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-rw-r--r--src/journal/mmap-cache.c668
1 files changed, 668 insertions, 0 deletions
diff --git a/src/journal/mmap-cache.c b/src/journal/mmap-cache.c
new file mode 100644
index 0000000..0dc453e
--- /dev/null
+++ b/src/journal/mmap-cache.c
@@ -0,0 +1,668 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+
+#include "alloc-util.h"
+#include "fd-util.h"
+#include "hashmap.h"
+#include "list.h"
+#include "log.h"
+#include "macro.h"
+#include "mmap-cache.h"
+#include "sigbus.h"
+#include "util.h"
+
+typedef struct Window Window;
+typedef struct Context Context;
+
+struct Window {
+ MMapCache *cache;
+
+ bool invalidated:1;
+ bool keep_always:1;
+ bool in_unused:1;
+
+ int prot;
+ void *ptr;
+ uint64_t offset;
+ size_t size;
+
+ MMapFileDescriptor *fd;
+
+ LIST_FIELDS(Window, by_fd);
+ LIST_FIELDS(Window, unused);
+
+ LIST_HEAD(Context, contexts);
+};
+
+struct Context {
+ MMapCache *cache;
+ unsigned id;
+ Window *window;
+
+ LIST_FIELDS(Context, by_window);
+};
+
+struct MMapFileDescriptor {
+ MMapCache *cache;
+ int fd;
+ bool sigbus;
+ LIST_HEAD(Window, windows);
+};
+
+struct MMapCache {
+ unsigned n_ref;
+ unsigned n_windows;
+
+ unsigned n_hit, n_missed;
+
+ Hashmap *fds;
+ Context *contexts[MMAP_CACHE_MAX_CONTEXTS];
+
+ LIST_HEAD(Window, unused);
+ Window *last_unused;
+};
+
+#define WINDOWS_MIN 64
+
+#if ENABLE_DEBUG_MMAP_CACHE
+/* Tiny windows increase mmap activity and the chance of exposing unsafe use. */
+# define WINDOW_SIZE (page_size())
+#else
+# define WINDOW_SIZE (8ULL*1024ULL*1024ULL)
+#endif
+
+MMapCache* mmap_cache_new(void) {
+ MMapCache *m;
+
+ m = new0(MMapCache, 1);
+ if (!m)
+ return NULL;
+
+ m->n_ref = 1;
+ return m;
+}
+
+static void window_unlink(Window *w) {
+ Context *c;
+
+ assert(w);
+
+ if (w->ptr)
+ munmap(w->ptr, w->size);
+
+ if (w->fd)
+ LIST_REMOVE(by_fd, w->fd->windows, w);
+
+ if (w->in_unused) {
+ if (w->cache->last_unused == w)
+ w->cache->last_unused = w->unused_prev;
+
+ LIST_REMOVE(unused, w->cache->unused, w);
+ }
+
+ LIST_FOREACH(by_window, c, w->contexts) {
+ assert(c->window == w);
+ c->window = NULL;
+ }
+}
+
+static void window_invalidate(Window *w) {
+ assert(w);
+
+ if (w->invalidated)
+ return;
+
+ /* Replace the window with anonymous pages. This is useful
+ * when we hit a SIGBUS and want to make sure the file cannot
+ * trigger any further SIGBUS, possibly overrunning the sigbus
+ * queue. */
+
+ assert_se(mmap(w->ptr, w->size, w->prot, MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, -1, 0) == w->ptr);
+ w->invalidated = true;
+}
+
+static void window_free(Window *w) {
+ assert(w);
+
+ window_unlink(w);
+ w->cache->n_windows--;
+ free(w);
+}
+
+_pure_ static bool window_matches(Window *w, int prot, uint64_t offset, size_t size) {
+ assert(w);
+ assert(size > 0);
+
+ return
+ prot == w->prot &&
+ offset >= w->offset &&
+ offset + size <= w->offset + w->size;
+}
+
+_pure_ static bool window_matches_fd(Window *w, MMapFileDescriptor *f, int prot, uint64_t offset, size_t size) {
+ assert(w);
+ assert(f);
+
+ return
+ w->fd &&
+ f->fd == w->fd->fd &&
+ window_matches(w, prot, offset, size);
+}
+
