Re: [PATCH 08/10] jump label v11: x86 support

[Steven Rostedt <rostedt@goodmis.org>]

I'm starting to play with this. I just updated my distcc to gcc 4.5.1 so
that I can.

On Fri, 2010-09-17 at 11:09 -0400, Jason Baron wrote:
> add x86 support for jump label. I'm keeping this patch separate so its clear to
> arch maintainers what was required for x86 support this new feature. hopefully,
> it wouldn't be too painful for other arches.
> 
> Signed-off-by: Jason Baron <jbaron@redhat.com>
> ---
>  arch/x86/Kconfig                  |    1 +
>  arch/x86/include/asm/jump_label.h |   47 +++++++++++++++++++++++++++++++++++
>  arch/x86/kernel/Makefile          |    2 +-
>  arch/x86/kernel/jump_label.c      |   49 +++++++++++++++++++++++++++++++++++++
>  arch/x86/kernel/module.c          |    3 ++
>  5 files changed, 101 insertions(+), 1 deletions(-)
>  create mode 100644 arch/x86/include/asm/jump_label.h
>  create mode 100644 arch/x86/kernel/jump_label.c
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 0c14369..a986079 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -60,6 +60,7 @@ config X86
>  	select ANON_INODES
>  	select HAVE_ARCH_KMEMCHECK
>  	select HAVE_USER_RETURN_NOTIFIER
> +	select HAVE_ARCH_JUMP_LABEL if !CC_OPTIMIZE_FOR_SIZE
>  
>  config INSTRUCTION_DECODER
>  	def_bool (KPROBES || PERF_EVENTS)
> diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
> new file mode 100644
> index 0000000..b4a2cb4
> --- /dev/null
> +++ b/arch/x86/include/asm/jump_label.h
> @@ -0,0 +1,47 @@
> +#ifndef _ASM_X86_JUMP_LABEL_H
> +#define _ASM_X86_JUMP_LABEL_H
> +
> +#ifdef __KERNEL__
> +
> +#include <linux/types.h>
> +#include <asm/nops.h>
> +
> +#define JUMP_LABEL_NOP_SIZE 5
> +
> +# define JUMP_LABEL_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t"
> +
> +# define JUMP_LABEL(key, label)					\
> +	do {							\
> +		asm goto("1:"					\
> +			JUMP_LABEL_INITIAL_NOP			\
> +			".pushsection __jump_table,  \"a\" \n\t"\
> +			_ASM_PTR "1b, %l[" #label "], %c0 \n\t" \
> +			".popsection \n\t"			\
> +			: :  "i" (key) :  : label);		\
> +	} while (0)
> +
> +#endif /* __KERNEL__ */
> +
> +#ifdef CONFIG_X86_64
> +
> +typedef u64 jump_label_t;
> +
> +struct jump_entry {
> +	jump_label_t code;
> +	jump_label_t target;
> +	jump_label_t key;
> +};
> +
> +#else
> +
> +typedef u32 jump_label_t;
> +
> +struct jump_entry {
> +	jump_label_t code;
> +	jump_label_t target;
> +	jump_label_t key;
> +};
> +
> +#endif

Why duplicate the structure? You typedef'd jump_label_t and used that in
the structure twice!

-- Steve


> +
> +#endif
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 11a9925..dfa1443 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -32,7 +32,7 @@ GCOV_PROFILE_paravirt.o		:= n
>  obj-y			:= process_$(BITS).o signal.o entry_$(BITS).o
>  obj-y			+= traps.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
>  obj-y			+= time.o ioport.o ldt.o dumpstack.o
> -obj-y			+= setup.o x86_init.o i8259.o irqinit.o
> +obj-y			+= setup.o x86_init.o i8259.o irqinit.o jump_label.o
>  obj-$(CONFIG_X86_VISWS)	+= visws_quirks.o
>  obj-$(CONFIG_X86_32)	+= probe_roms_32.o
>  obj-$(CONFIG_X86_32)	+= sys_i386_32.o i386_ksyms_32.o
> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> new file mode 100644
> index 0000000..b3c0f37
> --- /dev/null
> +++ b/arch/x86/kernel/jump_label.c
> @@ -0,0 +1,49 @@
> +/*
> + * jump label x86 support
> + *
> + * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
> + *
> + */
> +#include <linux/jump_label.h>
> +#include <linux/memory.h>
> +#include <linux/uaccess.h>
> +#include <linux/module.h>
> +#include <linux/list.h>
> +#include <linux/jhash.h>
> +#include <linux/cpu.h>
> +#include <asm/kprobes.h>
> +#include <asm/alternative.h>
> +
> +#ifdef HAVE_JUMP_LABEL
> +
> +union jump_code_union {
> +	char code[JUMP_LABEL_NOP_SIZE];
> +	struct {
> +		char jump;
> +		int offset;
> +	} __attribute__((packed));
> +};
> +
> +void arch_jump_label_transform(struct jump_entry *entry, enum jump_label_type type)
> +{
> +	union jump_code_union code;
> +
> +	if (type == JUMP_LABEL_ENABLE) {
> +		code.jump = 0xe9;
> +		code.offset = entry->target -
> +				(entry->code + JUMP_LABEL_NOP_SIZE);
> +	} else
> +		memcpy(&code, ideal_nop5, JUMP_LABEL_NOP_SIZE);
> +	get_online_cpus();
> +	mutex_lock(&text_mutex);
> +	text_poke_smp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
> +	mutex_unlock(&text_mutex);
> +	put_online_cpus();
> +}
> +
> +void arch_jump_label_text_poke_early(jump_label_t addr)
> +{
> +	text_poke_early((void *)addr, ideal_nop5, JUMP_LABEL_NOP_SIZE);
> +}
> +
> +#endif
> diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
> index e0bc186..5399f58 100644
> --- a/arch/x86/kernel/module.c
> +++ b/arch/x86/kernel/module.c
> @@ -239,6 +239,9 @@ int module_finalize(const Elf_Ehdr *hdr,
>  		apply_paravirt(pseg, pseg + para->sh_size);
>  	}
>  
> +	/* make jump label nops */
> +	jump_label_apply_nops(me);
> +
>  	return module_bug_finalize(hdr, sechdrs, me);
>  }
>