From: Steven Rostedt <rostedt@goodmis.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, amit.kachhap@arm.com,
catalin.marinas@arm.com, deller@gmx.de, duwe@suse.de,
James.Bottomley@HansenPartnership.com, james.morse@arm.com,
jeyu@kernel.org, jpoimboe@redhat.com, jthierry@redhat.com,
linux-parisc@vger.kernel.org, mingo@redhat.com,
peterz@infradead.org, svens@stackframe.org,
takahiro.akashi@linaro.org, will@kernel.org
Subject: Re: [PATCHv2 1/8] ftrace: add ftrace_init_nop()
Date: Mon, 4 Nov 2019 08:16:20 -0500 [thread overview]
Message-ID: <20191104081620.732320a8@grimm.local.home> (raw)
In-Reply-To: <20191029165832.33606-2-mark.rutland@arm.com>
On Tue, 29 Oct 2019 16:58:25 +0000
Mark Rutland <mark.rutland@arm.com> wrote:
> Architectures may need to perform special initialization of ftrace
> callsites, and today they do so by special-casing ftrace_make_nop() when
> the expected branch address is MCOUNT_ADDR. In some cases (e.g. for
> patchable-function-entry), we don't have an mcount-like symbol and don't
> want a synthetic MCOUNT_ADDR, but we may need to perform some
> initialization of callsites.
>
> To make it possible to separate initialization from runtime
> modification, and to handle cases without an mcount-like symbol, this
> patch adds an optional ftrace_init_nop() function that architectures can
> implement, which does not pass a branch address.
>
> Where an architecture does not provide ftrace_init_nop(), we will fall
> back to the existing behaviour of calling ftrace_make_nop() with
> MCOUNT_ADDR.
>
> At the same time, ftrace_code_disable() is renamed to
> ftrace_nop_initialize() to make it clearer that it is intended to
> intialize a callsite into a disabled state, and is not for disabling a
> callsite that has been runtime enabled. The kerneldoc description of rec
> arguments is updated to cover non-mcount callsites.
>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
-- Steve
> Cc: Torsten Duwe <duwe@suse.de>
> ---
> include/linux/ftrace.h | 35 ++++++++++++++++++++++++++++++++---
> kernel/trace/ftrace.c | 6 +++---
> 2 files changed, 35 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 8a8cb3c401b2..9867d90d635e 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -499,7 +499,7 @@ static inline int ftrace_disable_ftrace_graph_caller(void) { return 0; }
> /**
> * ftrace_make_nop - convert code into nop
> * @mod: module structure if called by module load initialization
> - * @rec: the mcount call site record
> + * @rec: the call site record (e.g. mcount/fentry)
> * @addr: the address that the call site should be calling
> *
> * This is a very sensitive operation and great care needs
> @@ -520,9 +520,38 @@ static inline int ftrace_disable_ftrace_graph_caller(void) { return 0; }
> extern int ftrace_make_nop(struct module *mod,
> struct dyn_ftrace *rec, unsigned long addr);
>
> +
> +/**
> + * ftrace_init_nop - initialize a nop call site
> + * @mod: module structure if called by module load initialization
> + * @rec: the call site record (e.g. mcount/fentry)
> + *
> + * This is a very sensitive operation and great care needs
> + * to be taken by the arch. The operation should carefully
> + * read the location, check to see if what is read is indeed
> + * what we expect it to be, and then on success of the compare,
> + * it should write to the location.
> + *
> + * The code segment at @rec->ip should contain the contents created by
> + * the compiler
> + *
> + * Return must be:
> + * 0 on success
> + * -EFAULT on error reading the location
> + * -EINVAL on a failed compare of the contents
> + * -EPERM on error writing to the location
> + * Any other value will be considered a failure.
> + */
> +#ifndef ftrace_init_nop
> +static inline int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
> +{
> + return ftrace_make_nop(mod, rec, MCOUNT_ADDR);
> +}
> +#endif
> +
> /**
> * ftrace_make_call - convert a nop call site into a call to addr
> - * @rec: the mcount call site record
> + * @rec: the call site record (e.g. mcount/fentry)
> * @addr: the address that the call site should call
> *
> * This is a very sensitive operation and great care needs
> @@ -545,7 +574,7 @@ extern int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr);
> #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> /**
> * ftrace_modify_call - convert from one addr to another (no nop)
> - * @rec: the mcount call site record
> + * @rec: the call site record (e.g. mcount/fentry)
> * @old_addr: the address expected to be currently called to
> * @addr: the address to change to
> *
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index f296d89be757..5259d4dea675 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -2494,14 +2494,14 @@ struct dyn_ftrace *ftrace_rec_iter_record(struct ftrace_rec_iter *iter)
> }
>
> static int
> -ftrace_code_disable(struct module *mod, struct dyn_ftrace *rec)
> +ftrace_nop_initialize(struct module *mod, struct dyn_ftrace *rec)
> {
> int ret;
>
> if (unlikely(ftrace_disabled))
> return 0;
>
> - ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
> + ret = ftrace_init_nop(mod, rec);
> if (ret) {
> ftrace_bug_type = FTRACE_BUG_INIT;
> ftrace_bug(ret, rec);
> @@ -2943,7 +2943,7 @@ static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs)
> * to the NOP instructions.
