1122 lines
28 KiB
C
1122 lines
28 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#define pr_fmt(fmt) "SMP alternatives: " fmt
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/mutex.h>
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#include <linux/list.h>
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#include <linux/stringify.h>
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#include <linux/mm.h>
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#include <linux/vmalloc.h>
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#include <linux/memory.h>
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#include <linux/stop_machine.h>
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#include <linux/slab.h>
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#include <linux/kdebug.h>
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#include <linux/kprobes.h>
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#include <linux/mmu_context.h>
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#include <linux/bsearch.h>
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#include <asm/text-patching.h>
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#include <asm/alternative.h>
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#include <asm/sections.h>
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#include <asm/pgtable.h>
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#include <asm/mce.h>
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#include <asm/nmi.h>
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#include <asm/cacheflush.h>
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#include <asm/tlbflush.h>
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#include <asm/io.h>
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#include <asm/fixmap.h>
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int __read_mostly alternatives_patched;
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EXPORT_SYMBOL_GPL(alternatives_patched);
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#define MAX_PATCH_LEN (255-1)
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static int __initdata_or_module debug_alternative;
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static int __init debug_alt(char *str)
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{
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debug_alternative = 1;
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return 1;
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}
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__setup("debug-alternative", debug_alt);
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static int noreplace_smp;
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static int __init setup_noreplace_smp(char *str)
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{
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noreplace_smp = 1;
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return 1;
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}
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__setup("noreplace-smp", setup_noreplace_smp);
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#define DPRINTK(fmt, args...) \
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do { \
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if (debug_alternative) \
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printk(KERN_DEBUG "%s: " fmt "\n", __func__, ##args); \
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} while (0)
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#define DUMP_BYTES(buf, len, fmt, args...) \
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do { \
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if (unlikely(debug_alternative)) { \
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int j; \
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\
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if (!(len)) \
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break; \
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\
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printk(KERN_DEBUG fmt, ##args); \
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for (j = 0; j < (len) - 1; j++) \
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printk(KERN_CONT "%02hhx ", buf[j]); \
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printk(KERN_CONT "%02hhx\n", buf[j]); \
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} \
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} while (0)
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/*
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* Each GENERIC_NOPX is of X bytes, and defined as an array of bytes
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* that correspond to that nop. Getting from one nop to the next, we
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* add to the array the offset that is equal to the sum of all sizes of
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* nops preceding the one we are after.
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*
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* Note: The GENERIC_NOP5_ATOMIC is at the end, as it breaks the
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* nice symmetry of sizes of the previous nops.
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*/
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#if defined(GENERIC_NOP1) && !defined(CONFIG_X86_64)
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static const unsigned char intelnops[] =
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{
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GENERIC_NOP1,
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GENERIC_NOP2,
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GENERIC_NOP3,
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GENERIC_NOP4,
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GENERIC_NOP5,
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GENERIC_NOP6,
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GENERIC_NOP7,
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GENERIC_NOP8,
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GENERIC_NOP5_ATOMIC
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};
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static const unsigned char * const intel_nops[ASM_NOP_MAX+2] =
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{
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NULL,
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intelnops,
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intelnops + 1,
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intelnops + 1 + 2,
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intelnops + 1 + 2 + 3,
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intelnops + 1 + 2 + 3 + 4,
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intelnops + 1 + 2 + 3 + 4 + 5,
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intelnops + 1 + 2 + 3 + 4 + 5 + 6,
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intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
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intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
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};
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#endif
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#ifdef K8_NOP1
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static const unsigned char k8nops[] =
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{
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K8_NOP1,
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K8_NOP2,
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K8_NOP3,
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K8_NOP4,
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K8_NOP5,
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K8_NOP6,
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K8_NOP7,
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K8_NOP8,
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K8_NOP5_ATOMIC
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};
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static const unsigned char * const k8_nops[ASM_NOP_MAX+2] =
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{
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NULL,
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k8nops,
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k8nops + 1,
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k8nops + 1 + 2,
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k8nops + 1 + 2 + 3,
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k8nops + 1 + 2 + 3 + 4,
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k8nops + 1 + 2 + 3 + 4 + 5,
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k8nops + 1 + 2 + 3 + 4 + 5 + 6,
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k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
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k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
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};
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#endif
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#if defined(K7_NOP1) && !defined(CONFIG_X86_64)
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static const unsigned char k7nops[] =
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{
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K7_NOP1,
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K7_NOP2,
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K7_NOP3,
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K7_NOP4,
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K7_NOP5,
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K7_NOP6,
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K7_NOP7,
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K7_NOP8,
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K7_NOP5_ATOMIC
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};
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static const unsigned char * const k7_nops[ASM_NOP_MAX+2] =
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{
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NULL,
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k7nops,
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k7nops + 1,
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k7nops + 1 + 2,
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k7nops + 1 + 2 + 3,
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k7nops + 1 + 2 + 3 + 4,
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k7nops + 1 + 2 + 3 + 4 + 5,
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k7nops + 1 + 2 + 3 + 4 + 5 + 6,
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k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
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k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
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};
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#endif
