Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755871Ab2EHSX4 (ORCPT ); Tue, 8 May 2012 14:23:56 -0400 Received: from mga01.intel.com ([192.55.52.88]:11241 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755699Ab2EHSXy (ORCPT ); Tue, 8 May 2012 14:23:54 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="150637105" From: Jarkko Sakkinen To: linux-kernel@vger.kernel.org Cc: linux-kbuild@vger.kernel.org, Michal Marek , Sam Ravnborg , Joseph Cihula , Shane Wang , hpa@linux.intel.com Subject: [PATCH 14/23] x86, realmode: Replace open-coded ljmpw with a macro Date: Tue, 8 May 2012 21:22:37 +0300 Message-Id: <1336501366-28617-15-git-send-email-jarkko.sakkinen@intel.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1336501366-28617-1-git-send-email-jarkko.sakkinen@intel.com> References: <1336501366-28617-1-git-send-email-jarkko.sakkinen@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4523 Lines: 156 From: "H. Peter Anvin" We cannot code an ljmpw to the real-mode segment directly, because gas refuses to assemble an ljmp with a symbolic segment. Instead of open-coding it everywhere, define a macro and use it for this case. This is specifically an ljmpw from a 16-bit segment. This is okay, as one should never enter real mode from a 32-bit segment: if one do, the CPU ends up in a bizarre (and useless) mode sometimes called "unreal mode" where segments behave like real mode but the default address and operand sizes is 32 bits. Signed-off-by: H. Peter Anvin --- arch/x86/realmode/rm/realmode.h | 16 ++++++++++++++++ arch/x86/realmode/rm/reboot_32.S | 6 ++---- arch/x86/realmode/rm/trampoline_32.S | 5 ++--- arch/x86/realmode/rm/trampoline_64.S | 5 ++--- arch/x86/realmode/rm/wakeup/wakeup_asm.S | 9 +++------ 5 files changed, 25 insertions(+), 16 deletions(-) create mode 100644 arch/x86/realmode/rm/realmode.h diff --git a/arch/x86/realmode/rm/realmode.h b/arch/x86/realmode/rm/realmode.h new file mode 100644 index 0000000..15ab633 --- /dev/null +++ b/arch/x86/realmode/rm/realmode.h @@ -0,0 +1,16 @@ +#ifndef ARCH_X86_REALMODE_RM_REALMODE_H +#define ARCH_X86_REALMODE_RM_REALMODE_H + +#ifdef __ASSEMBLY__ + +/* + * 16-bit ljmpw to the real_mode_seg + * + * This must be open-coded since gas will choke on using a + * relocatable symbol for the segment portion. + */ +#define LJMPW_RM(to) .byte 0xea ; .word (to), real_mode_seg + +#endif /* __ASSEMBLY__ */ + +#endif /* ARCH_X86_REALMODE_RM_REALMODE_H */ diff --git a/arch/x86/realmode/rm/reboot_32.S b/arch/x86/realmode/rm/reboot_32.S index 83803c2..e90f8c4 100644 --- a/arch/x86/realmode/rm/reboot_32.S +++ b/arch/x86/realmode/rm/reboot_32.S @@ -2,6 +2,7 @@ #include #include #include +#include "realmode.h" /* * The following code and data reboots the machine by switching to real @@ -82,10 +83,7 @@ machine_real_restart_asm16: 2: andb $0x10, %dl movl %edx, %cr0 - .byte 0xea /* ljmpw */ - .word 3f /* Offset */ - .word real_mode_seg /* Segment */ - + LJMPW_RM(3f) 3: testb $0, %al jz bios diff --git a/arch/x86/realmode/rm/trampoline_32.S b/arch/x86/realmode/rm/trampoline_32.S index 1315ef4..279f82e 100644 --- a/arch/x86/realmode/rm/trampoline_32.S +++ b/arch/x86/realmode/rm/trampoline_32.S @@ -29,6 +29,7 @@ #include #include #include +#include "realmode.h" .text .code16 @@ -38,9 +39,7 @@ trampoline_data: wbinvd # Needed for NUMA-Q should be harmless for others - .byte 0xea # ljmpw - .word 1f # Offset - .word real_mode_seg # Segment + LJMPW_RM(1f) 1: mov %cs, %ax # Code and data in the same place mov %ax, %ds diff --git a/arch/x86/realmode/rm/trampoline_64.S b/arch/x86/realmode/rm/trampoline_64.S index 77b72b4..7459c52 100644 --- a/arch/x86/realmode/rm/trampoline_64.S +++ b/arch/x86/realmode/rm/trampoline_64.S @@ -31,6 +31,7 @@ #include #include #include +#include "realmode.h" .text .balign PAGE_SIZE @@ -40,9 +41,7 @@ ENTRY(trampoline_data) cli # We should be safe anyway wbinvd - .byte 0xea # ljmpw - .word 1f # Offset - .word real_mode_seg # Segment + LJMPW_RM(1f) 1: mov %cs, %ax # Code and data in the same place mov %ax, %ds diff --git a/arch/x86/realmode/rm/wakeup/wakeup_asm.S b/arch/x86/realmode/rm/wakeup/wakeup_asm.S index 4c5c5f2..8064e1c 100644 --- a/arch/x86/realmode/rm/wakeup/wakeup_asm.S +++ b/arch/x86/realmode/rm/wakeup/wakeup_asm.S @@ -6,6 +6,7 @@ #include #include #include +#include "../realmode.h" #include "wakeup.h" .code16 @@ -36,9 +37,7 @@ wakeup_start: cli cld - .byte 0xea /* ljmpw */ - .word 3f - .word real_mode_seg + LJMPW_RM(3f) 3: /* Apparently some dimwit BIOS programmers don't know how to program a PM to RM transition, and we might end up here with @@ -59,9 +58,7 @@ wakeup_start: andb $~X86_CR0_PE, %al movl %eax, %cr0 - .byte 0xea /* ljmpw */ - .word 3f - .word real_mode_seg + LJMPW_RM(3f) 3: /* Set up segments */ movw %cs, %ax -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/