diff options
Diffstat (limited to 'arch/x86/kernel/alternative.c')
| -rw-r--r-- | arch/x86/kernel/alternative.c | 450 |
1 files changed, 450 insertions, 0 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c new file mode 100644 index 0000000..bd72d94 --- /dev/null +++ b/arch/x86/kernel/alternative.c @@ -0,0 +1,450 @@ +#include <linux/module.h> +#include <linux/sched.h> +#include <linux/spinlock.h> +#include <linux/list.h> +#include <linux/kprobes.h> +#include <linux/mm.h> +#include <linux/vmalloc.h> +#include <asm/alternative.h> +#include <asm/sections.h> +#include <asm/pgtable.h> +#include <asm/mce.h> +#include <asm/nmi.h> + +#define MAX_PATCH_LEN (255-1) + +#ifdef CONFIG_HOTPLUG_CPU +static int smp_alt_once; + +static int __init bootonly(char *str) +{ + smp_alt_once = 1; + return 1; +} +__setup("smp-alt-boot", bootonly); +#else +#define smp_alt_once 1 +#endif + +static int debug_alternative; + +static int __init debug_alt(char *str) +{ + debug_alternative = 1; + return 1; +} +__setup("debug-alternative", debug_alt); + +static int noreplace_smp; + +static int __init setup_noreplace_smp(char *str) +{ + noreplace_smp = 1; + return 1; +} +__setup("noreplace-smp", setup_noreplace_smp); + +#ifdef CONFIG_PARAVIRT +static int noreplace_paravirt = 0; + +static int __init setup_noreplace_paravirt(char *str) +{ + noreplace_paravirt = 1; + return 1; +} +__setup("noreplace-paravirt", setup_noreplace_paravirt); +#endif + +#define DPRINTK(fmt, args...) if (debug_alternative) \ + printk(KERN_DEBUG fmt, args) + +#ifdef GENERIC_NOP1 +/* Use inline assembly to define this because the nops are defined + as inline assembly strings in the include files and we cannot + get them easily into strings. */ +asm("\t.data\nintelnops: " + GENERIC_NOP1 GENERIC_NOP2 GENERIC_NOP3 GENERIC_NOP4 GENERIC_NOP5 GENERIC_NOP6 + GENERIC_NOP7 GENERIC_NOP8); +extern unsigned char intelnops[]; +static unsigned char *intel_nops[ASM_NOP_MAX+1] = { + NULL, + intelnops, + intelnops + 1, + intelnops + 1 + 2, + intelnops + 1 + 2 + 3, + intelnops + 1 + 2 + 3 + 4, + intelnops + 1 + 2 + 3 + 4 + 5, + intelnops + 1 + 2 + 3 + 4 + 5 + 6, + intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7, +}; +#endif + +#ifdef K8_NOP1 +asm("\t.data\nk8nops: " + K8_NOP1 K8_NOP2 K8_NOP3 K8_NOP4 K8_NOP5 K8_NOP6 + K8_NOP7 K8_NOP8); +extern unsigned char k8nops[]; +static unsigned char *k8_nops[ASM_NOP_MAX+1] = { + NULL, + k8nops, + k8nops + 1, + k8nops + 1 + 2, + k8nops + 1 + 2 + 3, + k8nops + 1 + 2 + 3 + 4, + k8nops + 1 + 2 + 3 + 4 + 5, + k8nops + 1 + 2 + 3 + 4 + 5 + 6, + k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7, +}; +#endif + +#ifdef K7_NOP1 +asm("\t.data\nk7nops: " + K7_NOP1 K7_NOP2 K7_NOP3 K7_NOP4 K7_NOP5 K7_NOP6 + K7_NOP7 K7_NOP8); +extern unsigned char k7nops[]; +static unsigned char *k7_nops[ASM_NOP_MAX+1] = { + NULL, + k7nops, + k7nops + 1, + k7nops + 1 + 2, + k7nops + 1 + 2 + 3, + k7nops + 1 + 2 + 3 + 4, + k7nops + 1 + 2 + 3 + 4 + 5, + k7nops + 1 + 2 + 3 + 4 + 5 + 6, + k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7, +}; +#endif + +#ifdef CONFIG_X86_64 + +extern char __vsyscall_0; +static inline unsigned char** find_nop_table(void) +{ + return k8_nops; +} + +#else /* CONFIG_X86_64 */ + +static struct nop { + int cpuid; + unsigned char **noptable; +} noptypes[] = { + { X86_FEATURE_K8, k8_nops }, + { X86_FEATURE_K7, k7_nops }, + { -1, NULL } +}; + +static unsigned char** find_nop_table(void) +{ + unsigned char **noptable = intel_nops; + int i; + + for (i = 0; noptypes[i].cpuid >= 0; i++) { + if (boot_cpu_has(noptypes[i].cpuid)) { + noptable = noptypes[i].noptable; + break; + } + } + return noptable; +} + +#endif /* CONFIG_X86_64 */ + +/* Use this to add nops to a buffer, then text_poke the whole buffer. */ +static void add_nops(void *insns, unsigned int len) +{ + unsigned char **noptable = find_nop_table(); + + while (len > 0) { + unsigned int noplen = len; + if (noplen > ASM_NOP_MAX) + noplen = ASM_NOP_MAX; + memcpy(insns, noptable[noplen], noplen); + insns += noplen; + len -= noplen; + } +} + +extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; +extern u8 *__smp_locks[], *__smp_locks_end[]; + +/* Replace instructions with better alternatives for this CPU type. + This runs before SMP is initialized to avoid SMP problems with + self modifying code. This implies that assymetric systems where + APs have less capabilities than the boot processor are not handled. + Tough. Make sure you disable such features by hand. */ + +void apply_alternatives(struct alt_instr *start, struct alt_instr *end) +{ + struct alt_instr *a; + char insnbuf[MAX_PATCH_LEN]; + + DPRINTK("%s: alt table %p -> %p\n", __FUNCTION__, start, end); + for (a = start; a < end; a++) { + u8 *instr = a->instr; + BUG_ON(a->replacementlen > a->instrlen); + BUG_ON(a->instrlen > sizeof(insnbuf)); + if (!boot_cpu_has(a->cpuid)) + continue; +#ifdef CONFIG_X86_64 + /* vsyscall code is not mapped yet. resolve it manually. */ + if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) { + instr = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__vsyscall_0)); + DPRINTK("%s: vsyscall fixup: %p => %p\n", + __FUNCTION__, a->instr, instr); + } +#endif + memcpy(insnbuf, a->replacement, a->replacementlen); + add_nops(insnbuf + a->replacementlen, + a->instrlen - a->replacementlen); + text_poke(instr, insnbuf, a->instrlen); + } +} + +#ifdef CONFIG_SMP + +static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end) +{ + u8 **ptr; + + for (ptr = start; ptr < end; ptr++) { + if (*ptr < text) + continue; + if (*ptr > text_end) + continue; + text_poke(*ptr, ((unsigned char []){0xf0}), 1); /* add lock prefix */ + }; +} + +static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end) +{ + u8 **ptr; + char insn[1]; + + if (noreplace_smp) + return; + + add_nops(insn, 1); + for (ptr = start; ptr < end; ptr++) { + if (*ptr < text) + continue; + if (*ptr > text_end) + continue; + text_poke(*ptr, insn, 1); + }; +} + +struct smp_alt_module { + /* what is this ??? */ + struct module *mod; + char *name; + + /* ptrs to lock prefixes */ + u8 **locks; + u8 **locks_end; + + /* .text segment, needed to avoid patching init code ;) */ + u8 *text; + u8 *text_end; + + struct list_head next; +}; +static LIST_HEAD(smp_alt_modules); +static DEFINE_SPINLOCK(smp_alt); + +void alternatives_smp_module_add(struct module *mod, char *name, + void *locks, void *locks_end, + void *text, void *text_end) +{ + struct smp_alt_module *smp; + unsigned long flags; + + if (noreplace_smp) + return; + + if (smp_alt_once) { + if (boot_cpu_has(X86_FEATURE_UP)) + alternatives_smp_unlock(locks, locks_end, + text, text_end); + return; + } + + smp = kzalloc(sizeof(*smp), GFP_KERNEL); + if (NULL == smp) + return; /* we'll run the (safe but slow) SMP code then ... */ + + smp->mod = mod; + smp->name = name; + smp->locks = locks; + smp->locks_end = locks_end; + smp->text = text; + smp->text_end = text_end; + DPRINTK("%s: locks %p -> %p, text %p -> %p, name %s\n", + __FUNCTION__, smp->locks, smp->locks_end, + smp->text, smp->text_end, smp->name); + + spin_lock_irqsave(&smp_alt, flags); + list_add_tail(&smp->next, &smp_alt_modules); + if (boot_cpu_has(X86_FEATURE_UP)) + alternatives_smp_unlock(smp->locks, smp->locks_end, + smp->text, smp->text_end); + spin_unlock_irqrestore(&smp_alt, flags); +} + +void alternatives_smp_module_del(struct module *mod) +{ + struct smp_alt_module *item; + unsigned long flags; + + if (smp_alt_once || noreplace_smp) + return; + + spin_lock_irqsave(&smp_alt, flags); + list_for_each_entry(item, &smp_alt_modules, next) { + if (mod != item->mod) + continue; + list_del(&item->next); + spin_unlock_irqrestore(&smp_alt, flags); + DPRINTK("%s: %s\n", __FUNCTION__, item->name); + kfree(item); + return; + } + spin_unlock_irqrestore(&smp_alt, flags); +} + +void alternatives_smp_switch(int smp) +{ + struct smp_alt_module *mod; + unsigned long flags; + +#ifdef CONFIG_LOCKDEP + /* + * A not yet fixed binutils section handling bug prevents + * alternatives-replacement from working reliably, so turn + * it off: + */ + printk("lockdep: not fixing up alternatives.