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#ifdef P6_NOP1
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static const unsigned char p6nops[] =
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{
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P6_NOP1,
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P6_NOP2,
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P6_NOP3,
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P6_NOP4,
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P6_NOP5,
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P6_NOP6,
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P6_NOP7,
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P6_NOP8,
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P6_NOP5_ATOMIC
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};
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static const unsigned char * const p6_nops[ASM_NOP_MAX+2] =
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{
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NULL,
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p6nops,
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p6nops + 1,
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p6nops + 1 + 2,
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p6nops + 1 + 2 + 3,
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p6nops + 1 + 2 + 3 + 4,
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p6nops + 1 + 2 + 3 + 4 + 5,
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p6nops + 1 + 2 + 3 + 4 + 5 + 6,
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p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
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p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
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};
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#endif
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/* Initialize these to a safe default */
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#ifdef CONFIG_X86_64
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const unsigned char * const *ideal_nops = p6_nops;
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#else
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const unsigned char * const *ideal_nops = intel_nops;
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#endif
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void __init arch_init_ideal_nops(void)
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{
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switch (boot_cpu_data.x86_vendor) {
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case X86_VENDOR_INTEL:
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/*
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* Due to a decoder implementation quirk, some
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* specific Intel CPUs actually perform better with
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* the "k8_nops" than with the SDM-recommended NOPs.
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*/
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if (boot_cpu_data.x86 == 6 &&
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boot_cpu_data.x86_model >= 0x0f &&
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boot_cpu_data.x86_model != 0x1c &&
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boot_cpu_data.x86_model != 0x26 &&
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boot_cpu_data.x86_model != 0x27 &&
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boot_cpu_data.x86_model < 0x30) {
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ideal_nops = k8_nops;
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} else if (boot_cpu_has(X86_FEATURE_NOPL)) {
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ideal_nops = p6_nops;
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} else {
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#ifdef CONFIG_X86_64
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ideal_nops = k8_nops;
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#else
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ideal_nops = intel_nops;
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#endif
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}
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break;
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case X86_VENDOR_HYGON:
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ideal_nops = p6_nops;
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return;
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case X86_VENDOR_AMD:
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if (boot_cpu_data.x86 > 0xf) {
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ideal_nops = p6_nops;
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return;
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}
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/* fall through */
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default:
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#ifdef CONFIG_X86_64
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ideal_nops = k8_nops;
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#else
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if (boot_cpu_has(X86_FEATURE_K8))
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ideal_nops = k8_nops;
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else if (boot_cpu_has(X86_FEATURE_K7))
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ideal_nops = k7_nops;
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else
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ideal_nops = intel_nops;
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#endif
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}
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}
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/* Use this to add nops to a buffer, then text_poke the whole buffer. */
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static void __init_or_module add_nops(void *insns, unsigned int len)
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{
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while (len > 0) {
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unsigned int noplen = len;
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if (noplen > ASM_NOP_MAX)
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noplen = ASM_NOP_MAX;
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memcpy(insns, ideal_nops[noplen], noplen);
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insns += noplen;
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len -= noplen;
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}
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}
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extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
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extern s32 __smp_locks[], __smp_locks_end[];
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void text_poke_early(void *addr, const void *opcode, size_t len);
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/*
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* Are we looking at a near JMP with a 1 or 4-byte displacement.
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*/
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static inline bool is_jmp(const u8 opcode)
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{
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return opcode == 0xeb || opcode == 0xe9;
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}
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static void __init_or_module
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recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insn_buff)
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{
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u8 *next_rip, *tgt_rip;
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s32 n_dspl, o_dspl;
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int repl_len;
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if (a->replacementlen != 5)
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return;
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o_dspl = *(s32 *)(insn_buff + 1);
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/* next_rip of the replacement JMP */
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next_rip = repl_insn + a->replacementlen;
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/* target rip of the replacement JMP */
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tgt_rip = next_rip + o_dspl;
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n_dspl = tgt_rip - orig_insn;
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DPRINTK("target RIP: %px, new_displ: 0x%x", tgt_rip, n_dspl);
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if (tgt_rip - orig_insn >= 0) {
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if (n_dspl - 2 <= 127)
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goto two_byte_jmp;
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else
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goto five_byte_jmp;
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/* negative offset */
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} else {
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if (((n_dspl - 2) & 0xff) == (n_dspl - 2))
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goto two_byte_jmp;
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else
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goto five_byte_jmp;
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}
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two_byte_jmp:
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n_dspl -= 2;
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insn_buff[0] = 0xeb;
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insn_buff[1] = (s8)n_dspl;
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add_nops(insn_buff + 2, 3);
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repl_len = 2;
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goto done;
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five_byte_jmp:
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n_dspl -= 5;
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insn_buff[0] = 0xe9;
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*(s32 *)&insn_buff[1] = n_dspl;
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repl_len = 5;
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done:
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DPRINTK("final displ: 0x%08x, JMP 0x%lx",
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n_dspl, (unsigned long)orig_insn + n_dspl + repl_len);
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}
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/*
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* "noinline" to cause control flow change and thus invalidate I$ and
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* cause refetch after modification.
