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um: Set __HAVE_ARCH_GATE_AREA for i386

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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>
This commit is contained in:
Richard Weinberger 2011-07-25 17:12:53 -07:00 committed by Linus Torvalds
parent b743ac54e5
commit 548f0a4e02
3 changed files with 65 additions and 1 deletions
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2
arch/um/sys-i386/Makefile
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@ -4,7 +4,7 @@
obj-y = bug.o bugs.o checksum.o delay.o fault.o ksyms.o ldt.o ptrace.o \
ptrace_user.o setjmp.o signal.o stub.o stub_segv.o syscalls.o sysrq.o \
sys_call_table.o tls.o atomic64_cx8_32.o
sys_call_table.o tls.o atomic64_cx8_32.o mem.o
obj-$(CONFIG_BINFMT_ELF) += elfcore.o

2
arch/um/sys-i386/asm/elf.h
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@ -105,6 +105,8 @@ extern unsigned long __kernel_vsyscall;
#define FIXADDR_USER_START VSYSCALL_BASE
#define FIXADDR_USER_END VSYSCALL_END
#define __HAVE_ARCH_GATE_AREA 1
/*
* Architecture-neutral AT_ values in 0-17, leave some room
* for more of them, start the x86-specific ones at 32.

62
arch/um/sys-i386/mem.c Normal file
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@ -0,0 +1,62 @@
/*
* Copyright (C) 2011 Richard Weinberger <richrd@nod.at>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/mm.h>
#include <asm/page.h>
#include <asm/mman.h>
static struct vm_area_struct gate_vma;
static int __init gate_vma_init(void)
{
if (!FIXADDR_USER_START)
return 0;
gate_vma.vm_mm = NULL;
gate_vma.vm_start = FIXADDR_USER_START;
gate_vma.vm_end = FIXADDR_USER_END;
gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
gate_vma.vm_page_prot = __P101;
/*
* Make sure the vDSO gets into every core dump.
* Dumping its contents makes post-mortem fully interpretable later
* without matching up the same kernel and hardware config to see
* what PC values meant.
*/
gate_vma.vm_flags |= VM_ALWAYSDUMP;
return 0;
}
__initcall(gate_vma_init);
struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
{
return FIXADDR_USER_START ? &gate_vma : NULL;
}
int in_gate_area_no_mm(unsigned long addr)
{
if (!FIXADDR_USER_START)
return 0;
if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
return 1;
return 0;
}
int in_gate_area(struct mm_struct *mm, unsigned long addr)
{
struct vm_area_struct *vma = get_gate_vma(mm);
if (!vma)
return 0;
return (addr >= vma->vm_start) && (addr < vma->vm_end);
}