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14251809b1
This fixes a problem seen by a number of people running UML on newer host kernels. init would hang with an infinite segfault loop. It turns out that the host kernel was providing a AT_SYSINFO_EHDR of 0xffffe000, which faked UML into believing that the host VDSO page could be reused. However, AT_SYSINFO pointed into the middle of the address space, and was unmapped as a result. Because UML was providing AT_SYSINFO_EHDR and AT_SYSINFO to its own processes, these would branch to nowhere when trying to use the VDSO. The fix is to also check the location of AT_SYSINFO when deciding whether to use the host's VDSO. Signed-off-by: Jeff Dike <jdike@addtoit.com> Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
80 lines
2.1 KiB
C
80 lines
2.1 KiB
C
/*
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* arch/um/kernel/elf_aux.c
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*
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* Scan the Elf auxiliary vector provided by the host to extract
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* information about vsyscall-page, etc.
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*
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* Copyright (C) 2004 Fujitsu Siemens Computers GmbH
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* Author: Bodo Stroesser (bodo.stroesser@fujitsu-siemens.com)
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*/
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#include <elf.h>
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#include <stddef.h>
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#include "init.h"
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#include "elf_user.h"
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#include "mem_user.h"
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#include <kern_constants.h>
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/* Use the one from the kernel - the host may miss it, if having old headers. */
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#if UM_ELF_CLASS == UM_ELFCLASS32
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typedef Elf32_auxv_t elf_auxv_t;
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#else
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typedef Elf64_auxv_t elf_auxv_t;
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#endif
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/* These are initialized very early in boot and never changed */
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char * elf_aux_platform;
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long elf_aux_hwcap;
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unsigned long vsyscall_ehdr;
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unsigned long vsyscall_end;
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unsigned long __kernel_vsyscall;
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__init void scan_elf_aux( char **envp)
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{
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long page_size = 0;
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elf_auxv_t * auxv;
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while ( *envp++ != NULL) ;
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for ( auxv = (elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
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switch ( auxv->a_type ) {
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case AT_SYSINFO:
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__kernel_vsyscall = auxv->a_un.a_val;
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/* See if the page is under TASK_SIZE */
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if (__kernel_vsyscall < (unsigned long) envp)
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__kernel_vsyscall = 0;
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break;
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case AT_SYSINFO_EHDR:
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vsyscall_ehdr = auxv->a_un.a_val;
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/* See if the page is under TASK_SIZE */
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if (vsyscall_ehdr < (unsigned long) envp)
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vsyscall_ehdr = 0;
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break;
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case AT_HWCAP:
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elf_aux_hwcap = auxv->a_un.a_val;
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break;
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case AT_PLATFORM:
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/* elf.h removed the pointer elements from
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* a_un, so we have to use a_val, which is
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* all that's left.
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*/
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elf_aux_platform =
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(char *) (long) auxv->a_un.a_val;
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break;
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case AT_PAGESZ:
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page_size = auxv->a_un.a_val;
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break;
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}
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}
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if ( ! __kernel_vsyscall || ! vsyscall_ehdr ||
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! elf_aux_hwcap || ! elf_aux_platform ||
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! page_size || (vsyscall_ehdr % page_size) ) {
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__kernel_vsyscall = 0;
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vsyscall_ehdr = 0;
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elf_aux_hwcap = 0;
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elf_aux_platform = "i586";
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}
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else {
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vsyscall_end = vsyscall_ehdr + page_size;
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}
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}
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