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 <asm/system_info.h>
   8
   9 int elf_check_arch(const struct elf32_hdr *x)
  10 {
  11         unsigned int eflags;
  12
  13         /* Make sure it's an ARM executable */
  14         if (x->e_machine != EM_ARM)
  15                 return 0;
  16
  17         /* Make sure the entry address is reasonable */
  18         if (x->e_entry & 1) {
  19                 if (!(elf_hwcap & HWCAP_THUMB))
  20                         return 0;
  21         } else if (x->e_entry & 3)
  22                 return 0;
  23
  24         eflags = x->e_flags;
  25         if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
  26                 unsigned int flt_fmt;
  27
  28                 /* APCS26 is only allowed if the CPU supports it */
  29                 if ((eflags & EF_ARM_APCS_26) && !(elf_hwcap & HWCAP_26BIT))
  30                         return 0;
  31
  32                 flt_fmt = eflags & (EF_ARM_VFP_FLOAT | EF_ARM_SOFT_FLOAT);
  33
  34                 /* VFP requires the supporting code */
  35                 if (flt_fmt == EF_ARM_VFP_FLOAT && !(elf_hwcap & HWCAP_VFP))
  36                         return 0;
  37         }
  38         return 1;
  39 }
  40 EXPORT_SYMBOL(elf_check_arch);
  41
  42 void elf_set_personality(const struct elf32_hdr *x)
  43 {
  44         unsigned int eflags = x->e_flags;
  45         unsigned int personality = current->personality & ~PER_MASK;
  46
  47         /*
  48          * We only support Linux ELF executables, so always set the
  49          * personality to LINUX.
  50          */
  51         personality |= PER_LINUX;
  52
  53         /*
  54          * APCS-26 is only valid for OABI executables
  55          */
  56         if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN &&
  57             (eflags & EF_ARM_APCS_26))
  58                 personality &= ~ADDR_LIMIT_32BIT;
  59         else
  60                 personality |= ADDR_LIMIT_32BIT;
  61
  62         set_personality(personality);
  63
  64         /*
  65          * Since the FPA coprocessor uses CP1 and CP2, and iWMMXt uses CP0
  66          * and CP1, we only enable access to the iWMMXt coprocessor if the
  67          * binary is EABI or softfloat (and thus, guaranteed not to use
  68          * FPA instructions.)
  69          */
  70         if (elf_hwcap & HWCAP_IWMMXT &&
  71             eflags & (EF_ARM_EABI_MASK | EF_ARM_SOFT_FLOAT)) {
  72                 set_thread_flag(TIF_USING_IWMMXT);
  73         } else {
  74                 clear_thread_flag(TIF_USING_IWMMXT);
  75         }
  76 }
  77 EXPORT_SYMBOL(elf_set_personality);
  78
  79 /*
  80  * Set READ_IMPLIES_EXEC if:
  81  *  - the binary requires an executable stack
  82  *  - we're running on a CPU which doesn't support NX.
  83  */
  84 int arm_elf_read_implies_exec(const struct elf32_hdr *x, int executable_stack)
  85 {
  86         if (executable_stack != EXSTACK_DISABLE_X)
  87                 return 1;
  88         if (cpu_architecture() < CPU_ARCH_ARMv6)
  89                 return 1;
  90         return 0;
  91 }
  92 EXPORT_SYMBOL(arm_elf_read_implies_exec);