arch/arm/kernel/elf.c

   1 #include <linux/export.h>
   2 #include <linux/sched.h>
   3 #include <linux/personality.h>
   4 #include <linux/binfmts.h>
   5 #include <linux/elf.h>
   6 #include <asm/system_info.h>
   7
   8 int elf_check_arch(const struct elf32_hdr *x)
   9 {
  10         unsigned int eflags;
  11
  12         /* Make sure it's an ARM executable */
  13         if (x->e_machine != EM_ARM)
  14                 return 0;
  15
  16         /* Make sure the entry address is reasonable */
  17         if (x->e_entry & 1) {
  18                 if (!(elf_hwcap & HWCAP_THUMB))
  19                         return 0;
  20         } else if (x->e_entry & 3)
  21                 return 0;
  22
  23         eflags = x->e_flags;
  24         if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
  25                 unsigned int flt_fmt;
  26
  27                 /* APCS26 is only allowed if the CPU supports it */
  28                 if ((eflags & EF_ARM_APCS_26) && !(elf_hwcap & HWCAP_26BIT))
  29                         return 0;
  30
  31                 flt_fmt = eflags & (EF_ARM_VFP_FLOAT | EF_ARM_SOFT_FLOAT);
  32
  33                 /* VFP requires the supporting code */
  34                 if (flt_fmt == EF_ARM_VFP_FLOAT && !(elf_hwcap & HWCAP_VFP))
  35                         return 0;
  36         }
  37         return 1;
  38 }
  39 EXPORT_SYMBOL(elf_check_arch);
  40
  41 void elf_set_personality(const struct elf32_hdr *x)
  42 {
  43         unsigned int eflags = x->e_flags;
  44         unsigned int personality = current->personality & ~PER_MASK;
  45
  46         /*
  47          * We only support Linux ELF executables, so always set the
  48          * personality to LINUX.
  49          */
  50         personality |= PER_LINUX;
  51
  52         /*
  53          * APCS-26 is only valid for OABI executables
  54          */
  55         if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN &&
  56             (eflags & EF_ARM_APCS_26))
  57                 personality &= ~ADDR_LIMIT_32BIT;
  58         else
  59                 personality |= ADDR_LIMIT_32BIT;
  60
  61         set_personality(personality);
  62
  63         /*
  64          * Since the FPA coprocessor uses CP1 and CP2, and iWMMXt uses CP0
  65          * and CP1, we only enable access to the iWMMXt coprocessor if the
  66          * binary is EABI or softfloat (and thus, guaranteed not to use
  67          * FPA instructions.)
  68          */
  69         if (elf_hwcap & HWCAP_IWMMXT &&
  70             eflags & (EF_ARM_EABI_MASK | EF_ARM_SOFT_FLOAT)) {
  71                 set_thread_flag(TIF_USING_IWMMXT);
  72         } else {
  73                 clear_thread_flag(TIF_USING_IWMMXT);
  74         }
  75 }
  76 EXPORT_SYMBOL(elf_set_personality);
  77
  78 /*
  79  * Set READ_IMPLIES_EXEC if:
  80  *  - the binary requires an executable stack
  81  *  - we're running on a CPU which doesn't support NX.
  82  */
  83 int arm_elf_read_implies_exec(const struct elf32_hdr *x, int executable_stack)
  84 {
  85         if (executable_stack != EXSTACK_DISABLE_X)
  86                 return 1;
  87         if (cpu_architecture() < CPU_ARCH_ARMv6)
  88                 return 1;
  89         return 0;
  90 }
  91 EXPORT_SYMBOL(arm_elf_read_implies_exec);