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*/
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static void __init_or_module noinline optimize_nops(struct alt_instr *a, u8 *instr)
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{
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unsigned long flags;
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int i;
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for (i = 0; i < a->padlen; i++) {
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if (instr[i] != 0x90)
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return;
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}
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local_irq_save(flags);
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add_nops(instr + (a->instrlen - a->padlen), a->padlen);
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local_irq_restore(flags);
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DUMP_BYTES(instr, a->instrlen, "%px: [%d:%d) optimized NOPs: ",
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instr, a->instrlen - a->padlen, a->padlen);
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}
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/*
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* Replace instructions with better alternatives for this CPU type. This runs
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* before SMP is initialized to avoid SMP problems with self modifying code.
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* This implies that asymmetric systems where APs have less capabilities than
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* the boot processor are not handled. Tough. Make sure you disable such
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* features by hand.
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*
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* Marked "noinline" to cause control flow change and thus insn cache
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* to refetch changed I$ lines.
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*/
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void __init_or_module noinline apply_alternatives(struct alt_instr *start,
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struct alt_instr *end)
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{
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struct alt_instr *a;
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u8 *instr, *replacement;
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u8 insn_buff[MAX_PATCH_LEN];
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DPRINTK("alt table %px, -> %px", start, end);
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/*
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* The scan order should be from start to end. A later scanned
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* alternative code can overwrite previously scanned alternative code.
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* Some kernel functions (e.g. memcpy, memset, etc) use this order to
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* patch code.
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*
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* So be careful if you want to change the scan order to any other
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* order.
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*/
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for (a = start; a < end; a++) {
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int insn_buff_sz = 0;
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instr = (u8 *)&a->instr_offset + a->instr_offset;
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replacement = (u8 *)&a->repl_offset + a->repl_offset;
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BUG_ON(a->instrlen > sizeof(insn_buff));
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BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
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if (!boot_cpu_has(a->cpuid)) {
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if (a->padlen > 1)
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optimize_nops(a, instr);
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continue;
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}
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DPRINTK("feat: %d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d), pad: %d",
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a->cpuid >> 5,
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a->cpuid & 0x1f,
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instr, instr, a->instrlen,
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replacement, a->replacementlen, a->padlen);
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DUMP_BYTES(instr, a->instrlen, "%px: old_insn: ", instr);
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DUMP_BYTES(replacement, a->replacementlen, "%px: rpl_insn: ", replacement);
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memcpy(insn_buff, replacement, a->replacementlen);
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insn_buff_sz = a->replacementlen;
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/*
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* 0xe8 is a relative jump; fix the offset.
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*
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* Instruction length is checked before the opcode to avoid
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* accessing uninitialized bytes for zero-length replacements.
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*/
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if (a->replacementlen == 5 && *insn_buff == 0xe8) {
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*(s32 *)(insn_buff + 1) += replacement - instr;
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DPRINTK("Fix CALL offset: 0x%x, CALL 0x%lx",
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*(s32 *)(insn_buff + 1),
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(unsigned long)instr + *(s32 *)(insn_buff + 1) + 5);
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}
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if (a->replacementlen && is_jmp(replacement[0]))
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recompute_jump(a, instr, replacement, insn_buff);
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if (a->instrlen > a->replacementlen) {
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add_nops(insn_buff + a->replacementlen,
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a->instrlen - a->replacementlen);
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insn_buff_sz += a->instrlen - a->replacementlen;
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}
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DUMP_BYTES(insn_buff, insn_buff_sz, "%px: final_insn: ", instr);
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text_poke_early(instr, insn_buff, insn_buff_sz);
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}
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}
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#ifdef CONFIG_SMP
