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elf.c

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/elf.h>

int elf_check_arch(const struct elf32_hdr *x)
{
      unsigned int eflags;

      /* Make sure it's an ARM executable */
      if (x->e_machine != EM_ARM)
            return 0;

      /* Make sure the entry address is reasonable */
      if (x->e_entry & 1) {
            if (!(elf_hwcap & HWCAP_THUMB))
                  return 0;
      } else if (x->e_entry & 3)
            return 0;

      eflags = x->e_flags;
      if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
            unsigned int flt_fmt;

            /* APCS26 is only allowed if the CPU supports it */
            if ((eflags & EF_ARM_APCS_26) && !(elf_hwcap & HWCAP_26BIT))
                  return 0;

            flt_fmt = eflags & (EF_ARM_VFP_FLOAT | EF_ARM_SOFT_FLOAT);

            /* VFP requires the supporting code */
            if (flt_fmt == EF_ARM_VFP_FLOAT && !(elf_hwcap & HWCAP_VFP))
                  return 0;
      }
      return 1;
}
EXPORT_SYMBOL(elf_check_arch);

void elf_set_personality(const struct elf32_hdr *x)
{
      unsigned int eflags = x->e_flags;
      unsigned int personality = PER_LINUX_32BIT;

      /*
       * APCS-26 is only valid for OABI executables
       */
      if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
            if (eflags & EF_ARM_APCS_26)
                  personality = PER_LINUX;
      }

      set_personality(personality);

      /*
       * Since the FPA coprocessor uses CP1 and CP2, and iWMMXt uses CP0
       * and CP1, we only enable access to the iWMMXt coprocessor if the
       * binary is EABI or softfloat (and thus, guaranteed not to use
       * FPA instructions.)
       */
      if (elf_hwcap & HWCAP_IWMMXT &&
          eflags & (EF_ARM_EABI_MASK | EF_ARM_SOFT_FLOAT)) {
            set_thread_flag(TIF_USING_IWMMXT);
      } else {
            clear_thread_flag(TIF_USING_IWMMXT);
      }
}
EXPORT_SYMBOL(elf_set_personality);

/*
 * Set READ_IMPLIES_EXEC if:
 *  - the binary requires an executable stack
 *  - we're running on a CPU which doesn't support NX.
 */
int arm_elf_read_implies_exec(const struct elf32_hdr *x, int executable_stack)
{
      if (executable_stack != EXSTACK_DISABLE_X)
            return 1;
      if (cpu_architecture() < CPU_ARCH_ARMv6)
            return 1;
#if !defined(CONFIG_AEABI) || defined(CONFIG_OABI_COMPAT)
      /*
       * If we have support for OABI programs, we can never allow NX
       * support - our signal syscall restart mechanism relies upon
       * being able to execute code placed on the user stack.
       */
      return 1;
#else
      return 0;
#endif
}
EXPORT_SYMBOL(arm_elf_read_implies_exec);

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