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Subject[PATCH v1 2/5] mips dynamic function tracer support
Date
From: Wu Zhangjin <wuzj@lemote.com>

dynamic function tracer need to replace "nop" to "jumps & links" and
something reversely.

Signed-off-by: Wu Zhangjin <wuzj@lemote.com>
---
arch/mips/Kconfig | 3 +
arch/mips/include/asm/ftrace.h | 10 ++
arch/mips/kernel/Makefile | 2 +
arch/mips/kernel/ftrace.c | 217 ++++++++++++++++++++++++++++++++++++++++
arch/mips/kernel/mcount.S | 31 ++++++
scripts/Makefile.build | 1 +
scripts/recordmcount.pl | 32 +++++-
7 files changed, 290 insertions(+), 6 deletions(-)
create mode 100644 arch/mips/kernel/ftrace.c
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index d5c01ca..0c00536 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -6,6 +6,9 @@ config MIPS
select HAVE_ARCH_KGDB
select HAVE_FUNCTION_TRACER
select HAVE_FUNCTION_TRACE_MCOUNT_TEST
+ select HAVE_DYNAMIC_FTRACE
+ select HAVE_FTRACE_MCOUNT_RECORD
+ select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE
# Horrible source of confusion. Die, die, die ...
select EMBEDDED
select RTC_LIB
diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
index 5f8ebcf..b4970c9 100644
--- a/arch/mips/include/asm/ftrace.h
+++ b/arch/mips/include/asm/ftrace.h
@@ -19,6 +19,16 @@
extern void _mcount(void);
#define mcount _mcount

+#ifdef CONFIG_DYNAMIC_FTRACE
+/* reloction of mcount call site is the same as the address */
+static inline unsigned long ftrace_call_adjust(unsigned long addr)
+{
+ return addr;
+}
+
+struct dyn_arch_ftrace {
+};
+#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_FUNCTION_TRACER */
#endif /* _ASM_MIPS_FTRACE_H */
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index d167dde..6b1a8a5 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -11,6 +11,7 @@ obj-y += cpu-probe.o branch.o entry.o genex.o irq.o process.o \
ifdef CONFIG_FUNCTION_TRACER
# Do not profile debug and lowlevel utilities
CFLAGS_REMOVE_mcount.o = -pg
+CFLAGS_REMOVE_ftrace.o = -pg
CFLAGS_REMOVE_early_printk.o = -pg
endif

@@ -31,6 +32,7 @@ obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-$(CONFIG_MODULES) += mips_ksyms.o module.o

obj-$(CONFIG_FUNCTION_TRACER) += mcount.o
+obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o

