547 lines
14 KiB
C
547 lines
14 KiB
C
#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/kprobes.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 <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/vsyscall.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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#define MAX_PATCH_LEN (255-1)
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#ifdef CONFIG_HOTPLUG_CPU
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static int smp_alt_once;
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static int __init bootonly(char *str)
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{
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smp_alt_once = 1;
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return 1;
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}
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__setup("smp-alt-boot", bootonly);
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#else
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#define smp_alt_once 1
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#endif
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static int 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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#ifdef CONFIG_PARAVIRT
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static int noreplace_paravirt = 0;
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static int __init setup_noreplace_paravirt(char *str)
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{
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noreplace_paravirt = 1;
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return 1;
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}
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__setup("noreplace-paravirt", setup_noreplace_paravirt);
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#endif
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#define DPRINTK(fmt, args...) if (debug_alternative) \
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printk(KERN_DEBUG fmt, args)
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#ifdef GENERIC_NOP1
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/* Use inline assembly to define this because the nops are defined
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as inline assembly strings in the include files and we cannot
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get them easily into strings. */
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asm("\t.section .rodata, \"a\"\nintelnops: "
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GENERIC_NOP1 GENERIC_NOP2 GENERIC_NOP3 GENERIC_NOP4 GENERIC_NOP5 GENERIC_NOP6
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GENERIC_NOP7 GENERIC_NOP8
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"\t.previous");
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extern const unsigned char intelnops[];
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static const unsigned char *const intel_nops[ASM_NOP_MAX+1] = {
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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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};
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#endif
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#ifdef K8_NOP1
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asm("\t.section .rodata, \"a\"\nk8nops: "
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K8_NOP1 K8_NOP2 K8_NOP3 K8_NOP4 K8_NOP5 K8_NOP6
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K8_NOP7 K8_NOP8
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"\t.previous");
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extern const unsigned char k8nops[];
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static const unsigned char *const k8_nops[ASM_NOP_MAX+1] = {
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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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};
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#endif
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#ifdef K7_NOP1
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asm("\t.section .rodata, \"a\"\nk7nops: "
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K7_NOP1 K7_NOP2 K7_NOP3 K7_NOP4 K7_NOP5 K7_NOP6
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K7_NOP7 K7_NOP8
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"\t.previous");
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extern const unsigned char k7nops[];
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static const unsigned char *const k7_nops[ASM_NOP_MAX+1] = {
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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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};
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#endif
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#ifdef P6_NOP1
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asm("\t.section .rodata, \"a\"\np6nops: "
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P6_NOP1 P6_NOP2 P6_NOP3 P6_NOP4 P6_NOP5 P6_NOP6
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P6_NOP7 P6_NOP8
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"\t.previous");
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extern const unsigned char p6nops[];
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static const unsigned char *const p6_nops[ASM_NOP_MAX+1] = {
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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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};
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#endif
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#ifdef CONFIG_X86_64
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extern char __vsyscall_0;
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const unsigned char *const *find_nop_table(void)
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{
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if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
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boot_cpu_has(X86_FEATURE_NOPL))
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return p6_nops;
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else
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return k8_nops;
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}
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#else /* CONFIG_X86_64 */
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const unsigned char *const *find_nop_table(void)
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{
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if (boot_cpu_has(X86_FEATURE_K8))
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return k8_nops;
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else if (boot_cpu_has(X86_FEATURE_K7))
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return k7_nops;
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else if (boot_cpu_has(X86_FEATURE_NOPL))
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return p6_nops;
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else
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return intel_nops;
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}
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#endif /* CONFIG_X86_64 */
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/* Use this to add nops to a buffer, then text_poke the whole buffer. */
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void add_nops(void *insns, unsigned int len)
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{
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const unsigned char *const *noptable = find_nop_table();
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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, noptable[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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EXPORT_SYMBOL_GPL(add_nops);
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extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
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extern u8 *__smp_locks[], *__smp_locks_end[];
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/* Replace instructions with better alternatives for this CPU type.
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This runs before SMP is initialized to avoid SMP problems with
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self modifying code. This implies that assymetric systems where
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APs have less capabilities than the boot processor are not handled.
