1// SPDX-License-Identifier: GPL-2.0
2#include <linux/export.h>
3#include <linux/sched.h>
4#include <linux/personality.h>
5#include <linux/binfmts.h>
6#include <linux/elf.h>
7#include <linux/elf-fdpic.h>
8#include <asm/system_info.h>
9
10int elf_check_arch(const struct elf32_hdr *x)
11{
12	unsigned int eflags;
13
14	/* Make sure it's an ARM executable */
15	if (x->e_machine != EM_ARM)
16		return 0;
17
18	/* Make sure the entry address is reasonable */
19	if (x->e_entry & 1) {
20		if (!(elf_hwcap & HWCAP_THUMB))
21			return 0;
22	} else if (x->e_entry & 3)
23		return 0;
24
25	eflags = x->e_flags;
26	if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
27		unsigned int flt_fmt;
28
29		/* APCS26 is only allowed if the CPU supports it */
30		if ((eflags & EF_ARM_APCS_26) && !(elf_hwcap & HWCAP_26BIT))
31			return 0;
32
33		flt_fmt = eflags & (EF_ARM_VFP_FLOAT | EF_ARM_SOFT_FLOAT);
34
35		/* VFP requires the supporting code */
36		if (flt_fmt == EF_ARM_VFP_FLOAT && !(elf_hwcap & HWCAP_VFP))
37			return 0;
38	}
39	return 1;
40}
41EXPORT_SYMBOL(elf_check_arch);
42
43void elf_set_personality(const struct elf32_hdr *x)
44{
45	unsigned int eflags = x->e_flags;
46	unsigned int personality = current->personality & ~PER_MASK;
47
48	/*
49	 * We only support Linux ELF executables, so always set the
50	 * personality to LINUX.
51	 */
52	personality |= PER_LINUX;
53
54	/*
55	 * APCS-26 is only valid for OABI executables
56	 */
57	if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN &&
58	    (eflags & EF_ARM_APCS_26))
59		personality &= ~ADDR_LIMIT_32BIT;
60	else
61		personality |= ADDR_LIMIT_32BIT;
62
63	set_personality(personality);
64
65	/*
66	 * Since the FPA coprocessor uses CP1 and CP2, and iWMMXt uses CP0
67	 * and CP1, we only enable access to the iWMMXt coprocessor if the
68	 * binary is EABI or softfloat (and thus, guaranteed not to use
69	 * FPA instructions.)
70	 */
71	if (elf_hwcap & HWCAP_IWMMXT &&
72	    eflags & (EF_ARM_EABI_MASK | EF_ARM_SOFT_FLOAT)) {
73		set_thread_flag(TIF_USING_IWMMXT);
74	} else {
75		clear_thread_flag(TIF_USING_IWMMXT);
76	}
77}
78EXPORT_SYMBOL(elf_set_personality);
79
80/*
81 * An executable for which elf_read_implies_exec() returns TRUE will
82 * have the READ_IMPLIES_EXEC personality flag set automatically.
83 *
84 * The decision process for determining the results are:
85 *
86 * �� �� �� �� �� ��    ��CPU: | lacks NX* ��| has NX     |
87 * ELF: �� �� �� ��    �� �� ��| �� �� �� �� �� ��| �� �� �� �� ��  |
88 * ---------------------|------------|------------|
89 * missing PT_GNU_STACK | exec-all �� | exec-all  ��|
90 * PT_GNU_STACK == RWX ��| exec-all �� | exec-stack��|
91 * PT_GNU_STACK == RW �� | exec-all  ��| exec-none  |
92 *
93 *  exec-all  : all PROT_READ user mappings are executable, except when
94 *              backed by files on a noexec-filesystem.
95 *  exec-none : only PROT_EXEC user mappings are executable.
96 *  exec-stack: only the stack and PROT_EXEC user mappings are executable.
97 *
98 *  *this column has no architectural effect: NX markings are ignored by
99 *   hardware, but may have behavioral effects when "wants X" collides with
100 *   "cannot be X" constraints in memory permission flags, as in
101 *   https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com
102 *
103 */
104int arm_elf_read_implies_exec(int executable_stack)
105{
106	if (executable_stack == EXSTACK_DEFAULT)
107		return 1;
108	if (cpu_architecture() < CPU_ARCH_ARMv6)
109		return 1;
110	return 0;
111}
112EXPORT_SYMBOL(arm_elf_read_implies_exec);
113
114#if defined(CONFIG_MMU) && defined(CONFIG_BINFMT_ELF_FDPIC)
115
116void elf_fdpic_arch_lay_out_mm(struct elf_fdpic_params *exec_params,
117			       struct elf_fdpic_params *interp_params,
118			       unsigned long *start_stack,
119			       unsigned long *start_brk)
120{
121	elf_set_personality(&exec_params->hdr);
122
123	exec_params->load_addr = 0x8000;
124	interp_params->load_addr = ELF_ET_DYN_BASE;
125	*start_stack = TASK_SIZE - SZ_16M;
126
127	if ((exec_params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) == ELF_FDPIC_FLAG_INDEPENDENT) {
128		exec_params->flags &= ~ELF_FDPIC_FLAG_ARRANGEMENT;
129		exec_params->flags |= ELF_FDPIC_FLAG_CONSTDISP;
130	}
131}
132
133#endif
134