> */
> if (!__is_defined(CC_USING_NOP_MCOUNT) &&
> - !ftrace_code_disable(mod, p))
> + !ftrace_nop_initialize(mod, p))
> break;
>
> update_cnt++;
next prev parent reply other threads:[~2019-11-04 13:22 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-29 16:58 [PATCHv2 0/8] arm64: ftrace cleanup + FTRACE_WITH_REGS Mark Rutland
2019-10-29 16:58 ` [PATCHv2 1/8] ftrace: add ftrace_init_nop() Mark Rutland
2019-10-30 15:00 ` Miroslav Benes
2019-11-02 12:19 ` Amit Daniel Kachhap
2019-11-04 13:11 ` Steven Rostedt
2019-11-05 6:59 ` Amit Kachhap
2019-11-04 13:36 ` Mark Rutland
2019-11-05 6:47 ` Amit Kachhap
2019-11-06 14:15 ` Mark Rutland
2019-11-07 4:40 ` Amit Kachhap
2019-11-04 13:16 ` Steven Rostedt [this message]
2019-11-04 13:38 ` Mark Rutland
2019-11-04 13:53 ` Steven Rostedt
2019-10-29 16:58 ` [PATCHv2 2/8] module/ftrace: handle patchable-function-entry Mark Rutland
2019-10-30 15:03 ` Torsten Duwe
2019-10-31 9:02 ` Mark Rutland
2019-10-31 11:42 ` Torsten Duwe
2019-10-31 13:00 ` Mark Rutland
2019-11-04 13:28 ` Steven Rostedt
2019-11-04 14:00 ` Mark Rutland
2019-11-04 13:25 ` Steven Rostedt
2019-11-04 15:51 ` Mark Rutland
2019-11-04 20:58 ` Helge Deller
2019-11-05 8:59 ` Miroslav Benes
2019-10-29 16:58 ` [PATCHv2 3/8] arm64: module: rework special section handling Mark Rutland
2019-10-30 15:25 ` Miroslav Benes
2019-10-29 16:58 ` [PATCHv2 4/8] arm64: module/ftrace: intialize PLT at load time Mark Rutland
2019-11-02 12:20 ` Amit Daniel Kachhap
2019-11-04 13:55 ` Mark Rutland
2019-10-29 16:58 ` [PATCHv2 5/8] arm64: insn: add encoder for MOV (register) Mark Rutland
2019-10-29 16:58 ` [PATCHv2 6/8] arm64: asm-offsets: add S_FP Mark Rutland
2019-10-29 16:58 ` [PATCHv2 7/8] arm64: implement ftrace with regs Mark Rutland
2019-11-02 12:21 ` Amit Daniel Kachhap
2019-11-04 13:51 ` Mark Rutland
[not found] ` <CANW9uyug8WKN2fR-FmcW-C_OO_OQ_AvukM+BR7wqiJ9eFQMO9Q@mail.gmail.com>
2019-11-15 7:45 ` Torsten Duwe
2019-11-15 13:59 ` Mark Rutland
2019-10-29 16:58 ` [PATCHv2 8/8] arm64: ftrace: minimize ifdeffery Mark Rutland
2019-10-30 17:02 ` [PATCHv2 0/8] arm64: ftrace cleanup + FTRACE_WITH_REGS Torsten Duwe
2019-10-31 17:16 ` Torsten Duwe
2019-11-01 9:08 ` Mark Rutland
2019-11-01 15:39 ` Sven Schnelle
2019-11-01 16:28 ` Mark Rutland
2019-11-02 12:12 ` Amit Daniel Kachhap
2019-11-04 12:56 ` Will Deacon
2019-11-04 13:03 ` Amit Kachhap
2019-11-04 14:04 ` Mark Rutland
2019-11-05 7:06 ` Amit Kachhap
2019-11-07 11:31 ` Catalin Marinas
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