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Diffstat (limited to 'tools/arch/x86/include/uapi/asm/unistd.h')
-rw-r--r--tools/arch/x86/include/uapi/asm/unistd.h9
1 files changed, 8 insertions, 1 deletions
diff --git a/tools/arch/x86/include/uapi/asm/unistd.h b/tools/arch/x86/include/uapi/asm/unistd.h
index 30d7d04d72d6..be5e2e747f50 100644
--- a/tools/arch/x86/include/uapi/asm/unistd.h
+++ b/tools/arch/x86/include/uapi/asm/unistd.h
@@ -2,7 +2,14 @@
#ifndef _UAPI_ASM_X86_UNISTD_H
#define _UAPI_ASM_X86_UNISTD_H
-/* x32 syscall flag bit */
+/*
+ * x32 syscall flag bit. Some user programs expect syscall NR macros
+ * and __X32_SYSCALL_BIT to have type int, even though syscall numbers
+ * are, for practical purposes, unsigned long.
+ *
+ * Fortunately, expressions like (nr & ~__X32_SYSCALL_BIT) do the right
+ * thing regardless.
+ */
#define __X32_SYSCALL_BIT 0x40000000
#ifndef __KERNEL__