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x86/selftests: Add test for mapping placement for 5-level paging
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5-level paging provides a 56-bit virtual address space for user space
application. But the kernel defaults to mappings below the 47-bit address
space boundary, which is the upper bound for 4-level paging, unless an
application explicitely request it by using a mmap(2) address hint above
the 47-bit boundary. The kernel prevents mappings which spawn across the
47-bit boundary unless mmap(2) was invoked with MAP_FIXED.

Add a self-test that covers the corner cases of the interface and validates
the correctness of the implementation.

[ tglx: Massaged changelog once more ]

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/20171115143607.81541-2-kirill.shutemov@linux.intel.com
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Kirill A. Shutemov authored and Thomas Gleixner committed Nov 16, 2017
1 parent 1e0f25d commit 97f404a
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177 changes: 177 additions & 0 deletions tools/testing/selftests/x86/5lvl.c
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@@ -0,0 +1,177 @@
#include <stdio.h>
#include <sys/mman.h>

#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))

#define PAGE_SIZE 4096
#define LOW_ADDR ((void *) (1UL << 30))
#define HIGH_ADDR ((void *) (1UL << 50))

struct testcase {
void *addr;
unsigned long size;
unsigned long flags;
const char *msg;
unsigned int low_addr_required:1;
unsigned int keep_mapped:1;
};

static struct testcase testcases[] = {
{
.addr = NULL,
.size = 2 * PAGE_SIZE,
.flags = MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(NULL)",
.low_addr_required = 1,
},
{
.addr = LOW_ADDR,
.size = 2 * PAGE_SIZE,
.flags = MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(LOW_ADDR)",
.low_addr_required = 1,
},
{
.addr = HIGH_ADDR,
.size = 2 * PAGE_SIZE,
.flags = MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(HIGH_ADDR)",
.keep_mapped = 1,
},
{
.addr = HIGH_ADDR,
.size = 2 * PAGE_SIZE,
.flags = MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(HIGH_ADDR) again",
.keep_mapped = 1,
},
{
.addr = HIGH_ADDR,
.size = 2 * PAGE_SIZE,
.flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
.msg = "mmap(HIGH_ADDR, MAP_FIXED)",
},
{
.addr = (void*) -1,
.size = 2 * PAGE_SIZE,
.flags = MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(-1)",
.keep_mapped = 1,
},
{
.addr = (void*) -1,
.size = 2 * PAGE_SIZE,
.flags = MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(-1) again",
},
{
.addr = (void *)((1UL << 47) - PAGE_SIZE),
.size = 2 * PAGE_SIZE,
.flags = MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap((1UL << 47), 2 * PAGE_SIZE)",
.low_addr_required = 1,
.keep_mapped = 1,
},
{
.addr = (void *)((1UL << 47) - PAGE_SIZE / 2),
.size = 2 * PAGE_SIZE,
.flags = MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap((1UL << 47), 2 * PAGE_SIZE / 2)",
.low_addr_required = 1,
.keep_mapped = 1,
},
{
.addr = (void *)((1UL << 47) - PAGE_SIZE),
.size = 2 * PAGE_SIZE,
.flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
.msg = "mmap((1UL << 47) - PAGE_SIZE, 2 * PAGE_SIZE, MAP_FIXED)",
},
{
.addr = NULL,
.size = 2UL << 20,
.flags = MAP_HUGETLB | MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(NULL, MAP_HUGETLB)",
.low_addr_required = 1,
},
{
.addr = LOW_ADDR,
.size = 2UL << 20,
.flags = MAP_HUGETLB | MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(LOW_ADDR, MAP_HUGETLB)",
.low_addr_required = 1,
},
{
.addr = HIGH_ADDR,
.size = 2UL << 20,
.flags = MAP_HUGETLB | MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(HIGH_ADDR, MAP_HUGETLB)",
.keep_mapped = 1,
},
{
.addr = HIGH_ADDR,
.size = 2UL << 20,
.flags = MAP_HUGETLB | MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(HIGH_ADDR, MAP_HUGETLB) again",
.keep_mapped = 1,
},
{
.addr = HIGH_ADDR,
.size = 2UL << 20,
.flags = MAP_HUGETLB | MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
.msg = "mmap(HIGH_ADDR, MAP_FIXED | MAP_HUGETLB)",
},
{
.addr = (void*) -1,
.size = 2UL << 20,
.flags = MAP_HUGETLB | MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(-1, MAP_HUGETLB)",
.keep_mapped = 1,
},
{
.addr = (void*) -1,
.size = 2UL << 20,
.flags = MAP_HUGETLB | MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap(-1, MAP_HUGETLB) again",
},
{
.addr = (void *)((1UL << 47) - PAGE_SIZE),
.size = 4UL << 20,
.flags = MAP_HUGETLB | MAP_PRIVATE | MAP_ANONYMOUS,
.msg = "mmap((1UL << 47), 4UL << 20, MAP_HUGETLB)",
.low_addr_required = 1,
.keep_mapped = 1,
},
{
.addr = (void *)((1UL << 47) - (2UL << 20)),
.size = 4UL << 20,
.flags = MAP_HUGETLB | MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
.msg = "mmap((1UL << 47) - (2UL << 20), 4UL << 20, MAP_FIXED | MAP_HUGETLB)",
},
};

int main(int argc, char **argv)
{
int i;
void *p;

for (i = 0; i < ARRAY_SIZE(testcases); i++) {
struct testcase *t = testcases + i;

p = mmap(t->addr, t->size, PROT_NONE, t->flags, -1, 0);

printf("%s: %p - ", t->msg, p);

if (p == MAP_FAILED) {
printf("FAILED\n");
continue;
}

if (t->low_addr_required && p >= (void *)(1UL << 47))
printf("FAILED\n");
else
printf("OK\n");
if (!t->keep_mapped)
munmap(p, t->size);
}
return 0;
}
2 changes: 1 addition & 1 deletion tools/testing/selftests/x86/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_sysc
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
vdso_restorer
TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip
TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip 5lvl

TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
TARGETS_C_64BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_64BIT_ONLY)
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