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Message-ID: <tip-e5684ec438a094bec0f7d5c52652c0901b48b613@git.kernel.org> Date: Tue, 8 May 2012 15:24:58 -0700 From: "tip-bot for H. Peter Anvin" <hpa@...ux.intel.com> To: linux-tip-commits@...r.kernel.org Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org, tglx@...utronix.de, hpa@...ux.intel.com Subject: [tip:x86/trampoline] x86, realmode: Replace open-coded ljmpw with a macro Commit-ID: e5684ec438a094bec0f7d5c52652c0901b48b613 Gitweb: http://git.kernel.org/tip/e5684ec438a094bec0f7d5c52652c0901b48b613 Author: H. Peter Anvin <hpa@...ux.intel.com> AuthorDate: Tue, 8 May 2012 21:22:37 +0300 Committer: H. Peter Anvin <hpa@...ux.intel.com> CommitDate: Tue, 8 May 2012 11:48:03 -0700 x86, realmode: Replace open-coded ljmpw with a macro 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 <hpa@...ux.intel.com> Link: http://lkml.kernel.org/r/1336501366-28617-15-git-send-email-jarkko.sakkinen@intel.com --- 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(-) 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 <linux/init.h> #include <asm/segment.h> #include <asm/page_types.h> +#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 <linux/init.h> #include <asm/segment.h> #include <asm/page_types.h> +#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 <asm/msr.h> #include <asm/segment.h> #include <asm/processor-flags.h> +#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 <asm/page_types.h> #include <asm/pgtable_types.h> #include <asm/processor-flags.h> +#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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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