LXR linux/arch/arm/kernel/elf.c

   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 * Set READ_IMPLIES_EXEC if:
  82 *  - the binary requires an executable stack
  83 *  - we're running on a CPU which doesn't support NX.
  84 */
  85int arm_elf_read_implies_exec(int executable_stack)
  86{
  87        if (executable_stack != EXSTACK_DISABLE_X)
  88                return 1;
  89        if (cpu_architecture() < CPU_ARCH_ARMv6)
  90                return 1;
  91        return 0;
  92}
  93EXPORT_SYMBOL(arm_elf_read_implies_exec);
  94
  95#if defined(CONFIG_MMU) && defined(CONFIG_BINFMT_ELF_FDPIC)
  96
  97void elf_fdpic_arch_lay_out_mm(struct elf_fdpic_params *exec_params,
  98                               struct elf_fdpic_params *interp_params,
  99                               unsigned long *start_stack,
 100                               unsigned long *start_brk)
 101{
 102        elf_set_personality(&exec_params->hdr);
 103
 104        exec_params->load_addr = 0x8000;
 105        interp_params->load_addr = ELF_ET_DYN_BASE;
 106        *start_stack = TASK_SIZE - SZ_16M;
 107
 108        if ((exec_params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) == ELF_FDPIC_FLAG_INDEPENDENT) {
 109                exec_params->flags &= ~ELF_FDPIC_FLAG_ARRANGEMENT;
 110                exec_params->flags |= ELF_FDPIC_FLAG_CONSTDISP;
 111        }
 112}
 113
 114#endif
 115