This adds __xn_sys_drop_u_mode, a syscall to deregister the u_mode user
space address passed on shadow creation for the current thread. We need
this in order to safely shut down a thread that wants to release its
u_mode memory (either malloc'ed or TLS-allocated). So far, the kernel
might have touched this memory even after the release which caused
subtle corruptions.
After we released u_mode, we can no longer make reliable decisions based
on it. For the fast mutex use case, we then assume the worst case, ie.
we enforce syscall-based acquisitions unconditionally. For the
assert_nrt case, we simply acquire the required information via
__xn_sys_current_info.
---
include/asm-generic/bits/current.h | 24 ++++++++----
include/asm-generic/syscall.h | 1 +
include/nucleus/thread.h | 2 +
ksrc/nucleus/shadow.c | 14 +++++++
src/rtdk/assert_context.c | 9 +++-
src/skins/common/current.c | 72 ++++++++++++++++++++++++++++--------
6 files changed, 95 insertions(+), 27 deletions(-)
diff --git a/include/asm-generic/bits/current.h
b/include/asm-generic/bits/current.h
index 0c3166b..f0e569c 100644
--- a/include/asm-generic/bits/current.h
+++ b/include/asm-generic/bits/current.h
@@ -2,7 +2,9 @@
#define _XENO_ASM_GENERIC_CURRENT_H
#include <pthread.h>
-#include <nucleus/types.h>
+#include <nucleus/thread.h>
+
+extern pthread_key_t xeno_current_mode_key;
#ifdef HAVE___THREAD
extern __thread xnhandle_t xeno_current __attribute__ ((tls_model
("initial-exec")));
@@ -19,15 +21,13 @@ static inline unsigned long xeno_get_current_mode(void)
return xeno_current_mode;
}
-static inline unsigned long *xeno_init_current_mode(void)
+static inline int xeno_primary_mode(void)
{
- return &xeno_current_mode;
+ return xeno_current_mode & XNRELAX;
}
-#define xeno_init_current_keys() do { } while (0)
#else /* ! HAVE___THREAD */
extern pthread_key_t xeno_current_key;
-extern pthread_key_t xeno_current_mode_key;
static inline xnhandle_t xeno_get_current(void)
{
@@ -41,14 +41,22 @@ static inline xnhandle_t xeno_get_current(void)
static inline unsigned long xeno_get_current_mode(void)
{
- return *(unsigned long *)pthread_getspecific(xeno_current_mode_key);
+ unsigned long *mode = pthread_getspecific(xeno_current_mode_key);
+
+ return mode ? *mode : -1;
}
-unsigned long *xeno_init_current_mode(void);
+static inline int xeno_primary_mode(void)
+{
+ unsigned long *mode = pthread_getspecific(xeno_current_mode_key);
-void xeno_init_current_keys(void);
+ return mode ? (*mode & XNRELAX) : 0;
+}
#endif /* ! HAVE___THREAD */
void xeno_set_current(void);
+unsigned long *xeno_init_current_mode(void);
+void xeno_init_current_keys(void);
+
#endif /* _XENO_ASM_GENERIC_CURRENT_H */
diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index 315822e..62f7aa2 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -46,6 +46,7 @@
#define __xn_sys_current 8 /* threadh = xnthread_handle(cur) */
#define __xn_sys_current_info 9 /* r = xnshadow_current_info(&info) */
#define __xn_sys_get_next_sigs 10 /* only unqueue pending signals. */
+#define __xn_sys_drop_u_mode 11 /* stop updating thread->u_mode */
#define XENOMAI_LINUX_DOMAIN 0
#define XENOMAI_XENO_DOMAIN 1
diff --git a/include/nucleus/thread.h b/include/nucleus/thread.h
index b2baccb..cb772f7 100644
--- a/include/nucleus/thread.h
+++ b/include/nucleus/thread.h
@@ -328,6 +328,8 @@ typedef struct xnthread {
#ifdef CONFIG_XENO_OPT_PERVASIVE
unsigned long __user *u_mode; /* Thread mode variable in userland. */
+ unsigned long u_mode_dump; /* u_mode points here once userland
dropped it. */
+
unsigned u_sigpending; /* One bit per skin */
#endif /* CONFIG_XENO_OPT_PERVASIVE */
diff --git a/ksrc/nucleus/shadow.c b/ksrc/nucleus/shadow.c
index d82d6c7..8431025 100644
--- a/ksrc/nucleus/shadow.c
+++ b/ksrc/nucleus/shadow.c
@@ -1967,6 +1967,18 @@ static int xnshadow_sys_get_next_sigs(struct pt_regs
*regs)
return -EINTR;
}
+static int xnshadow_sys_drop_u_mode(struct pt_regs *regs)
+{
+ xnthread_t *cur = xnshadow_thread(current);
+
+ if (!cur)
+ return -EPERM;
+
+ cur->u_mode = (unsigned long __user*)&cur->u_mode_dump;
+
+ return 0;
+}
+
