| /* mmap.c -- Memory allocation with mmap. |
| Copyright (C) 2012-2024 Free Software Foundation, Inc. |
| Written by Ian Lance Taylor, Google. |
| |
| Redistribution and use in source and binary forms, with or without |
| modification, are permitted provided that the following conditions are |
| met: |
| |
| (1) Redistributions of source code must retain the above copyright |
| notice, this list of conditions and the following disclaimer. |
| |
| (2) Redistributions in binary form must reproduce the above copyright |
| notice, this list of conditions and the following disclaimer in |
| the documentation and/or other materials provided with the |
| distribution. |
| |
| (3) The name of the author may not be used to |
| endorse or promote products derived from this software without |
| specific prior written permission. |
| |
| THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
| WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, |
| INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR |
| SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
| STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING |
| IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| POSSIBILITY OF SUCH DAMAGE. */ |
| |
| #include "config.h" |
| |
| #include <errno.h> |
| #include <string.h> |
| #include <stdlib.h> |
| #include <unistd.h> |
| #include <sys/types.h> |
| #include <sys/mman.h> |
| |
| #include "backtrace.h" |
| #include "internal.h" |
| |
| #ifndef HAVE_DECL_GETPAGESIZE |
| extern int getpagesize (void); |
| #endif |
| |
| /* Memory allocation on systems that provide anonymous mmap. This |
| permits the backtrace functions to be invoked from a signal |
| handler, assuming that mmap is async-signal safe. */ |
| |
| #ifndef MAP_ANONYMOUS |
| #define MAP_ANONYMOUS MAP_ANON |
| #endif |
| |
| #ifndef MAP_FAILED |
| #define MAP_FAILED ((void *)-1) |
| #endif |
| |
| /* A list of free memory blocks. */ |
| |
| struct backtrace_freelist_struct |
| { |
| /* Next on list. */ |
| struct backtrace_freelist_struct *next; |
| /* Size of this block, including this structure. */ |
| size_t size; |
| }; |
| |
| /* Free memory allocated by backtrace_alloc. */ |
| |
| static void |
| backtrace_free_locked (struct backtrace_state *state, void *addr, size_t size) |
| { |
| /* Just leak small blocks. We don't have to be perfect. Don't put |
| more than 16 entries on the free list, to avoid wasting time |
| searching when allocating a block. If we have more than 16 |
| entries, leak the smallest entry. */ |
| |
| if (size >= sizeof (struct backtrace_freelist_struct)) |
| { |
| size_t c; |
| struct backtrace_freelist_struct **ppsmall; |
| struct backtrace_freelist_struct **pp; |
| struct backtrace_freelist_struct *p; |
| |
| c = 0; |
| ppsmall = NULL; |
| for (pp = &state->freelist; *pp != NULL; pp = &(*pp)->next) |
| { |
| if (ppsmall == NULL || (*pp)->size < (*ppsmall)->size) |
| ppsmall = pp; |
| ++c; |
| } |
| if (c >= 16) |
| { |
| if (size <= (*ppsmall)->size) |
| return; |
| *ppsmall = (*ppsmall)->next; |
| } |
| |
| p = (struct backtrace_freelist_struct *) addr; |
| p->next = state->freelist; |
| p->size = size; |
| state->freelist = p; |
| } |
| } |
| |
| /* Allocate memory like malloc. If ERROR_CALLBACK is NULL, don't |
| report an error. */ |
| |
| void * |
| backtrace_alloc (struct backtrace_state *state, |
| size_t size, backtrace_error_callback error_callback, |
| void *data) |
| { |
| void *ret; |
| int locked; |
| struct backtrace_freelist_struct **pp; |
| size_t pagesize; |
| size_t asksize; |
| void *page; |
| |
| ret = NULL; |
| |
| /* If we can acquire the lock, then see if there is space on the |
| free list. If we can't acquire the lock, drop straight into |
| using mmap. __sync_lock_test_and_set returns the old state of |
| the lock, so we have acquired it if it returns 0. */ |
| |
| if (!state->threaded) |
| locked = 1; |
| else |
| locked = __sync_lock_test_and_set (&state->lock_alloc, 1) == 0; |
| |
| if (locked) |
| { |
| for (pp = &state->freelist; *pp != NULL; pp = &(*pp)->next) |
| { |
| if ((*pp)->size >= size) |
| { |
| struct backtrace_freelist_struct *p; |
| |
| p = *pp; |
| *pp = p->next; |
| |
| /* Round for alignment; we assume that no type we care about |
| is more than 8 bytes. */ |
| size = (size + 7) & ~ (size_t) 7; |
| if (size < p->size) |
