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Date: Thu, 3 Sep 2009 16:25:53 -0400
From: Jason Baron <jbaron@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: mathieu.desnoyers@...ymtl.ca, roland@...hat.com, rth@...hat.com,
mingo@...e.hu
Subject: [PATCH 1/4] RFC: basic jump label implementation
introduce basic infrastructure for jump patching:
-STATIC_JUMP_IF() macro
-jump table infrastructure
-jump/nop patching in the ftrace layer
Signed-off-by: Jason Baron <jbaron@...hat.com>
---
arch/x86/kernel/ftrace.c | 36 ++++++++++
include/asm-generic/vmlinux.lds.h | 11 +++
include/linux/ftrace.h | 3 +
include/linux/jump_label.h | 45 ++++++++++++
kernel/Makefile | 2 +-
kernel/jump_label.c | 138 +++++++++++++++++++++++++++++++++++++
6 files changed, 234 insertions(+), 1 deletions(-)
create mode 100644 include/linux/jump_label.h
create mode 100644 kernel/jump_label.c
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 9dbb527..0907b8c 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -67,6 +67,20 @@ static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
return calc.code;
}
+static unsigned char *ftrace_jump_replace(unsigned long ip, unsigned long addr)
+{
+ static union ftrace_code_union calc;
+
+ calc.e8 = 0xe9;
+ calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
+
+ /*
+ * No locking needed, this must be called via kstop_machine
+ * which in essence is like running on a uniprocessor machine.
+ */
+ return calc.code;
+}
+
/*
* Modifying code must take extra care. On an SMP machine, if
* the code being modified is also being executed on another CPU
@@ -278,6 +292,28 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
return ftrace_modify_code(rec->ip, old, new);
}
+int ftrace_make_jump(struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned char *new, *old;
+ unsigned long ip = rec->ip;
+
+ old = ftrace_nop_replace();
+ new = ftrace_jump_replace(ip, addr);
+
+ return ftrace_modify_code(rec->ip, old, new);
+}
+
+int ftrace_make_jump_nop(struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned char *new, *old;
+ unsigned long ip = rec->ip;
+
+ old = ftrace_jump_replace(ip, addr);
+ new = ftrace_nop_replace();
+
+ return ftrace_modify_code(rec->ip, old, new);
+}
+
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long ip = (unsigned long)(&ftrace_call);
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index a549465..d789646 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -212,6 +212,7 @@
*(__vermagic) /* Kernel version magic */ \
*(__markers_strings) /* Markers: strings */ \
*(__tracepoints_strings)/* Tracepoints: strings */ \
+ *(__jump_strings)/* Jump: strings */ \
} \
\
.rodata1 : AT(ADDR(.rodata1) - LOAD_OFFSET) { \
@@ -219,6 +220,8 @@
} \
\
BUG_TABLE \
+ JUMP_TABLE \
+ \
\
/* PCI quirks */ \
.pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \
@@ -563,6 +566,14 @@
#define BUG_TABLE
#endif
+#define JUMP_TABLE \
+ . = ALIGN(8); \
+ __jump_table : AT(ADDR(__jump_table) - LOAD_OFFSET) { \
+ VMLINUX_SYMBOL(__start___jump_table) = .; \
+ *(__jump_table) \
+ VMLINUX_SYMBOL(__stop___jump_table) = .; \
+ }
+
#ifdef CONFIG_PM_TRACE
#define TRACEDATA \
. = ALIGN(4); \
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index dc3b132..cf3d995 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -227,6 +227,9 @@ extern int ftrace_make_nop(struct module *mod,
* Any other value will be considered a failure.
