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authorJeff Dike <jdike@addtoit.com>2005-10-09 16:11:44 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-10 08:37:59 -0700
commit50f72b57946d565db74fae71bac23f3f319311c8 (patch)
tree88d18c8576258846723670a239e8782ddf33642e
parent3dd083255ddcfa87751fa8e32f61a9547a15a541 (diff)
[PATCH] uml: fix x86_64 with !CONFIG_FRAME_POINTER
UML/x86_64 doesn't run when built with frame pointers disabled. There was an implicit frame pointer assumption in the stub segfault handler. With frame pointers disabled, UML dies on handling its first page fault. The container-of part of this is from Paolo Giarrusso <blaisorblade@yahoo.it>. Signed-off-by: Jeff Dike <jdike@addtoit.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/um/sys-x86_64/stub_segv.c37
1 files changed, 28 insertions, 9 deletions
diff --git a/arch/um/sys-x86_64/stub_segv.c b/arch/um/sys-x86_64/stub_segv.c
index 65a131b362b6..d1e53bdf2e85 100644
--- a/arch/um/sys-x86_64/stub_segv.c
+++ b/arch/um/sys-x86_64/stub_segv.c
@@ -10,6 +10,22 @@
#include "uml-config.h"
#include "sysdep/sigcontext.h"
#include "sysdep/faultinfo.h"
+#include <stddef.h>
+
+/* Copied from sys-x86_64/signal.c - Can't find an equivalent definition
+ * in the libc headers anywhere.
+ */
+struct rt_sigframe
+{
+ char *pretcode;
+ struct ucontext uc;
+ struct siginfo info;
+};
+
+/* Copied here from <linux/kernel.h> - we're userspace. */
+#define container_of(ptr, type, member) ({ \
+ const typeof( ((type *)0)->member ) *__mptr = (ptr); \
+ (type *)( (char *)__mptr - offsetof(type,member) );})
void __attribute__ ((__section__ (".__syscall_stub")))
stub_segv_handler(int sig)
@@ -17,16 +33,19 @@ stub_segv_handler(int sig)
struct ucontext *uc;
__asm__("movq %%rdx, %0" : "=g" (uc) :);
- GET_FAULTINFO_FROM_SC(*((struct faultinfo *) UML_CONFIG_STUB_DATA),
- &uc->uc_mcontext);
+ GET_FAULTINFO_FROM_SC(*((struct faultinfo *) UML_CONFIG_STUB_DATA),
+ &uc->uc_mcontext);
- __asm__("movq %0, %%rax ; syscall": : "g" (__NR_getpid));
+ __asm__("movq %0, %%rax ; syscall": : "g" (__NR_getpid));
__asm__("movq %%rax, %%rdi ; movq %0, %%rax ; movq %1, %%rsi ;"
- "syscall": : "g" (__NR_kill), "g" (SIGUSR1));
- /* Two popqs to restore the stack to the state just before entering
- * the handler, one pops the return address, the other pops the frame
- * pointer.
+ "syscall": : "g" (__NR_kill), "g" (SIGUSR1) :
+ "%rdi", "%rax", "%rsi");
+ /* sys_sigreturn expects that the stack pointer will be 8 bytes into
+ * the signal frame. So, we use the ucontext pointer, which we know
+ * already, to get the signal frame pointer, and add 8 to that.
*/
- __asm__("popq %%rax ; popq %%rax ; movq %0, %%rax ; syscall" : : "g"
- (__NR_rt_sigreturn));
+ __asm__("movq %0, %%rsp": :
+ "g" ((unsigned long) container_of(uc, struct rt_sigframe,
+ uc) + 8));
+ __asm__("movq %0, %%rax ; syscall" : : "g" (__NR_rt_sigreturn));
}

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