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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/um/os-Linux/elf_aux.c
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/*

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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 ([email protected])

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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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