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[MTASCsft PATCH 18/??] MT-, AS- and AC-Safety docs: manual/memory.texi
- From: Alexandre Oliva <aoliva at redhat dot com>
- To: codonell at redhat dot com
- Cc: libc-alpha at sourceware dot org
- Date: Tue, 28 Jan 2014 00:28:40 -0200
- Subject: [MTASCsft PATCH 18/??] MT-, AS- and AC-Safety docs: manual/memory.texi
- Authentication-results: sourceware.org; auth=none
- References: <ortxelb5zd dot fsf at livre dot home> <or4n4uoncj dot fsf at livre dot home>
for ChangeLog
[BZ #12751]
* manual/memory.texi: Document MTASC-safety properties.
---
NEWS | 2
manual/memory.texi | 533 ++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 534 insertions(+), 1 deletion(-)
diff --git a/NEWS b/NEWS
index 52ae5fd..222d4df 100644
--- a/NEWS
+++ b/NEWS
@@ -10,7 +10,7 @@ Version 2.19
* The following bugs are resolved with this release:
156, 387, 431, 762, 832, 926, 2801, 4772, 6786, 6787, 6807, 6810, 7003,
- 9721, 9954, 10253, 10278, 11087, 11157, 11214, 12100, 12486, 12986,
+ 9721, 9954, 10253, 10278, 11087, 11157, 11214, 12100, 12486, 12751, 12986,
13028, 13982, 13985, 14029, 14032, 14120, 14143, 14155, 14286, 14547,
14699, 14752, 14782, 14876, 14910, 15004, 15048, 15073, 15089, 15128,
15218, 15268, 15277, 15308, 15362, 15374, 15400, 15425, 15427, 15483,
diff --git a/manual/memory.texi b/manual/memory.texi
index 55a6a50..4beb322 100644
--- a/manual/memory.texi
+++ b/manual/memory.texi
@@ -302,6 +302,245 @@ this function is in @file{stdlib.h}.
@comment malloc.h stdlib.h
@comment ISO
@deftypefun {void *} malloc (size_t @var{size})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c Malloc hooks and __morecore pointers, as well as such parameters as
+@c max_n_mmaps and max_mmapped_mem, are accessed without guards, so they
+@c could pose a thread safety issue; in order to not declare malloc
+@c MT-unsafe, it's modifying the hooks and parameters while multiple
+@c threads are active that is regarded as unsafe. An arena's next field
+@c is initialized and never changed again, except for main_arena's,
+@c that's protected by list_lock; next_free is only modified while
+@c list_lock is held too. All other data members of an arena, as well
+@c as the metadata of the memory areas assigned to it, are only modified
+@c while holding the arena's mutex (fastbin pointers use catomic ops
+@c because they may be modified by free without taking the arena's
+@c lock). Some reassurance was needed for fastbins, for it wasn't clear
+@c how they were initialized. It turns out they are always
+@c zero-initialized: main_arena's, for being static data, and other
+@c arena's, for being just-mmapped memory.
+
+@c Leaking file descriptors and memory in case of cancellation is
+@c unavoidable without disabling cancellation, but the lock situation is
+@c a bit more complicated: we don't have fallback arenas for malloc to
+@c be safe to call from within signal handlers. Error-checking mutexes
+@c or trylock could enable us to try and use alternate arenas, even with
+@c -DPER_THREAD (enabled by default), but supporting interruption
+@c (cancellation or signal handling) while holding the arena list mutex
+@c would require more work; maybe blocking signals and disabling async
+@c cancellation while manipulating the arena lists?
+
+@c __libc_malloc @asulock @aculock @acsfd @acsmem
+@c force_reg ok
+@c *malloc_hook unguarded
+@c arena_lookup ok
+@c tsd_getspecific ok, TLS
+@c arena_lock @asulock @aculock @acsfd @acsmem
+@c mutex_lock @asulock @aculock
+@c arena_get2 @asulock @aculock @acsfd @acsmem
+@c get_free_list @asulock @aculock
+@c mutex_lock (list_lock) dup @asulock @aculock
+@c mutex_unlock (list_lock) dup @aculock
+@c mutex_lock (arena lock) dup @asulock @aculock [returns locked]
+@c tsd_setspecific ok, TLS
+@c __get_nprocs ext ok @acsfd
+@c NARENAS_FROM_NCORES ok
+@c catomic_compare_and_exchange_bool_acq ok
+@c _int_new_arena ok @asulock @aculock @acsmem
+@c new_heap ok @acsmem
+@c mmap ok @acsmem
+@c munmap ok @acsmem
+@c mprotect ok
+@c chunk2mem ok
+@c set_head ok
+@c tsd_setspecific dup ok
+@c mutex_init ok
+@c mutex_lock (just-created mutex) ok, returns locked
+@c mutex_lock (list_lock) dup @asulock @aculock
+@c atomic_write_barrier ok
+@c mutex_unlock (list_lock) @aculock
+@c catomic_decrement ok
+@c reused_arena @asulock @aculock
+@c reads&writes next_to_use and iterates over arena next without guards
+@c those are harmless as long as we don't drop arenas from the
+@c NEXT list, and we never do; when a thread terminates,
+@c arena_thread_freeres prepends the arena to the free_list
+@c NEXT_FREE list, but NEXT is never modified, so it's safe!
