All of lore.kernel.org
 help / color / mirror / Atom feed
From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>,
	linux-arch@vger.kernel.org, linux-kbuild@vger.kernel.org,
	Christophe Leroy <christophe.leroy@c-s.fr>,
	Nicolas Pitre <nico@fluxnic.net>
Subject: [PATCH 3/4] kbuild: Allow LD_DEAD_CODE_DATA_ELIMINATION to be selectable if enabled
Date: Fri, 20 Apr 2018 17:34:13 +1000	[thread overview]
Message-ID: <20180420073414.23169-4-npiggin@gmail.com> (raw)
In-Reply-To: <20180420073414.23169-1-npiggin@gmail.com>

Architectures that are capable can select
HAVE_LD_DEAD_CODE_DATA_ELIMINATION to enable selection of that
option (as an EXPERT kernel option).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/Kconfig | 15 ---------------
 init/Kconfig | 27 +++++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 8e0d665c8d53..3234b73d4626 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -596,21 +596,6 @@ config CC_STACKPROTECTOR_AUTO
 
 endchoice
 
-config LD_DEAD_CODE_DATA_ELIMINATION
-	bool
-	help
-	  Select this if the architecture wants to do dead code and
-	  data elimination with the linker by compiling with
-	  -ffunction-sections -fdata-sections and linking with
-	  --gc-sections.
-
-	  This requires that the arch annotates or otherwise protects
-	  its external entry points from being discarded. Linker scripts
-	  must also merge .text.*, .data.*, and .bss.* correctly into
-	  output sections. Care must be taken not to pull in unrelated
-	  sections (e.g., '.text.init'). Typically '.' in section names
-	  is used to distinguish them from label names / C identifiers.
-
 config HAVE_ARCH_WITHIN_STACK_FRAMES
 	bool
 	help
diff --git a/init/Kconfig b/init/Kconfig
index f013afc74b11..1706d963766b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1038,6 +1038,33 @@ config CC_OPTIMIZE_FOR_SIZE
 
 endchoice
 
+config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
+	bool
+	help
+	  This requires that the arch annotates or otherwise protects
+	  its external entry points from being discarded. Linker scripts
+	  must also merge .text.*, .data.*, and .bss.* correctly into
+	  output sections. Care must be taken not to pull in unrelated
+	  sections (e.g., '.text.init'). Typically '.' in section names
+	  is used to distinguish them from label names / C identifiers.
+
+config LD_DEAD_CODE_DATA_ELIMINATION
+	bool "Dead code and data elimination (EXPERIMENTAL)"
+	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
+	depends on EXPERT
+	help
+	  Select this if the architecture wants to do dead code and
+	  data elimination with the linker by compiling with
+	  -ffunction-sections -fdata-sections, and linking with
+	  --gc-sections.
+
+	  This can reduce on disk and in-memory size of the kernel
+	  code and static data, particularly for small configs and
+	  on small systems. This has the possibility of introducing
+	  silently broken kernel if the required annotations are not
+	  present. This option is not well tested yet, so use at your
+	  own risk.
+
 config SYSCTL
 	bool
 
-- 
2.17.0


WARNING: multiple messages have this Message-ID (diff)
From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: linux-arch@vger.kernel.org, Nicolas Pitre <nico@fluxnic.net>,
	Nicholas Piggin <npiggin@gmail.com>,
	linux-kbuild@vger.kernel.org
Subject: [PATCH 3/4] kbuild: Allow LD_DEAD_CODE_DATA_ELIMINATION to be selectable if enabled
Date: Fri, 20 Apr 2018 17:34:13 +1000	[thread overview]
Message-ID: <20180420073414.23169-4-npiggin@gmail.com> (raw)
In-Reply-To: <20180420073414.23169-1-npiggin@gmail.com>

Architectures that are capable can select
HAVE_LD_DEAD_CODE_DATA_ELIMINATION to enable selection of that
option (as an EXPERT kernel option).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/Kconfig | 15 ---------------
 init/Kconfig | 27 +++++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 8e0d665c8d53..3234b73d4626 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -596,21 +596,6 @@ config CC_STACKPROTECTOR_AUTO
 
 endchoice
 
-config LD_DEAD_CODE_DATA_ELIMINATION
-	bool
-	help
-	  Select this if the architecture wants to do dead code and
-	  data elimination with the linker by compiling with
-	  -ffunction-sections -fdata-sections and linking with
-	  --gc-sections.
-
-	  This requires that the arch annotates or otherwise protects
-	  its external entry points from being discarded. Linker scripts
-	  must also merge .text.*, .data.*, and .bss.* correctly into
-	  output sections. Care must be taken not to pull in unrelated
-	  sections (e.g., '.text.init'). Typically '.' in section names
-	  is used to distinguish them from label names / C identifiers.
-
 config HAVE_ARCH_WITHIN_STACK_FRAMES
 	bool
 	help
diff --git a/init/Kconfig b/init/Kconfig
index f013afc74b11..1706d963766b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1038,6 +1038,33 @@ config CC_OPTIMIZE_FOR_SIZE
 
