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      1 /*
      2  * Userspace test harness for load_unaligned_zeropad. Creates two
      3  * pages and uses mprotect to prevent access to the second page and
      4  * a SEGV handler that walks the exception tables and runs the fixup
      5  * routine.
      6  *
      7  * The results are compared against a normal load that is that is
      8  * performed while access to the second page is enabled via mprotect.
      9  *
     10  * Copyright (C) 2014 Anton Blanchard <anton (at) au.ibm.com>, IBM
     11  *
     12  * This program is free software; you can redistribute it and/or
     13  * modify it under the terms of the GNU General Public License
     14  * as published by the Free Software Foundation; either version
     15  * 2 of the License, or (at your option) any later version.
     16  */
     17 
     18 #include <stdlib.h>
     19 #include <string.h>
     20 #include <stdio.h>
     21 #include <stdbool.h>
     22 #include <signal.h>
     23 #include <unistd.h>
     24 #include <sys/mman.h>
     25 
     26 #define FIXUP_SECTION ".ex_fixup"
     27 
     28 static inline unsigned long __fls(unsigned long x);
     29 
     30 #include "word-at-a-time.h"
     31 
     32 #include "utils.h"
     33 
     34 static inline unsigned long __fls(unsigned long x)
     35 {
     36 	int lz;
     37 
     38 	asm (PPC_CNTLZL "%0,%1" : "=r" (lz) : "r" (x));
     39 	return sizeof(unsigned long) - 1 - lz;
     40 }
     41 
     42 static int page_size;
     43 static char *mem_region;
     44 
     45 static int protect_region(void)
     46 {
     47 	if (mprotect(mem_region + page_size, page_size, PROT_NONE)) {
     48 		perror("mprotect");
     49 		return 1;
     50 	}
     51 
     52 	return 0;
     53 }
     54 
     55 static int unprotect_region(void)
     56 {
     57 	if (mprotect(mem_region + page_size, page_size, PROT_READ|PROT_WRITE)) {
     58 		perror("mprotect");
     59 		return 1;
     60 	}
     61 
     62 	return 0;
     63 }
     64 
     65 extern char __start___ex_table[];
     66 extern char __stop___ex_table[];
     67 
     68 #if defined(__powerpc64__)
     69 #define UCONTEXT_NIA(UC)	(UC)->uc_mcontext.gp_regs[PT_NIP]
     70 #elif defined(__powerpc__)
     71 #define UCONTEXT_NIA(UC)	(UC)->uc_mcontext.uc_regs->gregs[PT_NIP]
     72 #else
     73 #error implement UCONTEXT_NIA
     74 #endif
     75 
     76 struct extbl_entry {
     77 	int insn;
     78 	int fixup;
     79 };
     80 
     81 static void segv_handler(int signr, siginfo_t *info, void *ptr)
     82 {
     83 	ucontext_t *uc = (ucontext_t *)ptr;
     84 	unsigned long addr = (unsigned long)info->si_addr;
     85 	unsigned long *ip = &UCONTEXT_NIA(uc);
     86 	struct extbl_entry *entry = (struct extbl_entry *)__start___ex_table;
     87 
     88 	while (entry < (struct extbl_entry *)__stop___ex_table) {
     89 		unsigned long insn, fixup;
     90 
     91 		insn  = (unsigned long)&entry->insn + entry->insn;
     92 		fixup = (unsigned long)&entry->fixup + entry->fixup;
     93 
     94 		if (insn == *ip) {
     95 			*ip = fixup;
     96 			return;
     97 		}
     98 	}
     99 
    100 	printf("No exception table match for NIA %lx ADDR %lx\n", *ip, addr);
    101 	abort();
    102 }
    103 
    104 static void setup_segv_handler(void)
    105 {
    106 	struct sigaction action;
    107 
    108 	memset(&action, 0, sizeof(action));
    109 	action.sa_sigaction = segv_handler;
    110 	action.sa_flags = SA_SIGINFO;
    111 	sigaction(SIGSEGV, &action, NULL);
    112 }
    113 
    114 static int do_one_test(char *p, int page_offset)
    115 {
    116 	unsigned long should;
    117 	unsigned long got;
    118 
    119 	FAIL_IF(unprotect_region());
    120 	should = *(unsigned long *)p;
    121 	FAIL_IF(protect_region());
    122 
    123 	got = load_unaligned_zeropad(p);
    124 
    125 	if (should != got) {
    126 		printf("offset %u load_unaligned_zeropad returned 0x%lx, should be 0x%lx\n", page_offset, got, should);
    127 		return 1;
    128 	}
    129 
    130 	return 0;
    131 }
    132 
    133 static int test_body(void)
    134 {
    135 	unsigned long i;
    136 
    137 	page_size = getpagesize();
    138 	mem_region = mmap(NULL, page_size * 2, PROT_READ|PROT_WRITE,
    139 		MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
    140 
    141 	FAIL_IF(mem_region == MAP_FAILED);
    142 
    143 	for (i = 0; i < page_size; i++)
    144 		mem_region[i] = i;
    145 
    146 	memset(mem_region+page_size, 0, page_size);
    147 
    148 	setup_segv_handler();
    149 
    150 	for (i = 0; i < page_size; i++)
    151 		FAIL_IF(do_one_test(mem_region+i, i));
    152 
    153 	return 0;
    154 }
    155 
    156 int main(void)
    157 {
    158 	return test_harness(test_body, "load_unaligned_zeropad");
    159 }
    160