/arch/um/os-Linux/elf_aux.c

 1/*
 2 *  arch/um/kernel/elf_aux.c
 3 *
 4 *  Scan the Elf auxiliary vector provided by the host to extract
 5 *  information about vsyscall-page, etc.
 6 *
 7 *  Copyright (C) 2004 Fujitsu Siemens Computers GmbH
 8 *  Author: Bodo Stroesser (bodo.stroesser@fujitsu-siemens.com)
 9 */
10#include <elf.h>
11#include <stddef.h>
12#include "init.h"
13#include "elf_user.h"
14#include "mem_user.h"
15#include <kern_constants.h>
16
17/* Use the one from the kernel - the host may miss it, if having old headers. */
18#if UM_ELF_CLASS == UM_ELFCLASS32
19typedef Elf32_auxv_t elf_auxv_t;
20#else
21typedef Elf64_auxv_t elf_auxv_t;
22#endif
23
24/* These are initialized very early in boot and never changed */
25char * elf_aux_platform;
26long elf_aux_hwcap;
27unsigned long vsyscall_ehdr;
28unsigned long vsyscall_end;
29unsigned long __kernel_vsyscall;
30
31__init void scan_elf_aux( char **envp)
32{
33	long page_size = 0;
34	elf_auxv_t * auxv;
35
36	while ( *envp++ != NULL) ;
37
38	for ( auxv = (elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
39		switch ( auxv->a_type ) {
40			case AT_SYSINFO:
41				__kernel_vsyscall = auxv->a_un.a_val;
42				/* See if the page is under TASK_SIZE */
43				if (__kernel_vsyscall < (unsigned long) envp)
44					__kernel_vsyscall = 0;
45				break;
46			case AT_SYSINFO_EHDR:
47				vsyscall_ehdr = auxv->a_un.a_val;
48				/* See if the page is under TASK_SIZE */
49				if (vsyscall_ehdr < (unsigned long) envp)
50					vsyscall_ehdr = 0;
51				break;
52			case AT_HWCAP:
53				elf_aux_hwcap = auxv->a_un.a_val;
54				break;
55			case AT_PLATFORM:
56                                /* elf.h removed the pointer elements from
57                                 * a_un, so we have to use a_val, which is
58                                 * all that's left.
59                                 */
60				elf_aux_platform =
61					(char *) (long) auxv->a_un.a_val;
62				break;
63			case AT_PAGESZ:
64				page_size = auxv->a_un.a_val;
65				break;
66		}
67	}
68	if ( ! __kernel_vsyscall || ! vsyscall_ehdr ||
69	     ! elf_aux_hwcap || ! elf_aux_platform ||
70	     ! page_size || (vsyscall_ehdr % page_size) ) {
71		__kernel_vsyscall = 0;
72		vsyscall_ehdr = 0;
73		elf_aux_hwcap = 0;
74		elf_aux_platform = "i586";
75	}
76	else {
77		vsyscall_end = vsyscall_ehdr + page_size;
78	}
79}