diff options
Diffstat (limited to 'kernel/kprobes.c')
| -rw-r--r-- | kernel/kprobes.c | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 334f374..6524252 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -36,6 +36,7 @@ #include <linux/hash.h> #include <linux/init.h> #include <linux/module.h> +#include <linux/moduleloader.h> #include <asm/cacheflush.h> #include <asm/errno.h> #include <asm/kdebug.h> @@ -50,6 +51,106 @@ unsigned int kprobe_cpu = NR_CPUS; static DEFINE_SPINLOCK(kprobe_lock); static struct kprobe *curr_kprobe; +/* + * kprobe->ainsn.insn points to the copy of the instruction to be + * single-stepped. x86_64, POWER4 and above have no-exec support and + * stepping on the instruction on a vmalloced/kmalloced/data page + * is a recipe for disaster + */ +#define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t))) + +struct kprobe_insn_page { + struct hlist_node hlist; + kprobe_opcode_t *insns; /* Page of instruction slots */ + char slot_used[INSNS_PER_PAGE]; + int nused; +}; + +static struct hlist_head kprobe_insn_pages; + +/** + * get_insn_slot() - Find a slot on an executable page for an instruction. + * We allocate an executable page if there's no room on existing ones. + */ +kprobe_opcode_t *get_insn_slot(void) +{ + struct kprobe_insn_page *kip; + struct hlist_node *pos; + + hlist_for_each(pos, &kprobe_insn_pages) { + kip = hlist_entry(pos, struct kprobe_insn_page, hlist); + if (kip->nused < INSNS_PER_PAGE) { + int i; + for (i = 0; i < INSNS_PER_PAGE; i++) { + if (!kip->slot_used[i]) { + kip->slot_used[i] = 1; + kip->nused++; + return kip->insns + (i * MAX_INSN_SIZE); + } + } + /* Surprise! No unused slots. Fix kip->nused. */ + kip->nused = INSNS_PER_PAGE; + } + } + + /* All out of space. Need to allocate a new page. Use slot 0.*/ + kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL); + if (!kip) { + return NULL; + } + + /* + * Use module_alloc so this page is within +/- 2GB of where the + * kernel image and loaded module images reside. This is required + * so x86_64 can correctly handle the %rip-relative fixups. + */ + kip->insns = module_alloc(PAGE_SIZE); + if (!kip->insns) { + kfree(kip); + return NULL; + } + INIT_HLIST_NODE(&kip->hlist); + hlist_add_head(&kip->hlist, &kprobe_insn_pages); + memset(kip->slot_used, 0, INSNS_PER_PAGE); + kip->slot_used[0] = 1; + kip->nused = 1; + return kip->insns; +} + +void free_insn_slot(kprobe_opcode_t *slot) +{ + struct kprobe_insn_page *kip; + struct hlist_node *pos; + + hlist_for_each(pos, &kprobe_insn_pages) { + kip = hlist_entry(pos, struct kprobe_insn_page, hlist); + if (kip->insns <= slot && + slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) { + int i = (slot - kip->insns) / MAX_INSN_SIZE; + kip->slot_used[i] = 0; + kip->nused--; + if (kip->nused == 0) { + /* + * Page is no longer in use. Free it unless + * it's the last one. We keep the last one + * so as not to have to set it up again the + * next time somebody inserts a probe. + */ + hlist_del(&kip->hlist); + if (hlist_empty(&kprobe_insn_pages)) { + INIT_HLIST_NODE(&kip->hlist); + hlist_add_head(&kip->hlist, + &kprobe_insn_pages); + } else { + module_free(NULL, kip->insns); + kfree(kip); + } + } + return; + } + } +} + /* Locks kprobe: irqs must be disabled */ void lock_kprobes(void) { |
