diff options
Diffstat (limited to '')
| -rw-r--r-- | tools/testing/selftests/powerpc/mm/.gitignore | 1 | ||||
| -rw-r--r-- | tools/testing/selftests/powerpc/mm/Makefile | 7 | ||||
| -rw-r--r-- | tools/testing/selftests/powerpc/mm/exec_prot.c | 231 | ||||
| -rw-r--r-- | tools/testing/selftests/powerpc/mm/large_vm_gpr_corruption.c | 158 |
4 files changed, 395 insertions, 2 deletions
diff --git a/tools/testing/selftests/powerpc/mm/.gitignore b/tools/testing/selftests/powerpc/mm/.gitignore index aac4a59f9e28..4e1a294eec35 100644 --- a/tools/testing/selftests/powerpc/mm/.gitignore +++ b/tools/testing/selftests/powerpc/mm/.gitignore @@ -12,3 +12,4 @@ pkey_exec_prot pkey_siginfo stack_expansion_ldst stack_expansion_signal +large_vm_gpr_corruption diff --git a/tools/testing/selftests/powerpc/mm/Makefile b/tools/testing/selftests/powerpc/mm/Makefile index 40253abc6208..19dd0b2ea397 100644 --- a/tools/testing/selftests/powerpc/mm/Makefile +++ b/tools/testing/selftests/powerpc/mm/Makefile @@ -3,8 +3,9 @@ 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 \ - pkey_siginfo stack_expansion_signal stack_expansion_ldst + 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 TEST_GEN_PROGS_EXTENDED := tlbie_test @@ -19,7 +20,9 @@ $(OUTPUT)/prot_sao: ../utils.c $(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 <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"); +} diff --git a/tools/testing/selftests/powerpc/mm/large_vm_gpr_corruption.c b/tools/testing/selftests/powerpc/mm/large_vm_gpr_corruption.c new file mode 100644 index 000000000000..7da515f1da72 --- /dev/null +++ b/tools/testing/selftests/powerpc/mm/large_vm_gpr_corruption.c @@ -0,0 +1,158 @@ +// SPDX-License-Identifier: GPL-2.0+ +// +// Copyright 2022, Michael Ellerman, IBM Corp. +// +// Test that the 4PB address space SLB handling doesn't corrupt userspace registers +// (r9-r13) due to a SLB fault while saving the PPR. +// +// The bug was introduced in f384796c4 ("powerpc/mm: Add support for handling > 512TB +// address in SLB miss") and fixed in 4c2de74cc869 ("powerpc/64: Interrupts save PPR on +// stack rather than thread_struct"). +// +// To hit the bug requires the task struct and kernel stack to be in different segments. +// Usually that requires more than 1TB of RAM, or if that's not practical, boot the kernel +// with "disable_1tb_segments". +// +// The test works by creating mappings above 512TB, to trigger the large address space +// support. It creates 64 mappings, double the size of the SLB, to cause SLB faults on +// each access (assuming naive replacement). It then loops over those mappings touching +// each, and checks that r9-r13 aren't corrupted. +// +// It then forks another child and tries again, because a new child process will get a new +// kernel stack and thread struct allocated, which may be more optimally placed to trigger +// the bug. It would probably be better to leave the previous child processes hanging +// around, so that kernel stack & thread struct allocations are not reused, but that would +// amount to a 30 second fork bomb. The current design reliably triggers the bug on +// unpatched kernels. + +#include <signal.h> +#include <stdio.h> +#include <stdlib.h> +#include <sys/mman.h> +#include <sys/types.h> +#include <sys/wait.h> +#include <unistd.h> + +#include "utils.h" + +#ifndef MAP_FIXED_NOREPLACE +#define MAP_FIXED_NOREPLACE MAP_FIXED // "Should be safe" above 512TB +#endif + +#define BASE_ADDRESS (1ul << 50) // 1PB +#define STRIDE (2ul << 40) // 2TB +#define SLB_SIZE 32 +#define NR_MAPPINGS (SLB_SIZE * 2) + +static volatile sig_atomic_t signaled; + +static void signal_handler(int sig) +{ + signaled = 1; +} + +#define CHECK_REG(_reg) \ + if (_reg != _reg##_orig) { \ + printf(str(_reg) " corrupted! Expected 0x%lx != 0x%lx\n", _reg##_orig, \ + _reg); \ + _exit(1); \ + } + +static int touch_mappings(void) +{ + unsigned long r9_orig, r10_orig, r11_orig, r12_orig, r13_orig; + unsigned long r9, r10, r11, r12, r13; + unsigned long addr, *p; + int i; + + for (i = 0; i < NR_MAPPINGS; i++) { + addr = BASE_ADDRESS + (i * STRIDE); + p = (unsigned long *)addr; + + asm volatile("mr %0, %%r9 ;" // Read original GPR values + "mr %1, %%r10 ;" + "mr %2, %%r11 ;" + "mr %3, %%r12 ;" + "mr %4, %%r13 ;" + "std %10, 0(%11) ;" // Trigger SLB fault + "mr %5, %%r9 ;" // Save possibly corrupted values + "mr %6, %%r10 ;" + "mr %7, %%r11 ;" + "mr %8, %%r12 ;" + "mr %9, %%r13 ;" + "mr %%r9, %0 ;" // Restore original values + "mr %%r10, %1 ;" + "mr %%r11, %2 ;" + "mr %%r12, %3 ;" + "mr %%r13, %4 ;" + : "=&b"(r9_orig), "=&b"(r10_orig), "=&b"(r11_orig), + "=&b"(r12_orig), "=&b"(r13_orig), "=&b"(r9), "=&b"(r10), + "=&b"(r11), "=&b"(r12), "=&b"(r13) + : "b"(i), "b"(p) + : "r9", "r10", "r11", "r12", "r13"); + + CHECK_REG(r9); + CHECK_REG(r10); + CHECK_REG(r11); + CHECK_REG(r12); + CHECK_REG(r13); + } + + return 0; +} + +static int test(void) +{ + unsigned long page_size, addr, *p; + struct sigaction action; + bool hash_mmu; + int i, status; + pid_t pid; + + // This tests a hash MMU specific bug. + FAIL_IF(using_hash_mmu(&hash_mmu)); + SKIP_IF(!hash_mmu); + // 4K kernels don't support 4PB address space + SKIP_IF(sysconf(_SC_PAGESIZE) < 65536); + + page_size = sysconf(_SC_PAGESIZE); + + for (i = 0; i < NR_MAPPINGS; i++) { + addr = BASE_ADDRESS + (i * STRIDE); + + p = mmap((void *)addr, page_size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE, -1, 0); + if (p == MAP_FAILED) { + perror("mmap"); + printf("Error: couldn't mmap(), confirm kernel has 4PB support?\n"); + return 1; + } + } + + action.sa_handler = signal_handler; + action.sa_flags = SA_RESTART; + FAIL_IF(sigaction(SIGALRM, &action, NULL) < 0); + + // Seen to always crash in under ~10s on affected kernels. + alarm(30); + + while (!signaled) { + // Fork new processes, to increase the chance that we hit the case where + // the kernel stack and task struct are in different segments. + pid = fork(); + if (pid == 0) + exit(touch_mappings()); + + FAIL_IF(waitpid(-1, &status, 0) == -1); + FAIL_IF(WIFSIGNALED(status)); + FAIL_IF(!WIFEXITED(status)); + FAIL_IF(WEXITSTATUS(status)); + } + + return 0; +} + +int main(void) +{ + return test_harness(test, "large_vm_gpr_corruption"); +} |