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Date: Wed, 14 May 2008 09:32:18 -0400
From: Steven Rostedt <srostedt@...hat.com>
To: David Miller <davem@...emloft.net>
CC: mingo@...e.hu, acme@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2]: sparc64: Add ftrace support.
David Miller wrote:
> Signed-off-by: David S. Miller <davem@...emloft.net>
> ---
> arch/sparc64/Kconfig | 1 +
> arch/sparc64/Kconfig.debug | 2 +-
> arch/sparc64/kernel/Makefile | 1 +
> arch/sparc64/kernel/ftrace.c | 99 ++++++++++++++++++++++++++++++++++++++++++
> arch/sparc64/lib/mcount.S | 58 +++++++++++++++++++++++--
> 5 files changed, 156 insertions(+), 5 deletions(-)
> create mode 100644 arch/sparc64/kernel/ftrace.c
>
> diff --git a/arch/sparc64/Kconfig b/arch/sparc64/Kconfig
> index 4c40862..56344b1 100644
> --- a/arch/sparc64/Kconfig
> +++ b/arch/sparc64/Kconfig
> @@ -15,6 +15,7 @@ config SPARC64
> select HAVE_LMB
> select HAVE_ARCH_KGDB
> select HAVE_IMMEDIATE
> + select HAVE_FTRACE
>
> config GENERIC_TIME
> bool
> diff --git a/arch/sparc64/Kconfig.debug b/arch/sparc64/Kconfig.debug
> index 6a4d28a..d6d32d1 100644
> --- a/arch/sparc64/Kconfig.debug
> +++ b/arch/sparc64/Kconfig.debug
> @@ -33,7 +33,7 @@ config DEBUG_PAGEALLOC
>
> config MCOUNT
> bool
> - depends on STACK_DEBUG
> + depends on STACK_DEBUG || FTRACE
> default y
>
> config FRAME_POINTER
> diff --git a/arch/sparc64/kernel/Makefile b/arch/sparc64/kernel/Makefile
> index 311c797..52e933f 100644
> --- a/arch/sparc64/kernel/Makefile
> +++ b/arch/sparc64/kernel/Makefile
> @@ -14,6 +14,7 @@ obj-y := process.o setup.o cpu.o idprom.o \
> power.o sbus.o sparc64_ksyms.o chmc.o \
> visemul.o prom.o of_device.o hvapi.o sstate.o mdesc.o
>
> +obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
> obj-$(CONFIG_STACKTRACE) += stacktrace.o
> obj-$(CONFIG_PCI) += ebus.o pci_common.o \
> pci_psycho.o pci_sabre.o pci_schizo.o \
> diff --git a/arch/sparc64/kernel/ftrace.c b/arch/sparc64/kernel/ftrace.c
> new file mode 100644
> index 0000000..f449e6d
> --- /dev/null
> +++ b/arch/sparc64/kernel/ftrace.c
> @@ -0,0 +1,99 @@
> +#include <linux/spinlock.h>
> +#include <linux/hardirq.h>
> +#include <linux/ftrace.h>
> +#include <linux/percpu.h>
> +#include <linux/init.h>
> +#include <linux/list.h>
> +
> +static const u32 ftrace_nop = 0x01000000;
> +
> +notrace int ftrace_ip_converted(unsigned long ip)
FYI,
If you look in the kernel/Makefile you will see a way to have the whole
file not be traced. This will eliminate the need for the "notrace"
annotation on all functions. I haven't update the x86 version of ftrace
to do this so you probably just copied the old method from us.
If you add the following in arch/sparc64/kernel/Makefile
ifdef CONFIG_DYNAMIC_FTRACE
obj-y += ftrace.o
# Do not trace the ftrace code itself
ORIG_CFLAGS := $(KBUILD_CFLAGS)
KBUILD_CFLAGS = $(if $(filter-out ftrace, $(basename $(notdir $@))), \
$(ORIG_CFLAGS), \
$(subst -pg,,$(ORIG_CFLAGS)))
endif
Then you wont need the "notrace" annotations on the functions.
/me needs to send Ingo a patch to do this for x86 as well.
