diff options
Diffstat (limited to 'arch/x86/kernel/alternative.c')
| -rw-r--r-- | arch/x86/kernel/alternative.c | 124 |
1 files changed, 106 insertions, 18 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index de7353c0ce9c..70237732a6c7 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -7,6 +7,8 @@ #include <linux/mm.h> #include <linux/vmalloc.h> #include <linux/memory.h> +#include <linux/stop_machine.h> +#include <linux/slab.h> #include <asm/alternative.h> #include <asm/sections.h> #include <asm/pgtable.h> @@ -192,7 +194,7 @@ static void __init_or_module add_nops(void *insns, unsigned int len) } extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; -extern u8 *__smp_locks[], *__smp_locks_end[]; +extern s32 __smp_locks[], __smp_locks_end[]; static void *text_poke_early(void *addr, const void *opcode, size_t len); /* Replace instructions with better alternatives for this CPU type. @@ -205,7 +207,7 @@ void __init_or_module apply_alternatives(struct alt_instr *start, struct alt_instr *end) { struct alt_instr *a; - char insnbuf[MAX_PATCH_LEN]; + u8 insnbuf[MAX_PATCH_LEN]; DPRINTK("%s: alt table %p -> %p\n", __func__, start, end); for (a = start; a < end; a++) { @@ -223,6 +225,8 @@ void __init_or_module apply_alternatives(struct alt_instr *start, } #endif memcpy(insnbuf, a->replacement, a->replacementlen); + if (*insnbuf == 0xe8 && a->replacementlen == 5) + *(s32 *)(insnbuf + 1) += a->replacement - a->instr; add_nops(insnbuf + a->replacementlen, a->instrlen - a->replacementlen); text_poke_early(instr, insnbuf, a->instrlen); @@ -231,37 +235,41 @@ void __init_or_module apply_alternatives(struct alt_instr *start, #ifdef CONFIG_SMP -static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end) +static void alternatives_smp_lock(const s32 *start, const s32 *end, + u8 *text, u8 *text_end) { - u8 **ptr; + const s32 *poff; mutex_lock(&text_mutex); - for (ptr = start; ptr < end; ptr++) { - if (*ptr < text) - continue; - if (*ptr > text_end) + for (poff = start; poff < end; poff++) { + u8 *ptr = (u8 *)poff + *poff; + + if (!*poff || ptr < text || ptr >= text_end) continue; /* turn DS segment override prefix into lock prefix */ - text_poke(*ptr, ((unsigned char []){0xf0}), 1); + if (*ptr == 0x3e) + text_poke(ptr, ((unsigned char []){0xf0}), 1); }; mutex_unlock(&text_mutex); } -static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end) +static void alternatives_smp_unlock(const s32 *start, const s32 *end, + u8 *text, u8 *text_end) { - u8 **ptr; + const s32 *poff; if (noreplace_smp) return; mutex_lock(&text_mutex); - for (ptr = start; ptr < end; ptr++) { - if (*ptr < text) - continue; - if (*ptr > text_end) + for (poff = start; poff < end; poff++) { + u8 *ptr = (u8 *)poff + *poff; + + if (!*poff || ptr < text || ptr >= text_end) continue; /* turn lock prefix into DS segment override prefix */ - text_poke(*ptr, ((unsigned char []){0x3E}), 1); + if (*ptr == 0xf0) + text_poke(ptr, ((unsigned char []){0x3E}), 1); }; mutex_unlock(&text_mutex); } @@ -272,8 +280,8 @@ struct smp_alt_module { char *name; /* ptrs to lock prefixes */ - u8 **locks; - u8 **locks_end; + const s32 *locks; + const s32 *locks_end; /* .text segment, needed to avoid patching init code ;) */ u8 *text; @@ -390,6 +398,27 @@ void alternatives_smp_switch(int smp) mutex_unlock(&smp_alt); } +/* Return 1 if the address range is reserved for smp-alternatives */ +int alternatives_text_reserved(void *start, void *end) +{ + struct smp_alt_module *mod; + const s32 *poff; + u8 *text_start = start; + u8 *text_end = end; + + 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 #ifdef CONFIG_PARAVIRT @@ -552,3 +581,62 @@ void *__kprobes text_poke(void *addr, const void *opcode, size_t len) local_irq_restore(flags); return addr; } + +/* + * Cross-modifying kernel text with stop_machine(). + * This code originally comes from immediate value. + */ +static atomic_t stop_machine_first; +static int wrote_text; + +struct text_poke_params { + void *addr; + const void *opcode; + size_t len; +}; + +static int __kprobes stop_machine_text_poke(void *data) +{ + struct text_poke_params *tpp = data; + + if (atomic_dec_and_test(&stop_machine_first)) { + text_poke(tpp->addr, tpp->opcode, tpp->len); + smp_wmb(); /* Make sure other cpus see that this has run */ + wrote_text = 1; + } else { + while (!wrote_text) + cpu_relax(); + smp_mb(); /* Load wrote_text before following execution */ + } + + flush_icache_range((unsigned long)tpp->addr, + (unsigned long)tpp->addr + tpp->len); + return 0; +} + +/** + * text_poke_smp - Update instructions on a live kernel on SMP + * @addr: address to modify + * @opcode: source of the copy + * @len: length to copy + * + * Modify multi-byte instruction by using stop_machine() on SMP. This allows + * user to poke/set multi-byte text on SMP. Only non-NMI/MCE code modifying + * should be allowed, since stop_machine() does _not_ protect code against + * NMI and MCE. + * + * Note: Must be called under get_online_cpus() and text_mutex. + */ +void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len) +{ + struct text_poke_params tpp; + + tpp.addr = addr; + tpp.opcode = opcode; + tpp.len = len; + atomic_set(&stop_machine_first, 1); + wrote_text = 0; + stop_machine(stop_machine_text_poke, (void *)&tpp, NULL); + return addr; +} + |