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Message-ID: <315a7239-f5ce-474e-bd0d-f1deca3a7b26@arm.com>
Date: Mon, 12 Jan 2026 09:34:31 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Kevin Brodsky <kevin.brodsky@....com>, linux-mm@...ck.org,
linux-kselftest@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
David Hildenbrand <david@...nel.org>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Mark Brown
<broonie@...nel.org>, Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH v2 8/8] selftests/mm: report SKIP in pfnmap if a check
fails
On 07/01/2026 16:48, Kevin Brodsky wrote:
> pfnmap currently checks the target file in FIXTURE_SETUP(pfnmap),
> meaning once for every test, and skips the test if any check fails.
>
> The target file is the same for every test so this is a little
> overkill. More importantly, this approach means that the whole suite
> will report PASS even if all the tests are skipped because kernel
> configuration (e.g. CONFIG_STRICT_DEVMEM=y) prevented /dev/mem from
> being mapped, for instance.
>
> Let's ensure that KSFT_SKIP is returned as exit code if any check
> fails by performing the checks in pfnmap_init(), run once. That
> function also takes care of finding the offset of the pages to be
> mapped and saves it in a global. The file is still mapped/unmapped
> for every test, as some of them modify the mapping.
>
> Signed-off-by: Kevin Brodsky <kevin.brodsky@....com>
> ---
> tools/testing/selftests/mm/pfnmap.c | 81 ++++++++++++++++++++---------
> 1 file changed, 55 insertions(+), 26 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/pfnmap.c b/tools/testing/selftests/mm/pfnmap.c
> index 35b0e3ed54cd..e41d5464130b 100644
> --- a/tools/testing/selftests/mm/pfnmap.c
> +++ b/tools/testing/selftests/mm/pfnmap.c
> @@ -25,8 +25,11 @@
> #include "kselftest_harness.h"
> #include "vm_util.h"
>
> +#define DEV_MEM_NPAGES 2
> +
> static sigjmp_buf sigjmp_buf_env;
> static char *file = "/dev/mem";
> +static off_t file_offset;
>
> static void signal_handler(int sig)
> {
> @@ -88,7 +91,7 @@ static int find_ram_target(off_t *offset,
> break;
>
> /* We need two pages. */
> - if (end > start + 2 * pagesize) {
> + if (end > start + DEV_MEM_NPAGES * pagesize) {
> fclose(file);
> *offset = start;
> return 0;
> @@ -97,9 +100,49 @@ static int find_ram_target(off_t *offset,
> return -ENOENT;
> }
>
> +static void pfnmap_init(void)
> +{
> + size_t pagesize = getpagesize();
> + size_t size = DEV_MEM_NPAGES * pagesize;
> + int fd;
> + void *addr;
> +
> + if (strncmp(file, "/dev/mem", strlen("/dev/mem")) == 0) {
> + int err = find_ram_target(&file_offset, pagesize);
> +
> + if (err)
> + ksft_exit_skip("Cannot find ram target in '/proc/iomem': %s\n",
> + strerror(-err));
> + } else {
> + file_offset = 0;
> + }
> +
> + /*
> + * Make sure we can open and map the file, and perform some basic
> + * checks; skip the whole suite if anything goes wrong.
> + * A fresh mapping is then created for every test case by
> + * FIXTURE_SETUP(pfnmap).
> + */
> + fd = open(file, O_RDONLY);
> + if (fd < 0)
> + ksft_exit_skip("Cannot open '%s': %s\n", file, strerror(errno));
> +
> + addr = mmap(NULL, size, PROT_READ, MAP_SHARED, fd, file_offset);
> + if (addr == MAP_FAILED)
> + ksft_exit_skip("Cannot mmap '%s': %s\n", file, strerror(errno));
> +
> + if (!check_vmflag_pfnmap(addr))
> + ksft_exit_skip("Invalid file: '%s'. Not pfnmap'ed\n", file);
> +
> + if (test_read_access(addr, size))
> + ksft_exit_skip("Cannot read-access mmap'ed '%s'\n", file);
> +
> + munmap(addr, size);
> + close(fd);
> +}
> +
> FIXTURE(pfnmap)
> {
> - off_t offset;
> size_t pagesize;
> int dev_mem_fd;
> char *addr1;
> @@ -112,31 +155,13 @@ FIXTURE_SETUP(pfnmap)
> {
> self->pagesize = getpagesize();
>
> - if (strncmp(file, "/dev/mem", strlen("/dev/mem")) == 0) {
> - /* We'll require two physical pages throughout our tests ... */
> - if (find_ram_target(&self->offset, self->pagesize))
> - SKIP(return,
> - "Cannot find ram target in '/proc/iomem'\n");
> - } else {
> - self->offset = 0;
> - }
> -
> self->dev_mem_fd = open(file, O_RDONLY);
> - if (self->dev_mem_fd < 0)
> - SKIP(return, "Cannot open '%s'\n", file);
> + ASSERT_GE(self->dev_mem_fd, 0);
>
> - self->size1 = self->pagesize * 2;
> + self->size1 = DEV_MEM_NPAGES * self->pagesize;
> self->addr1 = mmap(NULL, self->size1, PROT_READ, MAP_SHARED,
> - self->dev_mem_fd, self->offset);
> - if (self->addr1 == MAP_FAILED)
> - SKIP(return, "Cannot mmap '%s'\n", file);
> -
> - if (!check_vmflag_pfnmap(self->addr1))
> - SKIP(return, "Invalid file: '%s'. Not pfnmap'ed\n", file);
I wonder if we still want this check per-fd, but upgraded to a fail?
Either way:
Reviewed-by: Ryan Roberts <ryan.roberts@....com>
> -
> - /* ... and want to be able to read from them. */
> - if (test_read_access(self->addr1, self->size1))
> - SKIP(return, "Cannot read-access mmap'ed '%s'\n", file);
> + self->dev_mem_fd, file_offset);
> + ASSERT_NE(self->addr1, MAP_FAILED);
>
> self->size2 = 0;
> self->addr2 = MAP_FAILED;
> @@ -189,7 +214,7 @@ TEST_F(pfnmap, munmap_split)
> */
> self->size2 = self->pagesize;
> self->addr2 = mmap(NULL, self->pagesize, PROT_READ, MAP_SHARED,
> - self->dev_mem_fd, self->offset);
> + self->dev_mem_fd, file_offset);
> ASSERT_NE(self->addr2, MAP_FAILED);
> }
>
> @@ -258,8 +283,12 @@ int main(int argc, char **argv)
> if (strcmp(argv[i], "--") == 0) {
> if (i + 1 < argc && strlen(argv[i + 1]) > 0)
> file = argv[i + 1];
> - return test_harness_run(i, argv);
> + argc = i;
> + break;
> }
> }
> +
> + pfnmap_init();
> +
> return test_harness_run(argc, argv);
> }
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