+@c mutex_trylock (arena lock) @asulock @aculock
+@c mutex_lock (arena lock) dup @asulock @aculock
+@c tsd_setspecific dup ok
+@c _int_malloc @acsfd @acsmem
+@c checked_request2size ok
+@c REQUEST_OUT_OF_RANGE ok
+@c request2size ok
+@c get_max_fast ok
+@c fastbin_index ok
+@c fastbin ok
+@c catomic_compare_and_exhange_val_acq ok
+@c malloc_printerr dup @mtsenv
+@c if we get to it, we're toast already, undefined behavior must have
+@c been invoked before
+@c libc_message @mtsenv [no leaks with cancellation disabled]
+@c FATAL_PREPARE ok
+@c pthread_setcancelstate disable ok
+@c libc_secure_getenv @mtsenv
+@c getenv @mtsenv
+@c open_not_cancel_2 dup @acsfd
+@c strchrnul ok
+@c WRITEV_FOR_FATAL ok
+@c writev ok
+@c mmap ok @acsmem
+@c munmap ok @acsmem
+@c BEFORE_ABORT @acsfd
+@c backtrace ok
+@c write_not_cancel dup ok
+@c backtrace_symbols_fd @aculock
+@c open_not_cancel_2 dup @acsfd
+@c read_not_cancel dup ok
+@c close_not_cancel_no_status dup @acsfd
+@c abort ok
+@c itoa_word ok
+@c abort ok
+@c check_remalloced_chunk ok/disabled
+@c chunk2mem dup ok
+@c alloc_perturb ok
+@c in_smallbin_range ok
+@c smallbin_index ok
+@c bin_at ok
+@c last ok
+@c malloc_consolidate ok
+@c get_max_fast dup ok
+@c clear_fastchunks ok
+@c unsorted_chunks dup ok
+@c fastbin dup ok
+@c atomic_exchange_acq ok
+@c check_inuse_chunk dup ok/disabled
+@c chunk_at_offset dup ok
+@c chunksize dup ok
+@c inuse_bit_at_offset dup ok
+@c unlink dup ok
+@c clear_inuse_bit_at_offset dup ok
+@c in_smallbin_range dup ok
+@c set_head dup ok
+@c malloc_init_state ok
+@c bin_at dup ok
+@c set_noncontiguous dup ok
+@c set_max_fast dup ok
+@c initial_top ok
+@c unsorted_chunks dup ok
+@c check_malloc_state ok/disabled
+@c set_inuse_bit_at_offset ok
+@c check_malloced_chunk ok/disabled
+@c largebin_index ok
+@c have_fastchunks ok
+@c unsorted_chunks ok
+@c bin_at ok
+@c chunksize ok
+@c chunk_at_offset ok
+@c set_head ok
+@c set_foot ok
+@c mark_bin ok
+@c idx2bit ok
+@c first ok
+@c unlink ok
+@c malloc_printerr dup ok
+@c in_smallbin_range dup ok
+@c idx2block ok
+@c idx2bit dup ok
+@c next_bin ok
+@c sysmalloc @acsfd @acsmem
+@c MMAP @acsmem
+@c set_head dup ok
+@c check_chunk ok/disabled
+@c chunk2mem dup ok
+@c chunksize dup ok
+@c chunk_at_offset dup ok
+@c heap_for_ptr ok
+@c grow_heap ok
+@c mprotect ok
+@c set_head dup ok
+@c new_heap @acsmem
+@c MMAP dup @acsmem
+@c munmap @acsmem
+@c top ok
+@c set_foot dup ok
+@c contiguous ok
+@c MORECORE ok
+@c *__morecore ok unguarded
+@c __default_morecore
+@c sbrk ok
+@c force_reg dup ok
+@c *__after_morecore_hook unguarded
+@c set_noncontiguous ok
+@c malloc_printerr dup ok
+@c _int_free (have_lock) @acsfd @acsmem [@asulock @aculock]
+@c chunksize dup ok
+@c mutex_unlock dup @aculock/!have_lock
+@c malloc_printerr dup ok
+@c check_inuse_chunk ok/disabled
+@c chunk_at_offset dup ok
+@c mutex_lock dup @asulock @aculock/@have_lock
+@c chunk2mem dup ok
+@c free_perturb ok
+@c set_fastchunks ok
+@c catomic_and ok
+@c fastbin_index dup ok
+@c fastbin dup ok
+@c catomic_compare_and_exchange_val_rel ok
+@c chunk_is_mmapped ok
+@c contiguous dup ok
+@c prev_inuse ok
+@c unlink dup ok
+@c inuse_bit_at_offset dup ok
+@c clear_inuse_bit_at_offset ok
+@c unsorted_chunks dup ok
+@c in_smallbin_range dup ok
+@c set_head dup ok
+@c set_foot dup ok
+@c check_free_chunk ok/disabled
+@c check_chunk dup ok/disabled
+@c have_fastchunks dup ok
+@c malloc_consolidate dup ok
+@c systrim ok
+@c MORECORE dup ok
+@c *__after_morecore_hook dup unguarded
+@c set_head dup ok
+@c check_malloc_state ok/disabled
+@c top dup ok
+@c heap_for_ptr dup ok
+@c heap_trim @acsfd @acsmem
+@c top dup ok
+@c chunk_at_offset dup ok
+@c prev_chunk ok
+@c chunksize dup ok
+@c prev_inuse dup ok
+@c delete_heap @acsmem
+@c munmap dup @acsmem
+@c unlink dup ok
+@c set_head dup ok
+@c shrink_heap @acsfd
+@c check_may_shrink_heap @acsfd
+@c open_not_cancel_2 @acsfd
+@c read_not_cancel ok
+@c close_not_cancel_no_status @acsfd
+@c MMAP dup ok
+@c madvise ok
+@c munmap_chunk @acsmem
+@c chunksize dup ok
+@c chunk_is_mmapped dup ok
+@c chunk2mem dup ok
+@c malloc_printerr dup ok
+@c munmap dup @acsmem
+@c check_malloc_state ok/disabled
+@c arena_get_retry @asulock @aculock @acsfd @acsmem
+@c mutex_unlock dup @aculock
+@c mutex_lock dup @asulock @aculock
+@c arena_get2 dup @asulock @aculock @acsfd @acsmem
+@c mutex_unlock @aculock
+@c mem2chunk ok
+@c chunk_is_mmapped ok
+@c arena_for_chunk ok
+@c chunk_non_main_arena ok
+@c heap_for_ptr ok
This function returns a pointer to a newly allocated block @var{size}
bytes long, or a null pointer if the block could not be allocated.
