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From: Masami Hiramatsu on 10 May 2010 13:50
Introduce text_poke_smp_batch(). This function modifies several
text areas with one stop_machine() on SMPr. Because calling
stop_machine() is heavy task, it is better to aggregate text_poke
requests.

Signed-off-by: Masami Hiramatsu <mhiramat(a)redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth(a)in.ibm.com>
Cc: Ingo Molnar <mingo(a)elte.hu>
Cc: Jim Keniston <jkenisto(a)us.ibm.com>
Cc: Jason Baron <jbaron(a)redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers(a)efficios.com>
---

arch/x86/include/asm/alternative.h | 7 +++++
arch/x86/kernel/alternative.c | 49 +++++++++++++++++++++++++++++-------
2 files changed, 47 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 03b6bb5..9a08773 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -176,7 +176,14 @@ static inline void apply_paravirt(struct paravirt_patch_site *start,
* On the local CPU you need to be protected again NMI or MCE handlers seeing an
* inconsistent instruction while you patch.
*/
+struct text_poke_param {
+ void *addr;
+ const void *opcode;
+ size_t len;
+};
+
extern void *text_poke(void *addr, const void *opcode, size_t len);
extern void *text_poke_smp(void *addr, const void *opcode, size_t len);
+extern void text_poke_smp_batch(struct text_poke_param *params, int n);

#endif /* _ASM_X86_ALTERNATIVE_H */
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 7023773..7256800 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -590,17 +590,21 @@ static atomic_t stop_machine_first;
static int wrote_text;

struct text_poke_params {
- void *addr;
- const void *opcode;
- size_t len;
+ struct text_poke_param *params;
+ int nparams;
};

static int __kprobes stop_machine_text_poke(void *data)
{
struct text_poke_params *tpp = data;
+ struct text_poke_param *p;
+ int i;

if (atomic_dec_and_test(&stop_machine_first)) {
- text_poke(tpp->addr, tpp->opcode, tpp->len);
+ for (i = 0; i < tpp->nparams; i++) {
+ p = &tpp->params[i];
+ text_poke(p->addr, p->opcode, p->len);
+ }
smp_wmb(); /* Make sure other cpus see that this has run */
wrote_text = 1;
} else {
@@ -609,8 +613,12 @@ static int __kprobes stop_machine_text_poke(void *data)
smp_mb(); /* Load wrote_text before following execution */
}

- flush_icache_range((unsigned long)tpp->addr,
- (unsigned long)tpp->addr + tpp->len);
+ for (i = 0; i < tpp->nparams; i++) {
+ p = &tpp->params[i];
+ flush_icache_range((unsigned long)p->addr,
+ (unsigned long)p->addr + p->len);
+ }
+
return 0;
}

@@ -630,13 +638,36 @@ static int __kprobes stop_machine_text_poke(void *data)
void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len)
{
struct text_poke_params tpp;
+ struct text_poke_param p;

- tpp.addr = addr;
- tpp.opcode = opcode;
- tpp.len = len;
+ p.addr = addr;
+ p.opcode = opcode;
+ p.len = len;
+ tpp.params = &p;
+ tpp.nparams = 1;
atomic_set(&stop_machine_first, 1);
wrote_text = 0;
stop_machine(stop_machine_text_poke, (void *)&tpp, NULL);
return addr;
}

+/**
+ * text_poke_smp_batch - Update instructions on a live kernel on SMP
+ * @params: an array of text_poke parameters
+ * @n: the number of elements in params.
+ *
+ * Modify multi-byte instruction by using stop_machine() on SMP. Since the
+ * stop_machine() is heavy task, it is better to aggregate text_poke requests
+ * and do it once if possible.
+ *
+ * Note: Must be called under get_online_cpus() and text_mutex.
+ */
+void __kprobes text_poke_smp_batch(struct text_poke_param *params, int n)
+{
+ struct text_poke_params tpp = {.params = params, .nparams = n};
+
+ atomic_set(&stop_machine_first, 1);
+ wrote_text = 0;
+ stop_machine(stop_machine_text_poke, (void *)&tpp, NULL);
+}
+


--
Masami Hiramatsu
e-mail: mhiramat(a)redhat.com
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Prev: [PATCH] idr: document that idr_for_each may be used under rcu_read_lock()
Next: [PATCH -tip 2/5] kprobes: Limit maximum number of optimization at once