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authorMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>2006-12-06 23:38:11 -0500
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-07 11:39:38 -0500
commitb4c6c34a530b4d1c626f4ac0a884e0a9b849378c (patch)
tree5705a4621b6668bced1969396465800256d76c76 /kernel
parentc15bb296403f1ce448384d58742e0dc04f49d664 (diff)
[PATCH] kprobes: enable booster on the preemptible kernel
When we are unregistering a kprobe-booster, we can't release its instruction buffer immediately on the preemptive kernel, because some processes might be preempted on the buffer. The freeze_processes() and thaw_processes() functions can clean most of processes up from the buffer. There are still some non-frozen threads who have the PF_NOFREEZE flag. If those threads are sleeping (not preempted) at the known place outside the buffer, we can ensure safety of freeing. However, the processing of this check routine takes a long time. So, this patch introduces the garbage collection mechanism of insn_slot. It also introduces the "dirty" flag to free_insn_slot because of efficiency. The "clean" instruction slots (dirty flag is cleared) are released immediately. But the "dirty" slots which are used by boosted kprobes, are marked as garbages. collect_garbage_slots() will be invoked to release "dirty" slots if there are more than INSNS_PER_PAGE garbage slots or if there are no unused slots. Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: "bibo,mao" <bibo.mao@intel.com> Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com> Cc: Yumiko Sugita <yumiko.sugita.yf@hitachi.com> Cc: Satoshi Oshima <soshima@redhat.com> Cc: Hideo Aoki <haoki@redhat.com> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/kprobes.c117
1 files changed, 96 insertions, 21 deletions
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 610c837ad9e0..17ec4afb0994 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -38,6 +38,7 @@
38#include <linux/module.h> 38#include <linux/module.h>
39#include <linux/moduleloader.h> 39#include <linux/moduleloader.h>
40#include <linux/kallsyms.h> 40#include <linux/kallsyms.h>
41#include <linux/freezer.h>
41#include <asm-generic/sections.h> 42#include <asm-generic/sections.h>
42#include <asm/cacheflush.h> 43#include <asm/cacheflush.h>
43#include <asm/errno.h> 44#include <asm/errno.h>
@@ -83,9 +84,36 @@ struct kprobe_insn_page {
83 kprobe_opcode_t *insns; /* Page of instruction slots */ 84 kprobe_opcode_t *insns; /* Page of instruction slots */
84 char slot_used[INSNS_PER_PAGE]; 85 char slot_used[INSNS_PER_PAGE];
85 int nused; 86 int nused;
87 int ngarbage;
86}; 88};
87 89
88static struct hlist_head kprobe_insn_pages; 90static struct hlist_head kprobe_insn_pages;
91static int kprobe_garbage_slots;
92static int collect_garbage_slots(void);
93
94static int __kprobes check_safety(void)
95{
96 int ret = 0;
97#if defined(CONFIG_PREEMPT) && defined(CONFIG_PM)
98 ret = freeze_processes();
99 if (ret == 0) {
100 struct task_struct *p, *q;
101 do_each_thread(p, q) {
102 if (p != current && p->state == TASK_RUNNING &&
103 p->pid != 0) {
104 printk("Check failed: %s is running\n",p->comm);
105 ret = -1;
106 goto loop_end;
107 }
108 } while_each_thread(p, q);
109 }
110loop_end:
111 thaw_processes();
112#else
113 synchronize_sched();
114#endif
115 return ret;
116}
89 117
90/** 118/**
91 * get_insn_slot() - Find a slot on an executable page for an instruction. 119 * get_insn_slot() - Find a slot on an executable page for an instruction.
