Re: [PATCH] selftests/mm: fix format warnings on 32-bit architectures

["Lorenzo Stoakes (ARM)" <ljs@kernel.org>]

On Tue, Nov 03, 2026 at 10:54:51AM -0500, Sasha Levin wrote:
> On 32-bit architectures size_t and uintptr_t are unsigned int and
> ssize_t is int, and with _FILE_OFFSET_BITS=64 off_t is long long, so
> printing them with %ld, %lu or %lx, or scanning /proc/self/maps into
> uintptr_t variables with %lx, warns:
>
>   hugetlb-read-hwpoison.c:32:58: warning: format '%lx' expects argument of type 'long unsigned int', but argument 3 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
>
> Print size_t with %zu and %zx, casting the nonnegative ssize_t read
> totals to size_t, print off_t as unsigned long long, and scan the
> addresses into unsigned long variables.
>
> split_huge_page_test also builds its debugfs commands from uint64_t
> addresses with %lx. write_debugfs() has no format attribute, so nothing
> warned, but on 32-bit the commands get the wrong addresses. Print them
> with PRIx64, add the attribute, and cast the pointers through uintptr_t,
> as casting them straight to uint64_t warns on 32-bit too.
>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

All looks reasonable so:

Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

> ---
> Found with a 32-bit build of the selftests with a 64-bit time_t (gcc 16
> and clang 21 with -m32 -D_TIME_BITS=64 -D_FILE_OFFSET_BITS=64);
> KernelCI's 32-bit arm builds show the same warnings. The changed files
> build without format warnings there now, and the x86_64 builds don't
> change. The other selftests get the same kind of fix in separate
> patches.
>
>  .../selftests/mm/hugetlb-read-hwpoison.c      | 25 +++++++-------
>  .../selftests/mm/hugetlb-soft-offline.c       |  2 +-
>  tools/testing/selftests/mm/mseal_test.c       |  2 +-
>  .../selftests/mm/split_huge_page_test.c       | 34 +++++++++----------
>  4 files changed, 32 insertions(+), 31 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/hugetlb-read-hwpoison.c b/tools/testing/selftests/mm/hugetlb-read-hwpoison.c
> index 31748a24448f8..91b954a078483 100644
> --- a/tools/testing/selftests/mm/hugetlb-read-hwpoison.c
> +++ b/tools/testing/selftests/mm/hugetlb-read-hwpoison.c
> @@ -29,15 +29,15 @@ static void report_status(enum test_status status, const char *test_name,
>  {
>  	switch (status) {
>  	case TEST_PASSED:
> -		ksft_test_result_pass("%s chunk_size=0x%lx\n",
> +		ksft_test_result_pass("%s chunk_size=0x%zx\n",
>  				      test_name, chunk_size);
>  		break;
>  	case TEST_FAILED:
> -		ksft_test_result_fail("%s chunk_size=0x%lx\n",
> +		ksft_test_result_fail("%s chunk_size=0x%zx\n",
>  				      test_name, chunk_size);
>  		break;
>  	case TEST_SKIPPED:
> -		ksft_test_result_skip("%s chunk_size=0x%lx\n",
> +		ksft_test_result_skip("%s chunk_size=0x%zx\n",
>  				      test_name, chunk_size);
>  		break;
>  	}
> @@ -62,7 +62,7 @@ static bool verify_chunk(char *buf, size_t len, char val)
>
>  	for (i = 0; i < len; ++i) {
>  		if (buf[i] != val) {
> -			ksft_print_msg("check fail: buf[%lu] = %u != %u\n",
> +			ksft_print_msg("check fail: buf[%zu] = %u != %u\n",
>  				       i, buf[i], val);
>  			return false;
>  		}
> @@ -79,8 +79,9 @@ static bool seek_read_hugepage_filemap(int fd, size_t len, size_t wr_chunk_size,
>  	ssize_t total_ret_count = 0;
>  	char val = offset / wr_chunk_size + offset % wr_chunk_size;
>
> -	ksft_print_msg("init val=%u with offset=0x%lx\n", val, offset);
> -	ksft_print_msg("expect to read 0x%lx bytes of data in total\n",
