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SubjectRe: [PATCH v3 4/4] test: add a test for the process_vmsplice syscall
On Wed, Nov 22, 2017 at 09:36:31PM +0200, Mike Rapoport wrote:
> From: Andrei Vagin <avagin@openvz.org>
>
> This test checks that process_vmsplice() can splice pages from a remote
> process and returns EFAULT, if process_vmsplice() tries to splice pages
> by an unaccessiable address.
>
> Signed-off-by: Andrei Vagin <avagin@openvz.org>
> ---
> tools/testing/selftests/process_vmsplice/Makefile | 5 +
> .../process_vmsplice/process_vmsplice_test.c | 188 +++++++++++++++++++++
> 2 files changed, 193 insertions(+)
> create mode 100644 tools/testing/selftests/process_vmsplice/Makefile
> create mode 100644 tools/testing/selftests/process_vmsplice/process_vmsplice_test.c
>
> diff --git a/tools/testing/selftests/process_vmsplice/Makefile b/tools/testing/selftests/process_vmsplice/Makefile
> new file mode 100644
> index 0000000..246d5a7
> --- /dev/null
> +++ b/tools/testing/selftests/process_vmsplice/Makefile
> @@ -0,0 +1,5 @@
> +CFLAGS += -I../../../../usr/include/
> +
> +TEST_GEN_PROGS := process_vmsplice_test
> +
> +include ../lib.mk
> diff --git a/tools/testing/selftests/process_vmsplice/process_vmsplice_test.c b/tools/testing/selftests/process_vmsplice/process_vmsplice_test.c
> new file mode 100644
> index 0000000..8abf59b
> --- /dev/null
> +++ b/tools/testing/selftests/process_vmsplice/process_vmsplice_test.c
> @@ -0,0 +1,188 @@
> +#define _GNU_SOURCE
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <sys/mman.h>
> +#include <sys/syscall.h>
> +#include <fcntl.h>
> +#include <sys/uio.h>
> +#include <errno.h>
> +#include <signal.h>
> +#include <sys/prctl.h>
> +#include <sys/wait.h>
> +
> +#include "../kselftest.h"
> +
> +#ifndef __NR_process_vmsplice
> +#define __NR_process_vmsplice 333
> +#endif
> +
> +#define pr_err(fmt, ...) \
> + ({ \
> + fprintf(stderr, "%s:%d:" fmt, \
> + __func__, __LINE__, ##__VA_ARGS__); \
> + KSFT_FAIL; \
> + })
> +#define pr_perror(fmt, ...) pr_err(fmt ": %m\n", ##__VA_ARGS__)
> +#define fail(fmt, ...) pr_err("FAIL:" fmt, ##__VA_ARGS__)
> +
> +static ssize_t process_vmsplice(pid_t pid, int fd, const struct iovec *iov,
> + unsigned long nr_segs, unsigned int flags)
> +{
> + return syscall(__NR_process_vmsplice, pid, fd, iov, nr_segs, flags);
> +
> +}
> +
> +#define MEM_SIZE (4096 * 100)
> +#define MEM_WRONLY_SIZE (4096 * 10)
> +
> +int main(int argc, char **argv)
> +{
> + char *addr, *addr_wronly;
> + int p[2];
> + struct iovec iov[2];
> + char buf[4096];
> + int status, ret;
> + pid_t pid;
> +
> + ksft_print_header();
> +
> + addr = mmap(0, MEM_SIZE, PROT_READ | PROT_WRITE,
> + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
> + if (addr == MAP_FAILED)
> + return pr_perror("Unable to create a mapping");
> +
> + addr_wronly = mmap(0, MEM_WRONLY_SIZE, PROT_WRITE,
> + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
> + if (addr_wronly == MAP_FAILED)
> + return pr_perror("Unable to create a write-only mapping");
> +
> + if (pipe(p))
> + return pr_perror("Unable to create a pipe");
> +
> + pid = fork();
> + if (pid < 0)
> + return pr_perror("Unable to fork");
> +
> + if (pid == 0) {
> + addr[0] = 'C';
> + addr[4096 + 128] = 'A';
> + addr[4096 + 128 + 4096 - 1] = 'B';
> +
> + if (prctl(PR_SET_PDEATHSIG, SIGKILL))
> + return pr_perror("Unable to set PR_SET_PDEATHSIG");
> + if (write(p[1], "c", 1) != 1)
> + return pr_perror("Unable to write data into pipe");
> +
> + while (1)
> + sleep(1);
> + return 1;
> + }
> + if (read(p[0], buf, 1) != 1) {
> + pr_perror("Unable to read data from pipe");
> + kill(pid, SIGKILL);
> + wait(&status);
> + return 1;
> + }
> +
> + munmap(addr, MEM_SIZE);
> + munmap(addr_wronly, MEM_WRONLY_SIZE);
> +
> + iov[0].iov_base = addr;
> + iov[0].iov_len = 1;
> +
> + iov[1].iov_base = addr + 4096 + 128;
> + iov[1].iov_len = 4096;
> +
> + /* check one iovec */
> + if (process_vmsplice(pid, p[1], iov, 1, SPLICE_F_GIFT) != 1)
> + return pr_perror("Unable to splice pages");

Shouldn't you check to see if the syscall is even present? You should
not error if it is not, as this test will then "fail" on kernels/arches
without the syscall enabled, which isn't the nicest.

thanks,

greg k-h

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