obj-$(CONFIG_CPU_LOONGSON2) += r4k_fpu.o r4k_switch.o
obj-$(CONFIG_CPU_MIPS32) += r4k_fpu.o r4k_switch.o
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
new file mode 100644
index 0000000..827c128
--- /dev/null
+++ b/arch/mips/kernel/ftrace.c
@@ -0,0 +1,217 @@
+/*
+ * Code for replacing ftrace calls with jumps.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ * Copyright (C) 2009 DSLab, Lanzhou University, China
+ * Author: Wu Zhangjin <wuzj@lemote.com>
+ *
+ * Thanks goes to Steven Rostedt for writing the original x86 version.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/hardirq.h>
+#include <linux/uaccess.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/ftrace.h>
+
+#include <asm/cacheflush.h>
+#include <asm/ftrace.h>
+#include <asm/asm.h>
+#include <asm/unistd.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
+#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
+
+static unsigned int ftrace_nop = 0x00000000;
+
+static unsigned char *ftrace_call_replace(unsigned long op_code,
+ unsigned long addr)
+{
+ static unsigned int op;
+
+ op = op_code | ((addr >> 2) & ADDR_MASK);
+
+ return (unsigned char *) &op;
+}
+
+static atomic_t nmi_running = ATOMIC_INIT(0);
+static int mod_code_status; /* holds return value of text write */
+static int mod_code_write; /* set when NMI should do the write */
+static void *mod_code_ip; /* holds the IP to write to */
+static void *mod_code_newcode; /* holds the text to write to the IP */
+
+static unsigned nmi_wait_count;
+static atomic_t nmi_update_count = ATOMIC_INIT(0);
+
+int ftrace_arch_read_dyn_info(char *buf, int size)
+{
+ int r;
+
+ r = snprintf(buf, size, "%u %u",
+ nmi_wait_count, atomic_read(&nmi_update_count));
+ return r;
+}
+
+static void ftrace_mod_code(void)
+{
+ /*
+ * Yes, more than one CPU process can be writing to mod_code_status.
+ * (and the code itself)
+ * But if one were to fail, then they all should, and if one were
+ * to succeed, then they all should.
+ */
+ mod_code_status = probe_kernel_write(mod_code_ip, mod_code_newcode,
+ MCOUNT_INSN_SIZE);
+
+ /* if we fail, then kill any new writers */
+ if (mod_code_status)
+ mod_code_write = 0;
+}
+
+void ftrace_nmi_enter(void)
+{
+ atomic_inc(&nmi_running);
+ /* Must have nmi_running seen before reading write flag */
+ smp_mb();
+ if (mod_code_write) {
+ ftrace_mod_code();
+ atomic_inc(&nmi_update_count);
+ }
+}
+
+void ftrace_nmi_exit(void)
+{
+ /* Finish all executions before clearing nmi_running */
+ smp_wmb();
+ atomic_dec(&nmi_running);
+}
+
+static void wait_for_nmi(void)
+{
+ int waited = 0;
+
+ while (atomic_read(&nmi_running)) {
+ waited = 1;
+ cpu_relax();
+ }
+
+ if (waited)
+ nmi_wait_count++;
+}
+
+static int do_ftrace_mod_code(unsigned long ip, void *new_code)
+{
+ mod_code_ip = (void *) ip;
+ mod_code_newcode = new_code;
+
+ /* The buffers need to be visible before we let NMIs write them */
+ smp_wmb();
+
+ mod_code_write = 1;
+
+ /* Make sure write bit is visible before we wait on NMIs */
+ smp_mb();
+
+ wait_for_nmi();
+
+ /* Make sure all running NMIs have finished before we write the code */
+ smp_mb();
+
+ ftrace_mod_code();
+
+ /* Make sure the write happens before clearing the bit */
+ smp_wmb();
+
+ mod_code_write = 0;
+
+ /* make sure NMIs see the cleared bit */
+ smp_mb();
+
+ wait_for_nmi();
+
+ return mod_code_status;
+}
+
+static unsigned char *ftrace_nop_replace(void)
+{
+ return (unsigned char *) &ftrace_nop;
+}
+
+static int
+ftrace_modify_code(unsigned long ip, unsigned char *old_code,
+ unsigned char *new_code)
+{
+ 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.
+ */
+
+ /* 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;
+
+ /* replace the text with the new text */
+ if (do_ftrace_mod_code(ip, new_code))
+ return -EPERM;
+
+ return 0;
+}
+
+int ftrace_make_nop(struct module *mod,
+ struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned char *new, *old;
+
+ old = ftrace_call_replace(JAL, addr);
+ new = ftrace_nop_replace();
+
+ return ftrace_modify_code(rec->ip, old, new);
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned char *new, *old;
+
+ old = ftrace_nop_replace();
+ new = ftrace_call_replace(JAL, addr);
+
+ return ftrace_modify_code(rec->ip, old, new);
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+ unsigned long ip = (unsigned long) (&ftrace_call);
+ unsigned char old[MCOUNT_INSN_SIZE], *new;
+ int ret;
+
+ memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
+ new = ftrace_call_replace(JAL, (unsigned long) func);
+ ret = ftrace_modify_code(ip, old, new);
+
+ return ret;
+}
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+ /* The return code is retured via data */
+ *(unsigned long *) data = 0;
+
+ return 0;
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
index 268724e..ce8a0ba 100644
--- a/arch/mips/kernel/mcount.S
+++ b/arch/mips/kernel/mcount.S
@@ -67,6 +67,35 @@
move ra, $1
.endm

