Frédéric,
> I saw that there is no implementation of ftrace in mips currently and
> I would like to know if someone is currently working on it. If not I
> would be glad
> to work on patches for that.
I do have an ftrace implementation in the queue. Static ftrace works as
far as I've tested but due to a restriction of the generic ftrace code the
MIPS code for dynamic ftrace can't work on most SMP systems - basically
only the R10000 and single core 34K SMP kernel variants have a chance to
work. For others cache flushing requires a call to smp_call_function but
that can't work because other CPUs are stopped at the time of the flush.
So that still needs some sorting.
Patch below.
Ralf
From: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Date: Wed, 10 Sep 2008 18:04:04 +0200
Subject: [PATCH] [MIPS] Implement fcount support for MIPS.
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
---
arch/mips/Kconfig | 5 ++
arch/mips/Makefile | 2 +
arch/mips/kernel/Makefile | 2 +
arch/mips/kernel/ftrace.c | 118 +++++++++++++++++++++++++++++++++++++
arch/mips/kernel/mips_ksyms.c | 6 ++
arch/mips/lib/Makefile | 2 +
arch/mips/lib/mcount.S | 128 +++++++++++++++++++++++++++++++++++++++++
include/asm-mips/ftrace.h | 14 +++++
8 files changed, 277 insertions(+), 0 deletions(-)
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 5f149b0..43202db 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1,6 +1,7 @@
config MIPS
bool
default y
+ select HAVE_FTRACE
select HAVE_IDE
select HAVE_OPROFILE
select HAVE_ARCH_KGDB
@@ -1503,6 +1504,10 @@ config MIPS_APSP_KSPD
"exit" syscall notifying other kernel modules the SP program is
exiting. You probably want to say yes here.
+config SYS_SUPPORTS_DYNAMIC_FTRACE
+ def_bool y
+ select HAVE_DYNAMIC_FTRACE if !SMP || CPU_R10000
+
config MIPS_CMP
bool "MIPS CMP framework support"
depends on SYS_SUPPORTS_MIPS_CMP
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 7f39fd8..ae9099b 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -14,7 +14,9 @@
KBUILD_DEFCONFIG := ip22_defconfig
+ifndef CONFIG_FTRACE
cflags-y := -ffunction-sections
+endif
#
# Select the object file format to substitute into the linker script.
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index d9da711..ea730e0 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -43,6 +43,8 @@ obj-$(CONFIG_CPU_TX39XX) += r2300_fpu.o r2300_switch.o
obj-$(CONFIG_CPU_TX49XX) += r4k_fpu.o r4k_switch.o
obj-$(CONFIG_CPU_VR41XX) += r4k_fpu.o r4k_switch.o
+obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
+
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_SMP_UP) += smp-up.o
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
new file mode 100644
index 0000000..e24ae47
--- /dev/null
+++ b/arch/mips/kernel/ftrace.c
@@ -0,0 +1,118 @@
+#include <linux/ftrace.h>
+#include <linux/init.h>
+#include <linux/uaccess.h>
+
+#include <asm/cacheflush.h>
+#include <asm/sgidefs.h>
+#include <asm/inst.h>
+#include <asm/ftrace.h>
+
+/*
+ * On O32 the gcc generated code sequence to invoke _mcount looks like
+ *
+ * move $1, $31 # save current return address
+ * subu $sp, $sp, 8 # _mcount pops 2 words from stack
+ * jal _mcount
+ * j $31
+ *
+ * If the _mcount call is nop'ed out we still need to pop the stack frame.
+ * So we use an addiu $sp, $sp, 8 instead. NABI doesn't allocate frames in
+ * such a nonsenical way so a normal nop does the magic.
+ */
+static const union mips_instruction ftrace_nop = {
+#if _MIPS_SIM == _MIPS_SIM_ABI32
+ .i_format.opcode = addiu_op, /* addiu $sp, $sp, 8 */
+ .i_format.rs = 29,
+ .i_format.rt = 29,
+ .i_format.simmediate = 8
+#else
+ .word = 0 /* normal nop */
+#endif
+};
+
+notrace unsigned char *ftrace_nop_replace(void)
+{
+ return (unsigned char *) ftrace_nop.byte;
+}
+
+notrace unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+{
+ static union mips_instruction inst;
+
+ if (unlikely(ip ^ addr) >> 26) {
+ WARN_ON_ONCE(1);
+ return NULL;
+ }
+
+ inst.j_format.opcode = jal_op;
+ inst.j_format.target = addr >> 2;
+
+ return (unsigned char *) &inst;
+}
+
+notrace int
+ftrace_modify_code(unsigned long ip, unsigned char *old_code,
+ unsigned char *new_code)
+{
+ unsigned int old = *(unsigned int *) old_code;
+ unsigned int new = *(unsigned int *) new_code;
+ unsigned int replaced;
+ int err;
+
+ err = __get_user(replaced, (unsigned int *) ip);
+ if (unlikely(err))
+ return 1;
+
+ err = __put_user(new, (unsigned int *) ip);
+ if (unlikely(err))
+ return 1;
+
+ if (unlikely(replaced != old && replaced != new))
+ return 2;
+
+ /*
+ * This is broken. We need to flush the icache on all processors
+ * but can't because ftrace_modify_code is executed with interrupts
+ * disabled ...