+static Window *window_add(MMapCache *m, MMapFileDescriptor *f, int prot, bool keep_always, uint64_t offset, size_t size, void *ptr) {
+ Window *w;
+
+ assert(m);
+ assert(f);
+
+ if (!m->last_unused || m->n_windows <= WINDOWS_MIN) {
+
+ /* Allocate a new window */
+ w = new0(Window, 1);
+ if (!w)
+ return NULL;
+ m->n_windows++;
+ } else {
+
+ /* Reuse an existing one */
+ w = m->last_unused;
+ window_unlink(w);
+ zero(*w);
+ }
+
+ w->cache = m;
+ w->fd = f;
+ w->prot = prot;
+ w->keep_always = keep_always;
+ w->offset = offset;
+ w->size = size;
+ w->ptr = ptr;
+
+ LIST_PREPEND(by_fd, f->windows, w);
+
+ return w;
+}
+
+static void context_detach_window(Context *c) {
+ Window *w;
+
+ assert(c);
+
+ if (!c->window)
+ return;
+
+ w = TAKE_PTR(c->window);
+ LIST_REMOVE(by_window, w->contexts, c);
+
+ if (!w->contexts && !w->keep_always) {
+ /* Not used anymore? */
+#if ENABLE_DEBUG_MMAP_CACHE
+ /* Unmap unused windows immediately to expose use-after-unmap
+ * by SIGSEGV. */
+ window_free(w);
+#else
+ LIST_PREPEND(unused, c->cache->unused, w);
+ if (!c->cache->last_unused)
+ c->cache->last_unused = w;
+
+ w->in_unused = true;
+#endif
+ }
+}
+
+static void context_attach_window(Context *c, Window *w) {
+ assert(c);
+ assert(w);
+
+ if (c->window == w)
+ return;
+
+ context_detach_window(c);
+
+ if (w->in_unused) {
+ /* Used again? */
+ LIST_REMOVE(unused, c->cache->unused, w);
+ if (c->cache->last_unused == w)
+ c->cache->last_unused = w->unused_prev;
+
+ w->in_unused = false;
+ }
+
+ c->window = w;
+ LIST_PREPEND(by_window, w->contexts, c);
+}
+
+static Context *context_add(MMapCache *m, unsigned id) {
+ Context *c;
+
+ assert(m);
+
+ c = m->contexts[id];
+ if (c)
+ return c;
+
+ c = new0(Context, 1);
+ if (!c)
+ return NULL;
+
+ c->cache = m;
+ c->id = id;
+
+ assert(!m->contexts[id]);
+ m->contexts[id] = c;
+
+ return c;
+}
+
+static void context_free(Context *c) {
+ assert(c);
+
+ context_detach_window(c);
+
+ if (c->cache) {
+ assert(c->cache->contexts[c->id] == c);
+ c->cache->contexts[c->id] = NULL;
+ }
+
+ free(c);
+}
+
+static MMapCache *mmap_cache_free(MMapCache *m) {
+ int i;
+
+ assert(m);
+
+ for (i = 0; i < MMAP_CACHE_MAX_CONTEXTS; i++)
+ if (m->contexts[i])
+ context_free(m->contexts[i]);
+
+ hashmap_free(m->fds);
+
+ while (m->unused)
+ window_free(m->unused);
+
+ return mfree(m);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(MMapCache, mmap_cache, mmap_cache_free);
+
+static int make_room(MMapCache *m) {
+ assert(m);
+
+ if (!m->last_unused)
+ return 0;
+
+ window_free(m->last_unused);
+ return 1;
+}
+
+static int try_context(
+ MMapCache *m,
+ MMapFileDescriptor *f,
+ int prot,
+ unsigned context,
+ bool keep_always,
+ uint64_t offset,
+ size_t size,
+ void **ret,
+ size_t *ret_size) {
+
+ Context *c;
+
+ assert(m);
+ assert(m->n_ref > 0);
+ assert(f);
+ assert(size > 0);
+ assert(ret);
+
+ c = m->contexts[context];
+ if (!c)
+ return 0;
+
+ assert(c->id == context);
+
+ if (!c->window)
+ return 0;
+
+ if (!window_matches_fd(c->window, f, prot, offset, size)) {
+
+ /* Drop the reference to the window, since it's unnecessary now */
+ context_detach_window(c);
+ return 0;
+ }
+
+ if (c->window->fd->sigbus)