> +	ksft_print_msg("init val=%u with offset=0x%llx\n", val,
> +		       (unsigned long long)offset);
> +	ksft_print_msg("expect to read 0x%zx bytes of data in total\n",
>  		       expected);
>  	if (lseek(fd, offset, SEEK_SET) < 0) {
>  		ksft_perror("seek failed");
> @@ -102,8 +103,8 @@ static bool seek_read_hugepage_filemap(int fd, size_t len, size_t wr_chunk_size,
>
>  		total_ret_count += ret_count;
>  	}
> -	ksft_print_msg("actually read 0x%lx bytes of data in total\n",
> -		       total_ret_count);
> +	ksft_print_msg("actually read 0x%zx bytes of data in total\n",
> +		       (size_t)total_ret_count);
>
>  	return total_ret_count == expected;
>  }
> @@ -116,7 +117,7 @@ static bool read_hugepage_filemap(int fd, size_t len,
>  	ssize_t total_ret_count = 0;
>  	char val = 0;
>
> -	ksft_print_msg("expect to read 0x%lx bytes of data in total\n",
> +	ksft_print_msg("expect to read 0x%zx bytes of data in total\n",
>  		       expected);
>  	while (total_ret_count < len) {
>  		ret_count = read(fd, buf, wr_chunk_size);
> @@ -133,8 +134,8 @@ static bool read_hugepage_filemap(int fd, size_t len,
>
>  		total_ret_count += ret_count;
>  	}
> -	ksft_print_msg("actually read 0x%lx bytes of data in total\n",
> -		       total_ret_count);
> +	ksft_print_msg("actually read 0x%zx bytes of data in total\n",
> +		       (size_t)total_ret_count);
>
>  	return total_ret_count == expected;
>  }
> @@ -293,7 +294,7 @@ int main(void)
>
>  	signal(SIGBUS, sigbus_handler);
>  	for (i = 0; i < ARRAY_SIZE(wr_chunk_sizes); ++i) {
> -		ksft_print_msg("Write/read chunk size=0x%lx\n",
> +		ksft_print_msg("Write/read chunk size=0x%zx\n",
>  			       wr_chunk_sizes[i]);
>
>  		fd = create_hugetlbfs_file(&file_stat);
> diff --git a/tools/testing/selftests/mm/hugetlb-soft-offline.c b/tools/testing/selftests/mm/hugetlb-soft-offline.c
> index d9565219378aa..9bdd78636dc2a 100644
> --- a/tools/testing/selftests/mm/hugetlb-soft-offline.c
> +++ b/tools/testing/selftests/mm/hugetlb-soft-offline.c
> @@ -56,7 +56,7 @@ static int do_soft_offline(int fd, size_t len, int expect_errno)
>  	}
>
>  	memset(filemap, 0xab, len);
> -	ksft_print_msg("Allocated %#lx bytes of hugetlb pages\n", len);
> +	ksft_print_msg("Allocated %#zx bytes of hugetlb pages\n", len);
>
>  	hwp_addr = filemap + len / 2;
>  	ret = madvise(hwp_addr, pagesize, MADV_SOFT_OFFLINE);
> diff --git a/tools/testing/selftests/mm/mseal_test.c b/tools/testing/selftests/mm/mseal_test.c
> index 1a05e6921fed7..cea6c47cf5091 100644
> --- a/tools/testing/selftests/mm/mseal_test.c
> +++ b/tools/testing/selftests/mm/mseal_test.c
> @@ -24,7 +24,7 @@ static unsigned long get_vma_size(void *addr, int *prot)
>  	FILE *maps;
>  	char line[256];
>  	int size = 0;
> -	uintptr_t  addr_start, addr_end;
> +	unsigned long addr_start, addr_end;
>  	char protstr[5];
>  	*prot = 0;
>
> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
> index 36a6719ff09a8..f8744b5dbf990 100644
> --- a/tools/testing/selftests/mm/split_huge_page_test.c
> +++ b/tools/testing/selftests/mm/split_huge_page_test.c
> @@ -32,9 +32,9 @@ int *expected_orders;
>  #define SMAP_PATH "/proc/self/smaps"
>  #define INPUT_MAX 80
>
> -#define PID_FMT "%d,0x%lx,0x%lx,%d"
> -#define PID_FMT_OFFSET "%d,0x%lx,0x%lx,%d,%d"
> -#define PATH_FMT "%s,0x%lx,0x%lx,%d"
> +#define PID_FMT "%d,0x%" PRIx64 ",0x%" PRIx64 ",%d"
> +#define PID_FMT_OFFSET "%d,0x%" PRIx64 ",0x%" PRIx64 ",%d,%d"
> +#define PATH_FMT "%s,0x%" PRIx64 ",0x%" PRIx64 ",%d"
>
>  const char *pagemap_proc = "/proc/self/pagemap";