*/
extern int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr);
+extern int ftrace_make_jump(struct dyn_ftrace *rec, unsigned long addr);
+extern int ftrace_make_jump_nop(struct dyn_ftrace *rec, unsigned long addr);
+
/* May be defined in arch */
extern int ftrace_arch_read_dyn_info(char *buf, int size);
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
new file mode 100644
index 0000000..1b80bbe
--- /dev/null
+++ b/include/linux/jump_label.h
@@ -0,0 +1,45 @@
+#ifndef _LINUX_JUMP_LABEL_H
+#define _LINUX_JUMP_LABEL_H
+
+#include <asm/nops.h>
+
+/* this will change to a compiler dependency that supports 'asm goto' */
+#define HAVE_JUMP_LABEL
+
+#ifdef HAVE_JUMP_LABEL
+
+#define JUMP_LABEL_NAME(tag) \
+ const char __sjstrtab_##tag[] \
+ __used __attribute__((section("__jump_strings"))) = #tag;
+
+#define JUMP_LABEL_IF(tag, label, cond) \
+ asm goto ("1:" /* 5-byte insn */ \
+ P6_NOP5 \
+ ".pushsection __jump_table, \"a\" \n\t" \
+ _ASM_PTR "1b, %l[" #label "], %c0 \n\t" \
+ ".popsection \n\t" \
+ : : "i" (__sjstrtab_##tag) : : label)
+
+int run_make_nop(char *name);
+int run_make_jump(char *name);
+
+#else
+
+#define JUMP_LABEL_NAME(tag)
+#define JUMP_LABEL_IF(tag, label, cond) \
+ if (unlikely(cond)) \
+ goto label;
+
+static inline int run_make_nop(char *name)
+{
+ return 0;
+}
+
+static inline int run_make_jump(char *name)
+{
+ return 0;
+}
+
+#endif
+
+#endif
diff --git a/kernel/Makefile b/kernel/Makefile
index ef1011b..d29ae98 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -10,7 +10,7 @@ obj-y = sched.o fork.o exec_domain.o panic.o printk.o \
kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
notifier.o ksysfs.o pm_qos_params.o sched_clock.o cred.o \
- async.o
+ async.o jump_label.o
obj-y += groups.o
ifdef CONFIG_FUNCTION_TRACER
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
new file mode 100644
index 0000000..f6be1eb
--- /dev/null
+++ b/kernel/jump_label.c
@@ -0,0 +1,138 @@
+#include <linux/init.h>
+#include <linux/debugfs.h>
+#include <linux/jump_label.h>
+#include <linux/stop_machine.h>
+#include <linux/ftrace.h>
+#include <linux/uaccess.h>
+
+#include <asm/cacheflush.h>
+
+JUMP_LABEL_NAME(trace);
+JUMP_LABEL_NAME(trace2);
+
+static int jump_enabled;
+static int jump_enabled2;
+
+#ifdef HAVE_JUMP_LABEL
+
+extern int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr);
+
+struct jump_entry {
+ unsigned long code;
+ unsigned long target;
+ char *name;
+};
+
+extern struct jump_entry __start___jump_table[];
+extern struct jump_entry __stop___jump_table[];
+
+struct jump_entry *find_jump_entry(char *name)
+{
+
+ struct jump_entry *iter;
+
+ for (iter = __start___jump_table; iter < __stop___jump_table; iter++) {
+ if (!strcmp(name, iter->name)) {
+ printk("find_jump_entry matched: %s\n", iter->name);
+ return iter;
+ }
+ }
+ return NULL;
+}
+
+/* hard coded for testing */
+static int enable_jump(void *ptr)
+{
+ struct dyn_ftrace rec;
+ struct jump_entry *jentry;
+ unsigned long code, target;
+ int ret;
+
+ jentry = ((struct jump_entry *)ptr);
+ code = jentry->code;
+ target = jentry->target;
+ rec.ip = code;
+ ret = ftrace_make_jump(&rec, target);
+
+ return 0;
+}
+
+/* hard coded for testing */
+static int enable_nop(void *ptr)
+{
+ struct dyn_ftrace rec;
+ struct jump_entry *jentry;
+ unsigned long code, target;
+ int ret;
+
+ jentry = ((struct jump_entry *)ptr);
+ code = jentry->code;
+ target = jentry->target;
+ rec.ip = code;
+ ret = ftrace_make_jump_nop(&rec, target);
+
+ return 0;
+}
+
+int run_make_jump(char *name)
+{
+ int ret;
+ struct jump_entry *jentry;
+
+ jentry = find_jump_entry(name);
+ if (!jentry)
+ return -ENOENT;
+
+ ret = ftrace_arch_code_modify_prepare();
+ WARN_ON(ret);
+ if (ret)
+ return -1;
+
+ stop_machine(enable_jump, (void *)jentry, NULL);
+
+ ret = ftrace_arch_code_modify_post_process();
+ WARN_ON(ret);
+
+ return 0;
+}
+
+int run_make_nop(char *name)
+{
+ int ret;
+ struct jump_entry *jentry;
+
+ jentry = find_jump_entry(name);
+ if (!jentry)
+ return -ENOENT;
+
+ ret = ftrace_arch_code_modify_prepare();
+ WARN_ON(ret);
+ if (ret)
+ return -1;
+
+ stop_machine(enable_nop, (void *)jentry, NULL);
+
+ ret = ftrace_arch_code_modify_post_process();
+ WARN_ON(ret);
+
+ return 0;
+}
+
+#endif
+
+static int __jump_label_init(void)
+{
+ struct jump_entry *iter;
+
+
+#ifdef HAVE_STATIC_JUMP
+ printk("__start___jump_table is: %p\n", __start___jump_table);
+ printk("__stop___jump_table is: %p\n", __stop___jump_table);
+ for(iter = __start___jump_table; iter < __stop___jump_table; iter++)
+ printk("jump label: code: %p, target: %p, name: %s\n", iter->code, iter->target, iter->name);
+#endif
+
+ return 0;
+}
+late_initcall(__jump_label_init);
+
--
1.6.2.5
--
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