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-all | 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 * 97 * *this column has no architectural effect: NX markings are ignored by 98 * hardware, but may have behavioral effects when "wants X" collides with 99 * "cannot be X" constraints in memory permission flags, as in 100 * https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com 101 * 102 */ 103 int arm_elf_read_implies_exec(int executable_stack) 104 { 105 if (executable_stack != EXSTACK_DISABLE_X) 106 return 1; 107 if (cpu_architecture() < CPU_ARCH_ARMv6) 108 return 1; 109 return 0; 110 } 111 EXPORT_SYMBOL(arm_elf_read_implies_exec); 112 113 #if defined(CONFIG_MMU) && defined(CONFIG_BINFMT_ELF_FDPIC) 114 115 void elf_fdpic_arch_lay_out_mm(struct elf_fdpic_params *exec_params, 116 struct elf_fdpic_params *interp_params, 117 unsigned long *start_stack, 118 unsigned long *start_brk) 119 { 120 elf_set_personality(&exec_params->hdr); 121 122 exec_params->load_addr = 0x8000; 123 interp_params->load_addr = ELF_ET_DYN_BASE; 124 *start_stack = TASK_SIZE - SZ_16M; 125 126 if ((exec_params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) == ELF_FDPIC_FLAG_INDEPENDENT) { 127 exec_params->flags &= ~ELF_FDPIC_FLAG_ARRANGEMENT; 128 exec_params->flags |= ELF_FDPIC_FLAG_CONSTDISP; 129 } 130 } 131 132 #endif 133