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static void alternatives_smp_lock(const s32 *start, const s32 *end,
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u8 *text, u8 *text_end)
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{
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const s32 *poff;
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for (poff = start; poff < end; poff++) {
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u8 *ptr = (u8 *)poff + *poff;
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if (!*poff || ptr < text || ptr >= text_end)
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continue;
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/* turn DS segment override prefix into lock prefix */
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if (*ptr == 0x3e)
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text_poke(ptr, ((unsigned char []){0xf0}), 1);
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}
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}
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static void alternatives_smp_unlock(const s32 *start, const s32 *end,
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u8 *text, u8 *text_end)
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{
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const s32 *poff;
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for (poff = start; poff < end; poff++) {
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u8 *ptr = (u8 *)poff + *poff;
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if (!*poff || ptr < text || ptr >= text_end)
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continue;
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/* turn lock prefix into DS segment override prefix */
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if (*ptr == 0xf0)
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text_poke(ptr, ((unsigned char []){0x3E}), 1);
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}
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}
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struct smp_alt_module {
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/* what is this ??? */
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struct module *mod;
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char *name;
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/* ptrs to lock prefixes */
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const s32 *locks;
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const s32 *locks_end;
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/* .text segment, needed to avoid patching init code ;) */
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u8 *text;
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u8 *text_end;
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struct list_head next;
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};
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static LIST_HEAD(smp_alt_modules);
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static bool uniproc_patched = false; /* protected by text_mutex */
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void __init_or_module alternatives_smp_module_add(struct module *mod,
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char *name,
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void *locks, void *locks_end,
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void *text, void *text_end)
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{
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struct smp_alt_module *smp;
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mutex_lock(&text_mutex);
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if (!uniproc_patched)
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goto unlock;
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if (num_possible_cpus() == 1)
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/* Don't bother remembering, we'll never have to undo it. */
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goto smp_unlock;
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smp = kzalloc(sizeof(*smp), GFP_KERNEL);
|
|
if (NULL == smp)
|
|
/* we'll run the (safe but slow) SMP code then ... */
|
|
goto unlock;
|
|
|
|
smp->mod = mod;
|
|
smp->name = name;
|
|
smp->locks = locks;
|
|
smp->locks_end = locks_end;
|
|
smp->text = text;
|
|
smp->text_end = text_end;
|
|
DPRINTK("locks %p -> %p, text %p -> %p, name %s\n",
|
|
smp->locks, smp->locks_end,
|
|
smp->text, smp->text_end, smp->name);
|
|
|
|
list_add_tail(&smp->next, &smp_alt_modules);
|
|
smp_unlock:
|
|
alternatives_smp_unlock(locks, locks_end, text, text_end);
|
|
unlock:
|
|
mutex_unlock(&text_mutex);
|
|
}
|
|
|
|
void __init_or_module alternatives_smp_module_del(struct module *mod)
|
|
{
|
|
struct smp_alt_module *item;
|
|
|
|
mutex_lock(&text_mutex);
|
|
list_for_each_entry(item, &smp_alt_modules, next) {
|
|
if (mod != item->mod)
|
|
continue;
|
|
list_del(&item->next);
|
|
kfree(item);
|
|
break;
|
|
}
|
|
mutex_unlock(&text_mutex);
|
|
}
|
|
|
|
void alternatives_enable_smp(void)
|
|
{
|
|
struct smp_alt_module *mod;
|
|
|
|
/* Why bother if there are no other CPUs? */
|
|
BUG_ON(num_possible_cpus() == 1);
|
|
|
|
mutex_lock(&text_mutex);
|
|
|
|
if (uniproc_patched) {
|
|
pr_info("switching to SMP code\n");
|
|
BUG_ON(num_online_cpus() != 1);
|
|
clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
|
|
clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
|
|
list_for_each_entry(mod, &smp_alt_modules, next)
|
|
alternatives_smp_lock(mod->locks, mod->locks_end,
|
|
mod->text, mod->text_end);
|
|
uniproc_patched = false;
|
|
}
|
|
mutex_unlock(&text_mutex);
|
|
}
|
|
|
|
/*
|
|
* Return 1 if the address range is reserved for SMP-alternatives.
|
|
* Must hold text_mutex.
|
|
*/
|
|
int alternatives_text_reserved(void *start, void *end)
|
|
{
|
|
struct smp_alt_module *mod;
|
|
const s32 *poff;
|
|
u8 *text_start = start;
|
|
u8 *text_end = end;
|
|
|
|
lockdep_assert_held(&text_mutex);
|
|
|
|
list_for_each_entry(mod, &smp_alt_modules, next) {
|
|
if (mod->text > text_end || mod->text_end < text_start)
|
|
continue;
|
|
for (poff = mod->locks; poff < mod->locks_end; poff++) {
|
|
const u8 *ptr = (const u8 *)poff + *poff;
|
|
|
|
if (text_start <= ptr && text_end > ptr)
|
|
return 1;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
#ifdef CONFIG_PARAVIRT
|
|
void __init_or_module apply_paravirt(struct paravirt_patch_site *start,
|
|
struct paravirt_patch_site *end)
|
|
{
|
|
struct paravirt_patch_site *p;
|
|
char insn_buff[MAX_PATCH_LEN];
|
|
|
|
for (p = start; p < end; p++) {
|
|
unsigned int used;
|
|
|
|
BUG_ON(p->len > MAX_PATCH_LEN);
|
|
/* prep the buffer with the original instructions */
|
|
memcpy(insn_buff, p->instr, p->len);
|
|
used = pv_ops.init.patch(p->type, insn_buff, (unsigned long)p->instr, p->len);
|
|
|
|
BUG_ON(used > p->len);
|
|
|
|
/* Pad the rest with nops */
|
|
add_nops(insn_buff + used, p->len - used);
|
|
text_poke_early(p->instr, insn_buff, p->len);
|
|
}
|
|
}
|
|
extern struct paravirt_patch_site __start_parainstructions[],
|
|
__stop_parainstructions[];
|
|
#endif /* CONFIG_PARAVIRT */
|
|
|
|
/*
|
|
* Self-test for the INT3 based CALL emulation code.
