Re: [PATCH] RISC-V: Make BSS section as the last section in

From: Palmer Dabbelt
Date: Thu Dec 20 2018 - 15:40:44 EST

On Mon, 17 Dec 2018 01:36:45 PST (-0800), anup@xxxxxxxxxxxxxx wrote:
On Mon, Nov 26, 2018 at 11:42 AM Anup Patel <anup@xxxxxxxxxxxxxx> wrote:

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 This
is not optimal for having minimal flat kernel Image size hence this
patch makes BSS section as the last section in RISC-V

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 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@xxxxxxxxxxxxxx>
arch/riscv/kernel/ | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/ b/arch/riscv/kernel/
index 65df1dfdc303..cc99eed44931 100644
--- a/arch/riscv/kernel/
+++ b/arch/riscv/kernel/
@@ -74,8 +74,6 @@ SECTIONS


@@ -83,6 +81,8 @@ SECTIONS

+ BSS_SECTION(0x10, 0x10, 0x10)
_end = .;


Hi All,

Any comment on this patch?

Sorry, I haven't had a chance to look at it yet. Aside from the macro issue mentioned by Nick it seems OK.