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SubjectRe: [PATCH 2/3] x86/asm/entry/32: Remove most of SYSCALL32 code, part 1
On 07/24/2015 07:50 PM, Andy Lutomirski wrote:
> On Fri, Jul 24, 2015 at 6:47 AM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
>> SYSCALL32 code is nearly identical to SYSCALL32, except for initial
>> section. Merge them.
>>
>> The removal is split into two parts, to make review eaiser. This is part 1.
>>
>> auditsys_entry_common and auditsys_exit macros are indented one more tab without
>> any changes. This prevents diff from becoming unreadable.
>> They will be removed in part 2.
>
> I need to read these more closely, which is, at present, exceeding my
> ability to look at asm. (See the big NMI thread.) I'll look soon.
>
> Meanwhile, this code is incredibly fragile wrt syscall restart.
> (Syscall restart on compat is really weird.) Do we have a decent test
> for it?

How about this? (Feel free to expand, this is a first cut only).

$ ./test_restart
[RUN] Test restart of read()
[OK] Restart of read() worked
[RUN] Test restart of recv()
[OK] Restart of recv() worked





#undef _GNU_SOURCE
#define _GNU_SOURCE 1
#undef __USE_GNU
#define __USE_GNU 1
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <sys/time.h>
//#include <sys/ptrace.h>
#include <sys/wait.h>

void signal_SA_RESTART_empty_mask(int sig, void (*handler)(int))
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
sa.sa_handler = handler;
sigaction(sig, &sa, NULL);
}

int make_writer(void)
{
int pid, fd[2];
if (pipe(fd)) exit(1);
pid = fork();
if (pid < 0) exit(1);
if (pid == 0) {
/* child */
usleep(50*1000);
write(fd[1], "123456789", 10);
exit(0);
}
close(fd[1]);
return fd[0];
}

int make_sender(void)
{
int pid, fd[2];
if (socketpair(AF_UNIX, SOCK_STREAM, 0, fd)) exit(1);
pid = fork();
if (pid < 0) exit(1);
if (pid == 0) {
/* child */
usleep(50*1000);
write(fd[1], "123456789", 10);
exit(0);
}
close(fd[1]);
return fd[0];
}

int got_sig;

void sighandler(int sig)
{
got_sig = 1;
}

void prepare(char buf[10])
{
got_sig = 0;
strcpy(buf, "qwertyuio");
ualarm(25*1000, 0);
}

int check(const char *test_type, int len, char buf[10])
{
int err = 0;
if (len != 10 || strcmp(buf, "123456789") != 0) {
printf("[FAIL]\tRestarted %s() returns wrong result\n", test_type);
err = 1;
}
if (!got_sig) {
printf("[FAIL]\tSignal was expected on %s read() but wasn't seen\n", test_type);
err = 1;
}
if (!err)
printf("[OK]\tRestart of %s() worked\n", test_type);
return err;
}

int main(int argc, char **argv, char **envp)
{
char buf[10];
int fd;
int len;
int err;

signal_SA_RESTART_empty_mask(SIGALRM, sighandler);

printf("[RUN]\tTest restart of read()\n");
fd = make_writer();
prepare(buf);
len = read(fd, buf, 10);
err = check("read", len, buf);
close(fd);

printf("[RUN]\tTest restart of recv()\n");
fd = make_sender();
prepare(buf);
len = recv(fd, buf, 10, MSG_PEEK);
err |= check("recv", len, buf);
if (!err) {
/* Check that restarted recv() indeed had MSG_PEEK:
* i.e. that it did not consume the data.
*/
strcpy(buf, "qwertyuio");
len = recv(fd, buf, 10, 0);
if (len != 10 || strcmp(buf, "123456789") != 0) {
printf("[FAIL]\tRestarted %s() had no MSG_PEEK flag\n", "recv");
err = 1;
}
}
close(fd);

return err;
}


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