ftrace, ia64: IA64 dynamic ftrace support

IA64 dynamic ftrace support.
The original _mcount stub for each function is like:
	alloc r40=ar.pfs,12,8,0
	mov r43=r0;;
	mov r42=b0
	mov r41=r1
	nop.i 0x0
	br.call.sptk.many b0 = _mcount;;

The patch convert it to below for nop:
	[MII] nop.m 0x0
	mov r3=ip
	nop.i 0x0
	[MLX] nop.m 0x0
	nop.x 0x0;;
This isn't completely nop, as there is one instuction 'mov r3=ip', but
it should be light and harmless for code follow it.

And below is for call
	[MII] nop.m 0x0
	mov r3=ip
	nop.i 0x0
	[MLX] nop.m 0x0
	brl.many .;;
In this way, only one instruction is changed to convert code between nop
and call. This should meet dyn-ftrace's requirement.
But this requires CPU support brl instruction, so dyn-ftrace isn't
supported for old Itanium system. Assume there are quite few such old
system running.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 262 insertions, 0 deletions

diff --git a/arch/ia64/kernel/Makefile b/arch/ia64/kernel/Makefile
index c381ea95489..ab6e7ec0bba 100644
--- a/arch/ia64/kernel/Makefile
+++ b/arch/ia64/kernel/Makefile
@@ -2,6 +2,10 @@
 # Makefile for the linux kernel.
 #
 
+ifdef CONFIG_DYNAMIC_FTRACE
+CFLAGS_REMOVE_ftrace.o = -pg
+endif
+
 extra-y	:= head.o init_task.o vmlinux.lds
 
 obj-y := acpi.o entry.o efi.o efi_stub.o gate-data.o fsys.o ia64_ksyms.o irq.o irq_ia64.o	\
@@ -28,6 +32,7 @@ obj-$(CONFIG_IA64_CYCLONE)	+= cyclone.o
 obj-$(CONFIG_CPU_FREQ)		+= cpufreq/
 obj-$(CONFIG_IA64_MCA_RECOVERY)	+= mca_recovery.o
 obj-$(CONFIG_KPROBES)		+= kprobes.o jprobes.o
+obj-$(CONFIG_DYNAMIC_FTRACE)	+= ftrace.o
 obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o crash.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_IA64_UNCACHED_ALLOCATOR)	+= uncached.o
diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S
index c2f7d798e2a..e0be92a6abb 100644
--- a/arch/ia64/kernel/entry.S
+++ b/arch/ia64/kernel/entry.S
@@ -1406,6 +1406,56 @@ GLOBAL_ENTRY(unw_init_running)
 END(unw_init_running)
 
 #ifdef CONFIG_FUNCTION_TRACER
+#ifdef CONFIG_DYNAMIC_FTRACE
+GLOBAL_ENTRY(_mcount)
+	br ftrace_stub
+END(_mcount)
+
+.here:
+	br.ret.sptk.many b0
+
+GLOBAL_ENTRY(ftrace_caller)
+	alloc out0 = ar.pfs, 8, 0, 4, 0
+	mov out3 = r0
+	;;
+	mov out2 = b0
+	add r3 = 0x20, r3
+	mov out1 = r1;
+	br.call.sptk.many b0 = ftrace_patch_gp
+	//this might be called from module, so we must patch gp
+ftrace_patch_gp:
+	movl gp=__gp
+	mov b0 = r3
+	;;
+.global ftrace_call;
+ftrace_call:
+{
+	.mlx
+	nop.m 0x0
+	movl r3 = .here;;
+}
+	alloc loc0 = ar.pfs, 4, 4, 2, 0
+	;;
+	mov loc1 = b0
+	mov out0 = b0
+	mov loc2 = r8
+	mov loc3 = r15
+	;;
+	adds out0 = -MCOUNT_INSN_SIZE, out0
+	mov out1 = in2
+	mov b6 = r3
+
+	br.call.sptk.many b0 = b6
+	;;
+	mov ar.pfs = loc0
+	mov b0 = loc1
+	mov r8 = loc2
+	mov r15 = loc3
+	br ftrace_stub
+	;;
+END(ftrace_caller)
+
+#else
 GLOBAL_ENTRY(_mcount)
 	movl r2 = ftrace_stub
 	movl r3 = ftrace_trace_function;;
@@ -1435,6 +1485,7 @@ GLOBAL_ENTRY(_mcount)
 	br ftrace_stub
 	;;
 END(_mcount)
+#endif
 
