[U-Boot] [PATCH] arm: lds: Remove libgcc eabi exception handling tables
Albert ARIBAUD
albert.u.boot at aribaud.net
Thu Sep 5 21:16:59 CEST 2013
Hi Michal,
On Thu, 25 Jul 2013 16:16:46 +0200, Michal Simek
<michal.simek at 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 at xilinx.com>
> Signed-off-by: Michal Simek <michal.simek at 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!
Amicalement,
--
Albert.
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