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authorJeff Dike2005-12-18 17:50:39 +0100
committerLinus Torvalds2005-12-18 11:19:44 -0800
commit5b7b15afee89d6940482259b54d0864b7b2302b0 (patch)
treea3294a2c1f14ff4ebc9d645189ad12070529a639 /arch
parent76c842d8f8096e2c98ff9ebe1db861363ff254e5 (diff)
[PATCH] uml skas0: stop gcc's insanity
With Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> UML skas0 stub has been miscompiling for many people (incidentally not the authors), depending on the used GCC versions. I think (and testing on some GCC versions shows) this patch avoids the fundamental issue which is behind this, namely gcc using the stack when we have just replaced it, behind gcc's back. The remapping and storage of the return value is hidden in a blob of asm, hopefully giving gcc no room for creativity. Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/um/include/sysdep-i386/stub.h29
-rw-r--r--arch/um/include/sysdep-x86_64/stub.h30
-rw-r--r--arch/um/kernel/skas/clone.c23
3 files changed, 46 insertions, 36 deletions
diff --git a/arch/um/include/sysdep-i386/stub.h b/arch/um/include/sysdep-i386/stub.h
index 6ba8cbbe0d36..b492b12b4a10 100644
--- a/arch/um/include/sysdep-i386/stub.h
+++ b/arch/um/include/sysdep-i386/stub.h
@@ -6,8 +6,12 @@
#ifndef __SYSDEP_STUB_H
#define __SYSDEP_STUB_H
+#include <sys/mman.h>
#include <asm/ptrace.h>
#include <asm/unistd.h>
+#include "stub-data.h"
+#include "kern_constants.h"
+#include "uml-config.h"
extern void stub_segv_handler(int sig);
extern void stub_clone_handler(void);
@@ -76,23 +80,22 @@ static inline long stub_syscall5(long syscall, long arg1, long arg2, long arg3,
return ret;
}
-static inline long stub_syscall6(long syscall, long arg1, long arg2, long arg3,
- long arg4, long arg5, long arg6)
+static inline void trap_myself(void)
{
- long ret;
-
- __asm__ volatile ("push %%ebp ; movl %%eax,%%ebp ; movl %1,%%eax ; "
- "int $0x80 ; pop %%ebp"
- : "=a" (ret)
- : "g" (syscall), "b" (arg1), "c" (arg2), "d" (arg3),
- "S" (arg4), "D" (arg5), "0" (arg6));
-
- return ret;
+ __asm("int3");
}
-static inline void trap_myself(void)
+static inline void remap_stack(int fd, unsigned long offset)
{
- __asm("int3");
+ __asm__ volatile ("movl %%eax,%%ebp ; movl %0,%%eax ; int $0x80 ;"
+ "movl %7, %%ebx ; movl %%eax, (%%ebx)"
+ : : "g" (STUB_MMAP_NR), "b" (UML_CONFIG_STUB_DATA),
+ "c" (UM_KERN_PAGE_SIZE),
+ "d" (PROT_READ | PROT_WRITE),
+ "S" (MAP_FIXED | MAP_SHARED), "D" (fd),
+ "a" (offset),
+ "i" (&((struct stub_data *) UML_CONFIG_STUB_DATA)->err)
+ : "memory");
}
#endif
diff --git a/arch/um/include/sysdep-x86_64/stub.h b/arch/um/include/sysdep-x86_64/stub.h
index c41689c13dc9..92e989f81761 100644
--- a/arch/um/include/sysdep-x86_64/stub.h
+++ b/arch/um/include/sysdep-x86_64/stub.h
@@ -6,8 +6,12 @@
#ifndef __SYSDEP_STUB_H
#define __SYSDEP_STUB_H
+#include <sys/mman.h>
#include <asm/unistd.h>
#include <sysdep/ptrace_user.h>
+#include "stub-data.h"
+#include "kern_constants.h"
+#include "uml-config.h"
extern void stub_segv_handler(int sig);
extern void stub_clone_handler(void);
@@ -81,23 +85,23 @@ static inline long stub_syscall5(long syscall, long arg1, long arg2, long arg3,
return ret;
}
-static inline long stub_syscall6(long syscall, long arg1, long arg2, long arg3,
- long arg4, long arg5, long arg6)
+static inline void trap_myself(void)
{
- long ret;
-
- __asm__ volatile ("movq %5,%%r10 ; movq %6,%%r8 ; "
- "movq %7, %%r9; " __syscall : "=a" (ret)
- : "0" (syscall), "D" (arg1), "S" (arg2), "d" (arg3),
- "g" (arg4), "g" (arg5), "g" (arg6)
- : __syscall_clobber, "r10", "r8", "r9" );
-
- return ret;
+ __asm("int3");
}
-static inline void trap_myself(void)
+static inline void remap_stack(long fd, unsigned long offset)
{
- __asm("int3");
+ __asm__ volatile ("movq %4,%%r10 ; movq %5,%%r8 ; "
+ "movq %6, %%r9; " __syscall "; movq %7, %%rbx ; "
+ "movq %%rax, (%%rbx)":
+ : "a" (STUB_MMAP_NR), "D" (UML_CONFIG_STUB_DATA),
+ "S" (UM_KERN_PAGE_SIZE),
+ "d" (PROT_READ | PROT_WRITE),
+ "g" (MAP_FIXED | MAP_SHARED), "g" (fd),
+ "g" (offset),
+ "i" (&((struct stub_data *) UML_CONFIG_STUB_DATA)->err)
+ : __syscall_clobber, "r10", "r8", "r9" );
}
#endif
diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c
index cb37ce9124a6..47b812b3bca8 100644
--- a/arch/um/kernel/skas/clone.c
+++ b/arch/um/kernel/skas/clone.c
@@ -18,11 +18,10 @@
* on some systems.
*/
-#define STUB_DATA(field) (((struct stub_data *) UML_CONFIG_STUB_DATA)->field)
-
void __attribute__ ((__section__ (".__syscall_stub")))
stub_clone_handler(void)
{
+ struct stub_data *data = (struct stub_data *) UML_CONFIG_STUB_DATA;
long err;
err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD,
@@ -35,17 +34,21 @@ stub_clone_handler(void)
if(err)
goto out;
- err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL,
- (long) &STUB_DATA(timer), 0);
+ err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL,
+ (long) &data->timer, 0);
if(err)
goto out;
- err = stub_syscall6(STUB_MMAP_NR, UML_CONFIG_STUB_DATA,
- UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
- MAP_FIXED | MAP_SHARED, STUB_DATA(fd),
- STUB_DATA(offset));
+ remap_stack(data->fd, data->offset);
+ goto done;
+
out:
- /* save current result. Parent: pid; child: retcode of mmap */
- STUB_DATA(err) = err;
+ /* save current result.
+ * Parent: pid;
+ * child: retcode of mmap already saved and it jumps around this
+ * assignment
+ */
+ data->err = err;
+ done:
trap_myself();
}