@end deftypefun
@@ -407,6 +646,21 @@ The prototype for this function is in @file{stdlib.h}.
@comment malloc.h stdlib.h
@comment ISO
@deftypefun void free (void *@var{ptr})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c __libc_free @asulock @aculock @acsfd @acsmem
+@c releasing memory into fastbins modifies the arena without taking
+@c its mutex, but catomic operations ensure safety. If two (or more)
+@c threads are running malloc and have their own arenas locked when
+@c each gets a signal whose handler free()s large (non-fastbin-able)
+@c blocks from each other's arena, we deadlock; this is a more general
+@c case of @asulock.
+@c *__free_hook unguarded
+@c mem2chunk ok
+@c chunk_is_mmapped ok, chunk bits not modified after allocation
+@c chunksize ok
+@c munmap_chunk dup @acsmem
+@c arena_for_chunk dup ok
+@c _int_free (!have_lock) dup @asulock @aculock @acsfd @acsmem
The @code{free} function deallocates the block of memory pointed at
by @var{ptr}.
@end deftypefun
@@ -414,6 +668,8 @@ by @var{ptr}.
@comment stdlib.h
@comment Sun
@deftypefun void cfree (void *@var{ptr})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c alias to free
This function does the same thing as @code{free}. It's provided for
backward compatibility with SunOS; you should use @code{free} instead.
@end deftypefun
@@ -471,6 +727,48 @@ is declared in @file{stdlib.h}.
@comment malloc.h stdlib.h
@comment ISO
@deftypefun {void *} realloc (void *@var{ptr}, size_t @var{newsize})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c It may call the implementations of malloc and free, so all of their
+@c issues arise, plus the realloc hook, also accessed without guards.
+
+@c __libc_realloc @asulock @aculock @acsfd @acsmem
+@c *__realloc_hook unguarded
+@c __libc_free dup @asulock @aculock @acsfd @acsmem
+@c __libc_malloc dup @asulock @aculock @acsfd @acsmem
+@c mem2chunk dup ok
+@c chunksize dup ok
+@c malloc_printerr dup ok
+@c checked_request2size dup ok
+@c chunk_is_mmapped dup ok
+@c mremap_chunk
+@c chunksize dup ok
+@c __mremap ok
+@c set_head dup ok
+@c MALLOC_COPY ok
+@c memcpy ok
+@c munmap_chunk dup @acsmem
+@c arena_for_chunk dup ok
+@c mutex_lock (arena mutex) dup @asulock @aculock
+@c _int_realloc @acsfd @acsmem
+@c malloc_printerr dup ok
+@c check_inuse_chunk dup ok/disabled
+@c chunk_at_offset dup ok
+@c chunksize dup ok
+@c set_head_size dup ok
+@c chunk_at_offset dup ok
+@c set_head dup ok
+@c chunk2mem dup ok
+@c inuse dup ok
+@c unlink dup ok
+@c _int_malloc dup @acsfd @acsmem
+@c mem2chunk dup ok
+@c MALLOC_COPY dup ok
+@c _int_free (have_lock) dup @acsfd @acsmem
+@c set_inuse_bit_at_offset dup ok
+@c set_head dup ok
+@c mutex_unlock (arena mutex) dup @aculock
+@c _int_free (!have_lock) dup @asulock @aculock @acsfd @acsmem
+
The @code{realloc} function changes the size of the block whose address is
@var{ptr} to be @var{newsize}.
@@ -530,6 +828,25 @@ is declared in @file{stdlib.h}.
@comment malloc.h stdlib.h
@comment ISO
@deftypefun {void *} calloc (size_t @var{count}, size_t @var{eltsize})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c Same caveats as malloc.