+ return -EIO;
+
+ c->window->keep_always = c->window->keep_always || keep_always;
+
+ *ret = (uint8_t*) c->window->ptr + (offset - c->window->offset);
+ if (ret_size)
+ *ret_size = c->window->size - (offset - c->window->offset);
+
+ return 1;
+}
+
+static int find_mmap(
+ MMapCache *m,
+ MMapFileDescriptor *f,
+ int prot,
+ unsigned context,
+ bool keep_always,
+ uint64_t offset,
+ size_t size,
+ void **ret,
+ size_t *ret_size) {
+
+ Window *w;
+ Context *c;
+
+ assert(m);
+ assert(m->n_ref > 0);
+ assert(f);
+ assert(size > 0);
+
+ if (f->sigbus)
+ return -EIO;
+
+ LIST_FOREACH(by_fd, w, f->windows)
+ if (window_matches(w, prot, offset, size))
+ break;
+
+ if (!w)
+ return 0;
+
+ c = context_add(m, context);
+ if (!c)
+ return -ENOMEM;
+
+ context_attach_window(c, w);
+ w->keep_always = w->keep_always || keep_always;
+
+ *ret = (uint8_t*) w->ptr + (offset - w->offset);
+ if (ret_size)
+ *ret_size = w->size - (offset - w->offset);
+
+ return 1;
+}
+
+static int mmap_try_harder(MMapCache *m, void *addr, MMapFileDescriptor *f, int prot, int flags, uint64_t offset, size_t size, void **res) {
+ void *ptr;
+
+ assert(m);
+ assert(f);
+ assert(res);
+
+ for (;;) {
+ int r;
+
+ ptr = mmap(addr, size, prot, flags, f->fd, offset);
+ if (ptr != MAP_FAILED)
+ break;
+ if (errno != ENOMEM)
+ return negative_errno();
+
+ r = make_room(m);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ return -ENOMEM;
+ }
+
+ *res = ptr;
+ return 0;
+}
+
+static int add_mmap(
+ MMapCache *m,
+ MMapFileDescriptor *f,
+ int prot,
+ unsigned context,
+ bool keep_always,
+ uint64_t offset,
+ size_t size,
+ struct stat *st,
+ void **ret,
+ size_t *ret_size) {
+
+ uint64_t woffset, wsize;
+ Context *c;
+ Window *w;
+ void *d;
+ int r;
+
+ assert(m);
+ assert(m->n_ref > 0);
+ assert(f);
+ assert(size > 0);
+ assert(ret);
+
+ woffset = offset & ~((uint64_t) page_size() - 1ULL);
+ wsize = size + (offset - woffset);
+ wsize = PAGE_ALIGN(wsize);
+
+ if (wsize < WINDOW_SIZE) {
+ uint64_t delta;
+
+ delta = PAGE_ALIGN((WINDOW_SIZE - wsize) / 2);
+
+ if (delta > offset)
+ woffset = 0;
+ else
+ woffset -= delta;
+
+ wsize = WINDOW_SIZE;
+ }
+
+ if (st) {
+ /* Memory maps that are larger then the files
+ underneath have undefined behavior. Hence, clamp
+ things to the file size if we know it */
+
+ if (woffset >= (uint64_t) st->st_size)
+ return -EADDRNOTAVAIL;
+
+ if (woffset + wsize > (uint64_t) st->st_size)
+ wsize = PAGE_ALIGN(st->st_size - woffset);
+ }
+
+ r = mmap_try_harder(m, NULL, f, prot, MAP_SHARED, woffset, wsize, &d);
+ if (r < 0)
+ return r;
+
+ c = context_add(m, context);
+ if (!c)
+ goto outofmem;
+
+ w = window_add(m, f, prot, keep_always, woffset, wsize, d);
+ if (!w)
+ goto outofmem;
+
+ context_attach_window(c, w);
+
+ *ret = (uint8_t*) w->ptr + (offset - w->offset);
+ if (ret_size)
+ *ret_size = w->size - (offset - w->offset);
+
+ return 1;
+
+outofmem:
+ (void) munmap(d, wsize);
+ return -ENOMEM;
+}
+
+int mmap_cache_get(
+ MMapCache *m,
+ MMapFileDescriptor *f,
+ int prot,
+ unsigned context,
+ bool keep_always,
+ uint64_t offset,
+ size_t size,
+ struct stat *st,
+ void **ret,
+ size_t *ret_size) {
+
+ int r;
