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(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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/* * 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");}