 endchoice
 
+config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
+	bool
+	help
+	  This requires that the arch annotates or otherwise protects
+	  its external entry points from being discarded. Linker scripts
+	  must also merge .text.*, .data.*, and .bss.* correctly into
+	  output sections. Care must be taken not to pull in unrelated
+	  sections (e.g., '.text.init'). Typically '.' in section names
+	  is used to distinguish them from label names / C identifiers.
+
+config LD_DEAD_CODE_DATA_ELIMINATION
+	bool "Dead code and data elimination (EXPERIMENTAL)"
+	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
+	depends on EXPERT
+	help
+	  Select this if the architecture wants to do dead code and
+	  data elimination with the linker by compiling with
+	  -ffunction-sections -fdata-sections, and linking with
+	  --gc-sections.
+
+	  This can reduce on disk and in-memory size of the kernel
+	  code and static data, particularly for small configs and
+	  on small systems. This has the possibility of introducing
+	  silently broken kernel if the required annotations are not
+	  present. This option is not well tested yet, so use at your
+	  own risk.
+
 config SYSCTL
 	bool
 
-- 
2.17.0

  parent reply	other threads:[~2018-04-20  7:34 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-20  7:34 [PATCH 0/4] LD_DEAD_CODE_DATA_ELIMINATION fixes and enabling for powerpc Nicholas Piggin
2018-04-20  7:34 ` Nicholas Piggin
2018-04-20  7:34 ` [PATCH 1/4] kbuild: Fix asm-generic/vmlinux.lds.h for LD_DEAD_CODE_DATA_ELIMINATION Nicholas Piggin
2018-04-20  7:34   ` Nicholas Piggin
2018-04-20  7:34 ` [PATCH 2/4] kbuild: LD_DEAD_CODE_DATA_ELIMINATION no -ffunction-sections/-fdata-sections for module build Nicholas Piggin
2018-04-20  7:34   ` Nicholas Piggin
2018-04-20  7:34 ` Nicholas Piggin [this message]
2018-04-20  7:34   ` [PATCH 3/4] kbuild: Allow LD_DEAD_CODE_DATA_ELIMINATION to be selectable if enabled Nicholas Piggin
2018-04-20  7:34 ` [PATCH 4/4] powerpc: Allow LD_DEAD_CODE_DATA_ELIMINATION to be selected Nicholas Piggin
2018-04-20  7:34   ` Nicholas Piggin
2018-04-20 10:00   ` Mathieu Malaterre
2018-04-20 10:00     ` Mathieu Malaterre
2018-04-20 10:41     ` Nicholas Piggin
2018-04-20 10:41       ` Nicholas Piggin
2018-04-20 20:08       ` Mathieu Malaterre
2018-04-20 20:08         ` Mathieu Malaterre
2018-04-21  2:48         ` Nicholas Piggin
2018-04-21  2:48           ` Nicholas Piggin
2018-05-02  9:17           ` Mathieu Malaterre
2018-05-02  9:17             ` Mathieu Malaterre
2018-05-02 12:24             ` Nicholas Piggin
2018-05-02 12:24               ` Nicholas Piggin
2018-05-14 19:10               ` Mathieu Malaterre
2018-05-14 19:10                 ` Mathieu Malaterre
2018-04-21  7:16         ` christophe leroy
2018-04-21  7:16           ` christophe leroy
2018-04-23 11:01           ` Mathieu Malaterre
2018-04-23 11:01             ` Mathieu Malaterre
2018-04-23 11:01             ` Mathieu Malaterre
2018-05-07  0:46       ` Masahiro Yamada
2018-05-07  0:46         ` Masahiro Yamada
2018-05-07  9:53         ` Nicholas Piggin
2018-05-07  9:53           ` Nicholas Piggin
2018-04-20 10:01   ` Christophe LEROY
2018-04-20 10:01     ` Christophe LEROY
2018-04-20 10:36     ` Nicholas Piggin
2018-04-20 10:36       ` Nicholas Piggin
2018-04-20 13:21       ` Christophe LEROY
2018-04-20 13:21         ` Christophe LEROY
2018-04-20 10:39   ` Christophe LEROY
2018-04-20 10:39     ` Christophe LEROY
2018-04-20  9:59 ` [PATCH 0/4] LD_DEAD_CODE_DATA_ELIMINATION fixes and enabling for powerpc Mathieu Malaterre
2018-04-20  9:59   ` Mathieu Malaterre
2018-04-20 10:02 ` Christophe LEROY
2018-04-20 10:02   ` Christophe LEROY

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180420073414.23169-4-npiggin@gmail.com \
    --to=npiggin@gmail.com \
    --cc=christophe.leroy@c-s.fr \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kbuild@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=nico@fluxnic.net \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.