 GLOBAL_ENTRY(ftrace_stub)
 	mov r3 = b0
diff --git a/arch/ia64/kernel/ftrace.c b/arch/ia64/kernel/ftrace.c
new file mode 100644
index 00000000000..7fc8c961b1f
--- /dev/null
+++ b/arch/ia64/kernel/ftrace.c
@@ -0,0 +1,206 @@
+/*
+ * Dynamic function tracing support.
+ *
+ * Copyright (C) 2008 Shaohua Li <shaohua.li@intel.com>
+ *
+ * For licencing details, see COPYING.
+ *
+ * Defines low-level handling of mcount calls when the kernel
+ * is compiled with the -pg flag. When using dynamic ftrace, the
+ * mcount call-sites get patched lazily with NOP till they are
+ * enabled. All code mutation routines here take effect atomically.
+ */
+
+#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+
+#include <asm/cacheflush.h>
+#include <asm/patch.h>
+
+/* In IA64, each function will be added below two bundles with -pg option */
+static unsigned char __attribute__((aligned(8)))
+ftrace_orig_code[MCOUNT_INSN_SIZE] = {
+	0x02, 0x40, 0x31, 0x10, 0x80, 0x05, /* alloc r40=ar.pfs,12,8,0 */
+	0xb0, 0x02, 0x00, 0x00, 0x42, 0x40, /* mov r43=r0;; */
+	0x05, 0x00, 0xc4, 0x00,             /* mov r42=b0 */
+	0x11, 0x48, 0x01, 0x02, 0x00, 0x21, /* mov r41=r1 */
+	0x00, 0x00, 0x00, 0x02, 0x00, 0x00, /* nop.i 0x0 */
+	0x08, 0x00, 0x00, 0x50              /* br.call.sptk.many b0 = _mcount;; */
+};
+
+struct ftrace_orig_insn {
+	u64 dummy1, dummy2, dummy3;
+	u64 dummy4:64-41+13;
+	u64 imm20:20;
+	u64 dummy5:3;
+	u64 sign:1;
+	u64 dummy6:4;
+};
+
+/* mcount stub will be converted below for nop */
+static unsigned char ftrace_nop_code[MCOUNT_INSN_SIZE] = {
+	0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
+	0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
+	0x00, 0x00, 0x04, 0x00,             /* nop.i 0x0 */
+	0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* nop.x 0x0;; */
+	0x00, 0x00, 0x04, 0x00
+};
+
+static unsigned char *ftrace_nop_replace(void)
+{
+	return ftrace_nop_code;
+}
+
+/*
+ * mcount stub will be converted below for call
+ * Note: Just the last instruction is changed against nop
+ * */
+static unsigned char __attribute__((aligned(8)))
+ftrace_call_code[MCOUNT_INSN_SIZE] = {
+	0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
+	0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
+	0x00, 0x00, 0x04, 0x00,             /* nop.i 0x0 */
+	0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
+	0xff, 0xff, 0xff, 0xff, 0x7f, 0x00, /* brl.many .;;*/
+	0xf8, 0xff, 0xff, 0xc8
+};
+
+struct ftrace_call_insn {
+	u64 dummy1, dummy2;
+	u64 dummy3:48;
+	u64 imm39_l:16;
+	u64 imm39_h:23;
+	u64 dummy4:13;
+	u64 imm20:20;
+	u64 dummy5:3;
+	u64 i:1;
+	u64 dummy6:4;
+};
+
+static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+{
+	struct ftrace_call_insn *code = (void *)ftrace_call_code;
+	unsigned long offset = addr - (ip + 0x10);
+
+	code->imm39_l = offset >> 24;
+	code->imm39_h = offset >> 40;
+	code->imm20 = offset >> 4;
+	code->i = offset >> 63;
+	return ftrace_call_code;
+}
+
+static int
