_offset + buf->size <= max_pool_size);
#if TIME_SCROLL
struct timeval time1;
gettimeofday(&time1, NULL);
struct timeval time2 = time1;
#endif
if (top_keep_rows > 0) {
/* Copy current 'top' region to its new location */
memmove(
(uint8_t *)buf->mmapped + (top_margin + rows) * buf->stride,
(uint8_t *)buf->mmapped + (top_margin + 0) * buf->stride,
top_keep_rows * buf->stride);
#if TIME_SCROLL
gettimeofday(&time2, NULL);
timersub(&time2, &time1, &tot);
LOG_INFO("memmove (top region): %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
}
/* Destroy old objects (they point to the old offset) */
buffer_destroy_dont_close(buf);
/* Free unused memory - everything up until the new offset */
const off_t trim_ofs = 0;
const off_t trim_len = new_offset;
if (fallocate(
buf->fd,
FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
trim_ofs, trim_len) < 0)
{
LOG_ERRNO("failed to trim SHM backing memory file");
goto err;
}
#if TIME_SCROLL
struct timeval time3;
gettimeofday(&time3, NULL);
timersub(&time3, &time2, &tot);
LOG_INFO("PUNCH HOLE: %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
/* Re-instantiate pixman+wl_buffer+raw pointersw */
bool ret = instantiate_offset(shm, buf, new_offset);
#if TIME_SCROLL
struct timeval time4;
gettimeofday(&time4, NULL);
timersub(&time4, &time3, &tot);
LOG_INFO("instantiate offset: %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
if (ret && bottom_keep_rows > 0) {
/* Copy 'bottom' region to its new location */
memmove(
(uint8_t *)buf->mmapped + buf->size - (bottom_margin + bottom_keep_rows) * buf->stride,
(uint8_t *)buf->mmapped + buf->size - (bottom_margin + rows + bottom_keep_rows) * buf->stride,
bottom_keep_rows * buf->stride);
#if TIME_SCROLL
struct timeval time5;
gettimeofday(&time5, NULL);
timersub(&time5, &time4, &tot);
LOG_INFO("memmove (bottom region): %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
}
return ret;
err:
abort();
return false;
}
static bool
shm_scroll_reverse(struct wl_shm *shm, struct buffer *buf, int rows,
int top_margin, int top_keep_rows,
int bottom_margin, int bottom_keep_rows)
{
assert(rows > 0);
const off_t diff = rows * buf->stride;
if (diff > buf->offset) {
LOG_DBG("memfd offset reverse wrap-around");
if (!wrap_buffer(shm, buf, (max_pool_size - buf->size) & ~(page_size() - 1)))
goto err;
}
off_t new_offset = buf->offset - diff;
assert(new_offset < buf->offset);
assert(new_offset <= max_pool_size);
#if TIME_SCROLL
struct timeval time0;
gettimeofday(&time0, NULL);
struct timeval tot;
struct timeval time1 = time0;
#endif
if (bottom_keep_rows > 0) {
/* Copy 'bottom' region to its new location */
memmove(
(uint8_t *)buf->mmapped + buf->size - (bottom_margin + rows + bottom_keep_rows) * buf->stride,
(uint8_t *)buf->mmapped + buf->size - (bottom_margin + bottom_keep_rows) * buf->stride,
bottom_keep_rows * buf->stride);
#if TIME_SCROLL
gettimeofday(&time1, NULL);
timersub(&time1, &time0, &tot);
LOG_INFO("memmove (bottom region): %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
}
/* Destroy old objects (they point to the old offset) */
buffer_destroy_dont_close(buf);
/* Free unused memory - everything after the relocated buffer */
const off_t trim_ofs = new_offset + buf->size;
const off_t trim_len = buf->mmap_size - trim_ofs;
if (fallocate(
buf->fd,
FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
trim_ofs, trim_len) < 0)
{
LOG_ERRNO("failed to trim SHM backing memory");
goto err;
}
#if TIME_SCROLL
struct timeval time2;
gettimeofday(&time2, NULL);
timersub(&time2, &time1, &tot);
LOG_INFO("fallocate: %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
/* Re-instantiate pixman+wl_buffer+raw pointers */
bool ret = instantiate_offset(shm, buf, new_offset);
#if TIME_SCROLL
struct timeval time3;
gettimeofday(&time3, NULL);
timersub(&time3, &time2, &tot);
LOG_INFO("instantiate offset: %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
if (ret && top_keep_rows > 0) {
/* Copy current 'top' region to its new location */
memmove(
(uint8_t *)buf->mmapped + (top_margin + 0) * buf->stride,
(uint8_t *)buf->mmapped + (top_margin + rows) * buf->stride,
top_keep_rows * buf->stride);
#if TIME_SCROLL
struct timeval time4;
gettimeofday(&time4, NULL);
timersub(&time4, &time2, &tot);
LOG_INFO("memmove (top region): %lds %ldus", tot.tv_sec, tot.tv_usec);
#endif
}
return ret;
err:
abort();
return false;
}
bool
shm_scroll(struct wl_shm *shm, struct buffer *buf, int rows,
int top_margin, int top_keep_rows,
int bottom_margin, int bottom_keep_rows)
{
if (!shm_can_scroll(buf))
return false;
assert(rows != 0);
return rows > 0
? shm_scroll_forward(shm, buf, rows, top_margin, top_keep_rows, bottom_margin, bottom_keep_rows)
: shm_scroll_reverse(shm, buf, -rows, top_margin, top_keep_rows, bottom_margin, bottom_keep_rows);
}
void
shm_purge(struct wl_shm *shm, unsigned long cookie)
{
LOG_DBG("cookie=%lx: purging all buffers", cookie);
/* Purge old buffers associated with this cookie */
tll_foreach(buffers, it) {
if (it->item.cookie != cookie)
continue;
assert(!it->item.busy);
buffer_destroy(&it->item);
tll_remove(buffers, it);
}
}