From: Masami Hiramatsu <mhiramat@redhat.com>
To: Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@elte.hu>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
lkml<linux-kernel@vger.kernel.org>
Cc: systemtap<systemtap@sources.redhat.com>,
DLE<dle-develop@lists.sourceforge.net>,
Masami Hiramatsu <mhiramat@redhat.com>,
Mathieu Desnoyers <compudj@krystal.dyndns.org>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Ingo Molnar <mingo@elte.hu>,
Jim Keniston <jkenisto@us.ibm.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Christoph Hellwig <hch@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Anders Kaseorg <andersk@ksplice.com>,
Tim Abbott <tabbott@ksplice.com>,
Andi Kleen <andi@firstfloor.org>,
Jason Baron <jbaron@redhat.com>
Subject: [PATCH -tip v7 07/11] x86: Add text_poke_smp for SMP cross modifying code
Date: Fri, 18 Dec 2009 18:12:00 -0000 [thread overview]
Message-ID: <20091218181619.21350.74673.stgit@dhcp-100-2-132.bos.redhat.com> (raw)
In-Reply-To: <20091218181527.21350.45287.stgit@dhcp-100-2-132.bos.redhat.com>
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@redhat.com>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Anders Kaseorg <andersk@ksplice.com>
Cc: Tim Abbott <tabbott@ksplice.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jason Baron <jbaron@redhat.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 69b74a7..812ee2c 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -155,10 +155,12 @@ 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 de7353c..7ce45d7 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>
@@ -552,3 +553,62 @@ 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@redhat.com
next prev parent reply other threads:[~2009-12-18 18:11 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-18 18:10 [PATCH -tip v7 00/11] kprobes: Kprobes jump optimization support Masami Hiramatsu
2009-12-18 18:10 ` [PATCH -tip v7 01/11] kprobes/x86: Cleanup RELATIVEJUMP_INSTRUCTION to RELATIVEJUMP_OPCODE Masami Hiramatsu
2009-12-18 18:11 ` [PATCH -tip v7 02/11] kprobes: Introduce generic insn_slot framework Masami Hiramatsu
2009-12-18 18:11 ` [PATCH -tip v7 03/11] kprobes: Introduce kprobes jump optimization Masami Hiramatsu
2009-12-18 18:11 ` [PATCH -tip v7 04/11] kprobes: Jump optimization sysctl interface Masami Hiramatsu
2009-12-18 18:11 ` [PATCH -tip v7 06/11] kprobes/x86: Cleanup save/restore registers Masami Hiramatsu
2009-12-18 18:11 ` [PATCH -tip v7 05/11] kprobes/x86: Boost probes when reentering Masami Hiramatsu
2009-12-18 18:12 ` [PATCH -tip v7 09/11] kprobes: Add documents of jump optimization Masami Hiramatsu
2009-12-18 18:12 ` [PATCH -tip v7 10/11] [RFC] x86: Introduce generic jump patching without stop_machine Masami Hiramatsu
2009-12-18 18:12 ` Masami Hiramatsu [this message]
2009-12-18 18:12 ` [PATCH -tip v7 08/11] kprobes/x86: Support kprobes jump optimization on x86 Masami Hiramatsu
2009-12-18 18:12 ` [PATCH -tip v7 11/11] [RFC] kprobes/x86: Use text_poke_fixup() for jump optimization Masami Hiramatsu
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