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Message-Id: <20070428175853.EF2B5151CA@wotan.suse.de> Date: Sat, 28 Apr 2007 19:58:53 +0200 (CEST) From: Andi Kleen <ak@...e.de> To: Vivek Goyal <vgoyal@...ibm.com>, linux-kernel@...r.kernel.org, patches@...-64.org Subject: [PATCH] [7/22] x86_64: cleanup segments From: Vivek Goyal <vgoyal@...ibm.com> Move __KERNEL32_CS up into the unused gdt entry. __KERNEL32_CS is used when entering the kernel so putting it first is useful when trying to keep boot gdt sizes to a minimum. Set the accessed bit on all gdt entries. We don't care so there is no need for the cpu to burn the extra cycles, and it potentially allows the pages to be immutable. Plus it is confusing when debugging and your gdt entries mysteriously change. Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com> Signed-off-by: Vivek Goyal <vgoyal@...ibm.com> Signed-off-by: Andi Kleen <ak@...e.de> --- arch/x86_64/kernel/head.S | 12 ++++++------ include/asm-x86_64/segment.h | 2 +- 2 files changed, 7 insertions(+), 7 deletions(-) Index: linux/arch/x86_64/kernel/head.S =================================================================== --- linux.orig/arch/x86_64/kernel/head.S +++ linux/arch/x86_64/kernel/head.S @@ -362,13 +362,13 @@ gdt: ENTRY(cpu_gdt_table) .quad 0x0000000000000000 /* NULL descriptor */ + .quad 0x00cf9b000000ffff /* __KERNEL32_CS */ + .quad 0x00af9b000000ffff /* __KERNEL_CS */ + .quad 0x00cf93000000ffff /* __KERNEL_DS */ + .quad 0x00cffb000000ffff /* __USER32_CS */ + .quad 0x00cff3000000ffff /* __USER_DS, __USER32_DS */ + .quad 0x00affb000000ffff /* __USER_CS */ .quad 0x0 /* unused */ - .quad 0x00af9a000000ffff /* __KERNEL_CS */ - .quad 0x00cf92000000ffff /* __KERNEL_DS */ - .quad 0x00cffa000000ffff /* __USER32_CS */ - .quad 0x00cff2000000ffff /* __USER_DS, __USER32_DS */ - .quad 0x00affa000000ffff /* __USER_CS */ - .quad 0x00cf9a000000ffff /* __KERNEL32_CS */ .quad 0,0 /* TSS */ .quad 0,0 /* LDT */ .quad 0,0,0 /* three TLS descriptors */ Index: linux/include/asm-x86_64/segment.h =================================================================== --- linux.orig/include/asm-x86_64/segment.h +++ linux/include/asm-x86_64/segment.h @@ -6,7 +6,7 @@ #define __KERNEL_CS 0x10 #define __KERNEL_DS 0x18 -#define __KERNEL32_CS 0x38 +#define __KERNEL32_CS 0x08 /* * we cannot use the same code segment descriptor for user and kernel - 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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