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/*
* This file and its contents are supplied under the terms of the
* Common Development and Distribution License ("CDDL"), version 1.0.
* You may only use this file in accordance with the terms of version
* 1.0 of the CDDL.
*
* A full copy of the text of the CDDL should have accompanied this
* source. A copy of the CDDL is also available via the Internet at
* http://www.illumos.org/license/CDDL.
*/
/*
* Copyright 2022 Oxide Computer Company
*/
#include <stdio.h>
#include <unistd.h>
#include <stropts.h>
#include <strings.h>
#include <signal.h>
#include <setjmp.h>
#include <sys/vmm.h>
#include <sys/vmm_dev.h>
#include <sys/mman.h>
#include <vmmapi.h>
/* Half of a leaf page table is 256 pages */
#define LOWER_SZ (256 * 4096)
#define UPPER_SZ LOWER_SZ
#define TOTAL_SZ (LOWER_SZ + UPPER_SZ)
#define LOWER_OFF 0
#define UPPER_OFF LOWER_SZ
#define PROT_ALL (PROT_READ | PROT_WRITE | PROT_EXEC)
enum test_memsegs {
MSEG_LOW = 0,
MSEG_HIGH = 1,
};
struct vmctx *
create_test_vm()
{
char name[VM_MAX_NAMELEN];
int res;
(void) snprintf(name, sizeof (name), "bhyve-test-memmap-%d", getpid());
res = vm_create(name, 0);
if (res != 0) {
return (NULL);
}
return (vm_open(name));
}
int
alloc_memseg(struct vmctx *ctx, int segid, size_t len, const char *name)
{
struct vm_memseg memseg = {
.segid = segid,
.len = len,
};
(void) strlcpy(memseg.name, name, sizeof (memseg.name));
int fd = vm_get_device_fd(ctx);
return (ioctl(fd, VM_ALLOC_MEMSEG, &memseg));
}
static sigjmp_buf segv_env;
void
sigsegv_handler(int sig)
{
siglongjmp(segv_env, 1);
}
int
main(int argc, char *argv[])
{
struct vmctx *ctx;
int res, fd;
void *guest_mem;
ctx = create_test_vm();
fd = vm_get_device_fd(ctx);
res = alloc_memseg(ctx, MSEG_LOW, LOWER_SZ, "mseg_low");
if (res != 0) {
perror("could not alloc low memseg");
goto bail;
}
res = alloc_memseg(ctx, MSEG_HIGH, UPPER_SZ, "mseg_high");
if (res != 0) {
perror("could not alloc high memseg");
goto bail;
}
res = vm_mmap_memseg(ctx, LOWER_OFF, MSEG_LOW, 0, LOWER_SZ, PROT_ALL);
if (res != 0) {
perror("could not map low memseg");
goto bail;
}
res = vm_mmap_memseg(ctx, UPPER_OFF, MSEG_HIGH, 0, UPPER_SZ, PROT_ALL);
if (res != 0) {
perror("could not map high memseg");
goto bail;
}
guest_mem = mmap(NULL, TOTAL_SZ, PROT_READ | PROT_WRITE, MAP_SHARED,
fd, 0);
if (guest_mem == MAP_FAILED) {
perror("could not mmap guest memory");
goto bail;
}
/* Fill memory with 0xff */
for (uintptr_t gpa = 0; gpa < TOTAL_SZ; gpa++) {
uint8_t *ptr = guest_mem + gpa;
*ptr = 0xff;
}
/* Unmap the lower memseg */
res = vm_munmap_memseg(ctx, LOWER_OFF, LOWER_SZ);
if (guest_mem == NULL) {
perror("could not unmap lower memseg");
goto bail;
}
/* Confirm upper contents are still correct/accessible */
for (uintptr_t gpa = UPPER_OFF; gpa < UPPER_OFF + UPPER_SZ; gpa++) {
uint8_t *ptr = guest_mem + gpa;
if (*ptr != 0xff) {
(void) printf("invalid mem contents at GPA %lx: %x\n",
gpa, *ptr);
goto bail;
}
*ptr = 0xee;
}
/*
* Attempt to access the lower contents, which should result in an
* expected (and thus handled) SIGSEGV.
*/
struct sigaction sa = {
.sa_handler = sigsegv_handler,
};
struct sigaction old_sa;
res = sigaction(SIGSEGV, &sa, &old_sa);
if (res != 0) {
perror("could not prep signal handling for bad access");
goto bail;
}
if (sigsetjmp(segv_env, 1) == 0) {
volatile uint8_t *ptr = guest_mem;
/*
* This access to the guest space should fail, since the memseg
* covering the lower part of the VM space has been unmapped.
*/
uint8_t tmp = *ptr;
(void) printf("access to %p (%x) should have failed\n", tmp);
goto bail;
}
/*
* Unmap and remap the space so any cached entries are dropped for the
* portion we expect is still accessible.
*/
res = munmap(guest_mem, TOTAL_SZ);
if (res != 0) {
perror("could not unmap lower memseg");
goto bail;
}
guest_mem = mmap(NULL, TOTAL_SZ, PROT_READ | PROT_WRITE, MAP_SHARED,
fd, 0);
if (guest_mem == MAP_FAILED) {
perror("could not re-mmap guest memory");
goto bail;
}
/* Check the upper portion for accessibility. */
if (sigsetjmp(segv_env, 1) == 0) {
volatile uint8_t *ptr = guest_mem + UPPER_OFF;
uint8_t tmp = *ptr;
if (tmp != 0xee) {
(void) printf("unexpected value at %p (%x)\n", ptr,
tmp);
goto bail;
}
res = sigaction(SIGSEGV, &old_sa, NULL);
if (res != 0) {
perror("could not restore SIGSEGV handler");
goto bail;
}
} else {
(void) printf("unexpected fault in upper mapping\n");
goto bail;
}
/* Unmap the upper memseg */
res = vm_munmap_memseg(ctx, UPPER_OFF, UPPER_SZ);
if (guest_mem == NULL) {
perror("could not unmap upper memseg");
goto bail;
}
/* mission accomplished */
vm_destroy(ctx);
return (0);
bail:
vm_destroy(ctx);
return (1);
}
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