|
|
*
|
|
* This exercises int3_emulate_call() to make sure INT3 pt_regs are set up
|
|
* properly and that there is a stack gap between the INT3 frame and the
|
|
* previous context. Without this gap doing a virtual PUSH on the interrupted
|
|
* stack would corrupt the INT3 IRET frame.
|
|
*
|
|
* See entry_{32,64}.S for more details.
|
|
*/
|
|
|
|
/*
|
|
* We define the int3_magic() function in assembly to control the calling
|
|
* convention such that we can 'call' it from assembly.
|
|
*/
|
|
|
|
extern void int3_magic(unsigned int *ptr); /* defined in asm */
|
|
|
|
asm (
|
|
" .pushsection .init.text, \"ax\", @progbits\n"
|
|
" .type int3_magic, @function\n"
|
|
"int3_magic:\n"
|
|
" movl $1, (%" _ASM_ARG1 ")\n"
|
|
" ret\n"
|
|
" .size int3_magic, .-int3_magic\n"
|
|
" .popsection\n"
|
|
);
|
|
|
|
extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */
|
|
|
|
static int __init
|
|
int3_exception_notify(struct notifier_block *self, unsigned long val, void *data)
|
|
{
|
|
struct die_args *args = data;
|
|
struct pt_regs *regs = args->regs;
|
|
|
|
if (!regs || user_mode(regs))
|
|
return NOTIFY_DONE;
|
|
|
|
if (val != DIE_INT3)
|
|
return NOTIFY_DONE;
|
|
|
|
if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip)
|
|
return NOTIFY_DONE;
|
|
|
|
int3_emulate_call(regs, (unsigned long)&int3_magic);
|
|
return NOTIFY_STOP;
|
|
}
|
|
|
|
static void __init int3_selftest(void)
|
|
{
|
|
static __initdata struct notifier_block int3_exception_nb = {
|
|
.notifier_call = int3_exception_notify,
|
|
.priority = INT_MAX-1, /* last */
|
|
};
|
|
unsigned int val = 0;
|
|
|
|
BUG_ON(register_die_notifier(&int3_exception_nb));
|
|
|
|
/*
|
|
* Basically: int3_magic(&val); but really complicated :-)
|
|
*
|
|
* Stick the address of the INT3 instruction into int3_selftest_ip,
|
|
* then trigger the INT3, padded with NOPs to match a CALL instruction
|
|
* length.
|
|
*/
|
|
asm volatile ("1: int3; nop; nop; nop; nop\n\t"
|
|
".pushsection .init.data,\"aw\"\n\t"
|
|
".align " __ASM_SEL(4, 8) "\n\t"
|
|
".type int3_selftest_ip, @object\n\t"
|
|
".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t"
|
|
"int3_selftest_ip:\n\t"
|
|
__ASM_SEL(.long, .quad) " 1b\n\t"
|
|
".popsection\n\t"
|
|
: ASM_CALL_CONSTRAINT
|
|
: __ASM_SEL_RAW(a, D) (&val)
|
|
: "memory");
|
|
|
|
BUG_ON(val != 1);
|
|
|
|
unregister_die_notifier(&int3_exception_nb);
|
|
}
|
|
|
|
void __init alternative_instructions(void)
|
|
{
|
|
int3_selftest();
|
|
|
|
/*
|
|
* The patching is not fully atomic, so try to avoid local
|
|
* interruptions that might execute the to be patched code.
|
|
* Other CPUs are not running.
|
|
*/
|
|
stop_nmi();
|
|
|
|
/*
|
|
* Don't stop machine check exceptions while patching.
|
|
* MCEs only happen when something got corrupted and in this
|
|
* case we must do something about the corruption.
|
|
* Ignoring it is worse than an unlikely patching race.
|
|
* Also machine checks tend to be broadcast and if one CPU
|
|
* goes into machine check the others follow quickly, so we don't
|
|
* expect a machine check to cause undue problems during to code
|
|
* patching.