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Tough. Make sure you disable such features by hand. */
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void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
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{
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struct alt_instr *a;
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char insnbuf[MAX_PATCH_LEN];
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DPRINTK("%s: alt table %p -> %p\n", __func__, start, end);
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for (a = start; a < end; a++) {
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u8 *instr = a->instr;
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BUG_ON(a->replacementlen > a->instrlen);
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BUG_ON(a->instrlen > sizeof(insnbuf));
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if (!boot_cpu_has(a->cpuid))
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continue;
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#ifdef CONFIG_X86_64
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/* vsyscall code is not mapped yet. resolve it manually. */
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if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) {
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instr = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__vsyscall_0));
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DPRINTK("%s: vsyscall fixup: %p => %p\n",
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__func__, a->instr, instr);
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}
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#endif
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memcpy(insnbuf, a->replacement, a->replacementlen);
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add_nops(insnbuf + a->replacementlen,
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a->instrlen - a->replacementlen);
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text_poke_early(instr, insnbuf, a->instrlen);
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}
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}
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#ifdef CONFIG_SMP
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static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end)
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{
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u8 **ptr;
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mutex_lock(&text_mutex);
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for (ptr = start; ptr < end; ptr++) {
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if (*ptr < text)
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continue;
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if (*ptr > text_end)
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continue;
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/* turn DS segment override prefix into lock prefix */
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text_poke(*ptr, ((unsigned char []){0xf0}), 1);
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};
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mutex_unlock(&text_mutex);
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}
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static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end)
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{
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u8 **ptr;
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if (noreplace_smp)
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return;
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mutex_lock(&text_mutex);
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for (ptr = start; ptr < end; ptr++) {
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if (*ptr < text)
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continue;
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if (*ptr > text_end)
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continue;
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/* turn lock prefix into DS segment override prefix */
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text_poke(*ptr, ((unsigned char []){0x3E}), 1);
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};
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mutex_unlock(&text_mutex);
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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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u8 **locks;
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u8 **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 DEFINE_MUTEX(smp_alt);
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static int smp_mode = 1; /* protected by smp_alt */
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void alternatives_smp_module_add(struct module *mod, 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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if (noreplace_smp)
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return;
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if (smp_alt_once) {
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if (boot_cpu_has(X86_FEATURE_UP))
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alternatives_smp_unlock(locks, locks_end,
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text, text_end);
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return;
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}
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smp = kzalloc(sizeof(*smp), GFP_KERNEL);
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if (NULL == smp)
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return; /* we'll run the (safe but slow) SMP code then ... */
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smp->mod = mod;
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smp->name = name;
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smp->locks = locks;
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smp->locks_end = locks_end;
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smp->text = text;
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smp->text_end = text_end;
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DPRINTK("%s: locks %p -> %p, text %p -> %p, name %s\n",
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__func__, smp->locks, smp->locks_end,
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smp->text, smp->text_end, smp->name);
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mutex_lock(&smp_alt);
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list_add_tail(&smp->next, &smp_alt_modules);
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if (boot_cpu_has(X86_FEATURE_UP))
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alternatives_smp_unlock(smp->locks, smp->locks_end,
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smp->text, smp->text_end);
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mutex_unlock(&smp_alt);
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}
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void alternatives_smp_module_del(struct module *mod)
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{
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struct smp_alt_module *item;
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if (smp_alt_once || noreplace_smp)
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return;
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mutex_lock(&smp_alt);
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list_for_each_entry(item, &smp_alt_modules, next) {
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if (mod != item->mod)
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continue;
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list_del(&item->next);
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mutex_unlock(&smp_alt);
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DPRINTK("%s: %s\n", __func__, item->name);
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kfree(item);
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return;
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}
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mutex_unlock(&smp_alt);
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}
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void alternatives_smp_switch(int smp)
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{
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struct smp_alt_module *mod;
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#ifdef CONFIG_LOCKDEP
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/*
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* Older binutils section handling bug prevented
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* alternatives-replacement from working reliably.
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*
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* If this still occurs then you should see a hang
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* or crash shortly after this line:
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*/
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printk("lockdep: fixing up alternatives.\n");
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#endif
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if (noreplace_smp || smp_alt_once)
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return;
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BUG_ON(!smp && (num_online_cpus() > 1));
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mutex_lock(&smp_alt);
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/*
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* Avoid unnecessary switches because it forces JIT based VMs to
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* throw away all cached translations, which can be quite costly.
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*/
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if (smp == smp_mode) {
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/* nothing */
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} else if (smp) {
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printk(KERN_INFO "SMP alternatives: switching to SMP code\n");
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clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
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clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
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list_for_each_entry(mod, &smp_alt_modules, next)
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alternatives_smp_lock(mod->locks, mod->locks_end,
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mod->text, mod->text_end);
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} else {
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printk(KERN_INFO "SMP alternatives: switching to UP code\n");
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set_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
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set_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
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list_for_each_entry(mod, &smp_alt_modules, next)
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alternatives_smp_unlock(mod->locks, mod->locks_end,
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mod->text, mod->text_end);
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}
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smp_mode = smp;
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mutex_unlock(&smp_alt);
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}
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#endif
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#ifdef CONFIG_PARAVIRT
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void apply_paravirt(struct paravirt_patch_site *start,
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struct paravirt_patch_site *end)
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{
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struct paravirt_patch_site *p;
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char insnbuf[MAX_PATCH_LEN];
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if (noreplace_paravirt)
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return;
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for (p = start; p < end; p++) {
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unsigned int used;
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BUG_ON(p->len > MAX_PATCH_LEN);
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/* prep the buffer with the original instructions */
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memcpy(insnbuf, p->instr, p->len);
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used = pv_init_ops.patch(p->instrtype, p->clobbers, insnbuf,
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(unsigned long)p->instr, p->len);
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BUG_ON(used > p->len);
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/* Pad the rest with nops */
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add_nops(insnbuf + used, p->len - used);
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text_poke_early(p->instr, insnbuf, p->len);
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}
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}
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extern struct paravirt_patch_site __start_parainstructions[],
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__stop_parainstructions[];
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#endif /* CONFIG_PARAVIRT */
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void __init alternative_instructions(void)
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{
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/* The patching is not fully atomic, so try to avoid local interruptions
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that might execute the to be patched code.
