// SPDX-License-Identifier: GPL-2.0
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/elf.h>
#include <linux/elf-fdpic.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);

/*
 * An executable for which elf_read_implies_exec() returns TRUE will
 * have the READ_IMPLIES_EXEC personality flag set automatically.
 *
 * The decision process for determining the results are:
 *
 *                 CPU: | lacks NX*  | has NX     |
 * ELF:                 |            |            |
 * ---------------------|------------|------------|
 * missing PT_GNU_STACK | exec-all   | exec-all   |
 * PT_GNU_STACK == RWX  | exec-all   | exec-stack |
 * PT_GNU_STACK == RW   | exec-all   | exec-none  |
 *
 *  exec-all  : all PROT_READ user mappings are executable, except when
 *              backed by files on a noexec-filesystem.
 *  exec-none : only PROT_EXEC user mappings are executable.
 *  exec-stack: only the stack and PROT_EXEC user mappings are executable.
 *
 *  *this column has no architectural effect: NX markings are ignored by
 *   hardware, but may have behavioral effects when "wants X" collides with
 *   "cannot be X" constraints in memory permission flags, as in
 *   https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com
 *
 */
int arm_elf_read_implies_exec(int executable_stack)
{
        if (executable_stack == EXSTACK_DEFAULT)
                return 1;
        if (cpu_architecture() < CPU_ARCH_ARMv6)
                return 1;
        return 0;
}
EXPORT_SYMBOL(arm_elf_read_implies_exec);

#if defined(CONFIG_MMU) && defined(CONFIG_BINFMT_ELF_FDPIC)

void elf_fdpic_arch_lay_out_mm(struct elf_fdpic_params *exec_params,
                               struct elf_fdpic_params *interp_params,
                               unsigned long *start_stack,
                               unsigned long *start_brk)
{
        elf_set_personality(&exec_params->hdr);

        exec_params->load_addr = 0x8000;
        interp_params->load_addr = ELF_ET_DYN_BASE;
        *start_stack = TASK_SIZE - SZ_16M;

        if ((exec_params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) == ELF_FDPIC_FLAG_INDEPENDENT) {
                exec_params->flags &= ~ELF_FDPIC_FLAG_ARRANGEMENT;
                exec_params->flags |= ELF_FDPIC_FLAG_CONSTDISP;
        }
}

#endif