static xnsysent_t __systab[] = {
[__xn_sys_migrate] = {&xnshadow_sys_migrate, __xn_exec_current},
[__xn_sys_arch] = {&xnshadow_sys_arch, __xn_exec_any},
@@ -1981,6 +1993,8 @@ static xnsysent_t __systab[] = {
{&xnshadow_sys_current_info, __xn_exec_shadow},
[__xn_sys_get_next_sigs] =
{&xnshadow_sys_get_next_sigs, __xn_exec_conforming},
+ [__xn_sys_drop_u_mode] =
+ {&xnshadow_sys_drop_u_mode, __xn_exec_shadow},
};
static void post_ppd_release(struct xnheap *h)
diff --git a/src/rtdk/assert_context.c b/src/rtdk/assert_context.c
index f67bcd8..bad19f3 100644
--- a/src/rtdk/assert_context.c
+++ b/src/rtdk/assert_context.c
@@ -30,9 +30,12 @@ void assert_nrt(void)
xnthread_info_t info;
int err;
- if (unlikely(xeno_get_current() != XN_NO_HANDLE &&
- !(xeno_get_current_mode() & XNRELAX))) {
+ if (xeno_get_current() != XN_NO_HANDLE)
+ return;
+ info.state = xeno_get_current_mode();
+
+ if (unlikely(!(info.state & XNRELAX) || info.state == -1)) {
err = XENOMAI_SYSCALL1(__xn_sys_current_info, &info);
if (err) {
@@ -41,7 +44,7 @@ void assert_nrt(void)
return;
}
- if (info.state & XNTRAPSW)
+ if ((info.state & (XNRELAX | XNTRAPSW)) == XNTRAPSW)
pthread_kill(pthread_self(), SIGXCPU);
}
}
diff --git a/src/skins/common/current.c b/src/skins/common/current.c
index 2922d6e..1b09390 100644
--- a/src/skins/common/current.c
+++ b/src/skins/common/current.c
@@ -1,10 +1,13 @@
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
+#include <pthread.h>
#include <asm/xenomai/syscall.h>
#include <nucleus/types.h>
+pthread_key_t xeno_current_mode_key;
+
#ifdef HAVE___THREAD
__thread __attribute__ ((tls_model ("initial-exec")))
xnhandle_t xeno_current = XN_NO_HANDLE;
@@ -16,36 +19,62 @@ static inline void __xeno_set_current(xnhandle_t current)
xeno_current = current;
}
#else /* !HAVE___THREAD */
-#include <pthread.h>
-
pthread_key_t xeno_current_key;
-pthread_key_t xeno_current_mode_key;
static inline void __xeno_set_current(xnhandle_t current)
{
pthread_setspecific(xeno_current_key, (void *)current);
}
+#endif /* !HAVE___THREAD */
-unsigned long *xeno_init_current_mode(void)
+static void free_current_mode(void *key)
{
- unsigned long *mode = malloc(sizeof(unsigned long));
- pthread_setspecific(xeno_current_mode_key, mode);
- return mode;
+ unsigned long *mode = key;
+ int err;
+
+ *mode = -1;
+
+ err = XENOMAI_SYSCALL0(__xn_sys_drop_u_mode);
+
+#ifndef HAVE___THREAD
+ if (err) {
+ static int warned;
+
+ if (!warned) {
+ warned = 1;
+ fprintf(stderr,
+ "\nXenomai: WARNING, this Xenomai kernel can "
+ "cause spurious application\n"
+ " crashes on thread termination.\n"
+ " To reduce the probality, we will "
+ "leak a few bytes heap now.\n"
+ );
+ }
+ } else
+ free(mode);
+#endif /* !HAVE___THREAD */
}
static void init_current_keys(void)
{
- int err = pthread_key_create(&xeno_current_key, NULL);
+ int err;
+
+#ifndef HAVE___THREAD
+ err = pthread_key_create(&xeno_current_key, NULL);
if (err)
goto error_exit;
+#endif /* !HAVE___THREAD */
- err = pthread_key_create(&xeno_current_mode_key, free);
- if (err) {
- error_exit:
- fprintf(stderr, "Xenomai: error creating TSD key: %s\n",
- strerror(err));
- exit(EXIT_FAILURE);
- }
+ err = pthread_key_create(&xeno_current_mode_key, free_current_mode);
+ if (err)
+ goto error_exit;
+
+ return;
+
+ error_exit:
+ fprintf(stderr, "Xenomai: error creating TSD key: %s\n",
+ strerror(err));
+ exit(EXIT_FAILURE);
}
void xeno_init_current_keys(void)
@@ -53,7 +82,6 @@ void xeno_init_current_keys(void)
static pthread_once_t xeno_init_current_keys_once = PTHREAD_ONCE_INIT;
pthread_once(&xeno_init_current_keys_once, init_current_keys);
}
-#endif /* !HAVE___THREAD */
void xeno_set_current(void)
{
@@ -68,3 +96,15 @@ void xeno_set_current(void)
}
__xeno_set_current(current);
}
+
+unsigned long *xeno_init_current_mode(void)
+{
+#ifdef HAVE___THREAD
+ unsigned long *mode = &xeno_current_mode;
+#else /* !HAVE___THREAD */
+ unsigned long *mode = malloc(sizeof(unsigned long));
+#endif /* !HAVE___THREAD */
+
+ pthread_setspecific(xeno_current_mode_key, mode);
+ return mode;
+}
--
1.6.0.2
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