1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  arch/um/kernel/elf_aux.c
4 *
5 *  Scan the ELF auxiliary vector provided by the host to extract
6 *  information about vsyscall-page, etc.
7 *
8 *  Copyright (C) 2004 Fujitsu Siemens Computers GmbH
9 *  Author: Bodo Stroesser (bodo.stroesser@fujitsu-siemens.com)
10 */
11#include <elf.h>
12#include <stddef.h>
13#include <init.h>
14#include <elf_user.h>
15#include <mem_user.h>
16
17typedef Elf32_auxv_t elf_auxv_t;
18
19/* These are initialized very early in boot and never changed */
20char * elf_aux_platform;
21extern long elf_aux_hwcap;
22unsigned long vsyscall_ehdr;
23unsigned long vsyscall_end;
24unsigned long __kernel_vsyscall;
25
26__init void scan_elf_aux( char **envp)
27{
28	long page_size = 0;
29	elf_auxv_t * auxv;
30
31	while ( *envp++ != NULL) ;
32
33	for ( auxv = (elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
34		switch ( auxv->a_type ) {
35			case AT_SYSINFO:
36				__kernel_vsyscall = auxv->a_un.a_val;
37				/* See if the page is under TASK_SIZE */
38				if (__kernel_vsyscall < (unsigned long) envp)
39					__kernel_vsyscall = 0;
40				break;
41			case AT_SYSINFO_EHDR:
42				vsyscall_ehdr = auxv->a_un.a_val;
43				/* See if the page is under TASK_SIZE */
44				if (vsyscall_ehdr < (unsigned long) envp)
45					vsyscall_ehdr = 0;
46				break;
47			case AT_HWCAP:
48				elf_aux_hwcap = auxv->a_un.a_val;
49				break;
50			case AT_PLATFORM:
51                                /* elf.h removed the pointer elements from
52                                 * a_un, so we have to use a_val, which is
53                                 * all that's left.
54                                 */
55				elf_aux_platform =
56					(char *) (long) auxv->a_un.a_val;
57				break;
58			case AT_PAGESZ:
59				page_size = auxv->a_un.a_val;
60				break;
61		}
62	}
63	if ( ! __kernel_vsyscall || ! vsyscall_ehdr ||
64	     ! elf_aux_hwcap || ! elf_aux_platform ||
65	     ! page_size || (vsyscall_ehdr % page_size) ) {
66		__kernel_vsyscall = 0;
67		vsyscall_ehdr = 0;
68		elf_aux_hwcap = 0;
69		elf_aux_platform = "i586";
70	}
71	else {
72		vsyscall_end = vsyscall_ehdr + page_size;
73	}
74}
75