On Mon, Jun 03, 2019 at 06:55:18PM +0200, Andrey Konovalov wrote:
This patch is a part of a series that extends arm64 kernel ABI to allow to pass tagged user pointers (with the top byte set to something else other than 0x00) as syscall arguments.
This patch adds a simple test, that calls the uname syscall with a tagged user pointer as an argument. Without the kernel accepting tagged user pointers the test fails with EFAULT.
Signed-off-by: Andrey Konovalov andreyknvl@google.com
BTW, you could add
Co-developed-by: Catalin Marinas catalin.marinas@arm.com
since I wrote the malloc() etc. hooks.
+static void *tag_ptr(void *ptr) +{
- unsigned long tag = rand() & 0xff;
- if (!ptr)
return ptr;- return (void *)((unsigned long)ptr | (tag << TAG_SHIFT));
+}
With the prctl() option, this function becomes (if you have a better idea, fine by me):
----------8<--------------- #include <stdlib.h> #include <sys/prctl.h>
#define TAG_SHIFT (56) #define TAG_MASK (0xffUL << TAG_SHIFT)
#define PR_SET_TAGGED_ADDR_CTRL 55 #define PR_GET_TAGGED_ADDR_CTRL 56 # define PR_TAGGED_ADDR_ENABLE (1UL << 0)
void *__libc_malloc(size_t size); void __libc_free(void *ptr); void *__libc_realloc(void *ptr, size_t size); void *__libc_calloc(size_t nmemb, size_t size);
static void *tag_ptr(void *ptr) { static int tagged_addr_err = 1; unsigned long tag = 0;
if (tagged_addr_err == 1) tagged_addr_err = prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0);
if (!ptr) return ptr; if (!tagged_addr_err) tag = rand() & 0xff;
return (void *)((unsigned long)ptr | (tag << TAG_SHIFT)); }