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