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Other CPUs are not running. */
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stop_nmi();
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/*
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* Don't stop machine check exceptions while patching.
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* MCEs only happen when something got corrupted and in this
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* case we must do something about the corruption.
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* Ignoring it is worse than a unlikely patching race.
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* Also machine checks tend to be broadcast and if one CPU
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* goes into machine check the others follow quickly, so we don't
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* expect a machine check to cause undue problems during to code
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* patching.
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*/
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apply_alternatives(__alt_instructions, __alt_instructions_end);
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/* switch to patch-once-at-boottime-only mode and free the
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* tables in case we know the number of CPUs will never ever
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* change */
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#ifdef CONFIG_HOTPLUG_CPU
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if (num_possible_cpus() < 2)
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smp_alt_once = 1;
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#endif
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#ifdef CONFIG_SMP
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if (smp_alt_once) {
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if (1 == num_possible_cpus()) {
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printk(KERN_INFO "SMP alternatives: switching to UP code\n");
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set_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
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set_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
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alternatives_smp_unlock(__smp_locks, __smp_locks_end,
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_text, _etext);
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}
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} else {
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alternatives_smp_module_add(NULL, "core kernel",
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__smp_locks, __smp_locks_end,
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_text, _etext);
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/* Only switch to UP mode if we don't immediately boot others */
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if (num_present_cpus() == 1 || setup_max_cpus <= 1)
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alternatives_smp_switch(0);
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}
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#endif
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apply_paravirt(__parainstructions, __parainstructions_end);
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if (smp_alt_once)
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free_init_pages("SMP alternatives",
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(unsigned long)__smp_locks,
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(unsigned long)__smp_locks_end);
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restart_nmi();
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}
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/**
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* text_poke_early - Update instructions on a live kernel at boot time
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* @addr: address to modify
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* @opcode: source of the copy
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* @len: length to copy
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*
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* When you use this code to patch more than one byte of an instruction
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* you need to make sure that other CPUs cannot execute this code in parallel.
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* Also no thread must be currently preempted in the middle of these
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* instructions. And on the local CPU you need to be protected again NMI or MCE
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* handlers seeing an inconsistent instruction while you patch.
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*/
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void *text_poke_early(void *addr, const void *opcode, size_t len)
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{
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unsigned long flags;
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local_irq_save(flags);
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memcpy(addr, opcode, len);
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local_irq_restore(flags);
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sync_core();
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/* Could also do a CLFLUSH here to speed up CPU recovery; but
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that causes hangs on some VIA CPUs. */
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return addr;
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}
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/**
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* text_poke - Update instructions on a live kernel
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* @addr: address to modify
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* @opcode: source of the copy
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* @len: length to copy
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*
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* Only atomic text poke/set should be allowed when not doing early patching.
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* It means the size must be writable atomically and the address must be aligned
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* in a way that permits an atomic write. It also makes sure we fit on a single
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* page.
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*
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* Note: Must be called under text_mutex.
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*/
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void *__kprobes text_poke(void *addr, const void *opcode, size_t len)
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{
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unsigned long flags;
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char *vaddr;
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struct page *pages[2];
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int i;
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if (!core_kernel_text((unsigned long)addr)) {
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pages[0] = vmalloc_to_page(addr);
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pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
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} else {
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pages[0] = virt_to_page(addr);
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WARN_ON(!PageReserved(pages[0]));
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pages[1] = virt_to_page(addr + PAGE_SIZE);
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}
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BUG_ON(!pages[0]);
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local_irq_save(flags);
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set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0]));
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if (pages[1])
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set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1]));
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vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0);
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memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
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clear_fixmap(FIX_TEXT_POKE0);
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if (pages[1])
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clear_fixmap(FIX_TEXT_POKE1);
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local_flush_tlb();
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sync_core();
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/* Could also do a CLFLUSH here to speed up CPU recovery; but
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that causes hangs on some VIA CPUs. */
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for (i = 0; i < len; i++)
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BUG_ON(((char *)addr)[i] != ((char *)opcode)[i]);
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local_irq_restore(flags);
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return addr;
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}
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