The quilt patch titled
Subject: selftests/mm: confirm VA exhaustion without reliance on correctness of mmap()
has been removed from the -mm tree. Its filename was
selftests-mm-confirm-va-exhaustion-without-reliance-on-correctness-of-mmap.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Dev Jain <dev.jain@xxxxxxx>
Subject: selftests/mm: confirm VA exhaustion without reliance on correctness of mmap()
Date: Thu, 21 Mar 2024 16:05:22 +0530
Currently, VA exhaustion is being checked by passing a hint to mmap() and
expecting it to fail.
While populating the lower VA space, mmap() fails because we have
exhausted the space.
Then, in validate_lower_address_hint(), because mmap() fails, we
confirm that we have indeed exhausted the space. There is a circular
logic involved here.
Assume that there is a bug in mmap(), also assume that it exists
independent of whether you pass a hint address or not; that for some
reason it is not able to find a 1GB chunk. My idea is to assert the
exhaustion against some other method.
This patch makes a stricter test by successful
write() calls from /proc/self/maps to a dump file, confirming that a free
chunk is indeed not available.
[dev.jain@xxxxxxx: replace SZ_1GB with MAP_CHUNK_SIZE, tidy-up]
Link: https://lkml.kernel.org/r/20240325042653.867055-1-dev.jain@xxxxxxx
Link: https://lkml.kernel.org/r/20240321103522.516097-1-dev.jain@xxxxxxx
Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/mm/virtual_address_range.c | 66 +++++++++++
1 file changed, 66 insertions(+)
--- a/tools/testing/selftests/mm/virtual_address_range.c~selftests-mm-confirm-va-exhaustion-without-reliance-on-correctness-of-mmap
+++ a/tools/testing/selftests/mm/virtual_address_range.c
@@ -12,6 +12,8 @@
#include <errno.h>
#include <sys/mman.h>
#include <sys/time.h>
+#include <fcntl.h>
+
#include "../kselftest.h"
/*
@@ -93,6 +95,66 @@ static int validate_lower_address_hint(v
return 1;
}
+static int validate_complete_va_space(void)
+{
+ unsigned long start_addr, end_addr, prev_end_addr;
+ char line[400];
+ char prot[6];
+ FILE *file;
+ int fd;
+
+ fd = open("va_dump", O_CREAT | O_WRONLY, 0600);
+ unlink("va_dump");
+ if (fd < 0) {
+ ksft_test_result_skip("cannot create or open dump file\n");
+ ksft_finished();
+ }
+
+ file = fopen("/proc/self/maps", "r");
+ if (file == NULL)
+ ksft_exit_fail_msg("cannot open /proc/self/maps\n");
+
+ prev_end_addr = 0;
+ while (fgets(line, sizeof(line), file)) {
+ unsigned long hop;
+
+ if (sscanf(line, "%lx-%lx %s[rwxp-]",
+ &start_addr, &end_addr, prot) != 3)
+ ksft_exit_fail_msg("cannot parse /proc/self/maps\n");
+
+ /* end of userspace mappings; ignore vsyscall mapping */
+ if (start_addr & (1UL << 63))
+ return 0;
+
+ /* /proc/self/maps must have gaps less than MAP_CHUNK_SIZE */
+ if (start_addr - prev_end_addr >= MAP_CHUNK_SIZE)
+ return 1;
+
+ prev_end_addr = end_addr;
+
+ if (prot[0] != 'r')
+ continue;
+
+ /*
+ * Confirm whether MAP_CHUNK_SIZE chunk can be found or not.
+ * If write succeeds, no need to check MAP_CHUNK_SIZE - 1
+ * addresses after that. If the address was not held by this
+ * process, write would fail with errno set to EFAULT.
+ * Anyways, if write returns anything apart from 1, exit the
+ * program since that would mean a bug in /proc/self/maps.
+ */
+ hop = 0;
+ while (start_addr + hop < end_addr) {
+ if (write(fd, (void *)(start_addr + hop), 1) != 1)
+ return 1;
+ lseek(fd, 0, SEEK_SET);
+
+ hop += MAP_CHUNK_SIZE;
+ }
+ }
+ return 0;
+}
+
int main(int argc, char *argv[])
{
char *ptr[NR_CHUNKS_LOW];
@@ -133,6 +195,10 @@ int main(int argc, char *argv[])
validate_addr(hptr[i], 1);
}
hchunks = i;
+ if (validate_complete_va_space()) {
+ ksft_test_result_fail("BUG in mmap() or /proc/self/maps\n");
+ ksft_finished();
+ }
for (i = 0; i < lchunks; i++)
munmap(ptr[i], MAP_CHUNK_SIZE);
_
Patches currently in -mm which might be from dev.jain@xxxxxxx are
