diff options
Diffstat (limited to 'arch/arm/kernel/elf.c')
| -rw-r--r-- | arch/arm/kernel/elf.c | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/arch/arm/kernel/elf.c b/arch/arm/kernel/elf.c new file mode 100644 index 000000000..254ab7138 --- /dev/null +++ b/arch/arm/kernel/elf.c @@ -0,0 +1,133 @@ +// 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 |