uml: stop gdb from deleting breakpoints when running UML

Sometimes when UML is debugged gdb miss breakpoints.

When process traced by gdb do fork, debugger remove breakpoints from
child address space. There is possibility to trace more than one fork,
but this not work with UML, I guess (only guess) there is a deadlock -
gdb waits for UML and UML waits for gdb.

When clone() is called with SIGCHLD and CLONE_VM flags, gdb see this
as PTRACE_EVENT_FORK not as PTRACE_EVENT_CLONE and remove breakpoints
from child and at the same time from traced process, because either
have the same address space.

Maybe it is possible to do fix in gdb, but I'm not sure if there is
easy way to find out if traced and child processes share memory. So I
do fix for UML, it simply do not call clone() with both SIGCHLD and
CLONE_VM flags together.  Additionally __WALL flag is used for
waitpid() to assure not miss clone and normal process events.

[ jdike - checkpatch fixes ]

Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/um/drivers/net_user.c b/arch/um/drivers/net_user.c
index 90d7f2e8ead8bcd4f9911bcd774b77f1da7acffd..29185cad9fff97328b8b3be7a4cf6dfba6130f47 100644 (file)
--- a/arch/um/drivers/net_user.c
+++ b/arch/um/drivers/net_user.c
@@ -201,7 +201,7 @@ static int change_tramp(char **argv, char *output, int output_len)
        close(fds[1]);
 
        if (pid > 0)
-               CATCH_EINTR(err = waitpid(pid, NULL, 0));
+               helper_wait(pid, 0, "change_tramp");
        return pid;
 }
 

diff --git a/arch/um/drivers/slip_user.c b/arch/um/drivers/slip_user.c
index 5f06204d68719d2ac0fba7bb7a9a8e8b38bfcee3..b8711e50da801582081409b2c1d43ce398c83b67 100644 (file)
--- a/arch/um/drivers/slip_user.c
+++ b/arch/um/drivers/slip_user.c
@@ -77,7 +77,7 @@ static int slip_tramp(char **argv, int fd)
 {
        struct slip_pre_exec_data pe_data;
        char *output;
-       int status, pid, fds[2], err, output_len;
+       int pid, fds[2], err, output_len;
 
        err = os_pipe(fds, 1, 0);
        if (err < 0) {
@@ -109,15 +109,7 @@ static int slip_tramp(char **argv, int fd)
        read_output(fds[0], output, output_len);
        printk("%s", output);
 
-       CATCH_EINTR(err = waitpid(pid, &status, 0));
-       if (err < 0)
-               err = errno;
-       else if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0)) {
-               printk(UM_KERN_ERR "'%s' didn't exit with status 0\n", argv[0]);
-               err = -EINVAL;
-       }
-       else err = 0;
-
+       err = helper_wait(pid, 0, argv[0]);
        close(fds[0]);
 
 out_free:

diff --git a/arch/um/drivers/slirp_user.c b/arch/um/drivers/slirp_user.c
index 1865089ff41a41d920eadf082a12e06de893785d..89c1be225fda5f23525f0799673ba37fe11b6483 100644 (file)
--- a/arch/um/drivers/slirp_user.c
+++ b/arch/um/drivers/slirp_user.c
@@ -79,7 +79,7 @@ out:
 static void slirp_close(int fd, void *data)
 {
        struct slirp_data *pri = data;
-       int status,err;
+       int err;
 
        close(fd);
        close(pri->slave);
@@ -98,18 +98,9 @@ static void slirp_close(int fd, void *data)
                       "(%d)\n", pri->pid, errno);
        }
 #endif
-
-       CATCH_EINTR(err = waitpid(pri->pid, &status, WNOHANG));
-       if (err < 0) {
-               printk(UM_KERN_ERR "slirp_close: waitpid returned %d\n", errno);
-               return;
-       }
-
-       if (err == 0) {
-               printk(UM_KERN_ERR "slirp_close: process %d has not exited\n",
-                      pri->pid);
+       err = helper_wait(pri->pid, 1, "slirp_close");
+       if (err < 0)
                return;
-       }
 