+
+@c __libc_calloc @asulock @aculock @acsfd @acsmem
+@c *__malloc_hook dup unguarded
+@c memset dup ok
+@c arena_get @asulock @aculock @acsfd @acsmem
+@c arena_lookup dup ok
+@c arena_lock dup @asulock @aculock @acsfd @acsmem
+@c top dup ok
+@c chunksize dup ok
+@c heap_for_ptr dup ok
+@c _int_malloc dup @acsfd @acsmem
+@c arena_get_retry dup @asulock @aculock @acsfd @acsmem
+@c mutex_unlock dup @aculock
+@c mem2chunk dup ok
+@c chunk_is_mmapped dup ok
+@c MALLOC_ZERO ok
+@c memset dup ok
This function allocates a block long enough to contain a vector of
@var{count} elements, each of size @var{eltsize}. Its contents are
cleared to zero before @code{calloc} returns.
@@ -622,6 +939,8 @@ power of two than that, use @code{aligned_alloc} or @code{posix_memalign}.
@comment stdlib.h
@deftypefun {void *} aligned_alloc (size_t @var{alignment}, size_t @var{size})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c Alias to memalign.
The @code{aligned_alloc} function allocates a block of @var{size} bytes whose
address is a multiple of @var{alignment}. The @var{alignment} must be a
power of two and @var{size} must be a multiple of @var{alignment}.
@@ -645,6 +964,29 @@ portability to modern non-POSIX systems than @code{posix_memalign}.
@comment malloc.h
@comment BSD
@deftypefun {void *} memalign (size_t @var{boundary}, size_t @var{size})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c Same issues as malloc. The padding bytes are safely freed in
+@c _int_memalign, with the arena still locked.
+
+@c __libc_memalign @asulock @aculock @acsfd @acsmem
+@c *__memalign_hook dup unguarded
+@c __libc_malloc dup @asulock @aculock @acsfd @acsmem
+@c arena_get dup @asulock @aculock @acsfd @acsmem
+@c _int_memalign @acsfd @acsmem
+@c _int_malloc dup @acsfd @acsmem
+@c checked_request2size dup ok
+@c mem2chunk dup ok
+@c chunksize dup ok
+@c chunk_is_mmapped dup ok
+@c set_head dup ok
+@c chunk2mem dup ok
+@c set_inuse_bit_at_offset dup ok
+@c set_head_size dup ok
+@c _int_free (have_lock) dup @acsfd @acsmem
+@c chunk_at_offset dup ok
+@c check_inuse_chunk dup ok
+@c arena_get_retry dup @asulock @aculock @acsfd @acsmem
+@c mutex_unlock dup @aculock
The @code{memalign} function allocates a block of @var{size} bytes whose
address is a multiple of @var{boundary}. The @var{boundary} must be a
power of two! The function @code{memalign} works by allocating a
@@ -670,6 +1012,10 @@ The @code{memalign} function is obsolete and @code{aligned_alloc} or
@comment stdlib.h
@comment POSIX
@deftypefun int posix_memalign (void **@var{memptr}, size_t @var{alignment}, size_t @var{size})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}}
+@c Calls memalign unless the requirements are not met (powerof2 macro is
+@c safe given an automatic variable as an argument) or there's a
+@c memalign hook (accessed unguarded, but safely).
The @code{posix_memalign} function is similar to the @code{memalign}
function in that it returns a buffer of @var{size} bytes aligned to a
multiple of @var{alignment}. But it adds one requirement to the
@@ -698,6 +1044,39 @@ systems that do not support @w{ISO C11}.
@comment malloc.h stdlib.h
@comment BSD
@deftypefun {void *} valloc (size_t @var{size})
+@safety{@prelim{}@mtunsafe{@mtuinit{}}@asunsafe{@asuinit{} @asulock{}}@acunsafe{@acuinit{} @aculock{} @acsfd{} @acsmem{}}}
+@c __libc_valloc @mtuinit @asuinit @asulock @aculock @acsfd @acsmem
+@c ptmalloc_init (once) @mtsenv @asulock @aculock @acsfd @acsmem
+@c _dl_addr @asucorrupt? @aculock
+@c __rtld_lock_lock_recursive (dl_load_lock) @asucorrupt? @aculock
+@c _dl_find_dso_for_object ok, iterates over dl_ns and its _ns_loaded objs
+@c the ok above assumes no partial updates on dl_ns and _ns_loaded
+@c that could confuse a _dl_addr call in a signal handler
+@c _dl_addr_inside_object ok
+@c determine_info ok
+@c __rtld_lock_unlock_recursive (dl_load_lock) @aculock
+@c thread_atfork @asulock @aculock @acsfd @acsmem
+@c __register_atfork @asulock @aculock @acsfd @acsmem
+@c lll_lock (__fork_lock) @asulock @aculock
+@c fork_handler_alloc @asulock @aculock @acsfd @acsmem
+@c calloc dup @asulock @aculock @acsfd @acsmem
+@c __linkin_atfork ok
+@c catomic_compare_and_exchange_bool_acq ok
+@c lll_unlock (__fork_lock) @aculock
+@c *_environ @mtsenv
+@c next_env_entry ok
+@c strcspn dup ok
+@c __libc_mallopt dup @mtasuconst:mallopt [setting mp_]
+@c __malloc_check_init @mtasuconst:malloc_hooks [setting hooks]
+@c *__malloc_initialize_hook unguarded, ok
+@c *__memalign_hook dup ok, unguarded
+@c arena_get dup @asulock @aculock @acsfd @acsmem
+@c _int_valloc @acsfd @acsmem
+@c malloc_consolidate dup ok
+@c _int_memalign dup @acsfd @acsmem
+@c arena_get_retry dup @asulock @aculock @acsfd @acsmem
+@c _int_memalign dup @acsfd @acsmem
+@c mutex_unlock dup @aculock
Using @code{valloc} is like using @code{memalign} and passing the page size
as the value of the second argument. It is implemented like this:
@@ -725,6 +1104,14 @@ interface, defined in @file{malloc.h}.
