From 98acee3f8db451eaab9fbd422e523c228aacf08c Mon Sep 17 00:00:00 2001 From: Nicholas Miehlbradt Date: Wed, 17 Aug 2022 15:06:40 +1000 Subject: selftests/powerpc: Add a test for execute-only memory 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 Signed-off-by: Russell Currey Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220817050640.406017-2-ruscur@russell.cc --- tools/testing/selftests/powerpc/mm/Makefile | 3 +- tools/testing/selftests/powerpc/mm/exec_prot.c | 231 +++++++++++++++++++++++++ 2 files changed, 233 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/powerpc/mm/exec_prot.c (limited to 'tools/testing/selftests/powerpc') diff --git a/tools/testing/selftests/powerpc/mm/Makefile b/tools/testing/selftests/powerpc/mm/Makefile index 27dc09d0bfee..19dd0b2ea397 100644 --- a/tools/testing/selftests/powerpc/mm/Makefile +++ b/tools/testing/selftests/powerpc/mm/Makefile @@ -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 diff --git a/tools/testing/selftests/powerpc/mm/exec_prot.c b/tools/testing/selftests/powerpc/mm/exec_prot.c new file mode 100644 index 000000000000..db75b2225de1 --- /dev/null +++ b/tools/testing/selftests/powerpc/mm/exec_prot.c @@ -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 +#include +#include +#include + +#include +#include + +#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"); +} -- cgit v1.2.3