| backtrace_free_locked (state, (char *) p + size, |
| p->size - size); |
| |
| ret = (void *) p; |
| |
| break; |
| } |
| } |
| |
| if (state->threaded) |
| __sync_lock_release (&state->lock_alloc); |
| } |
| |
| if (ret == NULL) |
| { |
| /* Allocate a new page. */ |
| |
| pagesize = getpagesize (); |
| asksize = (size + pagesize - 1) & ~ (pagesize - 1); |
| page = mmap (NULL, asksize, PROT_READ | PROT_WRITE, |
| MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); |
| if (page == MAP_FAILED) |
| { |
| if (error_callback) |
| error_callback (data, "mmap", errno); |
| } |
| else |
| { |
| size = (size + 7) & ~ (size_t) 7; |
| if (size < asksize) |
| backtrace_free (state, (char *) page + size, asksize - size, |
| error_callback, data); |
| |
| ret = page; |
| } |
| } |
| |
| return ret; |
| } |
| |
| /* Free memory allocated by backtrace_alloc. */ |
| |
| void |
| backtrace_free (struct backtrace_state *state, void *addr, size_t size, |
| backtrace_error_callback error_callback ATTRIBUTE_UNUSED, |
| void *data ATTRIBUTE_UNUSED) |
| { |
| int locked; |
| |
| /* If we are freeing a large aligned block, just release it back to |
| the system. This case arises when growing a vector for a large |
| binary with lots of debug info. Calling munmap here may cause us |
| to call mmap again if there is also a large shared library; we |
| just live with that. */ |
| if (size >= 16 * 4096) |
| { |
| size_t pagesize; |
| |
| pagesize = getpagesize (); |
| if (((uintptr_t) addr & (pagesize - 1)) == 0 |
| && (size & (pagesize - 1)) == 0) |
| { |
| /* If munmap fails for some reason, just add the block to |
| the freelist. */ |
| if (munmap (addr, size) == 0) |
| return; |
| } |
| } |
| |
| /* If we can acquire the lock, add the new space to the free list. |
| If we can't acquire the lock, just leak the memory. |
| __sync_lock_test_and_set returns the old state of the lock, so we |
| have acquired it if it returns 0. */ |
| |
| if (!state->threaded) |
| locked = 1; |
| else |
| locked = __sync_lock_test_and_set (&state->lock_alloc, 1) == 0; |
| |
| if (locked) |
| { |
| backtrace_free_locked (state, addr, size); |
| |
| if (state->threaded) |
| __sync_lock_release (&state->lock_alloc); |
| } |
| } |
| |
| /* Grow VEC by SIZE bytes. */ |
| |
| void * |
| backtrace_vector_grow (struct backtrace_state *state,size_t size, |
| backtrace_error_callback error_callback, |
| void *data, struct backtrace_vector *vec) |
| { |
| void *ret; |
| |
| if (size > vec->alc) |
| { |
| size_t pagesize; |
| size_t alc; |
| void *base; |
| |
| pagesize = getpagesize (); |
| alc = vec->size + size; |
| if (vec->size == 0) |
| alc = 16 * size; |
| else if (alc < pagesize) |
| { |
| alc *= 2; |
| if (alc > pagesize) |
| alc = pagesize; |
| } |
| else |
| { |
| alc *= 2; |
| alc = (alc + pagesize - 1) & ~ (pagesize - 1); |
| } |
| base = backtrace_alloc (state, alc, error_callback, data); |
| if (base == NULL) |
| return NULL; |
| if (vec->base != NULL) |
| { |
| memcpy (base, vec->base, vec->size); |
| backtrace_free (state, vec->base, vec->size + vec->alc, |
| error_callback, data); |
| } |
| vec->base = base; |
| vec->alc = alc - vec->size; |
| } |
| |
| ret = (char *) vec->base + vec->size; |
| vec->size += size; |
| vec->alc -= size; |
| return ret; |
| } |
| |
| /* Finish the current allocation on VEC. */ |
| |
| void * |
| backtrace_vector_finish ( |
| struct backtrace_state *state ATTRIBUTE_UNUSED, |
| struct backtrace_vector *vec, |
| backtrace_error_callback error_callback ATTRIBUTE_UNUSED, |
| void *data ATTRIBUTE_UNUSED) |
| { |
| void *ret; |
| |
| ret = vec->base; |
| vec->base = (char *) vec->base + vec->size; |
| vec->size = 0; |
| return ret; |
| } |
| |
| /* Release any extra space allocated for VEC. */ |
| |
| int |
| backtrace_vector_release (struct backtrace_state *state, |
| struct backtrace_vector *vec, |
| backtrace_error_callback error_callback, |
| void *data) |
| { |
| size_t size; |
| size_t alc; |
| size_t aligned; |
| |
| /* Make sure that the block that we free is aligned on an 8-byte |
| boundary. */ |
| size = vec->size; |
| alc = vec->alc; |
| aligned = (size + 7) & ~ (size_t) 7; |
| alc -= aligned - size; |
| |
| backtrace_free (state, (char *) vec->base + aligned, alc, |
| error_callback, data); |
| vec->alc = 0; |
| if (vec->size == 0) |
| vec->base = NULL; |
| return 1; |
| } |