>  const char *kpageflags_proc = "/proc/kpageflags";
> @@ -70,7 +70,7 @@ static int check_after_split_folio_orders(char *vaddr_start, size_t len,
>  	return status;
>  }
>
> -static void write_debugfs(const char *fmt, ...)
> +static __printf(1, 2) void write_debugfs(const char *fmt, ...)
>  {
>  	char input[INPUT_MAX];
>  	int ret;
> @@ -132,12 +132,12 @@ static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int nr_hp
>  	disable_khugepaged(one_page, len);
>
>  	/* split all THPs */
> -	write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
> -		      (uint64_t)one_page + len, 0);
> +	write_debugfs(PID_FMT, getpid(), (uint64_t)(uintptr_t)one_page,
> +		      (uint64_t)(uintptr_t)one_page + len, 0);
>
>  	for (i = 0; i < len; i++)
>  		if (one_page[i] != (char)0)
> -			ksft_exit_fail_msg("%ld byte corrupted\n", i);
> +			ksft_exit_fail_msg("%zu byte corrupted\n", i);
>
>  	if (!check_huge_anon(one_page, nr_hpages * pmd_pagesize, 0, pmd_pagesize))
>  		ksft_exit_fail_msg("Still AnonHugePages not split\n");
> @@ -181,12 +181,12 @@ static void split_pmd_thp_to_order(int order)
>  	disable_khugepaged(one_page, len);
>
>  	/* split all THPs */
> -	write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
> -		(uint64_t)one_page + len, order);
> +	write_debugfs(PID_FMT, getpid(), (uint64_t)(uintptr_t)one_page,
> +		(uint64_t)(uintptr_t)one_page + len, order);
>
>  	for (i = 0; i < len; i++)
>  		if (one_page[i] != (char)i)
> -			ksft_exit_fail_msg("%ld byte corrupted\n", i);
> +			ksft_exit_fail_msg("%zu byte corrupted\n", i);
>
>  	memset(expected_orders, 0, sizeof(int) * (pmd_order + 1));
>  	expected_orders[order] = 4 << (pmd_order - order);
> @@ -269,8 +269,8 @@ static void split_pte_mapped_thp(void)
>  	}
>
>  	/* Split all THPs through the remapped pages. */
> -	write_debugfs(PID_FMT, getpid(), (uint64_t)page_area,
> -		      (uint64_t)page_area + page_area_size, 0);
> +	write_debugfs(PID_FMT, getpid(), (uint64_t)(uintptr_t)page_area,
> +		      (uint64_t)(uintptr_t)page_area + page_area_size, 0);
>
>  	/* Corruption during mremap or split? */
>  	for (i = 0; i < page_area_size; i++) {
> @@ -536,16 +536,16 @@ static void split_thp_in_pagecache_to_order_at(size_t fd_size,
>  	 */
>  	if (offset == -1) {
>  		for (split_addr = addr; split_addr < addr + fd_size; split_addr += pmd_pagesize)
> -			write_debugfs(PID_FMT, getpid(), (uint64_t)split_addr,
> -				      (uint64_t)split_addr + pagesize, order);
> +			write_debugfs(PID_FMT, getpid(), (uint64_t)(uintptr_t)split_addr,
> +				      (uint64_t)(uintptr_t)split_addr + pagesize, order);
>
>  		expected_orders[order] = fd_size / (pagesize << order);
>  	} else {
>  		int times = fd_size / pmd_pagesize;
>
>  		for (split_addr = addr; split_addr < addr + fd_size; split_addr += pmd_pagesize)
> -			write_debugfs(PID_FMT_OFFSET, getpid(), (uint64_t)split_addr,
> -				      (uint64_t)split_addr + pagesize, order, offset);
> +			write_debugfs(PID_FMT_OFFSET, getpid(), (uint64_t)(uintptr_t)split_addr,
> +				      (uint64_t)(uintptr_t)split_addr + pagesize, order, offset);
>
>  		for (i = order + 1; i < pmd_order; i++)
>  			expected_orders[i] = times;
> @@ -554,7 +554,7 @@ static void split_thp_in_pagecache_to_order_at(size_t fd_size,
>
>  	for (i = 0; i < fd_size; i++)
>  		if (*(addr + i) != (char)i) {
> -			ksft_print_msg("%lu byte corrupted in the file\n", i);
> +			ksft_print_msg("%zu byte corrupted in the file\n", i);
>  			err = EXIT_FAILURE;
>  			goto out;
>  		}
> --
> 2.53.0
>

--
Cheers, Lorenzo