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>
This commit is contained in:
Shaohua Li 2009-01-09 11:29:49 +08:00 committed by Ingo Molnar
parent d3e75ff14b
commit a14a07b801
5 changed files with 277 additions and 0 deletions

View file

@ -21,6 +21,8 @@ config IA64
select HAVE_OPROFILE
select HAVE_KPROBES
select HAVE_KRETPROBES
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_DYNAMIC_FTRACE if (!ITANIUM)
select HAVE_FUNCTION_TRACER
select HAVE_DMA_ATTRS
select HAVE_KVM

View file

@ -8,6 +8,19 @@
extern void _mcount(unsigned long pfs, unsigned long r1, unsigned long b0, unsigned long r0);
#define mcount _mcount
#include <asm/kprobes.h>
/* In IA64, MCOUNT_ADDR is set in link time, so it's not a constant at compile time */
#define MCOUNT_ADDR (((struct fnptr *)mcount)->ip)
#define FTRACE_ADDR (((struct fnptr *)ftrace_caller)->ip)
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
/* second bundle, insn 2 */
return addr - 0x12;
}
struct dyn_arch_ftrace {
};
#endif
#endif /* CONFIG_FUNCTION_TRACER */

View file

@ -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

View file

@ -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

206
arch/ia64/kernel/ftrace.c Normal file
View file

@ -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;
}