+++ /dev/null
-/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
-
-/***
- This file is part of systemd.
-
- Copyright 2012 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
-***/
-
-#include <errno.h>
-#include <stdlib.h>
-#include <sys/mman.h>
-
-#include "hashmap.h"
-#include "list.h"
-#include "log.h"
-#include "util.h"
-#include "macro.h"
-#include "sigbus.h"
-#include "mmap-cache.h"
-
-typedef struct Window Window;
-typedef struct Context Context;
-typedef struct FileDescriptor FileDescriptor;
-
-struct Window {
- MMapCache *cache;
-
- bool invalidated;
- bool keep_always;
- bool in_unused;
-
- int prot;
- void *ptr;
- uint64_t offset;
- size_t size;
-
- FileDescriptor *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 FileDescriptor {
- MMapCache *cache;
- int fd;
- bool sigbus;
- LIST_HEAD(Window, windows);
-};
-
-struct MMapCache {
- int 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
-
-#ifdef 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;
-}
-
-MMapCache* mmap_cache_ref(MMapCache *m) {
- assert(m);
- assert(m->n_ref > 0);
-
- m->n_ref ++;
- 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 fd, int prot, uint64_t offset, size_t size) {
- assert(w);
- assert(fd >= 0);
- assert(size > 0);
-
- return
- w->fd &&
- fd == w->fd->fd &&
- prot == w->prot &&
- offset >= w->offset &&
- offset + size <= w->offset + w->size;
-}
-
-static Window *window_add(MMapCache *m) {
- Window *w;
-
- assert(m);
-
- 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;
- return w;
-}
-
-static void context_detach_window(Context *c) {
- Window *w;
-
- assert(c);
-
- if (!c->window)
- return;
-
- w = c->window;
- c->window = NULL;
- LIST_REMOVE(by_window, w->contexts, c);
-
- if (!w->contexts && !w->keep_always) {
- /* Not used anymore? */
-#ifdef 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 void fd_free(FileDescriptor *f) {
- assert(f);
-
- while (f->windows)
- window_free(f->windows);
-
- if (f->cache)
- assert_se(hashmap_remove(f->cache->fds, INT_TO_PTR(f->fd + 1)));
-
- free(f);
-}
-
-static FileDescriptor* fd_add(MMapCache *m, int fd) {
- FileDescriptor *f;
- int r;
-
- assert(m);
- assert(fd >= 0);
-
- f = hashmap_get(m->fds, INT_TO_PTR(fd + 1));
- if (f)
- return f;
-
- r = hashmap_ensure_allocated(&m->fds, NULL);
- if (r < 0)
- return NULL;
-
- f = new0(FileDescriptor, 1);
- if (!f)
- return NULL;
-
- f->cache = m;
- f->fd = fd;
-
- r = hashmap_put(m->fds, UINT_TO_PTR(fd + 1), f);
- if (r < 0) {
- free(f);
- return NULL;
- }
-
- return f;
-}
-
-static void mmap_cache_free(MMapCache *m) {
- FileDescriptor *f;
- int i;
-
- assert(m);
-
- for (i = 0; i < MMAP_CACHE_MAX_CONTEXTS; i++)
- if (m->contexts[i])
- context_free(m->contexts[i]);
-
- while ((f = hashmap_first(m->fds)))
- fd_free(f);
-
- hashmap_free(m->fds);
-
- while (m->unused)
- window_free(m->unused);
-
- free(m);
-}
-
-MMapCache* mmap_cache_unref(MMapCache *m) {
- assert(m);
- assert(m->n_ref > 0);
-
- m->n_ref --;
- if (m->n_ref == 0)
- mmap_cache_free(m);
-
- return NULL;
-}
-
-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,
- int fd,
- int prot,
- unsigned context,
- bool keep_always,
- uint64_t offset,
- size_t size,
- void **ret) {
-
- Context *c;
-
- assert(m);
- assert(m->n_ref > 0);
- assert(fd >= 0);
