Hi, David & Steve
Can we use 'jump lable' in Assembly? If it works, I guess this may
also give some help on improving the Ftrace implementation, e.g.
HAVE_FUNCTION_TRACE_MCOUNT_TEST and the other condition checking in
the mcount.S(or the corresponding part of the other ARCH's entry*.S).
For the C implementation,
kernel/trace/ftrace.c:
#ifndef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
/*
* For those archs that do not test ftrace_trace_stop in their
* mcount call site, we need to do it from C.
*/
static void ftrace_test_stop_func(unsigned long ip, unsigned long parent_ip)
{
if (function_trace_stop)
return;
__ftrace_trace_function(ip, parent_ip);
}
#endif
We may be easy to apply the jump lable above, but some ARCH selects
HAVE_FUNCTION_TRACE_MCOUNT_TEST and uses the assembly implementation,
let's use MIPS an example:
arch/mips/kernel/mcount.S:
#else /* ! CONFIG_DYNAMIC_FTRACE */
NESTED(_mcount, PT_SIZE, ra)
lw t1, function_trace_stop
bnez t1, ftrace_stub
When function_trace_stop is false, we can simply convert the above 2
lines to nops ;-)
Can we use 'jump lable' above for the condition check of
function_trace_stop or if there is such macros or functions to do so?
Best Regards,
Wu Zhangjin
On Wed, Dec 29, 2010 at 5:26 AM, David Daney <ddaney@xxxxxxxxxxxxxxxxxx> wrote:
> In order not to be left behind, we add jump label support for MIPS.
>
> Tested on 64-bit big endian (Octeon), and 32-bit little endian
> (malta/qemu).
>
> Signed-off-by: David Daney <ddaney@xxxxxxxxxxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Jason Baron <jbaron@xxxxxxxxxx>
> ---
>
> The only change from v3 is to guard the body of
> arch/mips/kernel/jump_label.c with #ifdef HAVE_JUMP_LABEL. This
> avoids compiler errors when CONFIG_JUMP_LABEL is selected, but the
> compiler does not support it.
>
> arch/mips/Kconfig | 1 +
> arch/mips/include/asm/jump_label.h | 48 ++++++++++++++++++++++++++++++++
> arch/mips/kernel/Makefile | 2 +
> arch/mips/kernel/jump_label.c | 54 ++++++++++++++++++++++++++++++++++++
> arch/mips/kernel/module.c | 5 +++
> 5 files changed, 110 insertions(+), 0 deletions(-)
> create mode 100644 arch/mips/include/asm/jump_label.h
> create mode 100644 arch/mips/kernel/jump_label.c
>
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 913d50d..12d0d0f 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -21,6 +21,7 @@ config MIPS
> select HAVE_DMA_API_DEBUG
> select HAVE_GENERIC_HARDIRQS
> select GENERIC_IRQ_PROBE
> + select HAVE_ARCH_JUMP_LABEL
>
> menu "Machine selection"
>
> diff --git a/arch/mips/include/asm/jump_label.h b/arch/mips/include/asm/jump_label.h
> new file mode 100644
> index 0000000..7622ccf
> --- /dev/null
> +++ b/arch/mips/include/asm/jump_label.h
> @@ -0,0 +1,48 @@
> +/*
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License. See the file "COPYING" in the main directory of this archive
> + * for more details.
> + *
> + * Copyright (c) 2010 Cavium Networks, Inc.