> +{
> + u32 insn = *(u32 *) ip;
> +
> + return (insn == ftrace_nop);
> +}
> +
> +notrace unsigned char *ftrace_nop_replace(void)
> +{
> + return (char *)&ftrace_nop;
> +}
> +
> +notrace unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
> +{
> + static u32 call;
> + s32 off;
> +
> + off = ((s32)addr - (s32)ip);
> + call = 0x40000000 | ((u32)off >> 2);
> +
> + return (unsigned char *) &call;
> +}
> +
> +notrace int
> +ftrace_modify_code(unsigned long ip, unsigned char *old_code,
> + unsigned char *new_code)
> +{
> + u32 old = *(u32 *)old_code;
> + u32 new = *(u32 *)new_code;
> + u32 replaced;
> + int faulted;
> +
> + __asm__ __volatile__(
> + "1: cas [%[ip]], %[old], %[new]\n"
> + " flush %[ip]\n"
> + " mov 0, %[faulted]\n"
> + "2:\n"
> + " .section .fixup,#alloc,#execinstr\n"
> + " .align 4\n"
> + "3: sethi %%hi(2b), %[faulted]\n"
> + " jmpl %[faulted] + %%lo(2b), %%g0\n"
> + " mov 1, %[faulted]\n"
> + " .previous\n"
> + " .section __ex_table,\"a\"\n"
> + " .align 4\n"
> + " .word 1b, 3b\n"
> + " .previous\n"
> + : "=r" (replaced), [faulted] "=r" (faulted)
> + : [new] "0" (new), [old] "r" (old), [ip] "r" (ip)
> + : "memory");
I'm so use to the %1 %2 and %3's I should update the x86 code to use the
names as well. (nice)
> +
> + if (replaced != old && replaced != new)
> + faulted = 2;
Thanks for putting in the "2", I may plan on doing something different
later if the code didn't "fault" but something else happened. I should
also make MACROS out of that and not uses 1 and 2.
> +
> + return faulted;
> +}
> +
> +notrace int ftrace_update_ftrace_func(ftrace_func_t func)
> +{
> + unsigned long ip = (unsigned long)(&ftrace_call);
> + unsigned char old[4], *new;
> +
> + memcpy(old, &ftrace_call, 4);
> + new = ftrace_call_replace(ip, (unsigned long)func);
> + return ftrace_modify_code(ip, old, new);
> +}
> +
> +notrace int ftrace_mcount_set(unsigned long *data)
> +{
> + unsigned long ip = (long)(&mcount_call);
> + unsigned long *addr = data;
> + unsigned char old[4], *new;
> +
> + /*
> + * Replace the mcount stub with a pointer to the
> + * ip recorder function.
> + */
> + memcpy(old, &mcount_call, 4);
> + 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/sparc64/lib/mcount.S b/arch/sparc64/lib/mcount.S
> index 9e4534b..7735a7a 100644
> --- a/arch/sparc64/lib/mcount.S
> +++ b/arch/sparc64/lib/mcount.S
> @@ -28,10 +28,13 @@ ovstack:
> .skip OVSTACKSIZE
> #endif
> .text
> - .align 32
> - .globl mcount, _mcount
> -mcount:
> + .align 32
> + .globl _mcount
> + .type _mcount,#function
> + .globl mcount
> + .type mcount,#function
> _mcount:
> +mcount:
> #ifdef CONFIG_STACK_DEBUG
> /*
> * Check whether %sp is dangerously low.
> @@ -55,6 +58,53 @@ _mcount:
> or %g3, %lo(panicstring), %o0
> call prom_halt
> nop
> +1:
> +#endif
> +#ifdef CONFIG_FTRACE
> +#ifdef CONFIG_DYNAMIC_FTRACE
> + mov %o7, %o0
> + .globl mcount_call
> +mcount_call:
> + call ftrace_stub
> + mov %o0, %o7
WOW! Sparc64 has some really efficient context saving!
> +#else
> + sethi %hi(ftrace_trace_function), %g1
> + sethi %hi(ftrace_stub), %g2
> + ldx [%g1 + %lo(ftrace_trace_function)], %g1
> + or %g2, %lo(ftrace_stub), %g2
> + cmp %g1, %g2
> + be,pn %icc, 1f
> + mov %i7, %o1
> + jmpl %g1, %g0
> + mov %o7, %o0
> + /* not reached */
> +1:
> #endif
> -1: retl
> +#endif
> + retl
> nop
> + .size _mcount,.-_mcount
> + .size mcount,.-mcount
> +
> +#ifdef CONFIG_FTRACE
> + .globl ftrace_stub
> + .type ftrace_stub,#function
> +ftrace_stub:
> + retl
> + nop
> + .size ftrace_stub,.-ftrace_stub
> +#ifdef CONFIG_DYNAMIC_FTRACE
> + .globl ftrace_caller
> + .type ftrace_caller,#function
> +ftrace_caller:
> + mov %i7, %o1
> + mov %o7, %o0
> + .globl ftrace_call
> +ftrace_call:
> + call ftrace_stub
> + mov %o0, %o7
> + retl
> + nop
> + .size ftrace_caller,.-ftrace_caller
> +#endif
> +#endif
Looks great!
Acked-by: Steven Rostedt <srostedt@...hat.com>
-- Steve
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