elf_aux.c

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/*
 *  arch/um/kernel/elf_aux.c
 *
 *  Scan the Elf auxiliary vector provided by the host to extract
 *  information about vsyscall-page, etc.
 *
 *  Copyright (C) 2004 Fujitsu Siemens Computers GmbH
 *  Author: Bodo Stroesser ([email protected])
 */
#include <elf.h>
#include <stddef.h>
#include <init.h>
#include <elf_user.h>
#include <mem_user.h>

typedef Elf32_auxv_t elf_auxv_t;

/* These are initialized very early in boot and never changed */
char * elf_aux_platform;
extern long elf_aux_hwcap;
unsigned long vsyscall_ehdr;
unsigned long vsyscall_end;
unsigned long __kernel_vsyscall;

__init void scan_elf_aux( char **envp)
{
    long page_size = 0;
    elf_auxv_t * auxv;

    while ( *envp++ != NULL) ;

    for ( auxv = (elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
        switch ( auxv->a_type ) {
            case AT_SYSINFO:
                __kernel_vsyscall = auxv->a_un.a_val;
                /* See if the page is under TASK_SIZE */
                if (__kernel_vsyscall < (unsigned long) envp)
                    __kernel_vsyscall = 0;
                break;
            case AT_SYSINFO_EHDR:
                vsyscall_ehdr = auxv->a_un.a_val;
                /* See if the page is under TASK_SIZE */
                if (vsyscall_ehdr < (unsigned long) envp)
                    vsyscall_ehdr = 0;
                break;
            case AT_HWCAP:
                elf_aux_hwcap = auxv->a_un.a_val;
                break;
            case AT_PLATFORM:
                                /* elf.h removed the pointer elements from
                                 * a_un, so we have to use a_val, which is
                                 * all that's left.
                                 */
                elf_aux_platform =
                    (char *) (long) auxv->a_un.a_val;
                break;
            case AT_PAGESZ:
                page_size = auxv->a_un.a_val;
                break;
        }
    }
    if ( ! __kernel_vsyscall || ! vsyscall_ehdr ||
         ! elf_aux_hwcap || ! elf_aux_platform ||
         ! page_size || (vsyscall_ehdr % page_size) ) {
        __kernel_vsyscall = 0;
        vsyscall_ehdr = 0;
        elf_aux_hwcap = 0;
        elf_aux_platform = "i586";
    }
    else {
        vsyscall_end = vsyscall_ehdr + page_size;
    }
}