> + */
> +#ifndef _ASM_MIPS_JUMP_LABEL_H
> +#define _ASM_MIPS_JUMP_LABEL_H
> +
> +#include <linux/types.h>
> +
> +#ifdef __KERNEL__
> +
> +#define JUMP_LABEL_NOP_SIZE 4
> +
> +#ifdef CONFIG_64BIT
> +#define WORD_INSN ".dword"
> +#else
> +#define WORD_INSN ".word"
> +#endif
> +
> +#define JUMP_LABEL(key, label) \
> + do { \
> + asm goto("1:\tnop\n\t" \
> + "nop\n\t" \
> + ".pushsection __jump_table, \"a\"\n\t" \
> + WORD_INSN " 1b, %l[" #label "], %0\n\t" \
> + ".popsection\n\t" \
> + : : "i" (key) : : label); \
> + } while (0)
> +
> +
> +#endif /* __KERNEL__ */
> +
> +#ifdef CONFIG_64BIT
> +typedef u64 jump_label_t;
> +#else
> +typedef u32 jump_label_t;
> +#endif
> +
> +struct jump_entry {
> + jump_label_t code;
> + jump_label_t target;
> + jump_label_t key;
> +};
> +
> +#endif /* _ASM_MIPS_JUMP_LABEL_H */
> diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
> index 3977397..cedee2b 100644
> --- a/arch/mips/kernel/Makefile
> +++ b/arch/mips/kernel/Makefile
> @@ -107,4 +107,6 @@ obj-$(CONFIG_MIPS_CPUFREQ) += cpufreq/
>
> obj-$(CONFIG_HW_PERF_EVENTS) += perf_event.o
>
> +obj-$(CONFIG_JUMP_LABEL) += jump_label.o
> +
> CPPFLAGS_vmlinux.lds := $(KBUILD_CFLAGS)
> diff --git a/arch/mips/kernel/jump_label.c b/arch/mips/kernel/jump_label.c
> new file mode 100644
> index 0000000..6001610
> --- /dev/null
> +++ b/arch/mips/kernel/jump_label.c
> @@ -0,0 +1,54 @@
> +/*
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License. See the file "COPYING" in the main directory of this archive
> + * for more details.
> + *
> + * Copyright (c) 2010 Cavium Networks, Inc.
> + */
> +
> +#include <linux/jump_label.h>
> +#include <linux/kernel.h>
> +#include <linux/memory.h>
> +#include <linux/mutex.h>
> +#include <linux/types.h>
> +#include <linux/cpu.h>
> +
> +#include <asm/cacheflush.h>
> +#include <asm/inst.h>
> +
> +#ifdef HAVE_JUMP_LABEL
> +
> +#define J_RANGE_MASK ((1ul << 28) - 1)
> +
> +void arch_jump_label_transform(struct jump_entry *e,
> + enum jump_label_type type)
> +{
> + union mips_instruction insn;
> + union mips_instruction *insn_p =
> + (union mips_instruction *)(unsigned long)e->code;
> +
> + /* Jump only works within a 256MB aligned region. */
> + BUG_ON((e->target & ~J_RANGE_MASK) != (e->code & ~J_RANGE_MASK));
> +
> + /* Target must have 4 byte alignment. */
> + BUG_ON((e->target & 3) != 0);
> +
> + if (type == JUMP_LABEL_ENABLE) {
> + insn.j_format.opcode = j_op;
> + insn.j_format.target = (e->target & J_RANGE_MASK) >> 2;
> + } else {
> + insn.word = 0; /* nop */
> + }
> +
> + get_online_cpus();
> + mutex_lock(&text_mutex);
> + *insn_p = insn;
> +
> + flush_icache_range((unsigned long)insn_p,
> + (unsigned long)insn_p + sizeof(*insn_p));
> +
> + mutex_unlock(&text_mutex);
> + put_online_cpus();
> +}
> +
> +#endif /* HAVE_JUMP_LABEL */
> diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
> index 6f51dda..bb9cde4 100644
> --- a/arch/mips/kernel/module.c
> +++ b/arch/mips/kernel/module.c
> @@ -30,6 +30,8 @@
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/spinlock.h>
> +#include <linux/jump_label.h>
> +
> #include <asm/pgtable.h> /* MODULE_START */
>
> struct mips_hi16 {
> @@ -390,6 +392,9 @@ int module_finalize(const Elf_Ehdr *hdr,
> const Elf_Shdr *s;
> char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
>
> + /* Make jump label nops. */
> + jump_label_apply_nops(me);
> +
> INIT_LIST_HEAD(&me->arch.dbe_list);
> for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
> if (strcmp("__dbe_table", secstrings + s->sh_name) != 0)
> --
> 1.7.2.3
>
>
>