+
+ assert(m);
+ assert(m->n_ref > 0);
+ assert(f);
+ assert(size > 0);
+ assert(ret);
+ assert(context < MMAP_CACHE_MAX_CONTEXTS);
+
+ /* Check whether the current context is the right one already */
+ r = try_context(m, f, prot, context, keep_always, offset, size, ret, ret_size);
+ if (r != 0) {
+ m->n_hit++;
+ return r;
+ }
+
+ /* Search for a matching mmap */
+ r = find_mmap(m, f, prot, context, keep_always, offset, size, ret, ret_size);
+ if (r != 0) {
+ m->n_hit++;
+ return r;
+ }
+
+ m->n_missed++;
+
+ /* Create a new mmap */
+ return add_mmap(m, f, prot, context, keep_always, offset, size, st, ret, ret_size);
+}
+
+unsigned mmap_cache_get_hit(MMapCache *m) {
+ assert(m);
+
+ return m->n_hit;
+}
+
+unsigned mmap_cache_get_missed(MMapCache *m) {
+ assert(m);
+
+ return m->n_missed;
+}
+
+static void mmap_cache_process_sigbus(MMapCache *m) {
+ bool found = false;
+ MMapFileDescriptor *f;
+ Iterator i;
+ int r;
+
+ assert(m);
+
+ /* Iterate through all triggered pages and mark their files as
+ * invalidated */
+ for (;;) {
+ bool ours;
+ void *addr;
+
+ r = sigbus_pop(&addr);
+ if (_likely_(r == 0))
+ break;
+ if (r < 0) {
+ log_error_errno(r, "SIGBUS handling failed: %m");
+ abort();
+ }
+
+ ours = false;
+ HASHMAP_FOREACH(f, m->fds, i) {
+ Window *w;
+
+ LIST_FOREACH(by_fd, w, f->windows) {
+ if ((uint8_t*) addr >= (uint8_t*) w->ptr &&
+ (uint8_t*) addr < (uint8_t*) w->ptr + w->size) {
+ found = ours = f->sigbus = true;
+ break;
+ }
+ }
+
+ if (ours)
+ break;
+ }
+
+ /* Didn't find a matching window, give up */
+ if (!ours) {
+ log_error("Unknown SIGBUS page, aborting.");
+ abort();
+ }
+ }
+
+ /* The list of triggered pages is now empty. Now, let's remap
+ * all windows of the triggered file to anonymous maps, so
+ * that no page of the file in question is triggered again, so
+ * that we can be sure not to hit the queue size limit. */
+ if (_likely_(!found))
+ return;
+
+ HASHMAP_FOREACH(f, m->fds, i) {
+ Window *w;
+
+ if (!f->sigbus)
+ continue;
+
+ LIST_FOREACH(by_fd, w, f->windows)
+ window_invalidate(w);
+ }
+}
+
+bool mmap_cache_got_sigbus(MMapCache *m, MMapFileDescriptor *f) {
+ assert(m);
+ assert(f);
+
+ mmap_cache_process_sigbus(m);
+
+ return f->sigbus;
+}
+
+MMapFileDescriptor* mmap_cache_add_fd(MMapCache *m, int fd) {
+ MMapFileDescriptor *f;
+ int r;
+
+ assert(m);
+ assert(fd >= 0);
+
+ f = hashmap_get(m->fds, FD_TO_PTR(fd));
+ if (f)
+ return f;
+
+ r = hashmap_ensure_allocated(&m->fds, NULL);
+ if (r < 0)
+ return NULL;
+
+ f = new0(MMapFileDescriptor, 1);
+ if (!f)
+ return NULL;
+
+ f->cache = m;
+ f->fd = fd;
+
+ r = hashmap_put(m->fds, FD_TO_PTR(fd), f);
+ if (r < 0)
+ return mfree(f);
+
+ return f;
+}
+
+void mmap_cache_free_fd(MMapCache *m, MMapFileDescriptor *f) {
+ assert(m);
+ assert(f);
+
+ /* Make sure that any queued SIGBUS are first dispatched, so
+ * that we don't end up with a SIGBUS entry we cannot relate
+ * to any existing memory map */
+
+ mmap_cache_process_sigbus(m);
+
+ while (f->windows)
+ window_free(f->windows);
+
+ if (f->cache)
+ assert_se(hashmap_remove(f->cache->fds, FD_TO_PTR(f->fd)));
+
+ free(f);
+}
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