- 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(c->window, fd, 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 |= keep_always;
-
- *ret = (uint8_t*) c->window->ptr + (offset - c->window->offset);
- return 1;
-}
-
-static int find_mmap(
- MMapCache *m,
- int fd,
- int prot,
- unsigned context,
- bool keep_always,
- uint64_t offset,
- size_t size,
- void **ret) {
-
- FileDescriptor *f;
- Window *w;
- Context *c;
-
- assert(m);
- assert(m->n_ref > 0);
- assert(fd >= 0);
- assert(size > 0);
-
- f = hashmap_get(m->fds, INT_TO_PTR(fd + 1));
- if (!f)
- return 0;
-
- assert(f->fd == fd);
-
- if (f->sigbus)
- return -EIO;
-
- LIST_FOREACH(by_fd, w, f->windows)
- if (window_matches(w, fd, 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 += keep_always;
-
- *ret = (uint8_t*) w->ptr + (offset - w->offset);
- return 1;
-}
-
-static int add_mmap(
- MMapCache *m,
- int fd,
- int prot,
- unsigned context,
- bool keep_always,
- uint64_t offset,
- size_t size,
- struct stat *st,
- void **ret) {
-
- uint64_t woffset, wsize;
- Context *c;
- FileDescriptor *f;
- Window *w;
- void *d;
- int r;
-
- assert(m);
- assert(m->n_ref > 0);
- assert(fd >= 0);
- 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);
- }
-
- for (;;) {
- d = mmap(NULL, wsize, prot, MAP_SHARED, fd, woffset);
- if (d != MAP_FAILED)
- break;
- if (errno != ENOMEM)
- return -errno;
-
- r = make_room(m);
- if (r < 0)
- return r;
- if (r == 0)
- return -ENOMEM;
- }
-
- c = context_add(m, context);
- if (!c)
- goto outofmem;
-
- f = fd_add(m, fd);
- if (!f)
- goto outofmem;
-
- w = window_add(m);
- if (!w)
- goto outofmem;
-
- w->keep_always = keep_always;
- w->ptr = d;
- w->offset = woffset;
- w->prot = prot;
- w->size = wsize;
- w->fd = f;
-
- LIST_PREPEND(by_fd, f->windows, w);
-
- context_detach_window(c);
- c->window = w;
- LIST_PREPEND(by_window, w->contexts, c);
-
- *ret = (uint8_t*) w->ptr + (offset - w->offset);
- return 1;
-
-outofmem:
- munmap(d, wsize);
- return -ENOMEM;
-}
-
-int mmap_cache_get(
- MMapCache *m,
- int fd,
- int prot,
- unsigned context,
- bool keep_always,
- uint64_t offset,
- size_t size,
- struct stat *st,
- void **ret) {
-
- int r;
-
- assert(m);
- assert(m->n_ref > 0);
- assert(fd >= 0);
- 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, fd, prot, context, keep_always, offset, size, ret);
- if (r != 0) {
- m->n_hit ++;
- return r;
- }
-
- /* Search for a matching mmap */
- r = find_mmap(m, fd, prot, context, keep_always, offset, size, ret);
- if (r != 0) {
- m->n_hit ++;
- return r;
- }
-
- m->n_missed++;
-
- /* Create a new mmap */
- return add_mmap(m, fd, prot, context, keep_always, offset, size, st, ret);
-}
-
-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;
- FileDescriptor *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, int fd) {
- FileDescriptor *f;
-
- assert(m);
- assert(fd >= 0);
-
- mmap_cache_process_sigbus(m);
-
- f = hashmap_get(m->fds, INT_TO_PTR(fd + 1));
- if (!f)
- return false;
-
- return f->sigbus;
-}
-
-void mmap_cache_close_fd(MMapCache *m, int fd) {
- FileDescriptor *f;
-
- assert(m);
- assert(fd >= 0);
-
- /* 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);
-
- f = hashmap_get(m->fds, INT_TO_PTR(fd + 1));
- if (!f)
- return;
-
- fd_free(f);
-}
~ianmdlvl / elogind.git / blobdiff