[PATCH] x86_64: Implement is_compat_task the right way

By setting a flag during a 32bit system call only
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/ia32/ia32entry.S

@@ -104,6 +104,7 @@ ENTRY(ia32_sysenter_target)
  	.quad 1b,ia32_badarg
  	.previous	
 	GET_THREAD_INFO(%r10)
+	orl    $TS_COMPAT,threadinfo_status(%r10)
 	testl  $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%r10)
 	CFI_REMEMBER_STATE
 	jnz  sysenter_tracesys
@@ -117,6 +118,7 @@ sysenter_do_call:
 	cli
 	testl	$_TIF_ALLWORK_MASK,threadinfo_flags(%r10)
 	jnz	int_ret_from_sys_call
+	andl    $~TS_COMPAT,threadinfo_status(%r10)
 	/* clear IF, that popfq doesn't enable interrupts early */
 	andl  $~0x200,EFLAGS-R11(%rsp) 
 	RESTORE_ARGS 1,24,1,1,1,1
@@ -203,6 +205,7 @@ ENTRY(ia32_cstar_target)
 	.quad 1b,ia32_badarg
 	.previous	
 	GET_THREAD_INFO(%r10)
+	orl   $TS_COMPAT,threadinfo_status(%r10)
 	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%r10)
 	CFI_REMEMBER_STATE
 	jnz   cstar_tracesys
@@ -216,6 +219,7 @@ cstar_do_call:
 	cli
 	testl $_TIF_ALLWORK_MASK,threadinfo_flags(%r10)
 	jnz  int_ret_from_sys_call
+	andl $~TS_COMPAT,threadinfo_status(%r10)
 	RESTORE_ARGS 1,-ARG_SKIP,1,1,1
 	movl RIP-ARGOFFSET(%rsp),%ecx
 	CFI_REGISTER rip,rcx
@@ -288,6 +292,7 @@ ENTRY(ia32_syscall)
 	   this could be a problem. */
 	SAVE_ARGS 0,0,1
 	GET_THREAD_INFO(%r10)
+	orl   $TS_COMPAT,threadinfo_status(%r10)
 	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%r10)
 	jnz ia32_tracesys
 ia32_do_syscall:	

arch/x86_64/kernel/asm-offsets.c

@@ -33,6 +33,7 @@ int main(void)
 	ENTRY(flags);
 	ENTRY(addr_limit);
 	ENTRY(preempt_count);
+	ENTRY(status);
 	BLANK();
 #undef ENTRY
 #define ENTRY(entry) DEFINE(pda_ ## entry, offsetof(struct x8664_pda, entry))

arch/x86_64/kernel/entry.S

@@ -313,6 +313,7 @@ int_with_check:
 	movl threadinfo_flags(%rcx),%edx
 	andl %edi,%edx
 	jnz   int_careful
+	andl    $~TS_COMPAT,threadinfo_status(%rcx)
 	jmp   retint_swapgs
 
 	/* Either reschedule or signal or syscall exit tracking needed. */

drivers/input/evdev.c

@@ -154,8 +154,10 @@ struct input_event_compat {
 	__s32 value;
 };
 
+/* Note to the author of this code: did it ever occur to
+   you why the ifdefs are needed? Think about it again. -AK */
 #ifdef CONFIG_X86_64
-#  define COMPAT_TEST test_thread_flag(TIF_IA32)
+#  define COMPAT_TEST is_compat_task()
 #elif defined(CONFIG_IA64)
 #  define COMPAT_TEST IS_IA32_PROCESS(ia64_task_regs(current))
 #elif defined(CONFIG_S390)

include/asm-x86_64/compat.h

@@ -202,4 +202,9 @@ static __inline__ void __user *compat_alloc_user_space(long len)
 	return (void __user *)regs->rsp - len; 
 }
 
+static inline int is_compat_task(void)
+{
+	return current_thread_info()->status & TS_COMPAT;
+}
+
 #endif /* _ASM_X86_64_COMPAT_H */

include/asm-x86_64/thread_info.h

@@ -138,6 +138,7 @@ static inline struct thread_info *stack_thread_info(void)
  * have to worry about atomic accesses.
  */
 #define TS_USEDFPU		0x0001	/* FPU was used by this task this quantum (SMP) */
+#define TS_COMPAT		0x0002	/* 32bit syscall active */
 
 #endif /* __KERNEL__ */