arch/arm/kernel/elf.c

   1 #include <linux/module.h>
   2 #include <linux/sched.h>
   3 #include <linux/personality.h>
   4 #include <linux/binfmts.h>
   5 #include <linux/elf.h>
   6
   7 int elf_check_arch(const struct elf32_hdr *x)
   8 {
   9         unsigned int eflags;
  10
  11         /* Make sure it's an ARM executable */
  12         if (x->e_machine != EM_ARM)
  13                 return 0;
  14
  15         /* Make sure the entry address is reasonable */
  16         if (x->e_entry & 1) {
  17                 if (!(elf_hwcap & HWCAP_THUMB))
  18                         return 0;
  19         } else if (x->e_entry & 3)
  20                 return 0;
  21
  22         eflags = x->e_flags;
  23         if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
  24                 unsigned int flt_fmt;
  25
  26                 /* APCS26 is only allowed if the CPU supports it */
  27                 if ((eflags & EF_ARM_APCS_26) && !(elf_hwcap & HWCAP_26BIT))
  28                         return 0;
  29
  30                 flt_fmt = eflags & (EF_ARM_VFP_FLOAT | EF_ARM_SOFT_FLOAT);
  31
  32                 /* VFP requires the supporting code */
  33                 if (flt_fmt == EF_ARM_VFP_FLOAT && !(elf_hwcap & HWCAP_VFP))
  34                         return 0;
  35         }
  36         return 1;
  37 }
  38 EXPORT_SYMBOL(elf_check_arch);
  39
  40 void elf_set_personality(const struct elf32_hdr *x)
  41 {
  42         unsigned int eflags = x->e_flags;
  43         unsigned int personality = PER_LINUX_32BIT;
  44
  45         /*
  46          * APCS-26 is only valid for OABI executables
  47          */
  48         if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
  49                 if (eflags & EF_ARM_APCS_26)
  50                         personality = PER_LINUX;
  51         }
  52
  53         set_personality(personality);
  54
  55         /*
  56          * Since the FPA coprocessor uses CP1 and CP2, and iWMMXt uses CP0
  57          * and CP1, we only enable access to the iWMMXt coprocessor if the
  58          * binary is EABI or softfloat (and thus, guaranteed not to use
  59          * FPA instructions.)
  60          */
  61         if (elf_hwcap & HWCAP_IWMMXT &&
  62             eflags & (EF_ARM_EABI_MASK | EF_ARM_SOFT_FLOAT)) {
  63                 set_thread_flag(TIF_USING_IWMMXT);
  64         } else {
  65                 clear_thread_flag(TIF_USING_IWMMXT);
  66         }
  67 }
  68 EXPORT_SYMBOL(elf_set_personality);
  69
  70 /*
  71  * Set READ_IMPLIES_EXEC if:
  72  *  - the binary requires an executable stack
  73  *  - we're running on a CPU which doesn't support NX.
  74  */
  75 int arm_elf_read_implies_exec(const struct elf32_hdr *x, int executable_stack)
  76 {
  77         if (executable_stack != EXSTACK_DISABLE_X)
  78                 return 1;
  79         if (cpu_architecture() < CPU_ARCH_ARMv6)
  80                 return 1;
  81 #if !defined(CONFIG_AEABI) || defined(CONFIG_OABI_COMPAT)
  82         /*
  83          * If we have support for OABI programs, we can never allow NX
  84          * support - our signal syscall restart mechanism relies upon
  85          * being able to execute code placed on the user stack.
  86          */
  87         return 1;
  88 #else
  89         return 0;
  90 #endif
  91 }
  92 EXPORT_SYMBOL(arm_elf_read_implies_exec);