linux-riscv.lists.infradead.org archive mirror
 help / color / mirror / Atom feed
From: anup@brainfault.org (Anup Patel)
To: linux-riscv@lists.infradead.org
Subject: [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
Date: Mon, 26 Nov 2018 11:38:02 +0530	[thread overview]
Message-ID: <20181126060802.19314-1-anup@brainfault.org> (raw)

The objcopy only emits loadable sections when creating flat kernel
Image. To have minimal possible size of flat kernel Image, we should
have all non-loadable sections after loadable sections.

Currently, execption table section (loadable section) is after BSS
section (non-loadable section) in the RISC-V vmlinux.lds.S. This
is not optimal for having minimal flat kernel Image size hence this
patch makes BSS section as the last section in RISC-V vmlinux.lds.S.

In addition, we make BSS section aligned to 16byte instead of PAGE
aligned which further reduces flat kernel Image size by few KBs.

The flat kernel Image size of Linux-4.20-rc4 using GCC 8.2.0 is
8819980 bytes with current RISC-V vmlinux.lds.S and it reduces to
7991740 bytes with this patch applied using GCC 8.2.0. In summary,
this patch reduces Linux-4.20-rc4 flat kernel Image size by 809 KB.

Signed-off-by: Anup Patel <anup@brainfault.org>
---
 arch/riscv/kernel/vmlinux.lds.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index 65df1dfdc303..cc99eed44931 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -74,8 +74,6 @@ SECTIONS
 		*(.sbss*)
 	}
 
-	BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
-
 	EXCEPTION_TABLE(0x10)
 	NOTES
 
@@ -83,6 +81,8 @@ SECTIONS
 		*(.rel.dyn*)
 	}
 
+	BSS_SECTION(0x10, 0x10, 0x10)
+
 	_end = .;
 
 	STABS_DEBUG
-- 
2.17.1

WARNING: multiple messages have this Message-ID (diff)
From: Anup Patel <anup@brainfault.org>
To: Palmer Dabbelt <palmer@sifive.com>, Albert Ou <aou@eecs.berkeley.edu>
Cc: Christoph Hellwig <hch@infradead.org>,
	Atish Patra <atish.patra@wdc.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	Anup Patel <anup@brainfault.org>
Subject: [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
Date: Mon, 26 Nov 2018 11:38:02 +0530	[thread overview]
Message-ID: <20181126060802.19314-1-anup@brainfault.org> (raw)
Message-ID: <20181126060802.Kg105WZWyZw4x0_VpLf5rgX15D-KEKBbS3-UzbFEuk8@z> (raw)

The objcopy only emits loadable sections when creating flat kernel
Image. To have minimal possible size of flat kernel Image, we should
have all non-loadable sections after loadable sections.

Currently, execption table section (loadable section) is after BSS
section (non-loadable section) in the RISC-V vmlinux.lds.S. This
is not optimal for having minimal flat kernel Image size hence this
patch makes BSS section as the last section in RISC-V vmlinux.lds.S.

In addition, we make BSS section aligned to 16byte instead of PAGE
aligned which further reduces flat kernel Image size by few KBs.

The flat kernel Image size of Linux-4.20-rc4 using GCC 8.2.0 is
8819980 bytes with current RISC-V vmlinux.lds.S and it reduces to
7991740 bytes with this patch applied using GCC 8.2.0. In summary,
this patch reduces Linux-4.20-rc4 flat kernel Image size by 809 KB.

Signed-off-by: Anup Patel <anup@brainfault.org>
---
 arch/riscv/kernel/vmlinux.lds.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index 65df1dfdc303..cc99eed44931 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -74,8 +74,6 @@ SECTIONS
 		*(.sbss*)
 	}
 
-	BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
-
 	EXCEPTION_TABLE(0x10)
 	NOTES
 
@@ -83,6 +81,8 @@ SECTIONS
 		*(.rel.dyn*)
 	}
 
+	BSS_SECTION(0x10, 0x10, 0x10)
+
 	_end = .;
 
 	STABS_DEBUG
-- 
2.17.1


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

             reply	other threads:[~2018-11-26  6:08 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-26  6:08 Anup Patel [this message]
2018-11-26  6:08 ` [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S Anup Patel
2018-11-29  7:36 ` Bin Meng
2018-11-29  7:36   ` Bin Meng
2018-12-17  9:36 ` Anup Patel
2018-12-17 12:59   ` Nick Kossifidis
2018-12-18  8:23     ` Anup Patel
2018-12-20 20:40   ` Palmer Dabbelt
2018-12-23 14:58     ` Anup Patel

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=20181126060802.19314-1-anup@brainfault.org \
    --to=anup@brainfault.org \
    --cc=linux-riscv@lists.infradead.org \
    /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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).