cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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elf.c (3926B)

      1// SPDX-License-Identifier: GPL-2.0
      2#include <linux/export.h>
      3#include <linux/sched.h>
      4#include <linux/personality.h>
      5#include <linux/binfmts.h>
      6#include <linux/elf.h>
      7#include <linux/elf-fdpic.h>
      8#include <asm/system_info.h>
      9
     10int elf_check_arch(const struct elf32_hdr *x)
     11{
     12	unsigned int eflags;
     13
     14	/* Make sure it's an ARM executable */
     15	if (x->e_machine != EM_ARM)
     16		return 0;
     17
     18	/* Make sure the entry address is reasonable */
     19	if (x->e_entry & 1) {
     20		if (!(elf_hwcap & HWCAP_THUMB))
     21			return 0;
     22	} else if (x->e_entry & 3)
     23		return 0;
     24
     25	eflags = x->e_flags;
     26	if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
     27		unsigned int flt_fmt;
     28
     29		/* APCS26 is only allowed if the CPU supports it */
     30		if ((eflags & EF_ARM_APCS_26) && !(elf_hwcap & HWCAP_26BIT))
     31			return 0;
     32
     33		flt_fmt = eflags & (EF_ARM_VFP_FLOAT | EF_ARM_SOFT_FLOAT);
     34
     35		/* VFP requires the supporting code */
     36		if (flt_fmt == EF_ARM_VFP_FLOAT && !(elf_hwcap & HWCAP_VFP))
     37			return 0;
     38	}
     39	return 1;
     40}
     41EXPORT_SYMBOL(elf_check_arch);
     42
     43void elf_set_personality(const struct elf32_hdr *x)
     44{
     45	unsigned int eflags = x->e_flags;
     46	unsigned int personality = current->personality & ~PER_MASK;
     47
     48	/*
     49	 * We only support Linux ELF executables, so always set the
     50	 * personality to LINUX.
     51	 */
     52	personality |= PER_LINUX;
     53
     54	/*
     55	 * APCS-26 is only valid for OABI executables
     56	 */
     57	if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN &&
     58	    (eflags & EF_ARM_APCS_26))
     59		personality &= ~ADDR_LIMIT_32BIT;
     60	else
     61		personality |= ADDR_LIMIT_32BIT;
     62
     63	set_personality(personality);
     64
     65	/*
     66	 * Since the FPA coprocessor uses CP1 and CP2, and iWMMXt uses CP0
     67	 * and CP1, we only enable access to the iWMMXt coprocessor if the
     68	 * binary is EABI or softfloat (and thus, guaranteed not to use
     69	 * FPA instructions.)
     70	 */
     71	if (elf_hwcap & HWCAP_IWMMXT &&
     72	    eflags & (EF_ARM_EABI_MASK | EF_ARM_SOFT_FLOAT)) {
     73		set_thread_flag(TIF_USING_IWMMXT);
     74	} else {
     75		clear_thread_flag(TIF_USING_IWMMXT);
     76	}
     77}
     78EXPORT_SYMBOL(elf_set_personality);
     79
     80/*
     81 * An executable for which elf_read_implies_exec() returns TRUE will
     82 * have the READ_IMPLIES_EXEC personality flag set automatically.
     83 *
     84 * The decision process for determining the results are:
     85 *
     86 *                 CPU: | lacks NX*  | has NX     |
     87 * ELF:                 |            |            |
     88 * ---------------------|------------|------------|
     89 * missing PT_GNU_STACK | exec-all   | exec-all   |
     90 * PT_GNU_STACK == RWX  | exec-all   | exec-stack |
     91 * PT_GNU_STACK == RW   | exec-all   | exec-none  |
     92 *
     93 *  exec-all  : all PROT_READ user mappings are executable, except when
     94 *              backed by files on a noexec-filesystem.
     95 *  exec-none : only PROT_EXEC user mappings are executable.
     96 *  exec-stack: only the stack and PROT_EXEC user mappings are executable.
     97 *
     98 *  *this column has no architectural effect: NX markings are ignored by
     99 *   hardware, but may have behavioral effects when "wants X" collides with
    100 *   "cannot be X" constraints in memory permission flags, as in
    101 *   https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com
    102 *
    103 */
    104int arm_elf_read_implies_exec(int executable_stack)
    105{
    106	if (executable_stack == EXSTACK_DEFAULT)
    107		return 1;
    108	if (cpu_architecture() < CPU_ARCH_ARMv6)
    109		return 1;
    110	return 0;
    111}
    112EXPORT_SYMBOL(arm_elf_read_implies_exec);
    113
    114#if defined(CONFIG_MMU) && defined(CONFIG_BINFMT_ELF_FDPIC)
    115
    116void elf_fdpic_arch_lay_out_mm(struct elf_fdpic_params *exec_params,
    117			       struct elf_fdpic_params *interp_params,
    118			       unsigned long *start_stack,
    119			       unsigned long *start_brk)
    120{
    121	elf_set_personality(&exec_params->hdr);
    122
    123	exec_params->load_addr = 0x8000;
    124	interp_params->load_addr = ELF_ET_DYN_BASE;
    125	*start_stack = TASK_SIZE - SZ_16M;
    126
    127	if ((exec_params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) == ELF_FDPIC_FLAG_INDEPENDENT) {
    128		exec_params->flags &= ~ELF_FDPIC_FLAG_ARRANGEMENT;
    129		exec_params->flags |= ELF_FDPIC_FLAG_CONSTDISP;
    130	}
    131}
    132
    133#endif