@pindex malloc.h
@deftypefun int mallopt (int @var{param}, int @var{value})
+@safety{@prelim{}@mtunsafe{@mtuinit{} @mtasuconst{:mallopt}}@asunsafe{@asuinit{} @asulock{}}@acunsafe{@acuinit{} @aculock{}}}
+@c __libc_mallopt @mtuinit @mtasuconst:mallopt @asuinit @asulock @aculock
+@c ptmalloc_init (once) dup @mtsenv @asulock @aculock @acsfd @acsmem
+@c mutex_lock (main_arena->mutex) @asulock @aculock
+@c malloc_consolidate dup ok
+@c set_max_fast ok
+@c mutex_unlock dup @aculock
+
When calling @code{mallopt}, the @var{param} argument specifies the
parameter to be set, and @var{value} the new value to be set. Possible
choices for @var{param}, as defined in @file{malloc.h}, are:
@@ -781,6 +1168,17 @@ declared in @file{mcheck.h}.
@comment mcheck.h
@comment GNU
@deftypefun int mcheck (void (*@var{abortfn}) (enum mcheck_status @var{status}))
+@safety{@prelim{}@mtunsafe{@mtasurace{:mcheck} @mtasuconst{:malloc_hooks}}@asunsafe{@asucorrupt{}}@acunsafe{@acucorrupt{}}}
+@c The hooks must be set up before malloc is first used, which sort of
+@c implies @mtuinit/@asuinit but since the function is a no-op if malloc
+@c was already used, that doesn't pose any safety issues. The actual
+@c problem is with the hooks, designed for single-threaded
+@c fully-synchronous operation: they manage an unguarded linked list of
+@c allocated blocks, and get temporarily overwritten before calling the
+@c allocation functions recursively while holding the old hooks. There
+@c are no guards for thread safety, and inconsistent hooks may be found
+@c within signal handlers or left behind in case of cancellation.
+
Calling @code{mcheck} tells @code{malloc} to perform occasional
consistency checks. These will catch things such as writing
past the end of a block that was allocated with @code{malloc}.
@@ -823,6 +1221,18 @@ must be called before the first such function.
@end deftypefun
@deftypefun {enum mcheck_status} mprobe (void *@var{pointer})
+@safety{@prelim{}@mtunsafe{@mtasurace{:mcheck} @mtasuconst{:malloc_hooks}}@asunsafe{@asucorrupt{}}@acunsafe{@acucorrupt{}}}
+@c The linked list of headers may be modified concurrently by other
+@c threads, and it may find a partial update if called from a signal
+@c handler. It's mostly read only, so cancelling it might be safe, but
+@c it will modify global state that, if cancellation hits at just the
+@c right spot, may be left behind inconsistent. This path is only taken
+@c if checkhdr finds an inconsistency. If the inconsistency could only
+@c occur because of earlier undefined behavior, that wouldn't be an
+@c additional safety issue problem, but because of the other concurrency
+@c issues in the mcheck hooks, the apparent inconsistency could be the
+@c result of mcheck's own internal data race. So, AC-Unsafe it is.
+
The @code{mprobe} function lets you explicitly check for inconsistencies
in a particular allocated block. You must have already called
@code{mcheck} at the beginning of the program, to do its occasional
@@ -1137,6 +1547,24 @@ space's data segment).
@comment malloc.h
@comment SVID
@deftypefun {struct mallinfo} mallinfo (void)
+@safety{@prelim{}@mtunsafe{@mtuinit{} @mtasuconst{:mallopt}}@asunsafe{@asuinit{} @asulock{}}@acunsafe{@acuinit{} @aculock{}}}
+@c Accessing mp_.n_mmaps and mp_.max_mmapped_mem, modified with atomics
+@c but non-atomically elsewhere, may get us inconsistent results. We
+@c mark the statistics as unsafe, rather than the fast-path functions
+@c that collect the possibly inconsistent data.
+
+@c __libc_mallinfo @mtuinit @mtasuconst:mallopt @asuinit @asulock @aculock
+@c ptmalloc_init (once) dup @mtsenv @asulock @aculock @acsfd @acsmem
+@c mutex_lock dup @asulock @aculock
+@c int_mallinfo @mtasuconst:mallopt [mp_ access on main_arena]
+@c malloc_consolidate dup ok
+@c check_malloc_state dup ok/disabled
+@c chunksize dup ok
+@c fastbin dupo ok
+@c bin_at dup ok
+@c last dup ok
+@c mutex_unlock @aculock
+
This function returns information about the current dynamic memory usage
in a structure of type @code{struct mallinfo}.
