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 
17 typedef Elf32_auxv_t elf_auxv_t;
18 
19 /* These are initialized very early in boot and never changed */
20 char * elf_aux_platform;
21 extern long elf_aux_hwcap;
22 unsigned long vsyscall_ehdr;
23 unsigned long vsyscall_end;
24 unsigned long __kernel_vsyscall;
25 
scan_elf_aux(char ** envp)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