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authorMasami Hiramatsu <mhiramat@redhat.com>2010-02-25 08:34:38 -0500
committerIngo Molnar <mingo@elte.hu>2010-02-25 17:49:26 +0100
commit3d55cc8a058ee96291d6d45b1e35121b9920eca3 (patch)
tree716a79a900c013082f02de127e1fae784997ce49
parentf007ea2685692bafb386820144cf73a14016fc7c (diff)
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 Jason and Mathieu! Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com> Cc: systemtap <systemtap@sources.redhat.com> Cc: DLE <dle-develop@lists.sourceforge.net> Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> 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: Anders Kaseorg <andersk@ksplice.com> Cc: Tim Abbott <tabbott@ksplice.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Jason Baron <jbaron@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> LKML-Reference: <20100225133438.6725.80273.stgit@localhost6.localdomain6> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--arch/x86/include/asm/alternative.h4
-rw-r--r--arch/x86/kernel/alternative.c60
2 files changed, 63 insertions, 1 deletions
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index ac80b7d70014..643d6ab3588b 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 e63b80e5861c..c41f13c15e8f 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>
@@ -570,3 +571,62 @@ 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;
+}
+