+ftrace_modify_code(unsigned long ip, unsigned char *old_code,
+		   unsigned char *new_code, int do_check)
+{
+	unsigned char replaced[MCOUNT_INSN_SIZE];
+
+	/*
+	 * Note: Due to modules and __init, code can
+	 *  disappear and change, we need to protect against faulting
+	 *  as well as code changing. We do this by using the
+	 *  probe_kernel_* functions.
+	 *
+	 * No real locking needed, this code is run through
+	 * kstop_machine, or before SMP starts.
+	 */
+
+	if (!do_check)
+		goto skip_check;
+
+	/* read the text we want to modify */
+	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
+		return -EFAULT;
+
+	/* Make sure it is what we expect it to be */
+	if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
+		return -EINVAL;
+
+skip_check:
+	/* replace the text with the new text */
+	if (probe_kernel_write(((void *)ip), new_code, MCOUNT_INSN_SIZE))
+		return -EPERM;
+	flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
+
+	return 0;
+}
+
+static int ftrace_make_nop_check(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned char __attribute__((aligned(8))) replaced[MCOUNT_INSN_SIZE];
+	unsigned long ip = rec->ip;
+
+	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
+		return -EFAULT;
+	if (rec->flags & FTRACE_FL_CONVERTED) {
+		struct ftrace_call_insn *call_insn, *tmp_call;
+
+		call_insn = (void *)ftrace_call_code;
+		tmp_call = (void *)replaced;
+		call_insn->imm39_l = tmp_call->imm39_l;
+		call_insn->imm39_h = tmp_call->imm39_h;
+		call_insn->imm20 = tmp_call->imm20;
+		call_insn->i = tmp_call->i;
+		if (memcmp(replaced, ftrace_call_code, MCOUNT_INSN_SIZE) != 0)
+			return -EINVAL;
+		return 0;
+	} else {
+		struct ftrace_orig_insn *call_insn, *tmp_call;
+
+		call_insn = (void *)ftrace_orig_code;
+		tmp_call = (void *)replaced;
+		call_insn->sign = tmp_call->sign;
+		call_insn->imm20 = tmp_call->imm20;
+		if (memcmp(replaced, ftrace_orig_code, MCOUNT_INSN_SIZE) != 0)
+			return -EINVAL;
+		return 0;
+	}
+}
+
+int ftrace_make_nop(struct module *mod,
+		    struct dyn_ftrace *rec, unsigned long addr)
+{
+	int ret;
+	char *new;
+
+	ret = ftrace_make_nop_check(rec, addr);
+	if (ret)
+		return ret;
+	new = ftrace_nop_replace();
+	return ftrace_modify_code(rec->ip, NULL, new, 0);
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned long ip = rec->ip;
+	unsigned char *old, *new;
+
+	old=  ftrace_nop_replace();
+	new = ftrace_call_replace(ip, addr);
+	return ftrace_modify_code(ip, old, new, 1);
+}
+
+/* in IA64, _mcount can't directly call ftrace_stub. Only jump is ok */
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+	unsigned long ip;
+	unsigned long addr = ((struct fnptr *)ftrace_call)->ip;
+
+	if (func == ftrace_stub)
+		return 0;
+	ip = ((struct fnptr *)func)->ip;
+
+	ia64_patch_imm64(addr + 2, ip);
+
+	flush_icache_range(addr, addr + 16);
+	return 0;
+}
+
+/* run from kstop_machine */
+int __init ftrace_dyn_arch_init(void *data)
+{
+	*(unsigned long *)data = 0;
+
+	return 0;
+}