linux/arch/i386
Zachary Amsden f2f30ebca6 [PATCH] x86: introduce a write acessor for updating the current LDT
Introduce a write acessor for updating the current LDT.  This is required
for hypervisors like Xen that do not allow LDT pages to be directly
written.

Testing - here's a fun little LDT test that can be trivially modified to
test limits as well.

/*
 * Copyright (c) 2005, Zachary Amsden (zach@vmware.com)
 * This is licensed under the GPL.
 */

#include <stdio.h>
#include <signal.h>
#include <asm/ldt.h>
#include <asm/segment.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/mman.h>
#define __KERNEL__
#include <asm/page.h>

void main(void)
{
        struct user_desc desc;
        char *code;
        unsigned long long tsc;

        code = (char *)mmap(0, 8192, PROT_EXEC|PROT_READ|PROT_WRITE,
                                 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
        desc.entry_number = 0;
        desc.base_addr = code;
        desc.limit = 1;
        desc.seg_32bit = 1;
        desc.contents = MODIFY_LDT_CONTENTS_CODE;
        desc.read_exec_only = 0;
        desc.limit_in_pages = 1;
        desc.seg_not_present = 0;
        desc.useable = 1;
        if (modify_ldt(1, &desc, sizeof(desc)) != 0) {
                perror("modify_ldt");
        }
        printf("code base is 0x%08x\n", (unsigned)code);
        code[0x0ffe] = 0x0f;  /* rdtsc */
        code[0x0fff] = 0x31;
        code[0x1000] = 0xcb;  /* lret */
        __asm__ __volatile("lcall $7,$0xffe" : "=A" (tsc));
        printf("TSC is 0x%016llx\n", tsc);
}

Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-05 00:06:13 -07:00
..
boot [PATCH] coverity: i386: build.c: negative return to unsigned fix 2005-06-28 21:20:33 -07:00
crypto [PATCH] arch/i386/crypto/aes.c: fix sparse warnings 2005-06-25 16:24:59 -07:00
kernel [PATCH] x86: introduce a write acessor for updating the current LDT 2005-09-05 00:06:13 -07:00
lib [PATCH] Remove i386_ksyms.c, almost. 2005-06-23 09:45:11 -07:00
mach-default [PATCH] x86_64: CPU hotplug support 2005-06-25 16:24:30 -07:00
mach-es7000 [PATCH] ES7000 platform update (i386) 2005-09-05 00:06:10 -07:00
mach-generic [PATCH] x86: sutomatically enable bigsmp when we have more than 8 CPUs 2005-09-05 00:06:10 -07:00
mach-visws [PATCH] visws: linkage fix 2005-08-07 10:00:38 -07:00
mach-voyager [PATCH] x86: more asm cleanups 2005-09-05 00:06:12 -07:00
math-emu [PATCH] i386: inline assembler: cleanup and encapsulate descriptor and task register management 2005-09-05 00:06:11 -07:00
mm [PATCH] i386: use set_pte macros in a couple places where they were missing 2005-09-05 00:06:12 -07:00
oprofile [PATCH] xen: x86: Rename usermode macro 2005-06-23 09:45:14 -07:00
pci [PATCH] x86: pci_assign_unassigned_resources() update 2005-08-30 11:14:48 -07:00
power [PATCH] x86: remove redundant TSS clearing 2005-09-05 00:06:13 -07:00
defconfig [PATCH] swsusp: kill config_pm_disk 2005-06-25 16:24:32 -07:00
Kconfig [PATCH] sparsemem extreme implementation 2005-09-05 00:05:38 -07:00
Kconfig.debug [PATCH] i386: add missing Kconfig help text 2005-07-27 16:25:58 -07:00
Makefile [PATCH] biarch compiler support for i386 2005-06-23 09:45:07 -07:00