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/* Copyright 2002,2003 Andi Kleen, SuSE Labs */
/* vsyscall handling for 32bit processes. Map a stub page into it
on demand because 32bit cannot reach the kernel's fixmaps */
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/stringify.h>
#include <asm/proto.h>
#include <asm/tlbflush.h>
#include <asm/ia32_unistd.h>
/* 32bit VDSOs mapped into user space. */
asm(".section \".init.data\",\"aw\"\n"
"syscall32_syscall:\n"
".incbin \"arch/x86_64/ia32/vsyscall-syscall.so\"\n"
"syscall32_syscall_end:\n"
"syscall32_sysenter:\n"
".incbin \"arch/x86_64/ia32/vsyscall-sysenter.so\"\n"
"syscall32_sysenter_end:\n"
".previous");
extern unsigned char syscall32_syscall[], syscall32_syscall_end[];
extern unsigned char syscall32_sysenter[], syscall32_sysenter_end[];
extern int sysctl_vsyscall32;
char *syscall32_page;
static int use_sysenter = -1;
/*
* Map the 32bit vsyscall page on demand.
*
* RED-PEN: This knows too much about high level VM.
*
* Alternative would be to generate a vma with appropriate backing options
* and let it be handled by generic VM.
*/
int __map_syscall32(struct mm_struct *mm, unsigned long address)
{
pgd_t *pgd;
pud_t *pud;
pte_t *pte;
pmd_t *pmd;
int err = -ENOMEM;
spin_lock(&mm->page_table_lock);
pgd = pgd_offset(mm, address);
pud = pud_alloc(mm, pgd, address);
if (pud) {
pmd = pmd_alloc(mm, pud, address);
if (pmd && (pte = pte_alloc_map(mm, pmd, address)) != NULL) {
if (pte_none(*pte)) {
set_pte(pte,
mk_pte(virt_to_page(syscall32_page),
PAGE_KERNEL_VSYSCALL32));
}
/* Flush only the local CPU. Other CPUs taking a fault
will just end up here again
This probably not needed and just paranoia. */
__flush_tlb_one(address);
err = 0;
}
}
spin_unlock(&mm->page_table_lock);
return err;
}
int map_syscall32(struct mm_struct *mm, unsigned long address)
{
int err;
down_read(&mm->mmap_sem);
err = __map_syscall32(mm, address);
up_read(&mm->mmap_sem);
return err;
}
static int __init init_syscall32(void)
{
syscall32_page = (void *)get_zeroed_page(GFP_KERNEL);
if (!syscall32_page)
panic("Cannot allocate syscall32 page");
SetPageReserved(virt_to_page(syscall32_page));
if (use_sysenter > 0) {
memcpy(syscall32_page, syscall32_sysenter,
syscall32_sysenter_end - syscall32_sysenter);
} else {
memcpy(syscall32_page, syscall32_syscall,
syscall32_syscall_end - syscall32_syscall);
}
return 0;
}
__initcall(init_syscall32);
/* May not be __init: called during resume */
void syscall32_cpu_init(void)
{
if (use_sysenter < 0)
use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);
/* Load these always in case some future AMD CPU supports
SYSENTER from compat mode too. */
checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
wrmsrl(MSR_CSTAR, ia32_cstar_target);
}
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