@end deftypefun
@@ -1235,6 +1663,20 @@ penalties for the program if the debugging mode is not enabled.
@comment mcheck.h
@comment GNU
@deftypefun void mtrace (void)
+@safety{@prelim{}@mtunsafe{@mtsenv{} @mtasurace{:mtrace} @mtasuconst{:malloc_hooks} @mtuinit{}}@asunsafe{@asuinit{} @ascuheap{} @asucorrupt{} @asulock{}}@acunsafe{@acuinit{} @acucorrupt{} @aculock{} @acsfd{} @acsmem{}}}
+@c Like the mcheck hooks, these are not designed with thread safety in
+@c mind, because the hook pointers are temporarily modified without
+@c regard to other threads, signals or cancellation.
+
+@c mtrace @mtuinit @mtasurace:mtrace @mtsenv @asuinit @ascuheap @asucorrupt @acuinit @acucorrupt @aculock @acsfd @acsmem
+@c __libc_secure_getenv dup @mtsenv
+@c malloc dup @ascuheap @acsmem
+@c fopen dup @ascuheap @asulock @aculock @acsmem @acsfd
+@c fcntl dup ok
+@c setvbuf dup @aculock
+@c fprintf dup (on newly-created stream) @aculock
+@c __cxa_atexit (once) dup @asulock @aculock @acsmem
+@c free dup @ascuheap @acsmem
When the @code{mtrace} function is called it looks for an environment
variable named @code{MALLOC_TRACE}. This variable is supposed to
contain a valid file name. The user must have write access. If the
@@ -1258,6 +1700,11 @@ systems. The prototype can be found in @file{mcheck.h}.
@comment mcheck.h
@comment GNU
@deftypefun void muntrace (void)
+@safety{@prelim{}@mtunsafe{@mtasurace{:mtrace} @mtasuconst{:malloc_hooks} @mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @acsmem{} @aculock{} @acsfd{}}}
+
+@c muntrace @mtasurace:mtrace @mtslocale @asucorrupt @ascuheap @acucorrupt @acsmem @aculock @acsfd
+@c fprintf (fputs) dup @mtslocale @asucorrupt @ascuheap @acsmem @aculock @acucorrupt
+@c fclose dup @ascuheap @asulock @aculock @acsmem @acsfd
The @code{muntrace} function can be called after @code{mtrace} was used
to enable tracing the @code{malloc} calls. If no (successful) call of
@code{mtrace} was made @code{muntrace} does nothing.
@@ -1569,6 +2016,20 @@ as an obstack, it must initialize the obstack by calling
@comment obstack.h
@comment GNU
@deftypefun int obstack_init (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{@acsmem{}}}
+@c obstack_init @mtsrace:obstack-ptr @acsmem
+@c _obstack_begin @acsmem
+@c chunkfun = obstack_chunk_alloc (suggested malloc)
+@c freefun = obstack_chunk_free (suggested free)
+@c *chunkfun @acsmem
+@c obstack_chunk_alloc user-supplied
+@c *obstack_alloc_failed_handler user-supplied
+@c -> print_and_abort (default)
+@c
+@c print_and_abort
+@c _ dup @ascuintl
+@c fxprintf dup @asucorrupt @aculock @acucorrupt
+@c exit @acucorrupt?
Initialize obstack @var{obstack-ptr} for allocation of objects. This
function calls the obstack's @code{obstack_chunk_alloc} function. If
allocation of memory fails, the function pointed to by
@@ -1624,6 +2085,10 @@ The most direct way to allocate an object in an obstack is with
@comment obstack.h
@comment GNU
@deftypefun {void *} obstack_alloc (struct obstack *@var{obstack-ptr}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_alloc @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c obstack_blank dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c obstack_finish dup @mtsrace:obstack-ptr @acucorrupt
This allocates an uninitialized block of @var{size} bytes in an obstack
and returns its address. Here @var{obstack-ptr} specifies which obstack
to allocate the block in; it is the address of the @code{struct obstack}
@@ -1658,6 +2123,10 @@ To allocate a block with specified contents, use the function
@comment obstack.h
@comment GNU
@deftypefun {void *} obstack_copy (struct obstack *@var{obstack-ptr}, void *@var{address}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_copy @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c obstack_grow dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c obstack_finish dup @mtsrace:obstack-ptr @acucorrupt
This allocates a block and initializes it by copying @var{size}
bytes of data starting at @var{address}. It calls
@code{obstack_alloc_failed_handler} if allocation of memory by
@@ -1667,6 +2136,10 @@ bytes of data starting at @var{address}. It calls
@comment obstack.h
@comment GNU
@deftypefun {void *} obstack_copy0 (struct obstack *@var{obstack-ptr}, void *@var{address}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_copy0 @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c obstack_grow0 dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c obstack_finish dup @mtsrace:obstack-ptr @acucorrupt
Like @code{obstack_copy}, but appends an extra byte containing a null
character. This extra byte is not counted in the argument @var{size}.
@end deftypefun
@@ -1699,6 +2172,10 @@ in the same obstack.