+#ifdef CONFIG_DYNAMIC_FTRACE
+
+LEAF(_mcount)
+ RESTORE_SP_FOR_32BIT
+ RETURN_BACK
+ END(_mcount)
+
+NESTED(ftrace_caller, PT_SIZE, ra)
+ RESTORE_SP_FOR_32BIT
+ lw t0, function_trace_stop
+ bnez t0, ftrace_stub
+ nop
+
+ MCOUNT_SAVE_REGS
+
+ MCOUNT_SET_ARGS
+ .globl ftrace_call
+ftrace_call:
+ jal ftrace_stub
+ nop
+
+ MCOUNT_RESTORE_REGS
+ .globl ftrace_stub
+ftrace_stub:
+ RETURN_BACK
+ END(ftrace_caller)
+
+#else /* ! CONFIG_DYNAMIC_FTRACE */
+
NESTED(_mcount, PT_SIZE, ra)
RESTORE_SP_FOR_32BIT
PTR_L t0, function_trace_stop
@@ -94,5 +123,7 @@ ftrace_stub:
RETURN_BACK
END(_mcount)

+#endif /* ! CONFIG_DYNAMIC_FTRACE */
+
.set at
.set reorder
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 5c4b7a4..548d575 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -207,6 +207,7 @@ endif

ifdef CONFIG_FTRACE_MCOUNT_RECORD
cmd_record_mcount = perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
+ "$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \
"$(if $(CONFIG_64BIT),64,32)" \
"$(OBJDUMP)" "$(OBJCOPY)" "$(CC)" "$(LD)" "$(NM)" "$(RM)" "$(MV)" \
"$(if $(part-of-module),1,0)" "$(@)";
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index 409596e..e963948 100755
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -100,13 +100,13 @@ $P =~ s@.*/@@g;

my $V = '0.1';

-if ($#ARGV < 7) {
- print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
+if ($#ARGV < 8) {
+ print "usage: $P arch endian bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
print "version: $V\n";
exit(1);
}

-my ($arch, $bits, $objdump, $objcopy, $cc,
+my ($arch, $endian, $bits, $objdump, $objcopy, $cc,
$ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;

# This file refers to mcount and shouldn't be ftraced, so lets' ignore it
@@ -213,6 +213,26 @@ if ($arch eq "x86_64") {
if ($is_module eq "0") {
$cc .= " -mconstant-gp";
}
+
+} elsif ($arch eq "mips") {
+ $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
+ $objdump .= " -Melf-trad".$endian."mips ";
+
+ if ($endian eq "big") {
+ $endian = " -EB ";
+ $ld .= " -melf".$bits."btsmip";
+ } else {
+ $endian = " -EL ";
+ $ld .= " -melf".$bits."ltsmip";
+ }
+
+ $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
+ $ld .= $endian;
+
+ if ($bits == 64) {
+ $type = ".dword";
+ }
+
} else {
die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
}
@@ -441,12 +461,12 @@ if ($#converts >= 0) {
#
# Step 5: set up each local function as a global
#
- `$objcopy $globallist $inputfile $globalobj`;
+ `$objcopy $globallist $inputfile $globalobj 2>&1 >/dev/null`;

#
# Step 6: Link the global version to our list.
#
- `$ld -r $globalobj $mcount_o -o $globalmix`;
+ `$ld -r $globalobj $mcount_o -o $globalmix 2>&1 >/dev/null`;

#
# Step 7: Convert the local functions back into local symbols
@@ -454,7 +474,7 @@ if ($#converts >= 0) {
`$objcopy $locallist $globalmix $inputfile`;

# Remove the temp files
- `$rm $globalobj $globalmix`;
+ `$rm $globalobj $globalmix 2>&1 >/dev/null`;

} else {

--
1.6.0.4


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