1/* Copyright 2002,2003 Andi Kleen, SuSE Labs */
2
3/* vsyscall handling for 32bit processes. Map a stub page into it
4   on demand because 32bit cannot reach the kernel's fixmaps */
5
6#include <linux/mm.h>
7#include <linux/string.h>
8#include <linux/kernel.h>
9#include <linux/gfp.h>
10#include <linux/init.h>
11#include <linux/stringify.h>
12#include <linux/security.h>
13#include <asm/proto.h>
14#include <asm/tlbflush.h>
15#include <asm/ia32_unistd.h>
16#include <asm/vsyscall32.h>
17
18extern unsigned char syscall32_syscall[], syscall32_syscall_end[];
19extern unsigned char syscall32_sysenter[], syscall32_sysenter_end[];
20extern int sysctl_vsyscall32;
21
22static struct page *syscall32_pages[1];
23static int use_sysenter = -1;
24
25struct linux_binprm;
26
27/* Setup a VMA at program startup for the vsyscall page */
28int syscall32_setup_pages(struct linux_binprm *bprm, int exstack)
29{
30	struct mm_struct *mm = current->mm;
31	int ret;
32
33	down_write(&mm->mmap_sem);
34	/*
35	 * MAYWRITE to allow gdb to COW and set breakpoints
36	 *
37	 * Make sure the vDSO gets into every core dump.
38	 * Dumping its contents makes post-mortem fully interpretable later
39	 * without matching up the same kernel and hardware config to see
40	 * what PC values meant.
41	 */
42	/* Could randomize here */
43	ret = install_special_mapping(mm, VSYSCALL32_BASE, PAGE_SIZE,
44				      VM_READ|VM_EXEC|
45				      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
46				      VM_ALWAYSDUMP,
47				      syscall32_pages);
48	up_write(&mm->mmap_sem);
49	return ret;
50}
51
52const char *arch_vma_name(struct vm_area_struct *vma)
53{
54	if (vma->vm_start == VSYSCALL32_BASE &&
55	    vma->vm_mm && vma->vm_mm->task_size == IA32_PAGE_OFFSET)
56		return "[vdso]";
57	return NULL;
58}
59
60static int __init init_syscall32(void)
61{
62	char *syscall32_page = (void *)get_zeroed_page(GFP_KERNEL);
63	if (!syscall32_page)
64		panic("Cannot allocate syscall32 page");
65	syscall32_pages[0] = virt_to_page(syscall32_page);
66 	if (use_sysenter > 0) {
67 		memcpy(syscall32_page, syscall32_sysenter,
68 		       syscall32_sysenter_end - syscall32_sysenter);
69 	} else {
70  		memcpy(syscall32_page, syscall32_syscall,
71  		       syscall32_syscall_end - syscall32_syscall);
72  	}
73	return 0;
74}
75
76__initcall(init_syscall32);
77
78/* May not be __init: called during resume */
79void syscall32_cpu_init(void)
80{
81	if (use_sysenter < 0)
82 		use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);
83
84	/* Load these always in case some future AMD CPU supports
85	   SYSENTER from compat mode too. */
86	checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
87	checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
88	checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
89
90	wrmsrl(MSR_CSTAR, ia32_cstar_target);
91}
92