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Date: Fri, 22 Jan 2010 13:55:42 -0500
From: Masami Hiramatsu <mhiramat@...hat.com>
To: Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...e.hu>,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
lkml <linux-kernel@...r.kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>,
Ingo Molnar <mingo@...e.hu>,
Jim Keniston <jkenisto@...ibm.com>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
Christoph Hellwig <hch@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Frederic Weisbecker <fweisbec@...il.com>,
"H. Peter Anvin" <hpa@...or.com>,
Anders Kaseorg <andersk@...lice.com>,
Tim Abbott <tabbott@...lice.com>,
Andi Kleen <andi@...stfloor.org>,
Jason Baron <jbaron@...hat.com>,
Mathieu Desnoyers <compudj@...stal.dyndns.org>,
systemtap <systemtap@...rces.redhat.com>,
DLE <dle-develop@...ts.sourceforge.net>
Subject: [PATCH -tip v8 7/9] x86: Add text_poke_smp for SMP cross modifying
code
Add generic text_poke_smp for SMP which uses stop_machine()
to synchronize modifying code.
This stop_machine() method is officially described at "7.1.3
Handling Self- and Cross-Modifying Code" on the intel's
software developer's manual 3A.
Since stop_machine() can't protect code against NMI/MCE, this
function can not modify those handlers. And also, this function
is basically for modifying multibyte-single-instruction. For
modifying multibyte-multi-instructions, we need another special
trap & detour code.
This code originaly comes from immediate values with stop_machine()
version. Thanks Mathieu!
Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Mathieu Desnoyers <compudj@...stal.dyndns.org>
Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Jim Keniston <jkenisto@...ibm.com>
Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Anders Kaseorg <andersk@...lice.com>
Cc: Tim Abbott <tabbott@...lice.com>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: Jason Baron <jbaron@...hat.com>
---
arch/x86/include/asm/alternative.h | 4 ++
arch/x86/kernel/alternative.c | 60 ++++++++++++++++++++++++++++++++++++
2 files changed, 63 insertions(+), 1 deletions(-)
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 3b5b828..09388c6 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -160,10 +160,12 @@ static inline void apply_paravirt(struct paravirt_patch_site *start,
* invalid instruction possible) or if the instructions are changed from a
* consistent state to another consistent state atomically.
* More care must be taken when modifying code in the SMP case because of
- * Intel's errata.
+ * Intel's errata. text_poke_smp() takes care that errata, but still
+ * doesn't support NMI/MCE handler code modifying.
* On the local CPU you need to be protected again NMI or MCE handlers seeing an
* inconsistent instruction while you patch.
*/
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);
#endif /* _ASM_X86_ALTERNATIVE_H */
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 2589ea4..aff169e 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -7,6 +7,7 @@
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <linux/memory.h>
+#include <linux/stop_machine.h>
#include <asm/alternative.h>
#include <asm/sections.h>
#include <asm/pgtable.h>
@@ -554,3 +555,62 @@ 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)
+ smp_rmb();
+ sync_core();
+ }
+
+ 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;
+}
+
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division
e-mail: mhiramat@...hat.com
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