linux-kernel - [PATCH 4/4] x86/syscalls: Make __X32_SYSCALL

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Date:   Wed,  3 Jul 2019 13:34:05 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 4/4] x86/syscalls: Make __X32_SYSCALL_BIT be unsigned long

Currently, it's an int.  This is bizarre.  Fortunately, the code
using it still works: ~__X32_SYSCALL_BIT is also int, so, if nr is
unsigned long, then C kindly sign-extends the ~__X32_SYSCALL_BIT
part, and we actually get the desired value.

This is far more subtle than it deserves to be.  Syscall numbers
are, for all practical purposes, unsigned long, so make
__X32_SYSCALL_BIT be unsigned long.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/include/uapi/asm/unistd.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/uapi/asm/unistd.h b/arch/x86/include/uapi/asm/unistd.h
index 30d7d04d72d6..196fdd02b8b1 100644
--- a/arch/x86/include/uapi/asm/unistd.h
+++ b/arch/x86/include/uapi/asm/unistd.h
@@ -3,7 +3,7 @@
 #define _UAPI_ASM_X86_UNISTD_H

 /* x32 syscall flag bit */
-#define __X32_SYSCALL_BIT	0x40000000
+#define __X32_SYSCALL_BIT	0x40000000UL

 #ifndef __KERNEL__
 # ifdef __i386__
-- 
2.21.0