--- a/arch/x86/ia32/ia32entry.S	2010-07-25 05:11:36.000000000 +0100
+++ a/arch/x86/ia32/ia32entry.S	2010-09-20 19:31:24.000000000 +0100
@@ -51,7 +51,12 @@ 
 	/*
 	 * Reload arg registers from stack in case ptrace changed them.
 	 * We don't reload %eax because syscall_trace_enter() returned
-	 * the value it wants us to use in the table lookup.
+	 * the %rax value we should see.  Instead, we just truncate that
+	 * value to 32 bits again as we did on entry from user mode.
+	 * If it's a new value set by user_regset during entry tracing,
+	 * this matches the normal truncation of the user-mode value.
+	 * If it's -1 to make us punt the syscall, then (u32)-1 is still
+	 * an appropriately invalid value.
 	 */
 	.macro LOAD_ARGS32 offset, _r9=0
 	.if \_r9
@@ -61,6 +66,7 @@ 
 	movl \offset+48(%rsp),%edx
 	movl \offset+56(%rsp),%esi
 	movl \offset+64(%rsp),%edi
+	movl %eax,%eax			/* zero extension */
 	.endm
 	
 	.macro CFI_STARTPROC32 simple
@@ -165,7 +171,7 @@ 
 	testl  $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
 	CFI_REMEMBER_STATE
 	jnz  sysenter_tracesys
-	cmpl	$(IA32_NR_syscalls-1),%eax
+	cmpq	$(IA32_NR_syscalls-1),%rax
 	ja	ia32_badsys
 sysenter_do_call:
 	IA32_ARG_FIXUP
@@ -212,7 +218,7 @@ 
 	movl $AUDIT_ARCH_I386,%edi	/* 1st arg: audit arch */
 	call audit_syscall_entry
 	movl RAX-ARGOFFSET(%rsp),%eax	/* reload syscall number */
-	cmpl $(IA32_NR_syscalls-1),%eax
+	cmpq $(IA32_NR_syscalls-1),%rax
 	ja ia32_badsys
 	movl %ebx,%edi			/* reload 1st syscall arg */
 	movl RCX-ARGOFFSET(%rsp),%esi	/* reload 2nd syscall arg */
@@ -265,7 +271,7 @@ 
 	call	syscall_trace_enter
 	LOAD_ARGS32 ARGOFFSET  /* reload args from stack in case ptrace changed it */
 	RESTORE_REST
-	cmpl	$(IA32_NR_syscalls-1),%eax
+	cmpq	$(IA32_NR_syscalls-1),%rax
 	ja	int_ret_from_sys_call /* sysenter_tracesys has set RAX(%rsp) */
 	jmp	sysenter_do_call
 	CFI_ENDPROC
@@ -342,7 +348,7 @@ 
 	testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
 	CFI_REMEMBER_STATE
 	jnz   cstar_tracesys
-	cmpl $IA32_NR_syscalls-1,%eax
+	cmpq $IA32_NR_syscalls-1,%rax
 	ja  ia32_badsys
 cstar_do_call:
 	IA32_ARG_FIXUP 1
@@ -400,7 +406,7 @@ 
 	LOAD_ARGS32 ARGOFFSET, 1  /* reload args from stack in case ptrace changed it */
 	RESTORE_REST
 	xchgl %ebp,%r9d
-	cmpl $(IA32_NR_syscalls-1),%eax
+	cmpq $(IA32_NR_syscalls-1),%rax
 	ja int_ret_from_sys_call /* cstar_tracesys has set RAX(%rsp) */
 	jmp cstar_do_call
 END(ia32_cstar_target)
@@ -463,7 +469,7 @@ 
 	orl   $TS_COMPAT,TI_status(%r10)
 	testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
 	jnz ia32_tracesys
-	cmpl $(IA32_NR_syscalls-1),%eax
+	cmpq $(IA32_NR_syscalls-1),%rax
 	ja ia32_badsys
 ia32_do_call:
 	IA32_ARG_FIXUP
@@ -482,7 +488,7 @@ 
 	call syscall_trace_enter
 	LOAD_ARGS32 ARGOFFSET  /* reload args from stack in case ptrace changed it */
 	RESTORE_REST
-	cmpl $(IA32_NR_syscalls-1),%eax
+	cmpq $(IA32_NR_syscalls-1),%rax
 	ja  int_ret_from_sys_call	/* ia32_tracesys has set RAX(%rsp) */
 	jmp ia32_do_call
 END(ia32_syscall)