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selftests/powerpc: Add a test for execute-only memory

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This selftest is designed to cover execute-only protections
on the Radix MMU but will also work with Hash.

The tests are based on those found in pkey_exec_test with modifications
to use the generic mprotect() instead of the pkey variants.

Signed-off-by: Nicholas Miehlbradt <nicholas@linux.ibm.com>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220817050640.406017-2-ruscur@russell.cc
This commit is contained in:
Nicholas Miehlbradt 2022-08-17 15:06:40 +10:00 committed by Michael Ellerman
parent 395cac7752
commit 98acee3f8d
2 changed files with 233 additions and 1 deletions
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3
tools/testing/selftests/powerpc/mm/Makefile
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@ -3,7 +3,7 @@ noarg:
$(MAKE) -C ../
TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors wild_bctr \
large_vm_fork_separation bad_accesses pkey_exec_prot \
large_vm_fork_separation bad_accesses exec_prot pkey_exec_prot \
pkey_siginfo stack_expansion_signal stack_expansion_ldst \
large_vm_gpr_corruption
TEST_PROGS := stress_code_patching.sh
@ -22,6 +22,7 @@ $(OUTPUT)/wild_bctr: CFLAGS += -m64
$(OUTPUT)/large_vm_fork_separation: CFLAGS += -m64
$(OUTPUT)/large_vm_gpr_corruption: CFLAGS += -m64
$(OUTPUT)/bad_accesses: CFLAGS += -m64
$(OUTPUT)/exec_prot: CFLAGS += -m64
$(OUTPUT)/pkey_exec_prot: CFLAGS += -m64
$(OUTPUT)/pkey_siginfo: CFLAGS += -m64