        pri->pid = -1;
 }

diff --git a/arch/um/drivers/ubd_user.c b/arch/um/drivers/ubd_user.c
index 41d254bd38df5222d06f6d08e643dda7469df524..48fc7452bc1d11e3f3aad9c40c6983dac8526fc9 100644 (file)
--- a/arch/um/drivers/ubd_user.c
+++ b/arch/um/drivers/ubd_user.c
@@ -49,8 +49,7 @@ int start_io_thread(unsigned long sp, int *fd_out)
                goto out_close;
        }
 
-       pid = clone(io_thread, (void *) sp, CLONE_FILES | CLONE_VM | SIGCHLD,
-                   NULL);
+       pid = clone(io_thread, (void *) sp, CLONE_FILES | CLONE_VM, NULL);
        if(pid < 0){
                err = -errno;
                printk("start_io_thread - clone failed : errno = %d\n", errno);

diff --git a/arch/um/include/os.h b/arch/um/include/os.h
index fbf0a87c6eaa80b681086f5cc32dd36f88208df5..6f0d1c741bcad5660be289861c4b71e48c088af2 100644 (file)
--- a/arch/um/include/os.h
+++ b/arch/um/include/os.h
@@ -214,7 +214,7 @@ extern int execvp_noalloc(char *buf, const char *file, char *const argv[]);
 extern int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv);
 extern int run_helper_thread(int (*proc)(void *), void *arg,
                             unsigned int flags, unsigned long *stack_out);
-extern int helper_wait(int pid);
+extern int helper_wait(int pid, int nohang, char *pname);
 
 
 /* tls.c */

diff --git a/arch/um/os-Linux/aio.c b/arch/um/os-Linux/aio.c
index 4158118c4a56bd21eeb9699a6588f82860a7374c..93dc0c80ebaf7d128f08125185a8ba65c5f6f770 100644 (file)
--- a/arch/um/os-Linux/aio.c
+++ b/arch/um/os-Linux/aio.c
@@ -218,7 +218,7 @@ static int init_aio_24(void)
                goto out_close_pipe;
 
        err = run_helper_thread(not_aio_thread, NULL,
-                               CLONE_FILES | CLONE_VM | SIGCHLD, &aio_stack);
+                               CLONE_FILES | CLONE_VM, &aio_stack);
        if (err < 0)
                goto out_close_pipe;
 
@@ -254,7 +254,7 @@ static int init_aio_26(void)
        }
 
        err = run_helper_thread(aio_thread, NULL,
-                               CLONE_FILES | CLONE_VM | SIGCHLD, &aio_stack);
+                               CLONE_FILES | CLONE_VM, &aio_stack);
        if (err < 0)
                return err;
 

diff --git a/arch/um/os-Linux/drivers/ethertap_user.c b/arch/um/os-Linux/drivers/ethertap_user.c
index 4ff553603449caced35699db9845d206d703635a..07ca0cb472acf40b1ed8976070e5f4e2ac2cba25 100644 (file)
--- a/arch/um/os-Linux/drivers/ethertap_user.c
+++ b/arch/um/os-Linux/drivers/ethertap_user.c
@@ -94,7 +94,7 @@ static int etap_tramp(char *dev, char *gate, int control_me,
                      int control_remote, int data_me, int data_remote)
 {
        struct etap_pre_exec_data pe_data;
-       int pid, status, err, n;
+       int pid, err, n;
        char version_buf[sizeof("nnnnn\0")];
        char data_fd_buf[sizeof("nnnnnn\0")];
        char gate_buf[sizeof("nnn.nnn.nnn.nnn\0")];
@@ -131,13 +131,7 @@ static int etap_tramp(char *dev, char *gate, int control_me,
        }
        if (c != 1) {
                printk(UM_KERN_ERR "etap_tramp : uml_net failed\n");
-               err = -EINVAL;
-               CATCH_EINTR(n = waitpid(pid, &status, 0));
-               if (n < 0)
-                       err = -errno;
-               else if (!WIFEXITED(status) || (WEXITSTATUS(status) != 1))
-                       printk(UM_KERN_ERR "uml_net didn't exit with "
-                              "status 1\n");
+               err = helper_wait(pid, 0, "uml_net");
        }
        return err;
 }

