From: Atish Patra <atish.patra@wdc.com>
To: linux-kernel@vger.kernel.org
Cc: Albert Ou <aou@eecs.berkeley.edu>,
Kees Cook <keescook@chromium.org>,
Anup Patel <anup@brainfault.org>,
linux-riscv@lists.infradead.org,
Atish Patra <atish.patra@wdc.com>,
Palmer Dabbelt <palmer@dabbelt.com>, Zong Li <zong.li@sifive.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Greentime Hu <greentime.hu@sifive.com>,
Andrew Morton <akpm@linux-foundation.org>,
Borislav Petkov <bp@suse.de>,
Michel Lespinasse <walken@google.com>,
Ard Biesheuvel <ardb@kernel.org>, Mike Rapoport <rppt@kernel.org>,
Jim Wilson <jimw@sifive.com>
Subject: [PATCH v2 4/6] RISC-V: Align the .init.text section
Date: Mon, 26 Oct 2020 16:02:52 -0700 [thread overview]
Message-ID: <20201026230254.911912-5-atish.patra@wdc.com> (raw)
In-Reply-To: <20201026230254.911912-1-atish.patra@wdc.com>
In order to improve kernel text protection, we need separate .init.text/
.init.data/.text in separate sections. However, RISC-V linker relaxation
code is not aware of any alignment between sections. As a result, it may
relax any RISCV_CALL relocations between sections to JAL without realizing
that an inter section alignment may move the address farther. That may
lead to a relocation truncated fit error. However, linker relaxation code
is aware of the individual section alignments.
The detailed discussion on this issue can be found here.
https://github.com/riscv/riscv-gnu-toolchain/issues/738
Keep the .init.text section aligned so that linker relaxation will take
that as a hint while relaxing inter section calls.
Here are the code size changes for each section because of this change.
section change in size (in bytes)
.head.text +4
.text +40
.init.text +6530
.exit.text +84
The only significant increase in size happened for .init.text because
all intra relocations also use 2MB alignment.
Suggested-by: Jim Wilson <jimw@sifive.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
arch/riscv/kernel/vmlinux.lds.S | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index 3ffbd6cbdb86..cacd7898ba7f 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -30,7 +30,13 @@ SECTIONS
. = ALIGN(PAGE_SIZE);
__init_begin = .;
- INIT_TEXT_SECTION(PAGE_SIZE)
+ __init_text_begin = .;
+ .init.text : AT(ADDR(.init.text) - LOAD_OFFSET) ALIGN(SECTION_ALIGN) { \
+ _sinittext = .; \
+ INIT_TEXT \
+ _einittext = .; \
+ }
+
. = ALIGN(8);
__soc_early_init_table : {
__soc_early_init_table_start = .;
--
2.25.1
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next prev parent reply other threads:[~2020-10-26 23:03 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-26 23:02 [PATCH v2 0/6] Improve kernel section protections Atish Patra
2020-10-26 23:02 ` [PATCH v2 1/6] RISC-V: Move __start_kernel to .head.text Atish Patra
2020-10-26 23:02 ` [PATCH v2 2/6] RISC-V: Initialize SBI early Atish Patra
2020-10-27 10:04 ` Mike Rapoport
2020-10-27 18:38 ` Atish Patra
2020-10-26 23:02 ` [PATCH v2 3/6] RISC-V: Enforce protections for kernel sections early Atish Patra
2020-10-27 10:00 ` Mike Rapoport
2020-10-27 18:38 ` Atish Patra
2020-10-26 23:02 ` Atish Patra [this message]
2020-10-26 23:02 ` [PATCH v2 5/6] RISC-V: Protect .init.text & .init.data Atish Patra
2020-10-27 10:45 ` Mike Rapoport
2020-10-29 19:21 ` Atish Patra
2020-10-30 8:49 ` Mike Rapoport
2020-10-30 20:29 ` Atish Patra
2020-10-26 23:02 ` [PATCH v2 6/6] RISC-V: Move dynamic relocation section under __init Atish Patra
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