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tools/selftests: add guard region test for /proc/$pid/pagemap

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Add a test to the guard region self tests to assert that the
/proc/$pid/pagemap information now made availabile to the user correctly
identifies and reports guard regions.

As a part of this change, update vm_util.h to add the new bit (note there
is no header file in the kernel where this is exposed, the user is
expected to provide their own mask) and utilise the helper functions there
for pagemap functionality.

[lorenzo.stoakes@oracle.com: fixup define name]
  Link: https://lkml.kernel.org/r/32e83941-e6f5-42ee-9292-a44c16463cf1@lucifer.local
Link: https://lkml.kernel.org/r/164feb0a43ae72650e6b20c3910213f469566311.1740139449.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes 2025-02-21 12:05:23 +00:00 • committed by Andrew Morton
parent 8e2f2aeb8b
commit f3b92176f4
2 changed files with 48 additions and 0 deletions
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47
tools/testing/selftests/mm/guard-regions.c
View file

@ -19,6 +19,7 @@
#include <sys/syscall.h>
#include <sys/uio.h>
#include <unistd.h>
#include "vm_util.h"
/*
* Ignore the checkpatch warning, as per the C99 standard, section 7.14.1.1:
@ -2032,4 +2033,50 @@ TEST_F(guard_regions, anon_zeropage)
ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
}
/*
* Assert that /proc/$pid/pagemap correctly identifies guard region ranges.
*/
TEST_F(guard_regions, pagemap)
{
const unsigned long page_size = self->page_size;
int proc_fd;
char *ptr;
int i;
proc_fd = open("/proc/self/pagemap", O_RDONLY);
ASSERT_NE(proc_fd, -1);
ptr = mmap_(self, variant, NULL, 10 * page_size,
PROT_READ | PROT_WRITE, 0, 0);
ASSERT_NE(ptr, MAP_FAILED);
/* Read from pagemap, and assert no guard regions are detected. */
for (i = 0; i < 10; i++) {
char *ptr_p = &ptr[i * page_size];
unsigned long entry = pagemap_get_entry(proc_fd, ptr_p);
unsigned long masked = entry & PM_GUARD_REGION;
ASSERT_EQ(masked, 0);
}
/* Install a guard region in every other page. */
for (i = 0; i < 10; i += 2) {
char *ptr_p = &ptr[i * page_size];
ASSERT_EQ(madvise(ptr_p, page_size, MADV_GUARD_INSTALL), 0);
}
/* Re-read from pagemap, and assert guard regions are detected. */
for (i = 0; i < 10; i++) {
char *ptr_p = &ptr[i * page_size];
unsigned long entry = pagemap_get_entry(proc_fd, ptr_p);
unsigned long masked = entry & PM_GUARD_REGION;
ASSERT_EQ(masked, i % 2 == 0 ? PM_GUARD_REGION : 0);
}
ASSERT_EQ(close(proc_fd), 0);
ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
}
TEST_HARNESS_MAIN

1
tools/testing/selftests/mm/vm_util.h
View file

@ -10,6 +10,7 @@
#define PM_SOFT_DIRTY BIT_ULL(55)
#define PM_MMAP_EXCLUSIVE BIT_ULL(56)
#define PM_UFFD_WP BIT_ULL(57)
#define PM_GUARD_REGION BIT_ULL(58)
#define PM_FILE BIT_ULL(61)
#define PM_SWAP BIT_ULL(62)
#define PM_PRESENT BIT_ULL(63)