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 v2] RISC-V: Make BSS section as the last section in vmlinux.lds.S
Date: Wed, 19 Dec 2018 18:06:57 +0530 [thread overview]
Message-ID: <20181219123657.61270-1-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. In summary, this patch reduces
Linux-4.20-rc4 flat kernel Image size by 809 KB.
Signed-off-by: Anup Patel <anup@brainfault.org>
---
Changes since v1:
- Introduce MAX_BYTES_PER_LONG define and use it in-place of
0x10 magic value
arch/riscv/kernel/vmlinux.lds.S | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index 65df1dfdc303..1e1395d63dab 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -18,6 +18,8 @@
#include <asm/cache.h>
#include <asm/thread_info.h>
+#define MAX_BYTES_PER_LONG 0x10
+
OUTPUT_ARCH(riscv)
ENTRY(_start)
@@ -74,8 +76,6 @@ SECTIONS
*(.sbss*)
}
- BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
-
EXCEPTION_TABLE(0x10)
NOTES
@@ -83,6 +83,10 @@ SECTIONS
*(.rel.dyn*)
}
+ BSS_SECTION(MAX_BYTES_PER_LONG,
+ MAX_BYTES_PER_LONG,
+ MAX_BYTES_PER_LONG)
+
_end = .;
STABS_DEBUG
--
2.17.1
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next reply other threads:[~2018-12-19 12:37 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-19 12:36 Anup Patel [this message]
2018-12-20 6:16 ` [PATCH v2] RISC-V: Make BSS section as the last section in vmlinux.lds.S Bin Meng
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