+ */
+ local_flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
+
+ return 0;
+}
+
+notrace 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(ip, (unsigned long)func);
+ ret = ftrace_modify_code(ip, old, new);
+
+ return ret;
+}
+
+notrace int ftrace_mcount_set(unsigned long *data)
+{
+ unsigned long ip = (unsigned long) &mcount_call;
+ unsigned long *addr = data;
+ unsigned char old[MCOUNT_INSN_SIZE], *new;
+
+ /*
+ * Replace the mcount stub with a pointer to the
+ * ip recorder function.
+ */
+ memcpy(old, &mcount_call, MCOUNT_INSN_SIZE);
+ new = ftrace_call_replace(ip, *addr);
+ *addr = ftrace_modify_code(ip, old, new);
+
+ return 0;
+}
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+ ftrace_mcount_set(data);
+
+ return 0;
+}
diff --git a/arch/mips/kernel/mips_ksyms.c b/arch/mips/kernel/mips_ksyms.c
index 225755d..18f5556 100644
--- a/arch/mips/kernel/mips_ksyms.c
+++ b/arch/mips/kernel/mips_ksyms.c
@@ -11,6 +11,7 @@
#include <linux/interrupt.h>
#include <linux/module.h>
#include <asm/checksum.h>
+#include <asm/ftrace.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
@@ -51,3 +52,8 @@ EXPORT_SYMBOL(csum_partial_copy_nocheck);
EXPORT_SYMBOL(__csum_partial_copy_user);
EXPORT_SYMBOL(invalid_pte_table);
+
+#ifdef CONFIG_FTRACE
+/* _mcount is defined in assembly */
+EXPORT_SYMBOL(_mcount);
+#endif
diff --git a/arch/mips/lib/Makefile b/arch/mips/lib/Makefile
index 8810dfb..c9ec0c3 100644
--- a/arch/mips/lib/Makefile
+++ b/arch/mips/lib/Makefile
@@ -27,5 +27,7 @@ obj-$(CONFIG_CPU_TX39XX) += r3k_dump_tlb.o
obj-$(CONFIG_CPU_TX49XX) += dump_tlb.o
obj-$(CONFIG_CPU_VR41XX) += dump_tlb.o
+obj-$(CONFIG_FTRACE) += mcount.o
+
# libgcc-style stuff needed in the kernel
obj-y += ashldi3.o ashrdi3.o cmpdi2.o lshrdi3.o ucmpdi2.o
diff --git a/arch/mips/lib/mcount.S b/arch/mips/lib/mcount.S
new file mode 100644
index 0000000..9817ce6
--- /dev/null
+++ b/arch/mips/lib/mcount.S
@@ -0,0 +1,128 @@
+#include <asm/regdef.h>
+#include <asm/ftrace.h>
+#include <asm/asm.h>
+
+/*
+ * The problem here is that _mcount() is not a normal function. It does
+ * not obey the calling conventions of a normal function. It takes its
+ * arguments in $at and $ra, and it is required to preserve $ra - and most
+ * other registers, in fact, if I remember correctly. The arguments have
+ * not yet been saved. You need to do this. Another bizarreness is that
+ * the caller needs to pop an extra 8 bytes for the O32.
