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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 
16 typedef Elf32_auxv_t elf_auxv_t;
17 
18 /* These are initialized very early in boot and never changed */
19 char * elf_aux_platform;
20 extern long elf_aux_hwcap;
21 unsigned long vsyscall_ehdr;
22 unsigned long vsyscall_end;
23 unsigned long __kernel_vsyscall;
24 
scan_elf_aux(char ** envp)25 __init void scan_elf_aux( char **envp)
26 {
27 	long page_size = 0;
28 	elf_auxv_t * auxv;
29 
30 	while ( *envp++ != NULL) ;
31 
32 	for ( auxv = (elf_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
33 		switch ( auxv->a_type ) {
34 			case AT_SYSINFO:
35 				__kernel_vsyscall = auxv->a_un.a_val;
36 				/* See if the page is under TASK_SIZE */
37 				if (__kernel_vsyscall < (unsigned long) envp)
38 					__kernel_vsyscall = 0;
39 				break;
40 			case AT_SYSINFO_EHDR:
41 				vsyscall_ehdr = auxv->a_un.a_val;
42 				/* See if the page is under TASK_SIZE */
43 				if (vsyscall_ehdr < (unsigned long) envp)
44 					vsyscall_ehdr = 0;
45 				break;
46 			case AT_HWCAP:
47 				elf_aux_hwcap = auxv->a_un.a_val;
48 				break;
49 			case AT_PLATFORM:
50                                 /* elf.h removed the pointer elements from
51                                  * a_un, so we have to use a_val, which is
52                                  * all that's left.
53                                  */
54 				elf_aux_platform =
55 					(char *) (long) auxv->a_un.a_val;
56 				break;
57 			case AT_PAGESZ:
58 				page_size = auxv->a_un.a_val;
59 				break;
60 		}
61 	}
62 	if ( ! __kernel_vsyscall || ! vsyscall_ehdr ||
63 	     ! elf_aux_hwcap || ! elf_aux_platform ||
64 	     ! page_size || (vsyscall_ehdr % page_size) ) {
65 		__kernel_vsyscall = 0;
66 		vsyscall_ehdr = 0;
67 		elf_aux_hwcap = 0;
68 		elf_aux_platform = "i586";
69 	}
70 	else {
71 		vsyscall_end = vsyscall_ehdr + page_size;
72 	}
73 }
74