At present the sandbox RAM buffer is not aligned to any particular address boundary. This makes the internal pointers somewhat random with respect to the associated RAM buffer addresses.
Align the buffer to the page size of the machine to help with this. Note that there is a header at the start of the allocated pointer. To avoid returning a pointer which is not aligned to a page boundary, we waste almost an entire page of memory for each allocation.
Signed-off-by: Simon Glass sjg@chromium.org ---
Changes in v10: - Explain the padding of the returned pointer in the commit message
Changes in v9: None Changes in v8: None Changes in v7: None Changes in v6: None Changes in v4: None Changes in v3: None Changes in v2: None
arch/sandbox/cpu/os.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c index 5839932b005..a1a982af2de 100644 --- a/arch/sandbox/cpu/os.c +++ b/arch/sandbox/cpu/os.c @@ -143,14 +143,15 @@ void os_tty_raw(int fd, bool allow_sigs) void *os_malloc(size_t length) { struct os_mem_hdr *hdr; + int page_size = getpagesize();
- hdr = mmap(NULL, length + sizeof(*hdr), PROT_READ | PROT_WRITE, - MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + hdr = mmap(NULL, length + page_size, + PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (hdr == MAP_FAILED) return NULL; hdr->length = length;
- return hdr + 1; + return (void *)hdr + page_size; }
void os_free(void *ptr)