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
10 int 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 }
41 EXPORT_SYMBOL(elf_check_arch);
42
43 void 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 }
78 EXPORT_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 */
104 int 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 }
112 EXPORT_SYMBOL(arm_elf_read_implies_exec);
113
114 #if defined(CONFIG_MMU) && defined(CONFIG_BINFMT_ELF_FDPIC)
115
116 void 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
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