On Thu, 30 Apr 2020 at 20:42, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
>
> gdb uses ptrace() to peek and poke bytes of the target's address space.
> The kernel must implement an vm_ops->access() handler or else gdb will
> be unable to inspect the pointer and report it as out-of-bounds. Worse
> than useless as it causes immediate suspicion of the valid GTT pointer.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> tests/i915/gem_mmap_gtt.c | 79 ++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 78 insertions(+), 1 deletion(-)
>
> diff --git a/tests/i915/gem_mmap_gtt.c b/tests/i915/gem_mmap_gtt.c
> index 1f4655af4..38b4d02d7 100644
> --- a/tests/i915/gem_mmap_gtt.c
> +++ b/tests/i915/gem_mmap_gtt.c
> @@ -34,8 +34,11 @@
> #include <inttypes.h>
> #include <pthread.h>
> #include <errno.h>
> -#include <sys/stat.h>
> +#include <signal.h>
> #include <sys/ioctl.h>
> +#include <sys/ptrace.h>
> +#include <sys/stat.h>
> +#include <sys/wait.h>
> #include "drm.h"
>
> #include "igt.h"
> @@ -501,6 +504,78 @@ test_write_gtt(int fd)
> munmap(src, OBJECT_SIZE);
> }
>
> +static void *memchr_inv(const void *s, int c, size_t n)
> +{
> + const uint8_t *us = s;
> + const uint8_t uc = c;
> +
> +#pragma GCC diagnostic push
> +#pragma GCC diagnostic ignored "-Wcast-qual"
> + while (n--) {
> + if (*us != uc)
> + return (void *) us;
> + us++;
> + }
> +#pragma GCC diagnostic pop
> +
> + return NULL;
> +}
> +
> +static void
> +test_ptrace(int fd)
> +{
> + unsigned long AA, CC;
> + unsigned long *gtt, *cpy;
> + uint32_t bo;
> + pid_t pid;
> +
> + memset(&AA, 0xaa, sizeof(AA));
> + memset(&CC, 0x55, sizeof(CC));
> +
> + cpy = malloc(OBJECT_SIZE);
> + memset(cpy, AA, OBJECT_SIZE);
> +
> + bo = gem_create(fd, OBJECT_SIZE);
> + gtt = mmap_bo(fd, bo, OBJECT_SIZE);
> + memset(gtt, CC, OBJECT_SIZE);
> + gem_close(fd, bo);
> +
> + igt_assert(!memchr_inv(gtt, CC, OBJECT_SIZE));
> + igt_assert(!memchr_inv(cpy, AA, OBJECT_SIZE));
> +
> + igt_fork(child, 1) {
> + ptrace(PTRACE_TRACEME, 0, NULL, NULL);
> + raise(SIGSTOP);
> + }
> +
> + /* Wait for the child to ready themselves [SIGSTOP] */
> + pid = wait(NULL);
> +
> + ptrace(PTRACE_ATTACH, pid, NULL, NULL);
> + for (int i = 0; i < OBJECT_SIZE / sizeof(long); i++) {
> + long ret;
> +
> + ret = ptrace(PTRACE_PEEKDATA, pid, gtt + i);
> + igt_assert_eq_u64(ret, CC);
> + cpy[i] = ret;
> +
> + ret = ptrace(PTRACE_POKEDATA, pid, gtt + i, AA);
> + igt_assert_eq(ret, 0l);
igt_assert_eq_u64() ?
Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