|
|
*/
|
|
|
|
#if defined(CONFIG_NUMA_AWARE_SPINLOCKS)
|
|
cna_configure_spin_lock_slowpath();
|
|
#endif
|
|
|
|
apply_alternatives(__alt_instructions, __alt_instructions_end);
|
|
|
|
#ifdef CONFIG_SMP
|
|
/* Patch to UP if other cpus not imminent. */
|
|
if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) {
|
|
uniproc_patched = true;
|
|
alternatives_smp_module_add(NULL, "core kernel",
|
|
__smp_locks, __smp_locks_end,
|
|
_text, _etext);
|
|
}
|
|
|
|
if (!uniproc_patched || num_possible_cpus() == 1) {
|
|
free_init_pages("SMP alternatives",
|
|
(unsigned long)__smp_locks,
|
|
(unsigned long)__smp_locks_end);
|
|
}
|
|
#endif
|
|
|
|
apply_paravirt(__parainstructions, __parainstructions_end);
|
|
|
|
restart_nmi();
|
|
alternatives_patched = 1;
|
|
}
|
|
|
|
/**
|
|
* text_poke_early - Update instructions on a live kernel at boot time
|
|
* @addr: address to modify
|
|
* @opcode: source of the copy
|
|
* @len: length to copy
|
|
*
|
|
* When you use this code to patch more than one byte of an instruction
|
|
* you need to make sure that other CPUs cannot execute this code in parallel.
|
|
* Also no thread must be currently preempted in the middle of these
|
|
* instructions. And on the local CPU you need to be protected against NMI or
|
|
* MCE handlers seeing an inconsistent instruction while you patch.
|
|
*/
|
|
void __init_or_module text_poke_early(void *addr, const void *opcode,
|
|
size_t len)
|
|
{
|
|
unsigned long flags;
|
|
|
|
if (boot_cpu_has(X86_FEATURE_NX) &&
|
|
is_module_text_address((unsigned long)addr)) {
|
|
/*
|
|
* Modules text is marked initially as non-executable, so the
|
|
* code cannot be running and speculative code-fetches are
|
|
* prevented. Just change the code.
|
|
*/
|
|
memcpy(addr, opcode, len);
|
|
} else {
|
|
local_irq_save(flags);
|
|
memcpy(addr, opcode, len);
|
|
local_irq_restore(flags);
|
|
sync_core();
|
|
|
|
/*
|
|
* Could also do a CLFLUSH here to speed up CPU recovery; but
|
|
* that causes hangs on some VIA CPUs.
|
|
*/
|
|
}
|
|
}
|
|
|
|
__ro_after_init struct mm_struct *poking_mm;
|
|
__ro_after_init unsigned long poking_addr;
|
|
|
|
static void *__text_poke(void *addr, const void *opcode, size_t len)
|
|
{
|
|
bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE;
|
|
struct page *pages[2] = {NULL};
|
|
temp_mm_state_t prev;
|
|
unsigned long flags;
|
|
pte_t pte, *ptep;
|
|
spinlock_t *ptl;
|
|
pgprot_t pgprot;
|
|
|
|
/*
|
|
* While boot memory allocator is running we cannot use struct pages as
|
|
* they are not yet initialized. There is no way to recover.
|
|
*/
|
|
BUG_ON(!after_bootmem);
|
|
|
|
if (!core_kernel_text((unsigned long)addr)) {
|
|
pages[0] = vmalloc_to_page(addr);
|
|
if (cross_page_boundary)
|
|
pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
|
|
} else {
|
|
pages[0] = virt_to_page(addr);
|
|
WARN_ON(!PageReserved(pages[0]));
|
|
if (cross_page_boundary)
|
|
pages[1] = virt_to_page(addr + PAGE_SIZE);
|
|
}
|
|
/*
|
|
* If something went wrong, crash and burn since recovery paths are not
|
|
* implemented.
|
|
*/
|
|
BUG_ON(!pages[0] || (cross_page_boundary && !pages[1]));
|
|
|
|
local_irq_save(flags);
|
|
|
|
/*
|
|
* Map the page without the global bit, as TLB flushing is done with
|
|
* flush_tlb_mm_range(), which is intended for non-global PTEs.
|
|
*/
|
|
pgprot = __pgprot(pgprot_val(PAGE_KERNEL) & ~_PAGE_GLOBAL);
|
|
|
|
/*
|
|
* The lock is not really needed, but this allows to avoid open-coding.
|
|
*/
|
|
ptep = get_locked_pte(poking_mm, poking_addr, &ptl);
|
|
|
|
/*
|
|
* This must not fail; preallocated in poking_init().
|
|
*/
|
|
VM_BUG_ON(!ptep);
|
|
|
|
pte = mk_pte(pages[0], pgprot);
|
|
set_pte_at(poking_mm, poking_addr, ptep, pte);
|
|
|
|
if (cross_page_boundary) {
|
|
pte = mk_pte(pages[1], pgprot);
|
|
set_pte_at(poking_mm, poking_addr + PAGE_SIZE, ptep + 1, pte);
|
|
}
|
|
|
|
/*
|
|
* Loading the temporary mm behaves as a compiler barrier, which
|
|
* guarantees that the PTE will be set at the time memcpy() is done.
|
|
*/
|
|
prev = use_temporary_mm(poking_mm);
|
|
|
|
kasan_disable_current();
|
|
memcpy((u8 *)poking_addr + offset_in_page(addr), opcode, len);
|
|
kasan_enable_current();
|
|
|
|
/*
|
|
* Ensure that the PTE is only cleared after the instructions of memcpy
|
|
* were issued by using a compiler barrier.
