[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 <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

6 files changed, 39 insertions, 17 deletions

diff --git a/arch/um/include/sysdep-i386/stub.h b/arch/um/include/sysdep-i386/stub.h
index a49ceb199ee5..6ba8cbbe0d36 100644
--- a/arch/um/include/sysdep-i386/stub.h
+++ b/arch/um/include/sysdep-i386/stub.h
@@ -16,6 +16,15 @@ extern void stub_clone_handler(void);
 #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;
diff --git a/arch/um/include/sysdep-x86_64/stub.h b/arch/um/include/sysdep-x86_64/stub.h
index 2bd6e7a97286..c41689c13dc9 100644
--- a/arch/um/include/sysdep-x86_64/stub.h
+++ b/arch/um/include/sysdep-x86_64/stub.h
@@ -6,7 +6,6 @@
 #ifndef __SYSDEP_STUB_H
 #define __SYSDEP_STUB_H
 
-#include <asm/ptrace.h>
 #include <asm/unistd.h>
 #include <sysdep/ptrace_user.h>
 
@@ -20,6 +19,17 @@ extern void stub_clone_handler(void);
 #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)
 {
         long ret;
diff --git a/arch/um/sys-i386/Makefile b/arch/um/sys-i386/Makefile
index 6dfeb70f6957..150059dbee12 100644
--- a/arch/um/sys-i386/Makefile
+++ b/arch/um/sys-i386/Makefile
@@ -5,7 +5,7 @@ obj-y = bitops.o bugs.o checksum.o delay.o fault.o ksyms.o ldt.o ptrace.o \
 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
 
diff --git a/arch/um/sys-i386/stub_segv.c b/arch/um/sys-i386/stub_segv.c
index 1e88b275edac..a37f672ec964 100644
--- a/arch/um/sys-i386/stub_segv.c
+++ b/arch/um/sys-i386/stub_segv.c
@@ -3,9 +3,11 @@
  * 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"
 
@@ -13,13 +15,14 @@ void __attribute__ ((__section__ (".__syscall_stub")))
 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 $0x80": : "g" (__NR_kill), "g" (SIGUSR1));
+        pid = stub_syscall0(__NR_getpid);
+        stub_syscall2(__NR_kill, pid, SIGUSR1);
+
         /* Load pointer to sigcontext into esp, since we need to leave
          * the stack in its original form when we do the sigreturn here, by
          * hand.
diff --git a/arch/um/sys-x86_64/Makefile b/arch/um/sys-x86_64/Makefile
index ea977df395a1..00b2025427df 100644
--- a/arch/um/sys-x86_64/Makefile
+++ b/arch/um/sys-x86_64/Makefile
@@ -12,7 +12,7 @@ lib-y = bitops.o bugs.o csum-partial.o delay.o fault.o ldt.o mem.o memcpy.o \
 obj-y := ksyms.o
 obj-$(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
diff --git a/arch/um/sys-x86_64/stub_segv.c b/arch/um/sys-x86_64/stub_segv.c
index d1e53bdf2e85..a27099533198 100644
--- a/arch/um/sys-x86_64/stub_segv.c
+++ b/arch/um/sys-x86_64/stub_segv.c
@@ -3,14 +3,14 @@
  * 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.
@@ -31,21 +31,21 @@ void __attribute__ ((__section__ (".__syscall_stub")))
 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));
 }