[LTP] [PATCH 3/3] mmap24: add test for MAP_32BIT address limit

[Petr Vorel]

Hi Andrea,

> Add a test verifying that mmap() with the MAP_32BIT flag restricts
> mappings to the first 2GB of address space and fails with ENOMEM
> when the 32-bit address space is exhausted without falling back to
> higher addresses.

Thanks!

...
> +++ b/testcases/kernel/syscalls/mmap/mmap24.c
...
> +
> +		if ((unsigned long)addr + CHUNK_SZ > ADDR_LIMIT) {
> +			tst_res(TFAIL, "mapping at %p + %zu exceeds 2GB limit",
%zu is wrong on 32 bit.

../../../../include/tst_test.h:75:55: warning: format ‘%zu’ expects argument of type ‘size_t’, but argument 6 has type ‘long unsigned int’ [-Wformat=]
   75 |                 tst_res_(__FILE__, __LINE__, (ttype), (arg_fmt), ##__VA_ARGS__);\
      |                                                       ^~~~~~~~~
mmap24.c:63:25: note: in expansion of macro ‘tst_res’
   63 |                         tst_res(TFAIL, "mapping at %p + %zu exceeds 2GB limit",
      |                         ^~~~~~~

> +				addr, CHUNK_SZ);
> +			addrs[num_chunks++] = addr;
> +			cleanup();
> +			return;
> +		}
> +
> +		((char *)addr)[0] = 'a';
> +		((char *)addr)[CHUNK_SZ - 1] = 'z';
> +
> +		addrs[num_chunks++] = addr;
> +	}
> +
> +	if (!failed_with_enomem) {
> +		tst_res(TFAIL, "32-bit address space was not exhausted");
> +	} else if (!num_chunks) {
> +		tst_res(TFAIL, "failed to map any chunk with MAP_32BIT");
> +	} else {
> +		tst_res(TPASS,
> +			"Mapped %zu MB across %zu chunks within 2GB before ENOMEM",
And here as well.
> +			(num_chunks * CHUNK_SZ) / TST_MB, num_chunks);
> +	}
> +
> +	cleanup();
> +}
> +
> +static struct tst_test test = {
> +	.cleanup = cleanup,
> +	.test_all = run,
> +	.supported_archs = (const char *const []){
> +		"x86_64",
> +		NULL
> +	},
> +};


BTW I was wondering if I can get this failing when running on VM with really
small RAM, but even with 249 MB I get get mapped 928 MB (or 960 MB when I run
with -i):

mmap24.c:81: TPASS: Mapped 928 MB across 29 chunks within 2GB before ENOMEM

What am I missing?

Anyway, LGTM.
Reviewed-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

Before merge please:

diff --git testcases/kernel/syscalls/mmap/mmap24.c testcases/kernel/syscalls/mmap/mmap24.c
index 50de620f42..94d092b809 100644
--- testcases/kernel/syscalls/mmap/mmap24.c
+++ testcases/kernel/syscalls/mmap/mmap24.c
@@ -60,7 +60,7 @@ static void run(void)
 		}
 
 		if ((unsigned long)addr + CHUNK_SZ > ADDR_LIMIT) {
-			tst_res(TFAIL, "mapping at %p + %zu exceeds 2GB limit",
+			tst_res(TFAIL, "mapping at %p + %lu exceeds 2GB limit",
 				addr, CHUNK_SZ);
 			addrs[num_chunks++] = addr;
 			cleanup();
@@ -79,7 +79,7 @@ static void run(void)
 		tst_res(TFAIL, "failed to map any chunk with MAP_32BIT");
 	} else {
 		tst_res(TPASS,
-			"Mapped %zu MB across %zu chunks within 2GB before ENOMEM",
+			"Mapped %lu MB across %zu chunks within 2GB before ENOMEM",
 			(num_chunks * CHUNK_SZ) / TST_MB, num_chunks);
 	}