@comment obstack.h
@comment GNU
@deftypefun void obstack_free (struct obstack *@var{obstack-ptr}, void *@var{object})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{}}}
+@c obstack_free @mtsrace:obstack-ptr @acucorrupt
+@c (obstack_free) @mtsrace:obstack-ptr @acucorrupt
+@c *freefun dup user-supplied
If @var{object} is a null pointer, everything allocated in the obstack
is freed. Otherwise, @var{object} must be the address of an object
allocated in the obstack. Then @var{object} is freed, along with
@@ -1803,6 +2280,13 @@ already added to the growing object will become part of the other object.
@comment obstack.h
@comment GNU
@deftypefun void obstack_blank (struct obstack *@var{obstack-ptr}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_blank @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c _obstack_newchunk @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c *chunkfun dup @acsmem
+@c *obstack_alloc_failed_handler dup user-supplied
+@c *freefun
+@c obstack_blank_fast dup @mtsrace:obstack-ptr
The most basic function for adding to a growing object is
@code{obstack_blank}, which adds space without initializing it.
@end deftypefun
@@ -1810,6 +2294,10 @@ The most basic function for adding to a growing object is
@comment obstack.h
@comment GNU
@deftypefun void obstack_grow (struct obstack *@var{obstack-ptr}, void *@var{data}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_grow @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c _obstack_newchunk dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c memcpy ok
To add a block of initialized space, use @code{obstack_grow}, which is
the growing-object analogue of @code{obstack_copy}. It adds @var{size}
bytes of data to the growing object, copying the contents from
@@ -1819,6 +2307,12 @@ bytes of data to the growing object, copying the contents from
@comment obstack.h
@comment GNU
@deftypefun void obstack_grow0 (struct obstack *@var{obstack-ptr}, void *@var{data}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_grow0 @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c (no sequence point between storing NUL and incrementing next_free)
+@c (multiple changes to next_free => @acucorrupt)
+@c _obstack_newchunk dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c memcpy ok
This is the growing-object analogue of @code{obstack_copy0}. It adds
@var{size} bytes copied from @var{data}, followed by an additional null
character.
@@ -1827,6 +2321,10 @@ character.
@comment obstack.h
@comment GNU
@deftypefun void obstack_1grow (struct obstack *@var{obstack-ptr}, char @var{c})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_1grow @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c _obstack_newchunk dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c obstack_1grow_fast dup @mtsrace:obstack-ptr @acucorrupt @acsmem
To add one character at a time, use the function @code{obstack_1grow}.
It adds a single byte containing @var{c} to the growing object.
@end deftypefun
@@ -1834,6 +2332,10 @@ It adds a single byte containing @var{c} to the growing object.
@comment obstack.h
@comment GNU
@deftypefun void obstack_ptr_grow (struct obstack *@var{obstack-ptr}, void *@var{data})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_ptr_grow @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c _obstack_newchunk dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c obstack_ptr_grow_fast dup @mtsrace:obstack-ptr
Adding the value of a pointer one can use the function
@code{obstack_ptr_grow}. It adds @code{sizeof (void *)} bytes
containing the value of @var{data}.
@@ -1842,6 +2344,10 @@ containing the value of @var{data}.
@comment obstack.h
@comment GNU
@deftypefun void obstack_int_grow (struct obstack *@var{obstack-ptr}, int @var{data})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_int_grow @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c _obstack_newchunk dup @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c obstack_int_grow_fast dup @mtsrace:obstack-ptr
A single value of type @code{int} can be added by using the
@code{obstack_int_grow} function. It adds @code{sizeof (int)} bytes to
the growing object and initializes them with the value of @var{data}.
@@ -1850,6 +2356,8 @@ the growing object and initializes them with the value of @var{data}.
@comment obstack.h
@comment GNU
@deftypefun {void *} obstack_finish (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{}}}
+@c obstack_finish @mtsrace:obstack-ptr @acucorrupt
When you are finished growing the object, use the function
@code{obstack_finish} to close it off and return its final address.
@@ -1869,6 +2377,7 @@ declared as follows:
@comment obstack.h
@comment GNU
@deftypefun int obstack_object_size (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
This function returns the current size of the growing object, in bytes.
Remember to call this function @emph{before} finishing the object.
After it is finished, @code{obstack_object_size} will return zero.
@@ -1912,6 +2421,7 @@ in the current chunk. It is declared as follows:
@comment obstack.h
@comment GNU
@deftypefun int obstack_room (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
This returns the number of bytes that can be added safely to the current
growing object (or to an object about to be started) in obstack
@var{obstack} using the fast growth functions.
@@ -1923,6 +2433,9 @@ for adding data to a growing object:
@comment obstack.h
@comment GNU
@deftypefun void obstack_1grow_fast (struct obstack *@var{obstack-ptr}, char @var{c})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acunsafe{@acucorrupt{} @acsmem{}}}
+@c obstack_1grow_fast @mtsrace:obstack-ptr @acucorrupt @acsmem
+@c (no sequence point between copying c and incrementing next_free)
The function @code{obstack_1grow_fast} adds one byte containing the
character @var{c} to the growing object in obstack @var{obstack-ptr}.
@end deftypefun
@@ -1930,6 +2443,8 @@ character @var{c} to the growing object in obstack @var{obstack-ptr}.
