Adding upstream version 247.3.upstream/247.3upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 669 insertions, 0 deletions

diff --git a/src/journal/mmap-cache.c b/src/journal/mmap-cache.c
new file mode 100644
index 0000000..9882016
--- /dev/null
+++ b/src/journal/mmap-cache.c
@@ -0,0 +1,669 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+
+#include "alloc-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "hashmap.h"
+#include "list.h"
+#include "log.h"
+#include "macro.h"
+#include "memory-util.h"
+#include "mmap-cache.h"
+#include "sigbus.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 = new(Window, 1);
+                if (!w)
+                        return NULL;
+                m->n_windows++;
+        } else {
+
+                /* Reuse an existing one */
+                w = m->last_unused;
+                window_unlink(w);
+        }
+
+        *w = (Window) {
+                .cache = m,
+                .fd = f,
+                .prot = prot,
+                .keep_always = keep_always,
+                .offset = offset,
+                .size = size,
+                .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;
+        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) {
+                        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) {
+                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);
+}