\n"); + return; +#endif + + if (noreplace_smp || smp_alt_once) + return; + BUG_ON(!smp && (num_online_cpus() > 1)); + + spin_lock_irqsave(&smp_alt, flags); + if (smp) { + printk(KERN_INFO "SMP alternatives: switching to SMP code\n"); + clear_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability); + clear_bit(X86_FEATURE_UP, cpu_data[0].x86_capability); + list_for_each_entry(mod, &smp_alt_modules, next) + alternatives_smp_lock(mod->locks, mod->locks_end, + mod->text, mod->text_end); + } else { + printk(KERN_INFO "SMP alternatives: switching to UP code\n"); + set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability); + set_bit(X86_FEATURE_UP, cpu_data[0].x86_capability); + list_for_each_entry(mod, &smp_alt_modules, next) + alternatives_smp_unlock(mod->locks, mod->locks_end, + mod->text, mod->text_end); + } + spin_unlock_irqrestore(&smp_alt, flags); +} + +#endif + +#ifdef CONFIG_PARAVIRT +void apply_paravirt(struct paravirt_patch_site *start, + struct paravirt_patch_site *end) +{ + struct paravirt_patch_site *p; + char insnbuf[MAX_PATCH_LEN]; + + if (noreplace_paravirt) + return; + + for (p = start; p < end; p++) { + unsigned int used; + + BUG_ON(p->len > MAX_PATCH_LEN); + /* prep the buffer with the original instructions */ + memcpy(insnbuf, p->instr, p->len); + used = paravirt_ops.patch(p->instrtype, p->clobbers, insnbuf, + (unsigned long)p->instr, p->len); + + BUG_ON(used > p->len); + + /* Pad the rest with nops */ + add_nops(insnbuf + used, p->len - used); + text_poke(p->instr, insnbuf, p->len); + } +} +extern struct paravirt_patch_site __start_parainstructions[], + __stop_parainstructions[]; +#endif /* CONFIG_PARAVIRT */ + +void __init alternative_instructions(void) +{ + unsigned long flags; + + /* 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(); +#ifdef CONFIG_X86_MCE + stop_mce(); +#endif + + local_irq_save(flags); + apply_alternatives(__alt_instructions, __alt_instructions_end); + + /* switch to patch-once-at-boottime-only mode and free the + * tables in case we know the number of CPUs will never ever + * change */ +#ifdef CONFIG_HOTPLUG_CPU + if (num_possible_cpus() < 2) + smp_alt_once = 1; +#endif + +#ifdef CONFIG_SMP + if (smp_alt_once) { + if (1 == num_possible_cpus()) { + printk(KERN_INFO "SMP alternatives: switching to UP code\n"); + set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability); + set_bit(X86_FEATURE_UP, cpu_data[0].x86_capability); + alternatives_smp_unlock(__smp_locks, __smp_locks_end, + _text, _etext); + } + free_init_pages("SMP alternatives", + (unsigned long)__smp_locks, + (unsigned long)__smp_locks_end); + } else { + alternatives_smp_module_add(NULL, "core kernel", + __smp_locks, __smp_locks_end, + _text, _etext); + alternatives_smp_switch(0); + } +#endif + apply_paravirt(__parainstructions, __parainstructions_end); + local_irq_restore(flags); + + restart_nmi(); +#ifdef CONFIG_X86_MCE + restart_mce(); +#endif +} + +/* + * Warning: + * 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 again NMI or MCE handlers + * seeing an inconsistent instruction while you patch. + */ +void __kprobes text_poke(void *addr, unsigned char *opcode, int len) +{ + memcpy(addr, opcode, len); + sync_core(); + /* Could also do a CLFLUSH here to speed up CPU recovery; but + that causes hangs on some VIA CPUs. */ +} |