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malloc: Update heap dumping/undumping comments [BZ #23351]

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Also remove a few now-unused declarations and definitions.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Florian Weimer 2018-06-29 14:54:59 +02:00
parent 339124ab42
commit 524d796d5f
3 changed files with 16 additions and 52 deletions
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10
ChangeLog
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@ -1,3 +1,13 @@
2018-06-29 Florian Weimer <fweimer@redhat.com>
[BZ #23351]
* malloc/hooks.c: Update comments on restoring of dumped heaps.
(disallow_malloc_check): Remove variable.
(__malloc_check_init): Adjust.
(malloc_set_state): Update comment.
* malloc/malloc.c (__malloc_get_state, __malloc_set_state): Remove
declarations.
2018-06-29 Rafal Luzynski <digitalfreak@lingonborough.com>
[BZ #23140]

42
malloc/hooks.c
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@ -52,30 +52,10 @@ memalign_hook_ini (size_t alignment, size_t sz, const void *caller)
/* Whether we are using malloc checking. */
static int using_malloc_checking;
/* A flag that is set by malloc_set_state, to signal that malloc checking
must not be enabled on the request from the user (via the MALLOC_CHECK_
environment variable). It is reset by __malloc_check_init to tell
malloc_set_state that the user has requested malloc checking.
The purpose of this flag is to make sure that malloc checking is not
enabled when the heap to be restored was constructed without malloc
checking, and thus does not contain the required magic bytes.
Otherwise the heap would be corrupted by calls to free and realloc. If
it turns out that the heap was created with malloc checking and the
user has requested it malloc_set_state just calls __malloc_check_init
again to enable it. On the other hand, reusing such a heap without
further malloc checking is safe. */
static int disallow_malloc_check;
/* Activate a standard set of debugging hooks. */
void
__malloc_check_init (void)
{
if (disallow_malloc_check)
{
disallow_malloc_check = 0;
return;
}
using_malloc_checking = 1;
__malloc_hook = malloc_check;
__free_hook = free_check;
@ -407,21 +387,11 @@ memalign_check (size_t alignment, size_t bytes, const void *caller)
#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_25)
/* Get/set state: malloc_get_state() records the current state of all
malloc variables (_except_ for the actual heap contents and `hook'
function pointers) in a system dependent, opaque data structure.
This data structure is dynamically allocated and can be free()d
after use. malloc_set_state() restores the state of all malloc
variables to the previously obtained state. This is especially
useful when using this malloc as part of a shared library, and when
the heap contents are saved/restored via some other method. The
primary example for this is GNU Emacs with its `dumping' procedure.
`Hook' function pointers are never saved or restored by these
functions, with two exceptions: If malloc checking was in use when
malloc_get_state() was called, then malloc_set_state() calls
__malloc_check_init() if possible; if malloc checking was not in
use in the recorded state but the user requested malloc checking,
then the hooks are reset to 0. */
/* Support for restoring dumped heaps contained in historic Emacs
executables. The heap saving feature (malloc_get_state) is no
longer implemented in this version of glibc, but we have a heap
rewriter in malloc_set_state which transforms the heap into a
version compatible with current malloc. */
#define MALLOC_STATE_MAGIC 0x444c4541l
#define MALLOC_STATE_VERSION (0 * 0x100l + 5l) /* major*0x100 + minor */
@ -476,7 +446,7 @@ malloc_set_state (void *msptr)
if ((ms->version & ~0xffl) > (MALLOC_STATE_VERSION & ~0xffl))
return -2;
/* We do not need to perform locking here because __malloc_set_state
/* We do not need to perform locking here because malloc_set_state
must be called before the first call into the malloc subsytem
(usually via __malloc_initialize_hook). pthread_create always
calls calloc and thus must be called only afterwards, so there

16
malloc/malloc.c
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@ -697,22 +697,6 @@ size_t __malloc_usable_size(void*);
*/
void __malloc_stats(void);
/*
malloc_get_state(void);
Returns the state of all malloc variables in an opaque data
structure.
*/
void* __malloc_get_state(void);
/*
malloc_set_state(void* state);
Restore the state of all malloc variables from data obtained with
malloc_get_state().
*/
int __malloc_set_state(void*);
/*
posix_memalign(void **memptr, size_t alignment, size_t size);