On Sat, Aug 6, 2022 at 1:52 AM Ingo Molnar mingo@kernel.org wrote:
- Kyle Huey me@kylehuey.com wrote:
From: Kyle Huey me@kylehuey.com
This tests PTRACE_SETREGSET with NT_X86_XSTATE modifying PKRU directly and removing the PKRU bit from XSTATE_BV.
Signed-off-by: Kyle Huey me@kylehuey.com
tools/testing/selftests/vm/pkey-x86.h | 12 +++ tools/testing/selftests/vm/protection_keys.c | 88 +++++++++++++++++++- 2 files changed, 98 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/vm/pkey-x86.h b/tools/testing/selftests/vm/pkey-x86.h index b078ce9c6d2a..72c14cd3ddc7 100644 --- a/tools/testing/selftests/vm/pkey-x86.h +++ b/tools/testing/selftests/vm/pkey-x86.h @@ -104,6 +104,18 @@ static inline int cpu_has_pkeys(void) return 1; }
+static inline int cpu_max_xsave_size(void) +{
unsigned long XSTATE_CPUID = 0xd;unsigned int eax;unsigned int ebx;unsigned int ecx;unsigned int edx;__cpuid_count(XSTATE_CPUID, 0, eax, ebx, ecx, edx);return ecx;+}
static inline u32 pkey_bit_position(int pkey) { return pkey * PKEY_BITS_PER_PKEY; diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c index 291bc1e07842..27759d3ed9cd 100644 --- a/tools/testing/selftests/vm/protection_keys.c +++ b/tools/testing/selftests/vm/protection_keys.c @@ -18,12 +18,13 @@
- do a plain mprotect() to a mprotect_pkey() area and make sure the pkey sticks
- Compile like this:
- gcc -o protection_keys -O2 -g -std=gnu99 -pthread -Wall protection_keys.c -lrt -ldl -lm
- gcc -m32 -o protection_keys_32 -O2 -g -std=gnu99 -pthread -Wall protection_keys.c -lrt -ldl -lm
- gcc -mxsave -o protection_keys -O2 -g -std=gnu99 -pthread -Wall protection_keys.c -lrt -ldl -lm
*/
- gcc -mxsave -m32 -o protection_keys_32 -O2 -g -std=gnu99 -pthread -Wall protection_keys.c -lrt -ldl -lm
#define _GNU_SOURCE #define __SANE_USERSPACE_TYPES__ #include <errno.h> +#include <linux/elf.h> #include <linux/futex.h> #include <time.h> #include <sys/time.h> @@ -1550,6 +1551,86 @@ void test_implicit_mprotect_exec_only_memory(int *ptr, u16 pkey) do_not_expect_pkey_fault("plain read on recently PROT_EXEC area"); }
+#if defined(__i386__) || defined(__x86_64__) +void test_ptrace_modifies_pkru(int *ptr, u16 pkey) +{
pid_t child;int status, ret;int pkey_offset = pkey_reg_xstate_offset();size_t xsave_size = cpu_max_xsave_size();void *xsave;u32 *pkey_register;u64 *xstate_bv;struct iovec iov;child = fork();pkey_assert(child >= 0);dprintf3("[%d] fork() ret: %d\n", getpid(), child);if (!child) {u32 pkey_register = read_pkey_reg();ptrace(PTRACE_TRACEME, 0, 0, 0);raise(SIGSTOP);/** need __read_pkey_reg() version so we do not do shadow_pkey_reg* checking*/if (pkey_register == __read_pkey_reg())exit(1);raise(SIGSTOP);exit(__read_pkey_reg());}pkey_assert(child == waitpid(child, &status, 0));dprintf3("[%d] waitpid(%d) status: %x\n", getpid(), child, status);pkey_assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP);xsave = (void *)malloc(xsave_size);pkey_assert(xsave > 0);iov.iov_base = xsave;iov.iov_len = xsave_size;ret = ptrace(PTRACE_GETREGSET, child, (void *)NT_X86_XSTATE, &iov);pkey_assert(ret == 0);pkey_register = (u32 *)(xsave + pkey_offset);pkey_assert(*pkey_register == read_pkey_reg());*pkey_register = !read_pkey_reg();ret = ptrace(PTRACE_SETREGSET, child, (void *)NT_X86_XSTATE, &iov);pkey_assert(ret == 0);ret = ptrace(PTRACE_CONT, child, 0, 0);pkey_assert(ret == 0);pkey_assert(child == waitpid(child, &status, 0));dprintf3("[%d] waitpid(%d) status: %x\n", getpid(), child, status);pkey_assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP);ret = ptrace(PTRACE_GETREGSET, child, (void *)NT_X86_XSTATE, &iov);pkey_assert(ret == 0);xstate_bv = (u64 *)(xsave + 512);*xstate_bv &= ~(1 << 9);ret = ptrace(PTRACE_SETREGSET, child, (void *)NT_X86_XSTATE, &iov);pkey_assert(ret == 0);ret = ptrace(PTRACE_CONT, child, 0, 0);pkey_assert(ret == 0);pkey_assert(child == waitpid(child, &status, 0));dprintf3("[%d] waitpid(%d) status: %x\n", getpid(), child, status);pkey_assert(WIFEXITED(status));pkey_assert(WEXITSTATUS(status) == 0);free(xsave);LGTM.
May I ask for a bit more in terms of testing the ABI: writing some non-trivial (not all-zero and not all-ones) value into the PKRU register, forcing the child task to go through a FPU save/restore context switch and then reading it back and verifying the value, or something like that?
Can you elaborate a bit on what you mean here? I'm not sure what "a FPU save/restore context switch" is. The XSTATE (and everything else) will be saved/restored at the ptrace stops (for the raise(SIGSTOP)s) already.
- Kyle
Thanks,
Ingo