|
|
*/
|
|
barrier();
|
|
|
|
pte_clear(poking_mm, poking_addr, ptep);
|
|
if (cross_page_boundary)
|
|
pte_clear(poking_mm, poking_addr + PAGE_SIZE, ptep + 1);
|
|
|
|
/*
|
|
* Loading the previous page-table hierarchy requires a serializing
|
|
* instruction that already allows the core to see the updated version.
|
|
* Xen-PV is assumed to serialize execution in a similar manner.
|
|
*/
|
|
unuse_temporary_mm(prev);
|
|
|
|
/*
|
|
* Flushing the TLB might involve IPIs, which would require enabled
|
|
* IRQs, but not if the mm is not used, as it is in this point.
|
|
*/
|
|
flush_tlb_mm_range(poking_mm, poking_addr, poking_addr +
|
|
(cross_page_boundary ? 2 : 1) * PAGE_SIZE,
|
|
PAGE_SHIFT, false);
|
|
|
|
/*
|
|
* If the text does not match what we just wrote then something is
|
|
* fundamentally screwy; there's nothing we can really do about that.
|
|
*/
|
|
BUG_ON(memcmp(addr, opcode, len));
|
|
|
|
pte_unmap_unlock(ptep, ptl);
|
|
local_irq_restore(flags);
|
|
return addr;
|
|
}
|
|
|
|
/**
|
|
* text_poke - Update instructions on a live kernel
|
|
* @addr: address to modify
|
|
* @opcode: source of the copy
|
|
* @len: length to copy
|
|
*
|
|
* Only atomic text poke/set should be allowed when not doing early patching.
|
|
* It means the size must be writable atomically and the address must be aligned
|
|
* in a way that permits an atomic write. It also makes sure we fit on a single
|
|
* page.
|
|
*
|
|
* Note that the caller must ensure that if the modified code is part of a
|
|
* module, the module would not be removed during poking. This can be achieved
|
|
* by registering a module notifier, and ordering module removal and patching
|
|
* trough a mutex.
|
|
*/
|
|
void *text_poke(void *addr, const void *opcode, size_t len)
|
|
{
|
|
lockdep_assert_held(&text_mutex);
|
|
|
|
return __text_poke(addr, opcode, len);
|
|
}
|
|
|
|
/**
|
|
* text_poke_kgdb - Update instructions on a live kernel by kgdb
|
|
* @addr: address to modify
|
|
* @opcode: source of the copy
|
|
* @len: length to copy
|
|
*
|
|
* Only atomic text poke/set should be allowed when not doing early patching.
|
|
* It means the size must be writable atomically and the address must be aligned
|
|
* in a way that permits an atomic write. It also makes sure we fit on a single
|
|
* page.
|
|
*
|
|
* Context: should only be used by kgdb, which ensures no other core is running,
|
|
* despite the fact it does not hold the text_mutex.
|
|
*/
|
|
void *text_poke_kgdb(void *addr, const void *opcode, size_t len)
|
|
{
|
|
return __text_poke(addr, opcode, len);
|
|
}
|
|
|
|
static void do_sync_core(void *info)
|
|
{
|
|
sync_core();
|
|
}
|
|
|
|
static struct bp_patching_desc {
|
|
struct text_poke_loc *vec;
|
|
int nr_entries;
|
|
} bp_patching;
|
|
|
|
static int patch_cmp(const void *key, const void *elt)
|
|
{
|
|
struct text_poke_loc *tp = (struct text_poke_loc *) elt;
|
|
|
|
if (key < tp->addr)
|
|
return -1;
|
|
if (key > tp->addr)
|
|
return 1;
|
|
return 0;
|
|
}
|
|
NOKPROBE_SYMBOL(patch_cmp);
|
|
|
|
int poke_int3_handler(struct pt_regs *regs)
|
|
{
|
|
struct text_poke_loc *tp;
|
|
unsigned char int3 = 0xcc;
|
|
void *ip;
|
|
|
|
/*
|
|
* Having observed our INT3 instruction, we now must observe
|
|
* bp_patching.nr_entries.
|
|
*
|
|
* nr_entries != 0 INT3
|
|
* WMB RMB
|
|
* write INT3 if (nr_entries)
|
|
*
|
|
* Idem for other elements in bp_patching.
|
|
*/
|
|
smp_rmb();
|
|
|
|
if (likely(!bp_patching.nr_entries))
|
|
return 0;
|
|
|
|
if (user_mode(regs))
|
|
return 0;
|
|
|
|
/*
|
|
* Discount the sizeof(int3). See text_poke_bp_batch().
|
|
*/
|
|
ip = (void *) regs->ip - sizeof(int3);
|
|
|
|
/*
|
|
* Skip the binary search if there is a single member in the vector.
