Re: [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
On Fri, Dec 21, 2018 at 2:10 AM Palmer Dabbelt wrote: > > On Mon, 17 Dec 2018 01:36:45 PST (-0800), a...@brainfault.org wrote: > > On Mon, Nov 26, 2018 at 11:42 AM Anup Patel 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 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 > >> --- > >> 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 > >> > > > > 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. I have send v2 to address Nick's comment. Regards, Anup
Re: [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
On Mon, 17 Dec 2018 01:36:45 PST (-0800), a...@brainfault.org wrote: On Mon, Nov 26, 2018 at 11:42 AM Anup Patel 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 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 --- 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 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.
Re: [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
On Mon, Dec 17, 2018 at 6:29 PM Nick Kossifidis wrote: > > Στις 2018-12-17 11:36, Anup Patel έγραψε: > > On Mon, Nov 26, 2018 at 11:42 AM Anup Patel > > 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 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 > >> --- > >> 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 > >> > > > > Hi All, > > > > Any comment on this patch? > > > > Regards, > > Anup > > > > Just a note on coding style, you should be using a macro instead of 0x10 > so that those who read the code can understand what it is and also a few > comments since searching through the commit logs to understand why you > used it isn't optimal. RISC-V can support 32bit, 64bit and 128bit machine-word sizes. The 0x10 number is the machine-word size in bytes for 128bit RISC-V CPU (i.e. maximum machine-word size). I will add a macro MAX_BYTES_PER_LONG in vmlinux.lds.S and use it in-place of 0x10 Regards, Anup
Re: [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
Στις 2018-12-17 11:36, Anup Patel έγραψε: On Mon, Nov 26, 2018 at 11:42 AM Anup Patel 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 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 --- 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 Hi All, Any comment on this patch? Regards, Anup Just a note on coding style, you should be using a macro instead of 0x10 so that those who read the code can understand what it is and also a few comments since searching through the commit logs to understand why you used it isn't optimal. Regards, Nick
Re: [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
On Mon, Nov 26, 2018 at 11:42 AM Anup Patel 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 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 > --- > 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 > Hi All, Any comment on this patch? Regards, Anup
Re: [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
On Mon, Nov 26, 2018 at 2:12 PM Anup Patel 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 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 > --- > arch/riscv/kernel/vmlinux.lds.S | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > Reviewed-by: Bin Meng Tested-by: Bin Meng
Re: [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
On Mon, Nov 26, 2018 at 2:12 PM Anup Patel 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 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 > --- > arch/riscv/kernel/vmlinux.lds.S | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > Reviewed-by: Bin Meng Tested-by: Bin Meng
[PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
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 --- 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
[PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S
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 --- 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
