linux-kernel - [RFC v2 PATCH 3/7] x86/syscall: unconditionally prototype {ia32,x32}_sys_call

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Date:   Mon, 10 May 2021 11:53:12 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [RFC v2 PATCH 3/7] x86/syscall: unconditionally prototype {ia32,x32}_sys_call_table[]

From: "H. Peter Anvin (Intel)" <hpa@...or.com>

Even if these APIs are disabled, and the arrays therefore do not
exist, having the prototypes allows us to use IS_ENABLED() rather than
using #ifdefs.

If something ends up trying to actually *use* these arrays a linker
error will ensue.

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
---
 arch/x86/include/asm/syscall.h | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index 4e20054d7533..f6593cafdbd9 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -21,13 +21,12 @@ extern const sys_call_ptr_t sys_call_table[];
 
 #if defined(CONFIG_X86_32)
 #define ia32_sys_call_table sys_call_table
-#endif
-
-#if defined(CONFIG_IA32_EMULATION)
+#else
+/*
+ * These may not exist, but still put the prototypes in so we
+ * can use IS_ENABLED().
+ */
 extern const sys_call_ptr_t ia32_sys_call_table[];
-#endif
-
-#ifdef CONFIG_X86_X32_ABI
 extern const sys_call_ptr_t x32_sys_call_table[];
 #endif
 
-- 
2.31.1