elf.c

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#include <linux/export.h>
#include <linux/sched.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/elf.h>
#include <asm/system_info.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 = current->personality & ~PER_MASK;

    /*
     * We only support Linux ELF executables, so always set the
     * personality to LINUX.
     */
    personality |= PER_LINUX;

    /*
     * APCS-26 is only valid for OABI executables
     */
    if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN &&
        (eflags & EF_ARM_APCS_26))
        personality &= ~ADDR_LIMIT_32BIT;
    else
        personality |= ADDR_LIMIT_32BIT;

    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;
    return 0;
}
EXPORT_SYMBOL(arm_elf_read_implies_exec);