diff --git a/arch/um/os-Linux/drivers/tuntap_user.c b/arch/um/os-Linux/drivers/tuntap_user.c
index 6c55d3c8ead8d00b56b2f2e48e6050a17750a9e6..1037a3b6386ee95f4ff746f764fd1200dc5411f3 100644 (file)
--- a/arch/um/os-Linux/drivers/tuntap_user.c
+++ b/arch/um/os-Linux/drivers/tuntap_user.c
@@ -107,7 +107,7 @@ static int tuntap_open_tramp(char *gate, int *fd_out, int me, int remote,
                       "errno = %d\n", errno);
                return err;
        }
-       CATCH_EINTR(waitpid(pid, NULL, 0));
+       helper_wait(pid, 0, "tuntap_open_tramp");
 
        cmsg = CMSG_FIRSTHDR(&msg);
        if (cmsg == NULL) {

diff --git a/arch/um/os-Linux/helper.c b/arch/um/os-Linux/helper.c
index 7a72dbb61b0d6d19d37d67ee44fc7bd4c64e93c5..fba3f0fefeef7ca78d3edd685f24e8d5d4c254bc 100644 (file)
--- a/arch/um/os-Linux/helper.c
+++ b/arch/um/os-Linux/helper.c
@@ -76,7 +76,7 @@ int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
        data.fd = fds[1];
        data.buf = __cant_sleep() ? kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
                                        kmalloc(PATH_MAX, UM_GFP_KERNEL);
-       pid = clone(helper_child, (void *) sp, CLONE_VM | SIGCHLD, &data);
+       pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
        if (pid < 0) {
                ret = -errno;
                printk("run_helper : clone failed, errno = %d\n", errno);
@@ -101,7 +101,7 @@ int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
                        ret = n;
                        kill(pid, SIGKILL);
                }
-               CATCH_EINTR(waitpid(pid, NULL, 0));
+               CATCH_EINTR(waitpid(pid, NULL, __WCLONE));
        }
 
 out_free2:
@@ -126,7 +126,7 @@ int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
                return -ENOMEM;
 
        sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
-       pid = clone(proc, (void *) sp, flags | SIGCHLD, arg);
+       pid = clone(proc, (void *) sp, flags, arg);
        if (pid < 0) {
                err = -errno;
                printk("run_helper_thread : clone failed, errno = %d\n",
@@ -134,7 +134,7 @@ int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
                return err;
        }
        if (stack_out == NULL) {
-               CATCH_EINTR(pid = waitpid(pid, &status, 0));
+               CATCH_EINTR(pid = waitpid(pid, &status, __WCLONE));
                if (pid < 0) {
                        err = -errno;
                        printk("run_helper_thread - wait failed, errno = %d\n",
@@ -150,14 +150,30 @@ int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
        return pid;
 }
 
-int helper_wait(int pid)
+int helper_wait(int pid, int nohang, char *pname)
 {
-       int ret;
+       int ret, status;
+       int wflags = __WCLONE;
 
-       CATCH_EINTR(ret = waitpid(pid, NULL, WNOHANG));
+       if (nohang)
+               wflags |= WNOHANG;
+
+       if (!pname)
+               pname = "helper_wait";
+
+       CATCH_EINTR(ret = waitpid(pid, &status, wflags));
        if (ret < 0) {
-               ret = -errno;
-               printk("helper_wait : waitpid failed, errno = %d\n", errno);
-       }
-       return ret;
+               printk(UM_KERN_ERR "%s : waitpid process %d failed, "
+                      "errno = %d\n", pname, pid, errno);
+               return -errno;
+       } else if (nohang && ret == 0) {
+               printk(UM_KERN_ERR "%s : process %d has not exited\n",
+                      pname, pid);
+               return -ECHILD;
+       } else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+               printk(UM_KERN_ERR "%s : process %d didn't exit with "
+                      "status 0\n", pname, pid);
+               return -ECHILD;
+       } else
+               return 0;
 }

diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
index 37781db4cecad92a5849bb86d7fca6a3812e627e..bda5c3150d6c798254dd974e7780286971c8f6d7 100644 (file)
--- a/arch/um/os-Linux/process.c
+++ b/arch/um/os-Linux/process.c
@@ -101,7 +101,7 @@ void os_kill_process(int pid, int reap_child)
 {
        kill(pid, SIGKILL);
        if (reap_child)
-               CATCH_EINTR(waitpid(pid, NULL, 0));
+               CATCH_EINTR(waitpid(pid, NULL, __WALL));
 }
 
 /* This is here uniquely to have access to the userspace errno, i.e. the one
@@ -130,7 +130,7 @@ void os_kill_ptraced_process(int pid, int reap_child)
        ptrace(PTRACE_KILL, pid);
        ptrace(PTRACE_CONT, pid);
        if (reap_child)
-               CATCH_EINTR(waitpid(pid, NULL, 0));
+               CATCH_EINTR(waitpid(pid, NULL, __WALL));
 }
 
 /* Don't use the glibc version, which caches the result in TLS. It misses some

diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index d77c81d7068a06309ecf935ee0ccb9938d4cd8b6..e8b7a97e83d3eb8d75785b6a44e29492ae81efcf 100644 (file)
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -64,7 +64,7 @@ void wait_stub_done(int pid)
        int n, status, err;
 
        while (1) {
-               CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
+               CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
                if ((n < 0) || !WIFSTOPPED(status))
                        goto bad_wait;
 
@@ -153,7 +153,7 @@ static void handle_trap(int pid, struct uml_pt_regs *regs,
                        panic("handle_trap - continuing to end of syscall "
                              "failed, errno = %d\n", errno);
 
-               CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
+               CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
                if ((err < 0) || !WIFSTOPPED(status) ||
                   (WSTOPSIG(status) != SIGTRAP + 0x80)) {
                         err = ptrace_dump_regs(pid);
@@ -255,16 +255,18 @@ int start_userspace(unsigned long stub_stack)
                panic("start_userspace : mmap failed, errno = %d", errno);
        sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 
-       flags = CLONE_FILES | SIGCHLD;
+       flags = CLONE_FILES;
        if (proc_mm)
                flags |= CLONE_VM;
+       else
+               flags |= SIGCHLD;
 
        pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
        if (pid < 0)
                panic("start_userspace : clone failed, errno = %d", errno);
 
        do {
-               CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
+               CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
                if (n < 0)
                        panic("start_userspace : wait failed, errno = %d",
                              errno);
@@ -314,7 +316,7 @@ void userspace(struct uml_pt_regs *regs)
                              "pid=%d, ptrace operation = %d, errno = %d\n",
                              pid, op, errno);
 
-               CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
+               CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
                if (err < 0)
                        panic("userspace - waitpid failed, errno = %d\n",
                              errno);

diff --git a/arch/um/os-Linux/util.c b/arch/um/os-Linux/util.c
index ef095436a78c24f669dfc54d1ef8af9eb376687d..3e058ce9ffb6cd044a8fbf5ff33883b46b649348 100644 (file)
--- a/arch/um/os-Linux/util.c
+++ b/arch/um/os-Linux/util.c
@@ -141,7 +141,7 @@ void os_dump_core(void)
         * nothing reasonable to do if that fails.
         */
 
-       while ((pid = waitpid(-1, NULL, WNOHANG)) > 0)
+       while ((pid = waitpid(-1, NULL, WNOHANG | __WALL)) > 0)
                os_kill_ptraced_process(pid, 0);
 
        abort();