+ */
+
+#if _MIPS_SIM == _ABIO32
+#define POP_EXTRA 8
+#define ARG_SAVE 16
+#define N_ARG_REGS 4
+#else
+#define POP_EXTRA 0
+#define ARG_SAVE 0
+#define N_ARG_REGS 8
+#endif
+
+ .macro save_mcount_frame
+ PTR_SUBU sp, sp, ARG_SAVE + (N_ARG_REGS + 4) * LONGSIZE
+ LONG_S AT, ARG_SAVE + 0 * LONGSIZE(sp)
+ LONG_S ra, ARG_SAVE + 1 * LONGSIZE(sp)
+ LONG_S a0, ARG_SAVE + 2 * LONGSIZE(sp)
+ LONG_S a1, ARG_SAVE + 3 * LONGSIZE(sp)
+ LONG_S a2, ARG_SAVE + 4 * LONGSIZE(sp)
+ LONG_S a3, ARG_SAVE + 5 * LONGSIZE(sp)
+#if _MIPS_SIM == _ABI64
+ LONG_S a4, ARG_SAVE + 6 * LONGSIZE(sp)
+ LONG_S a5, ARG_SAVE + 7 * LONGSIZE(sp)
+ LONG_S a6, ARG_SAVE + 8 * LONGSIZE(sp)
+ LONG_S a7, ARG_SAVE + 9 * LONGSIZE(sp)
+#endif
+ LONG_S v0, ARG_SAVE + (2 + N_ARG_REGS) * LONGSIZE(sp)
+ .endm
+
+ .macro restore_mcount_frame
+ LONG_L AT, ARG_SAVE + 0 * LONGSIZE(sp)
+ LONG_L ra, ARG_SAVE + 1 * LONGSIZE(sp)
+ LONG_L a0, ARG_SAVE + 2 * LONGSIZE(sp)
+ LONG_L a1, ARG_SAVE + 3 * LONGSIZE(sp)
+ LONG_L a2, ARG_SAVE + 4 * LONGSIZE(sp)
+ LONG_L a3, ARG_SAVE + 5 * LONGSIZE(sp)
+#if _MIPS_SIM == _ABI64
+ LONG_L a4, ARG_SAVE + 6 * LONGSIZE(sp)
+ LONG_L a5, ARG_SAVE + 7 * LONGSIZE(sp)
+ LONG_L a6, ARG_SAVE + 8 * LONGSIZE(sp)
+ LONG_L a7, ARG_SAVE + 9 * LONGSIZE(sp)
+#endif
+ LONG_L v0, ARG_SAVE + (2 + N_ARG_REGS) * LONGSIZE(sp)
+ PTR_ADDU sp, sp, ARG_SAVE + (N_ARG_REGS + 4) * LONGSIZE + POP_EXTRA
+ .endm
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+LEAF(_mcount)
+ .set push
+ .set noreorder
+ .set noat
+ save_mcount_frame
+ PTR_SUBU a0, ra, 2 * MCOUNT_INSN_SIZE
+
+FEXPORT(mcount_call)
+ jal ftrace_stub
+ nop
+
+ restore_mcount_frame
+ jr ra
+ move ra, AT
+ .set pop
+ END(_mcount)
+
+LEAF(ftrace_caller)
+ .set push
+ .set noreorder
+ .set noat
+ save_mcount_frame
+ PTR_SUBU a0, ra, 2 * MCOUNT_INSN_SIZE
+ move a1, AT
+
+FEXPORT(ftrace_call)
+ jal ftrace_stub
+ nop
+
+ restore_mcount_frame
+ jr ra
+ move ra, AT
+ .set pop
+ END(ftrace_caller)
+
+#else
+
+LEAF(_mcount)
+ .set push
+ .set noreorder
+ .set noat
+ PTR_L t0, ftrace_trace_function
+ PTR_LA t1, ftrace_stub
+ bne t0, t1, trace
+ nop
+
+#if POP_EXTRA
+ PTR_ADDIU sp, sp, 8
+#endif
+ jr ra
+ move ra, AT
+
+trace:
+ save_mcount_frame
+ PTR_SUBU a0, ra, 2 * MCOUNT_INSN_SIZE
+ move a1, AT
+ jalr t0
+ nop
+ restore_mcount_frame
+ jr ra
+ move ra, AT
+ .set pop
+ END(_mcount)
+
+#endif /* !CONFIG_DYNAMIC_FTRACE */
+
+LEAF(ftrace_stub)
+ jr ra
+ END(ftrace_stub)
diff --git a/include/asm-mips/ftrace.h b/include/asm-mips/ftrace.h
new file mode 100644
index 0000000..f0479ce
--- /dev/null
+++ b/include/asm-mips/ftrace.h
@@ -0,0 +1,14 @@
+#ifndef __ASM_FTRACE_H
+#define __ASM_FTRACE_H
+
+#ifdef CONFIG_FTRACE
+#define MCOUNT_ADDR ((long)(_mcount))
+#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */
+
+#ifndef __ASSEMBLY__
+extern void _mcount(void);
+#endif
+
+#endif /* CONFIG_FTRACE */
+
+#endif /* __ASM_FTRACE_H */
