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um: Set __HAVE_ARCH_GATE_AREA for i386
When UML is unable to reuse the host's vDSO FIXADDR_USER_START is zero. To handle this special case correclty we have to implement custom gate area helper methods. Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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548f0a4e02
3 changed files with 65 additions and 1 deletions
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@ -4,7 +4,7 @@
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obj-y = bug.o bugs.o checksum.o delay.o fault.o ksyms.o ldt.o ptrace.o \
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ptrace_user.o setjmp.o signal.o stub.o stub_segv.o syscalls.o sysrq.o \
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sys_call_table.o tls.o atomic64_cx8_32.o
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sys_call_table.o tls.o atomic64_cx8_32.o mem.o
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obj-$(CONFIG_BINFMT_ELF) += elfcore.o
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@ -105,6 +105,8 @@ extern unsigned long __kernel_vsyscall;
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#define FIXADDR_USER_START VSYSCALL_BASE
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#define FIXADDR_USER_END VSYSCALL_END
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#define __HAVE_ARCH_GATE_AREA 1
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/*
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* Architecture-neutral AT_ values in 0-17, leave some room
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* for more of them, start the x86-specific ones at 32.
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62
arch/um/sys-i386/mem.c
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62
arch/um/sys-i386/mem.c
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@ -0,0 +1,62 @@
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/*
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* Copyright (C) 2011 Richard Weinberger <richrd@nod.at>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/mm.h>
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#include <asm/page.h>
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#include <asm/mman.h>
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static struct vm_area_struct gate_vma;
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static int __init gate_vma_init(void)
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{
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if (!FIXADDR_USER_START)
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return 0;
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gate_vma.vm_mm = NULL;
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gate_vma.vm_start = FIXADDR_USER_START;
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gate_vma.vm_end = FIXADDR_USER_END;
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gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
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gate_vma.vm_page_prot = __P101;
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/*
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* Make sure the vDSO gets into every core dump.
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* Dumping its contents makes post-mortem fully interpretable later
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* without matching up the same kernel and hardware config to see
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* what PC values meant.
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*/
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gate_vma.vm_flags |= VM_ALWAYSDUMP;
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return 0;
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}
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__initcall(gate_vma_init);
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struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
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{
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return FIXADDR_USER_START ? &gate_vma : NULL;
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}
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int in_gate_area_no_mm(unsigned long addr)
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{
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if (!FIXADDR_USER_START)
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return 0;
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if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
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return 1;
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return 0;
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}
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int in_gate_area(struct mm_struct *mm, unsigned long addr)
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{
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struct vm_area_struct *vma = get_gate_vma(mm);
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if (!vma)
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return 0;
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return (addr >= vma->vm_start) && (addr < vma->vm_end);
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}
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