Magic-Mirror/gecko-dev
1
0
Fork 0
mirror of https://github.com/mozilla/gecko-dev.git synced 2025-02-16 13:56:29 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Bug 920558 - map anonymous pages differently on ARM and x86; r=glandium

Browse Source
This commit is contained in:
Nathan Froyd 2013-09-26 11:17:05 -04:00
parent 7bb922a1d8
commit 0dd69ef1ca
1 changed files with 25 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
mozglue/linker/Mappable.cpp
View File

@ -185,22 +185,27 @@ public:
/* The Gecko crash reporter is confused by adjacent memory mappings of
* the same file and chances are we're going to map from the same file
* descriptor right away. To avoid problems with the crash reporter,
* create an empty anonymous page before and after the ashmem mapping.
* We create two anonymous pages because on some platforms, subsequent
* mappings are placed at adjacent, increasing memory addresses (ARM)
* and on others, such mappings are placed at adjacent, decreasing
* memory addresses (x86). It is more convenient to just do two pages
* everywhere than to twiddle with platform-specific #defines.
* create an empty anonymous page before or after the ashmem mapping,
* depending on how mappings grow in the address space.
*/
size_t anon_mapping_length = length + 2 * PAGE_SIZE;
#if defined(__arm__)
void *buf = ::mmap(NULL, length + PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (buf != MAP_FAILED) {
::mmap(AlignedEndPtr(reinterpret_cast<char *>(buf) + length, PAGE_SIZE),
PAGE_SIZE, PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
DEBUG_LOG("Decompression buffer of size 0x%x in ashmem \"%s\", mapped @%p",
length, str, buf);
return new _MappableBuffer(fd.forget(), buf, length);
}
#elif defined(__i386__)
size_t anon_mapping_length = length + PAGE_SIZE;
void *buf = ::mmap(NULL, anon_mapping_length, PROT_NONE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (buf != MAP_FAILED) {
char *first_page = reinterpret_cast<char *>(buf);
char *map_page = first_page + PAGE_SIZE;
char *last_page = map_page + ((length + PAGE_SIZE - 1) & PAGE_MASK);
void *actual_buf = ::mmap(map_page, last_page - map_page, PROT_READ | PROT_WRITE,
void *actual_buf = ::mmap(map_page, length, PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_SHARED, fd, 0);
if (actual_buf == MAP_FAILED) {
::munmap(buf, anon_mapping_length);
@ -212,6 +217,9 @@ public:
length, str, actual_buf);
return new _MappableBuffer(fd.forget(), actual_buf, length);
}
#else
#error need to add a case for your CPU
#endif
#else
/* On Linux, use /dev/shm as base directory for temporary files, assuming
* it's on tmpfs */
@ -250,8 +258,14 @@ public:
#ifdef ANDROID
~_MappableBuffer() {
/* Free the additional pages we allocated. See _MappableBuffer::Create */
::munmap(*this - PAGE_SIZE, GetLength() + 2 * PAGE_SIZE);
/* Free the additional page we allocated. See _MappableBuffer::Create */
#if defined(__arm__)
::munmap(AlignedEndPtr(*this + GetLength(), PAGE_SIZE), PAGE_SIZE);
#elif defined(__i386__)
::munmap(*this - PAGE_SIZE, GetLength() + PAGE_SIZE);
#else
#error need to add a case for your CPU
#endif
}
#endif