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author | Richard Earnshaw <rearnsha@arm.com> | 2020-12-18 19:00:49 +0000 |
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committer | Richard Earnshaw <rearnsha@arm.com> | 2020-12-18 19:23:04 +0000 |
commit | 55d7ba96fc3ac977c6f692f7c6739688a6dc91a1 (patch) | |
tree | e4ac78357111f9662be83c84fdab8fe9628e0a10 /malloc/arena.c | |
parent | 3ee6ea717154add17183296ac6788478ba3051a7 (diff) | |
download | glibc-55d7ba96fc3ac977c6f692f7c6739688a6dc91a1.tar.gz glibc-55d7ba96fc3ac977c6f692f7c6739688a6dc91a1.tar.xz glibc-55d7ba96fc3ac977c6f692f7c6739688a6dc91a1.zip |
malloc: Basic support for memory tagging in the malloc() family
This patch adds the basic support for memory tagging. Various flavours are supported, particularly being able to turn on tagged memory at run-time: this allows the same code to be used on systems where memory tagging support is not present without neededing a separate build of glibc. Also, depending on whether the kernel supports it, the code will use mmap for the default arena if morecore does not, or cannot support tagged memory (on AArch64 it is not available). All the hooks use function pointers to allow this to work without needing ifuncs.
Diffstat (limited to 'malloc/arena.c')
-rw-r--r-- | malloc/arena.c | 59 |
1 files changed, 56 insertions, 3 deletions
diff --git a/malloc/arena.c b/malloc/arena.c index 3c9c0ecd86..ba833a2d98 100644 --- a/malloc/arena.c +++ b/malloc/arena.c @@ -274,17 +274,52 @@ next_env_entry (char ***position) #endif -#ifdef SHARED +#if defined(SHARED) || defined(USE_MTAG) static void * __failing_morecore (ptrdiff_t d) { return (void *) MORECORE_FAILURE; } +#endif +#ifdef SHARED extern struct dl_open_hook *_dl_open_hook; libc_hidden_proto (_dl_open_hook); #endif +#ifdef USE_MTAG + +/* Generate a new (random) tag value for PTR and tag the memory it + points to upto the end of the usable size for the chunk containing + it. Return the newly tagged pointer. */ +static void * +__mtag_tag_new_usable (void *ptr) +{ + if (ptr) + { + mchunkptr cp = mem2chunk(ptr); + /* This likely will never happen, but we can't handle retagging + chunks from the dumped main arena. So just return the + existing pointer. */ + if (DUMPED_MAIN_ARENA_CHUNK (cp)) + return ptr; + ptr = __libc_mtag_tag_region (__libc_mtag_new_tag (ptr), + CHUNK_AVAILABLE_SIZE (cp) - CHUNK_HDR_SZ); + } + return ptr; +} + +/* Generate a new (random) tag value for PTR, set the tags for the + memory to the new tag and initialize the memory contents to VAL. + In practice this function will only be called with VAL=0, but we + keep this parameter to maintain the same prototype as memset. */ +static void * +__mtag_tag_new_memset (void *ptr, int val, size_t size) +{ + return __libc_mtag_memset_with_tag (__libc_mtag_new_tag (ptr), val, size); +} +#endif + static void ptmalloc_init (void) { @@ -293,6 +328,24 @@ ptmalloc_init (void) __malloc_initialized = 0; +#ifdef USE_MTAG + if ((TUNABLE_GET_FULL (glibc, mem, tagging, int32_t, NULL) & 1) != 0) + { + /* If the environment says that we should be using tagged memory + and that morecore does not support tagged regions, then + disable it. */ + if (__MTAG_SBRK_UNTAGGED) + __morecore = __failing_morecore; + + __mtag_mmap_flags = __MTAG_MMAP_FLAGS; + __tag_new_memset = __mtag_tag_new_memset; + __tag_region = __libc_mtag_tag_region; + __tag_new_usable = __mtag_tag_new_usable; + __tag_at = __libc_mtag_address_get_tag; + __mtag_granule_mask = ~(size_t)(__MTAG_GRANULE_SIZE - 1); + } +#endif + #ifdef SHARED /* In case this libc copy is in a non-default namespace, never use brk. Likewise if dlopened from statically linked program. The @@ -509,7 +562,7 @@ new_heap (size_t size, size_t top_pad) } } } - if (__mprotect (p2, size, PROT_READ | PROT_WRITE) != 0) + if (__mprotect (p2, size, MTAG_MMAP_FLAGS | PROT_READ | PROT_WRITE) != 0) { __munmap (p2, HEAP_MAX_SIZE); return 0; @@ -539,7 +592,7 @@ grow_heap (heap_info *h, long diff) { if (__mprotect ((char *) h + h->mprotect_size, (unsigned long) new_size - h->mprotect_size, - PROT_READ | PROT_WRITE) != 0) + MTAG_MMAP_FLAGS | PROT_READ | PROT_WRITE) != 0) return -2; h->mprotect_size = new_size; |