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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 11:37:59 -0400
commit50f72b57946d565db74fae71bac23f3f319311c8 (patch)
tree88d18c8576258846723670a239e8782ddf33642e /arch/um
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>
Diffstat (limited to 'arch/um')
-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 @@
10#include "uml-config.h" 10#include "uml-config.h"
11#include "sysdep/sigcontext.h" 11#include "sysdep/sigcontext.h"
12#include "sysdep/faultinfo.h" 12#include "sysdep/faultinfo.h"
13#include <stddef.h>
14
15/* Copied from sys-x86_64/signal.c - Can't find an equivalent definition
16 * in the libc headers anywhere.
17 */
18struct rt_sigframe
19{
20 char *pretcode;
21 struct ucontext uc;
22 struct siginfo info;
23};
24
25/* Copied here from <linux/kernel.h> - we're userspace. */
26#define container_of(ptr, type, member) ({ \
27 const typeof( ((type *)0)->member ) *__mptr = (ptr); \
28 (type *)( (char *)__mptr - offsetof(type,member) );})
13 29
14void __attribute__ ((__section__ (".__syscall_stub"))) 30void __attribute__ ((__section__ (".__syscall_stub")))
15stub_segv_handler(int sig) 31stub_segv_handler(int sig)
@@ -17,16 +33,19 @@ stub_segv_handler(int sig)
17 struct ucontext *uc; 33 struct ucontext *uc;
18 34
19 __asm__("movq %%rdx, %0" : "=g" (uc) :); 35 __asm__("movq %%rdx, %0" : "=g" (uc) :);
20 GET_FAULTINFO_FROM_SC(*((struct faultinfo *) UML_CONFIG_STUB_DATA), 36 GET_FAULTINFO_FROM_SC(*((struct faultinfo *) UML_CONFIG_STUB_DATA),
21 &uc->uc_mcontext); 37 &uc->uc_mcontext);
22 38
23 __asm__("movq %0, %%rax ; syscall": : "g" (__NR_getpid)); 39 __asm__("movq %0, %%rax ; syscall": : "g" (__NR_getpid));
24 __asm__("movq %%rax, %%rdi ; movq %0, %%rax ; movq %1, %%rsi ;" 40 __asm__("movq %%rax, %%rdi ; movq %0, %%rax ; movq %1, %%rsi ;"
25 "syscall": : "g" (__NR_kill), "g" (SIGUSR1)); 41 "syscall": : "g" (__NR_kill), "g" (SIGUSR1) :
26 /* Two popqs to restore the stack to the state just before entering 42 "%rdi", "%rax", "%rsi");
27 * the handler, one pops the return address, the other pops the frame 43 /* sys_sigreturn expects that the stack pointer will be 8 bytes into
28 * pointer. 44 * the signal frame. So, we use the ucontext pointer, which we know
45 * already, to get the signal frame pointer, and add 8 to that.
29 */ 46 */
30 __asm__("popq %%rax ; popq %%rax ; movq %0, %%rax ; syscall" : : "g" 47 __asm__("movq %0, %%rsp": :
31 (__NR_rt_sigreturn)); 48 "g" ((unsigned long) container_of(uc, struct rt_sigframe,
49 uc) + 8));
50 __asm__("movq %0, %%rax ; syscall" : : "g" (__NR_rt_sigreturn));
32} 51}