@comment obstack.h
@comment GNU
@deftypefun void obstack_ptr_grow_fast (struct obstack *@var{obstack-ptr}, void *@var{data})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
+@c obstack_ptr_grow_fast @mtsrace:obstack-ptr
The function @code{obstack_ptr_grow_fast} adds @code{sizeof (void *)}
bytes containing the value of @var{data} to the growing object in
obstack @var{obstack-ptr}.
@@ -1938,6 +2453,8 @@ obstack @var{obstack-ptr}.
@comment obstack.h
@comment GNU
@deftypefun void obstack_int_grow_fast (struct obstack *@var{obstack-ptr}, int @var{data})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
+@c obstack_int_grow_fast @mtsrace:obstack-ptr
The function @code{obstack_int_grow_fast} adds @code{sizeof (int)} bytes
containing the value of @var{data} to the growing object in obstack
@var{obstack-ptr}.
@@ -1946,6 +2463,8 @@ containing the value of @var{data} to the growing object in obstack
@comment obstack.h
@comment GNU
@deftypefun void obstack_blank_fast (struct obstack *@var{obstack-ptr}, int @var{size})
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
+@c obstack_blank_fast @mtsrace:obstack-ptr
The function @code{obstack_blank_fast} adds @var{size} bytes to the
growing object in obstack @var{obstack-ptr} without initializing them.
@end deftypefun
@@ -2004,6 +2523,7 @@ still growing it.
@comment obstack.h
@comment GNU
@deftypefun {void *} obstack_base (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asucorrupt{}}@acsafe{}}
This function returns the tentative address of the beginning of the
currently growing object in @var{obstack-ptr}. If you finish the object
immediately, it will have that address. If you make it larger first, it
@@ -2017,6 +2537,7 @@ chunk).
@comment obstack.h
@comment GNU
@deftypefun {void *} obstack_next_free (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{}@asunsafe{@asucorrupt{}}@acsafe{}}
This function returns the address of the first free byte in the current
chunk of obstack @var{obstack-ptr}. This is the end of the currently
growing object. If no object is growing, @code{obstack_next_free}
@@ -2026,6 +2547,8 @@ returns the same value as @code{obstack_base}.
@comment obstack.h
@comment GNU
@deftypefun int obstack_object_size (struct obstack *@var{obstack-ptr})
+@c dup
+@safety{@prelim{}@mtsafe{@mtsrace{:obstack-ptr}}@assafe{}@acsafe{}}
This function returns the size in bytes of the currently growing object.
This is equivalent to
@@ -2050,6 +2573,7 @@ this:
@comment obstack.h
@comment GNU
@deftypefn Macro int obstack_alignment_mask (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
The value is a bit mask; a bit that is 1 indicates that the corresponding
bit in the address of an object should be 0. The mask value should be one
less than a power of 2; the effect is that all object addresses are
@@ -2117,6 +2641,7 @@ not to waste too much memory in the portion of the last chunk not yet used.
@comment obstack.h
@comment GNU
@deftypefn Macro int obstack_chunk_size (struct obstack *@var{obstack-ptr})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
This returns the chunk size of the given obstack.
@end deftypefn
@@ -2236,6 +2761,7 @@ a BSD extension.
@comment stdlib.h
@comment GNU, BSD
@deftypefun {void *} alloca (size_t @var{size})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
The return value of @code{alloca} is the address of a block of @var{size}
bytes of memory, allocated in the stack frame of the calling function.
@end deftypefun
@@ -2418,6 +2944,7 @@ system calls.
@comment unistd.h
@comment BSD
@deftypefun int brk (void *@var{addr})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
@code{brk} sets the high end of the calling process' data segment to
@var{addr}.
@@ -2460,6 +2987,8 @@ exceed the process' data storage limit.
@comment unistd.h
@comment BSD
@deftypefun void *sbrk (ptrdiff_t @var{delta})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+
This function is the same as @code{brk} except that you specify the new
end of the data segment as an offset @var{delta} from the current end
and on success the return value is the address of the resulting end of
@@ -2599,6 +3128,7 @@ this requirement.
@comment sys/mman.h
@comment POSIX.1b
@deftypefun int mlock (const void *@var{addr}, size_t @var{len})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
@code{mlock} locks a range of the calling process' virtual pages.
@@ -2652,6 +3182,7 @@ wouldn't know what address to tell @code{mlock}.
@comment sys/mman.h
@comment POSIX.1b
@deftypefun int munlock (const void *@var{addr}, size_t @var{len})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
@code{munlock} unlocks a range of the calling process' virtual pages.
@@ -2664,6 +3195,7 @@ failure.
@comment sys/mman.h
@comment POSIX.1b
@deftypefun int mlockall (int @var{flags})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
@code{mlockall} locks all the pages in a process' virtual memory address
space, and/or any that are added to it in the future. This includes the
@@ -2740,6 +3272,7 @@ with @code{munlockall} and @code{munlock}.
@comment sys/mman.h
@comment POSIX.1b
@deftypefun int munlockall (void)
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
@code{munlockall} unlocks every page in the calling process' virtual
address space and turn off @code{MCL_FUTURE} future locking mode.
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Toolchain Engineer