[PATCH] uml: properly invoke x86_64 system calls

This patch makes stub_segv use the stub_syscall macros. This was needed
anyway, but the bug that prompted this was the discovery that gcc was storing
stuff in RCX, which is trashed across a system call. This is exactly the sort
of problem that the new macros fix.

There is a stub_syscall0 for getpid. stub_segv was changed to be a libc file,
and that caused some include changes.

Signed-off-by: Jeff Dike <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/um/include/sysdep-i386/stub.h

···
 #define STUB_MMAP_NR __NR_mmap2
 #define MMAP_OFFSET(o) ((o) >> PAGE_SHIFT)
 
+static inline long stub_syscall0(long syscall)
+{
+	long ret;
+
+	__asm__ volatile ("int $0x80" : "=a" (ret) : "0" (syscall));
+
+	return ret;
+}
+
 static inline long stub_syscall1(long syscall, long arg1)
 {
 	long ret;

arch/um/include/sysdep-x86_64/stub.h

···
 #ifndef __SYSDEP_STUB_H
 #define __SYSDEP_STUB_H
 
-#include <asm/ptrace.h>
 #include <asm/unistd.h>
 #include <sysdep/ptrace_user.h>
 
···
 
 #define __syscall_clobber "r11","rcx","memory"
 #define __syscall "syscall"
+
+static inline long stub_syscall0(long syscall)
+{
+	long ret;
+
+	__asm__ volatile (__syscall
+		: "=a" (ret)
+		: "0" (syscall) : __syscall_clobber );
+
+	return ret;
+}
 
 static inline long stub_syscall2(long syscall, long arg1, long arg2)
 {

arch/um/sys-i386/Makefile

···
 obj-$(CONFIG_HIGHMEM) += highmem.o
 obj-$(CONFIG_MODULES) += module.o
 
-USER_OBJS := bugs.o ptrace_user.o sigcontext.o fault.o
+USER_OBJS := bugs.o ptrace_user.o sigcontext.o fault.o stub_segv.o
 
 SYMLINKS = bitops.c semaphore.c highmem.c module.c
 

arch/um/sys-i386/stub_segv.c

···
  * Licensed under the GPL
  */
 
-#include <asm/signal.h>
+#include <signal.h>
+#include <sys/select.h> /* The only way I can see to get sigset_t */
 #include <asm/unistd.h>
 #include "uml-config.h"
+#include "sysdep/stub.h"
 #include "sysdep/sigcontext.h"
 #include "sysdep/faultinfo.h"
 
···
 stub_segv_handler(int sig)
 {
 	struct sigcontext *sc = (struct sigcontext *) (&sig + 1);
+	int pid;
 
 	GET_FAULTINFO_FROM_SC(*((struct faultinfo *) UML_CONFIG_STUB_DATA),
 			      sc);
 
-	__asm__("movl %0, %%eax ; int $0x80": : "g" (__NR_getpid));
-	__asm__("movl %%eax, %%ebx ; movl %0, %%eax ; movl %1, %%ecx ;"
-		"int $0x80": : "g" (__NR_kill), "g" (SIGUSR1));
+	pid = stub_syscall0(__NR_getpid);
+	stub_syscall2(__NR_kill, pid, SIGUSR1);
+
 	/* Load pointer to sigcontext into esp, since we need to leave
 	 * the stack in its original form when we do the sigreturn here, by
 	 * hand.

arch/um/sys-x86_64/Makefile

···
 obj-y := ksyms.o
 obj-$(CONFIG_MODULES) += module.o um_module.o
 
-USER_OBJS := ptrace_user.o sigcontext.o
+USER_OBJS := ptrace_user.o sigcontext.o stub_segv.o
 
 SYMLINKS = bitops.c csum-copy.S csum-partial.c csum-wrappers.c ldt.c memcpy.S \
 	thunk.S module.c

arch/um/sys-x86_64/stub_segv.c

···
  * Licensed under the GPL
  */
 
-#include <asm/signal.h>
+#include <stddef.h>
+#include <signal.h>
 #include <linux/compiler.h>
 #include <asm/unistd.h>
-#include <asm/ucontext.h>
 #include "uml-config.h"
 #include "sysdep/sigcontext.h"
 #include "sysdep/faultinfo.h"
-#include <stddef.h>
+#include "sysdep/stub.h"
 
 /* Copied from sys-x86_64/signal.c - Can't find an equivalent definition
  * in the libc headers anywhere.
···
 stub_segv_handler(int sig)
 {
 	struct ucontext *uc;
+        int pid;
 
 	__asm__("movq %%rdx, %0" : "=g" (uc) :);
 	GET_FAULTINFO_FROM_SC(*((struct faultinfo *) UML_CONFIG_STUB_DATA),
 			      &uc->uc_mcontext);
 
-	__asm__("movq %0, %%rax ; syscall": : "g" (__NR_getpid));	
-	__asm__("movq %%rax, %%rdi ; movq %0, %%rax ; movq %1, %%rsi ;"
-		"syscall": : "g" (__NR_kill), "g" (SIGUSR1) : 
-		"%rdi", "%rax", "%rsi");
+	pid = stub_syscall0(__NR_getpid);
+	stub_syscall2(__NR_kill, pid, SIGUSR1);
+
 	/* 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__("movq %0, %%rsp": : 
+	__asm__("movq %0, %%rsp; movq %1, %%rax ; syscall": :
 		"g" ((unsigned long) container_of(uc, struct rt_sigframe, 
-						  uc) + 8));
-	__asm__("movq %0, %%rax ; syscall" : : "g" (__NR_rt_sigreturn));
+						  uc) + 8),
+                "g" (__NR_rt_sigreturn));
 }