231
tools/testing/selftests/powerpc/mm/exec_prot.c Normal file
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@ -0,0 +1,231 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright 2022, Nicholas Miehlbradt, IBM Corporation
* based on pkey_exec_prot.c
*
* Test if applying execute protection on pages works as expected.
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <sys/mman.h>
#include "pkeys.h"
#define PPC_INST_NOP 0x60000000
#define PPC_INST_TRAP 0x7fe00008
#define PPC_INST_BLR 0x4e800020
static volatile sig_atomic_t fault_code;
static volatile sig_atomic_t remaining_faults;
static volatile unsigned int *fault_addr;
static unsigned long pgsize, numinsns;
static unsigned int *insns;
static bool pkeys_supported;
static bool is_fault_expected(int fault_code)
{
if (fault_code == SEGV_ACCERR)
return true;
/* Assume any pkey error is fine since pkey_exec_prot test covers them */
if (fault_code == SEGV_PKUERR && pkeys_supported)
return true;
return false;
}
static void trap_handler(int signum, siginfo_t *sinfo, void *ctx)
{
/* Check if this fault originated from the expected address */
if (sinfo->si_addr != (void *)fault_addr)
sigsafe_err("got a fault for an unexpected address\n");
_exit(1);
}
static void segv_handler(int signum, siginfo_t *sinfo, void *ctx)
{
fault_code = sinfo->si_code;
/* Check if this fault originated from the expected address */
if (sinfo->si_addr != (void *)fault_addr) {
sigsafe_err("got a fault for an unexpected address\n");
_exit(1);
}
/* Check if too many faults have occurred for a single test case */
if (!remaining_faults) {
sigsafe_err("got too many faults for the same address\n");
_exit(1);
}
/* Restore permissions in order to continue */
if (is_fault_expected(fault_code)) {
if (mprotect(insns, pgsize, PROT_READ | PROT_WRITE | PROT_EXEC)) {
sigsafe_err("failed to set access permissions\n");
_exit(1);
}
} else {
sigsafe_err("got a fault with an unexpected code\n");
_exit(1);
}
remaining_faults--;
}
static int check_exec_fault(int rights)
{
/*
* Jump to the executable region.
*
* The first iteration also checks if the overwrite of the
* first instruction word from a trap to a no-op succeeded.
*/
fault_code = -1;
remaining_faults = 0;
if (!(rights & PROT_EXEC))
remaining_faults = 1;
FAIL_IF(mprotect(insns, pgsize, rights) != 0);
asm volatile("mtctr %0; bctrl" : : "r"(insns));
FAIL_IF(remaining_faults != 0);
if (!(rights & PROT_EXEC))
FAIL_IF(!is_fault_expected(fault_code));
return 0;
}
static int test(void)
{
struct sigaction segv_act, trap_act;
int i;
/* Skip the test if the CPU doesn't support Radix */
SKIP_IF(!have_hwcap2(PPC_FEATURE2_ARCH_3_00));
/* Check if pkeys are supported */
pkeys_supported = pkeys_unsupported() == 0;
/* Setup SIGSEGV handler */
segv_act.sa_handler = 0;
segv_act.sa_sigaction = segv_handler;
FAIL_IF(sigprocmask(SIG_SETMASK, 0, &segv_act.sa_mask) != 0);
segv_act.sa_flags = SA_SIGINFO;
segv_act.sa_restorer = 0;
FAIL_IF(sigaction(SIGSEGV, &segv_act, NULL) != 0);
/* Setup SIGTRAP handler */
trap_act.sa_handler = 0;
trap_act.sa_sigaction = trap_handler;
FAIL_IF(sigprocmask(SIG_SETMASK, 0, &trap_act.sa_mask) != 0);
trap_act.sa_flags = SA_SIGINFO;
trap_act.sa_restorer = 0;
FAIL_IF(sigaction(SIGTRAP, &trap_act, NULL) != 0);
/* Setup executable region */
pgsize = getpagesize();
numinsns = pgsize / sizeof(unsigned int);
insns = (unsigned int *)mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
FAIL_IF(insns == MAP_FAILED);
/* Write the instruction words */
for (i = 1; i < numinsns - 1; i++)
insns[i] = PPC_INST_NOP;
/*
* Set the first instruction as an unconditional trap. If
* the last write to this address succeeds, this should
* get overwritten by a no-op.
*/
insns[0] = PPC_INST_TRAP;
/*
* Later, to jump to the executable region, we use a branch
* and link instruction (bctrl) which sets the return address
* automatically in LR. Use that to return back.
*/
insns[numinsns - 1] = PPC_INST_BLR;
/*
* Pick the first instruction's address from the executable
* region.
*/
fault_addr = insns;
/*
* Read an instruction word from the address when the page
* is execute only. This should generate an access fault.
*/
fault_code = -1;
remaining_faults = 1;
printf("Testing read on --x, should fault...");
FAIL_IF(mprotect(insns, pgsize, PROT_EXEC) != 0);
i = *fault_addr;
FAIL_IF(remaining_faults != 0 || !is_fault_expected(fault_code));
printf("ok!\n");
/*
* Write an instruction word to the address when the page
* execute only. This should also generate an access fault.
*/
fault_code = -1;
remaining_faults = 1;
printf("Testing write on --x, should fault...");
FAIL_IF(mprotect(insns, pgsize, PROT_EXEC) != 0);
*fault_addr = PPC_INST_NOP;
FAIL_IF(remaining_faults != 0 || !is_fault_expected(fault_code));
printf("ok!\n");
printf("Testing exec on ---, should fault...");
FAIL_IF(check_exec_fault(PROT_NONE));
printf("ok!\n");
printf("Testing exec on r--, should fault...");
FAIL_IF(check_exec_fault(PROT_READ));
printf("ok!\n");
printf("Testing exec on -w-, should fault...");
FAIL_IF(check_exec_fault(PROT_WRITE));
printf("ok!\n");
printf("Testing exec on rw-, should fault...");
FAIL_IF(check_exec_fault(PROT_READ | PROT_WRITE));
printf("ok!\n");
printf("Testing exec on --x, should succeed...");
FAIL_IF(check_exec_fault(PROT_EXEC));
printf("ok!\n");
printf("Testing exec on r-x, should succeed...");
FAIL_IF(check_exec_fault(PROT_READ | PROT_EXEC));
printf("ok!\n");
printf("Testing exec on -wx, should succeed...");
FAIL_IF(check_exec_fault(PROT_WRITE | PROT_EXEC));
printf("ok!\n");
printf("Testing exec on rwx, should succeed...");
FAIL_IF(check_exec_fault(PROT_READ | PROT_WRITE | PROT_EXEC));
printf("ok!\n");
/* Cleanup */
FAIL_IF(munmap((void *)insns, pgsize));
return 0;
}
int main(void)
{
return test_harness(test, "exec_prot");
}