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/*
* Copyright (c) 2021, Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Assertions.h>
#include <LibCore/ArgsParser.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
static void write8(void* ptr) { *(volatile uint8_t*)ptr = 1; }
static void write16(void* ptr) { *(volatile uint16_t*)ptr = 1; }
static void write32(void* ptr) { *(volatile uint32_t*)ptr = 1; }
static void write64(void* ptr) { *(volatile double*)ptr = 1.0; }
// A u64 write might be translated by the compiler as a 32-then-32-bit write:
// static void write64_bad(void* ptr) { *(volatile uint64_t*)ptr = 1.0; }
// Let's hope this won't be translated like that.
// Godbolt says yes: https://godbolt.org/z/1b9WGo
static void run_test(void* region, ssize_t offset, size_t bits)
{
void* ptr = (char*)region + offset;
printf("Writing to %p\n", ptr);
switch (bits) {
case 8:
write8(ptr);
break;
case 16:
write16(ptr);
break;
case 32:
write32(ptr);
break;
case 64:
write64(ptr);
break;
default:
VERIFY_NOT_REACHED();
}
}
int main(int argc, char** argv)
{
bool do_static = false;
int size = 10 * PAGE_SIZE;
int offset = 10 * PAGE_SIZE - 1;
int bits = 16;
auto args_parser = Core::ArgsParser();
args_parser.set_general_help(
"Access out of bounds memory; a great testcase for UserEmulator.");
args_parser.add_option(do_static, "Use a static region instead of an mmap'ed region. Fixes 'size' to 10*PAGESIZE = 40960. (Default: false)", "static", 'S');
args_parser.add_option(size, "The size of the region to allocate. (Default: 10*PAGESIZE = 40960)", "size", 's', "size");
args_parser.add_option(offset, "The signed offset at which to start writing. (Default: 10*PAGESIZE-1 = 40959)", "offset", 'o', "offset");
args_parser.add_option(bits, "Amount of bits to write in a single instruction. (Default: 16)", "bits", 'b', "bits");
args_parser.parse(argc, argv);
if (do_static)
size = 10 * PAGE_SIZE;
printf("Writing %d bits to %s region of size %d at offset %d.\n",
bits, do_static ? "static" : "MMAP", size, offset);
if (do_static) {
// Let's just hope the linker puts nothing after it!
static unsigned char region[PAGE_SIZE * 10] = { 0 };
run_test(region, offset, 64);
} else {
void* region = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
VERIFY(region);
run_test(region, offset, bits);
}
printf("FAIL (should have caused SIGSEGV)\n");
return 1;
}
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