[U-Boot] [PATCH] arm: lds: Remove libgcc eabi exception handling tables

[Michal Simek <monstr@monstr.eu>]

On 09/05/2013 09:16 PM, Albert ARIBAUD wrote:
> Hi Michal,
> 
> On Thu, 25 Jul 2013 16:16:46 +0200, Michal Simek
> <michal.simek@xilinx.com> wrote:
> 
>> Remove ARM eabi exception handling tables (for frame unwinding).
>> AFAICT, u-boot stubs away the frame unwiding routines, so the tables will
>> more or less just consume space. It should be OK to remove them.
>>
>> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
>> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
>> ---
>> This patch was sent to ML as RFC (May 9)
>>
>> Here is the origin response in connection to this patch.
>>
>> Ok, so Michal and I just did some fiddling with zynq builds and
>> *exidx* sections.
>>
>> By default the *exidx* sections are between rodata and data, so
>> removing them causes many apparent changes at the binary level.
>> However, builds of zynq based on ARM master with the patch above vs
>> master with a patch mapping *exidx* sections after BSS gives identical
>> binaries. Thus the RFC has no functional effect.
>>
>> Also, ARM EHABI states that [exception] Tables are not required for ABI
>> compliance at the C/Assembler level but are required for C++.
>>
>> http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038a/IHI0038A_ehabi.pdf
>>
>> So as long as we don't put any C++ code in U-Boot (a prospect that I
>> don't see happening any time soon), this RFC is safe and either is a
>> no-op or removes useless bytes from the binary.
>>
>> ---
>>  arch/arm/cpu/u-boot.lds | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds
>> index 3037885..8894c8a 100644
>> --- a/arch/arm/cpu/u-boot.lds
>> +++ b/arch/arm/cpu/u-boot.lds
>> @@ -113,4 +113,6 @@ SECTIONS
>>  	/DISCARD/ : { *(.plt*) }
>>  	/DISCARD/ : { *(.interp*) }
>>  	/DISCARD/ : { *(.gnu*) }
>> +	/DISCARD/ : { *(.ARM.exidx*) }
>> +	/DISCARD/ : { *(.gnu.linkonce.armexidx.*) }
>>  }
>> --
>> 1.8.2.3
>>
> 
> Applied to u-boot-arm/master, thanks!
> 

Ok. Thanks,
Michal


-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform


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