linux-kernel - [PATCH v4 3/6] x86/entry: Compile entry_SYSCALL32

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Date:   Fri, 23 Jun 2023 14:14:06 +0300
From:   Nikolay Borisov <nik.borisov@...e.com>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, mohocko@...e.com, jslaby@...e.cz,
        Nikolay Borisov <nik.borisov@...e.com>
Subject: [PATCH v4 3/6] x86/entry: Compile entry_SYSCALL32_ignore() unconditionally

To limit the IA32 exposure on 64bit kernels while keeping the
flexibility for the user to enable it when required, the compile time
enable/disable via CONFIG_IA32_EMULATION is not good enough and will
be complemented with a kernel command line option.

Right now entry_SYSCALL32_ignore() is only compiled when
CONFIG_IA32_EMULATION=n, but boot-time enable- / disablement obviously
requires it to be unconditionally available.

Remove the #ifndef CONFIG_IA32_EMULATION guard.

Signed-off-by: Nikolay Borisov <nik.borisov@...e.com>
---
 arch/x86/entry/entry_64.S | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index ccce0ccd8589..7068af44008a 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1514,7 +1514,6 @@ SYM_CODE_START(asm_exc_nmi)
 	iretq
 SYM_CODE_END(asm_exc_nmi)

-#ifndef CONFIG_IA32_EMULATION
 /*
  * This handles SYSCALL from 32-bit code.  There is no way to program
  * MSRs to fully disable 32-bit SYSCALL.
@@ -1525,7 +1524,6 @@ SYM_CODE_START(entry_SYSCALL32_ignore)
 	mov	$-ENOSYS, %eax
 	sysretl
 SYM_CODE_END(entry_SYSCALL32_ignore)
-#endif

 .pushsection .text, "ax"
 	__FUNC_ALIGN
-- 
2.34.1