aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>2005-09-22 21:44:16 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-22 22:17:36 -0700
commit546fe1cbf91d4d62e3849517c31a2327c992e5c5 (patch)
treec2be2cd1eb19e04c49d22ec77119973fa8f0ea13
parent69e1e688f5698287b45fbff22a01de91b20804cd (diff)
[PATCH] uml: fix hang in TT mode on fault
The current code doesn't handle well general protection faults on the host - it thinks that cr2 is always the address of a page fault. While actually, on general protection faults, that address is not accessible, so we'd better assume we couldn't satisfy the fault. Currently instead we think we've fixed it, so we go back, retry the instruction and fault again endlessly. This leads to the kernel hanging when doing copy_from_user(dest, -1, ...) in TT mode, since reading *(-1) causes a GFP, and we don't support kernel preemption. Thanks to Luo Xin for testing UML with LTP and reporting the failures he got. Cc: Luo Xin <luothing@sina.com> Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Cc: Jeff Dike <jdike@addtoit.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/um/kernel/trap_kern.c11
-rw-r--r--arch/um/kernel/tt/uaccess_user.c11
2 files changed, 19 insertions, 3 deletions
diff --git a/arch/um/kernel/trap_kern.c b/arch/um/kernel/trap_kern.c
index 87cc6fd76ce..90690b9b1f3 100644
--- a/arch/um/kernel/trap_kern.c
+++ b/arch/um/kernel/trap_kern.c
@@ -18,6 +18,7 @@
#include "asm/a.out.h"
#include "asm/current.h"
#include "asm/irq.h"
+#include "sysdep/sigcontext.h"
#include "user_util.h"
#include "kern_util.h"
#include "kern.h"
@@ -125,7 +126,15 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, void *sc)
}
else if(current->mm == NULL)
panic("Segfault with no mm");
- err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
+
+ if (SEGV_IS_FIXABLE(&fi))
+ err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
+ else {
+ err = -EFAULT;
+ /* A thread accessed NULL, we get a fault, but CR2 is invalid.
+ * This code is used in __do_copy_from_user() of TT mode. */
+ address = 0;
+ }
catcher = current->thread.fault_catcher;
if(!err)
diff --git a/arch/um/kernel/tt/uaccess_user.c b/arch/um/kernel/tt/uaccess_user.c
index f01475512ec..8c220f054b6 100644
--- a/arch/um/kernel/tt/uaccess_user.c
+++ b/arch/um/kernel/tt/uaccess_user.c
@@ -22,8 +22,15 @@ int __do_copy_from_user(void *to, const void *from, int n,
__do_copy, &faulted);
TASK_REGS(get_current())->tt = save;
- if(!faulted) return(0);
- else return(n - (fault - (unsigned long) from));
+ if(!faulted)
+ return 0;
+ else if (fault)
+ return n - (fault - (unsigned long) from);
+ else
+ /* In case of a general protection fault, we don't have the
+ * fault address, so NULL is used instead. Pretend we didn't
+ * copy anything. */
+ return n;
}
static void __do_strncpy(void *dst, const void *src, int count)