|
|
*/
|
|
if (unlikely(bp_patching.nr_entries > 1)) {
|
|
tp = bsearch(ip, bp_patching.vec, bp_patching.nr_entries,
|
|
sizeof(struct text_poke_loc),
|
|
patch_cmp);
|
|
if (!tp)
|
|
return 0;
|
|
} else {
|
|
tp = bp_patching.vec;
|
|
if (tp->addr != ip)
|
|
return 0;
|
|
}
|
|
|
|
/* set up the specified breakpoint detour */
|
|
regs->ip = (unsigned long) tp->detour;
|
|
|
|
return 1;
|
|
}
|
|
NOKPROBE_SYMBOL(poke_int3_handler);
|
|
|
|
/**
|
|
* text_poke_bp_batch() -- update instructions on live kernel on SMP
|
|
* @tp: vector of instructions to patch
|
|
* @nr_entries: number of entries in the vector
|
|
*
|
|
* Modify multi-byte instruction by using int3 breakpoint on SMP.
|
|
* We completely avoid stop_machine() here, and achieve the
|
|
* synchronization using int3 breakpoint.
|
|
*
|
|
* The way it is done:
|
|
* - For each entry in the vector:
|
|
* - add a int3 trap to the address that will be patched
|
|
* - sync cores
|
|
* - For each entry in the vector:
|
|
* - update all but the first byte of the patched range
|
|
* - sync cores
|
|
* - For each entry in the vector:
|
|
* - replace the first byte (int3) by the first byte of
|
|
* replacing opcode
|
|
* - sync cores
|
|
*/
|
|
void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries)
|
|
{
|
|
int patched_all_but_first = 0;
|
|
unsigned char int3 = 0xcc;
|
|
unsigned int i;
|
|
|
|
lockdep_assert_held(&text_mutex);
|
|
|
|
bp_patching.vec = tp;
|
|
bp_patching.nr_entries = nr_entries;
|
|
|
|
/*
|
|
* Corresponding read barrier in int3 notifier for making sure the
|
|
* nr_entries and handler are correctly ordered wrt. patching.
|
|
*/
|
|
smp_wmb();
|
|
|
|
/*
|
|
* First step: add a int3 trap to the address that will be patched.
|
|
*/
|
|
for (i = 0; i < nr_entries; i++)
|
|
text_poke(tp[i].addr, &int3, sizeof(int3));
|
|
|
|
on_each_cpu(do_sync_core, NULL, 1);
|
|
|
|
/*
|
|
* Second step: update all but the first byte of the patched range.
|
|
*/
|
|
for (i = 0; i < nr_entries; i++) {
|
|
if (tp[i].len - sizeof(int3) > 0) {
|
|
text_poke((char *)tp[i].addr + sizeof(int3),
|
|
(const char *)tp[i].opcode + sizeof(int3),
|
|
tp[i].len - sizeof(int3));
|
|
patched_all_but_first++;
|
|
}
|
|
}
|
|
|
|
if (patched_all_but_first) {
|
|
/*
|
|
* According to Intel, this core syncing is very likely
|
|
* not necessary and we'd be safe even without it. But
|
|
* better safe than sorry (plus there's not only Intel).
|
|
*/
|
|
on_each_cpu(do_sync_core, NULL, 1);
|
|
}
|
|
|
|
/*
|
|
* Third step: replace the first byte (int3) by the first byte of
|
|
* replacing opcode.
|
|
*/
|
|
for (i = 0; i < nr_entries; i++)
|
|
text_poke(tp[i].addr, tp[i].opcode, sizeof(int3));
|
|
|
|
on_each_cpu(do_sync_core, NULL, 1);
|
|
/*
|
|
* sync_core() implies an smp_mb() and orders this store against
|
|
* the writing of the new instruction.
|
|
*/
|
|
bp_patching.vec = NULL;
|
|
bp_patching.nr_entries = 0;
|
|
}
|
|
|
|
/**
|
|
* text_poke_bp() -- update instructions on live kernel on SMP
|
|
* @addr: address to patch
|
|
* @opcode: opcode of new instruction
|
|
* @len: length to copy
|
|
* @handler: address to jump to when the temporary breakpoint is hit
|
|
*
|
|
* Update a single instruction with the vector in the stack, avoiding
|
|
* dynamically allocated memory. This function should be used when it is
|
|
* not possible to allocate memory.
|
|
*/
|
|
void text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
|
|
{
|
|
struct text_poke_loc tp = {
|
|
.detour = handler,
|
|
.addr = addr,
|
|
.len = len,
|
|
};
|
|
|
|
if (len > POKE_MAX_OPCODE_SIZE) {
|
|
WARN_ONCE(1, "len is larger than %d\n", POKE_MAX_OPCODE_SIZE);
|
|
return;
|
|
}
|
|
|
|
memcpy((void *)tp.opcode, opcode, len);
|
|
|
|
text_poke_bp_batch(&tp, 1);
|
|
}
|