@@ -96,6 +124,7 @@ kprobe_opcode_t __kprobes *get_insn_slot(void)
96 struct kprobe_insn_page *kip; 124 struct kprobe_insn_page *kip;
97 struct hlist_node *pos; 125 struct hlist_node *pos;
98 126
127 retry:
99 hlist_for_each(pos, &kprobe_insn_pages) { 128 hlist_for_each(pos, &kprobe_insn_pages) {
100 kip = hlist_entry(pos, struct kprobe_insn_page, hlist); 129 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
101 if (kip->nused < INSNS_PER_PAGE) { 130 if (kip->nused < INSNS_PER_PAGE) {
@@ -112,7 +141,11 @@ kprobe_opcode_t __kprobes *get_insn_slot(void)
112 } 141 }
113 } 142 }
114 143
115 /* All out of space. Need to allocate a new page. Use slot 0.*/ 144 /* If there are any garbage slots, collect it and try again. */
145 if (kprobe_garbage_slots && collect_garbage_slots() == 0) {
146 goto retry;
147 }
148 /* All out of space. Need to allocate a new page. Use slot 0. */
116 kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL); 149 kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
117 if (!kip) { 150 if (!kip) {
118 return NULL; 151 return NULL;
@@ -133,10 +166,62 @@ kprobe_opcode_t __kprobes *get_insn_slot(void)
133 memset(kip->slot_used, 0, INSNS_PER_PAGE); 166 memset(kip->slot_used, 0, INSNS_PER_PAGE);
134 kip->slot_used[0] = 1; 167 kip->slot_used[0] = 1;
135 kip->nused = 1; 168 kip->nused = 1;
169 kip->ngarbage = 0;
136 return kip->insns; 170 return kip->insns;
137} 171}
138 172
139void __kprobes free_insn_slot(kprobe_opcode_t *slot) 173/* Return 1 if all garbages are collected, otherwise 0. */
174static int __kprobes collect_one_slot(struct kprobe_insn_page *kip, int idx)
175{
176 kip->slot_used[idx] = 0;
177 kip->nused--;
178 if (kip->nused == 0) {
179 /*
180 * Page is no longer in use. Free it unless
181 * it's the last one. We keep the last one
182 * so as not to have to set it up again the
183 * next time somebody inserts a probe.
184 */
185 hlist_del(&kip->hlist);
186 if (hlist_empty(&kprobe_insn_pages)) {
187 INIT_HLIST_NODE(&kip->hlist);
188 hlist_add_head(&kip->hlist,
189 &kprobe_insn_pages);
190 } else {
191 module_free(NULL, kip->insns);
192 kfree(kip);
193 }
194 return 1;
195 }
196 return 0;
197}
198
199static int __kprobes collect_garbage_slots(void)
200{
201 struct kprobe_insn_page *kip;
202 struct hlist_node *pos, *next;
203
204 /* Ensure no-one is preepmted on the garbages */
205 if (check_safety() != 0)
206 return -EAGAIN;
207
208 hlist_for_each_safe(pos, next, &kprobe_insn_pages) {
209 int i;
210 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
211 if (kip->ngarbage == 0)
212 continue;
213 kip->ngarbage = 0; /* we will collect all garbages */
214 for (i = 0; i < INSNS_PER_PAGE; i++) {
215 if (kip->slot_used[i] == -1 &&
216 collect_one_slot(kip, i))
217 break;
218 }
219 }
220 kprobe_garbage_slots = 0;
221 return 0;
222}
223
224void __kprobes free_insn_slot(kprobe_opcode_t * slot, int dirty)
140{ 225{
141 struct kprobe_insn_page *kip; 226 struct kprobe_insn_page *kip;
142 struct hlist_node *pos; 227 struct hlist_node *pos;
@@ -146,28 +231,18 @@ void __kprobes free_insn_slot(kprobe_opcode_t *slot)
146 if (kip->insns <= slot && 231 if (kip->insns <= slot &&
147 slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) { 232 slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {
148 int i = (slot - kip->insns) / MAX_INSN_SIZE; 233 int i = (slot - kip->insns) / MAX_INSN_SIZE;
149 kip->slot_used[i] = 0; 234 if (dirty) {
150 kip->nused--; 235 kip->slot_used[i] = -1;
151 if (kip->nused == 0) { 236 kip->ngarbage++;
152 /* 237 } else {
153 * Page is no longer in use. Free it unless 238 collect_one_slot(kip, i);
154 * it's the last one. We keep the last one
155 * so as not to have to set it up again the
156 * next time somebody inserts a probe.
157 */
158 hlist_del(&kip->hlist);
159 if (hlist_empty(&kprobe_insn_pages)) {
160 INIT_HLIST_NODE(&kip->hlist);
161 hlist_add_head(&kip->hlist,
162 &kprobe_insn_pages);
163 } else {
164 module_free(NULL, kip->insns);
165 kfree(kip);
166 }
167 } 239 }
168 return; 240 break;
169 } 241 }
170 } 242 }
243 if (dirty && (++kprobe_garbage_slots > INSNS_PER_PAGE)) {
244 collect_garbage_slots();
245 }
171} 246}
172#endif 247#endif
173 248