tools/testing/selftests/powerpc/mm/bad_accesses.c

Source file repositories/reference/linux-study-clean/tools/testing/selftests/powerpc/mm/bad_accesses.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/powerpc/mm/bad_accesses.c
Extension
.c
Size
3180 bytes
Lines
145
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0+
//
// Copyright 2019, Michael Ellerman, IBM Corp.
//
// Test that out-of-bounds reads/writes behave as expected.

#include <setjmp.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

#include "utils.h"

// Old distros (Ubuntu 16.04 at least) don't define this
#ifndef SEGV_BNDERR
#define SEGV_BNDERR	3
#endif

// 64-bit kernel is always here
#define PAGE_OFFSET	(0xcul << 60)

static unsigned long kernel_virt_end;

static volatile int fault_code;
static volatile unsigned long fault_addr;
static jmp_buf setjmp_env;

static void segv_handler(int n, siginfo_t *info, void *ctxt_v)
{
	fault_code = info->si_code;
	fault_addr = (unsigned long)info->si_addr;
	siglongjmp(setjmp_env, 1);
}

int bad_access(char *p, bool write)
{
	char x = 0;

	fault_code = 0;
	fault_addr = 0;

	if (sigsetjmp(setjmp_env, 1) == 0) {
		if (write)
			*p = 1;
		else
			x = *p;

		printf("Bad - no SEGV! (%c)\n", x);
		return 1;
	}

	// If we see MAPERR that means we took a page fault rather than an SLB
	// miss. We only expect to take page faults for addresses within the
	// valid kernel range.
	FAIL_IF(fault_code == SEGV_MAPERR && \
		(fault_addr < PAGE_OFFSET || fault_addr >= kernel_virt_end));

	FAIL_IF(fault_code != SEGV_MAPERR && fault_code != SEGV_BNDERR);

	return 0;
}

static int test(void)
{
	unsigned long i, j, addr, region_shift, page_shift, page_size;
	struct sigaction sig;
	bool hash_mmu;

	sig = (struct sigaction) {
		.sa_sigaction = segv_handler,
		.sa_flags = SA_SIGINFO,
	};

	FAIL_IF(sigaction(SIGSEGV, &sig, NULL) != 0);

	FAIL_IF(using_hash_mmu(&hash_mmu));

	page_size = sysconf(_SC_PAGESIZE);
	if (page_size == (64 * 1024))
		page_shift = 16;
	else
		page_shift = 12;

	if (page_size == (64 * 1024) || !hash_mmu) {
		region_shift = 52;

Annotation

Implementation Notes