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From: Fangrui Song <i@maskray.me>
To: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>,
	Andrew Waterman <andrew@sifive.com>,
	Jim Wilson <jim.wilson.gcc@gmail.com>,
	Nelson Chu <nelson@rivosinc.com>,
	binutils@sourceware.org, Prabhakar <prabhakar.csengg@gmail.com>
Subject: Re: [RFC PATCH] ld/emulparams: elf32lriscv-defs: Add support tune the text segment start address
Date: Sat, 17 Dec 2022 22:24:04 -0800	[thread overview]
Message-ID: <20221218062404.cn75smc4pperrsd7@gmail.com> (raw)
In-Reply-To: <20221216214310.13155-1-prabhakar.mahadev-lad.rj@bp.renesas.com>

On 2022-12-16, Lad Prabhakar via Binutils wrote:
>On the RISC-V architecture the TEXT_START_ADDR defaults to 0x10000. On
>some RISC-V platforms we want to set this offset to something else. So
>this patch provides a way to tune the text segment start address.
>elf32lriscv-defs.sh now checks for DEFAULT_TEXT_START_ADDR variable and
>if being set it overrides TEXT_START_ADDR to the value set by
>DEFAULT_TEXT_START_ADDR or else defaults to 0x10000.
>
>Renesas RZ/Five RISC-V SoC has Instruction local memory and Data local
>memory (ILM & DLM) which maps between region 0x30000 - 0x4FFFF. When the
>virtual address falls in this range the MMU doesn't trigger a page
>fault and assumes the virtual address as physical address and causes
>undesired behaviours of statically applications/libraries. Hence introduce
>an option to tune the TEXT_START_ADDR.
>
>Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
>---
>Hi All,
>
>This patch is inspired from the current ld/emulparams/nds32elf_linux.sh file
>where similar approach is being used and DEFAULT_TEXT_START_ADDR variable is
>checked to adjust the TEXT_START_ADDR for the platform.
>
>I am not sure if this is the right approach the above issue has been discussed
>on the ML [0].
>
>[0] https://sourceware.org/pipermail/binutils/2022-November/124813.html
>
>Cheers,
>Prabhakar
>---
> ld/emulparams/elf32lriscv-defs.sh | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
>diff --git a/ld/emulparams/elf32lriscv-defs.sh b/ld/emulparams/elf32lriscv-defs.sh
>index b823cedacab..026aef4714b 100644
>--- a/ld/emulparams/elf32lriscv-defs.sh
>+++ b/ld/emulparams/elf32lriscv-defs.sh
>@@ -27,7 +27,11 @@ case "$target" in
> esac
>
> IREL_IN_PLT=
>-TEXT_START_ADDR=0x10000
>+if [ -z ${DEFAULT_TEXT_START_ADDR+x} ]; then
>+    TEXT_START_ADDR=0x10000
>+else
>+    TEXT_START_ADDR=$DEFAULT_TEXT_START_ADDR
>+fi
> MAXPAGESIZE="CONSTANT (MAXPAGESIZE)"
> COMMONPAGESIZE="CONSTANT (COMMONPAGESIZE)"
>
>-- 
>2.17.1
>

Changing ld does not look like a good change to me.  This tuning can be
placed at the compiler driver side as that is the usual place to tune
these things. We can ask users to specify -Wl,-Ttext-segment= (with lld
use --image-base= instead) . If that is inconvenient, with Clang you can
add the option to a configuration file
(https://clang.llvm.org/docs/UsersManual.html#configuration-files).
With GCC there may be an option to add a fragment to the default specs
file.

  parent reply	other threads:[~2022-12-18  6:24 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-16 21:43 Lad Prabhakar
2022-12-17  9:19 ` Andrew Waterman
2022-12-18  6:24 ` Fangrui Song [this message]
2022-12-18 22:44   ` Lad, Prabhakar
2022-12-18 23:09     ` Fangrui Song
2022-12-19  9:02       ` Lad, Prabhakar
2022-12-19  5:00     ` Jeff Law
2022-12-19  9:11       ` Lad, Prabhakar
2022-12-19 21:33         ` Palmer Dabbelt
2022-12-21 13:24           ` Nelson Chu
2022-12-21 20:15             ` Lad, Prabhakar
2022-12-22  2:12               ` Nelson Chu
2022-12-21 20:06           ` Lad, Prabhakar

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