linux-kernel - [PATCH v2 2/2] riscv: Disable text-data gap in flat binaries

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Message-Id: <20210407154924.1557489-3-damien.lemoal@wdc.com>
Date:   Thu,  8 Apr 2021 00:49:24 +0900
From:   Damien Le Moal <damien.lemoal@....com>
To:     Palmer Dabbelt <palmer@...belt.com>,
        linux-riscv@...ts.infradead.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-kernel@...r.kernel.org
Cc:     Max Filippov <jcmvbkbc@...il.com>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Anup Patel <anup.patel@....com>, Christoph Hellwig <hch@....de>
Subject: [PATCH v2 2/2] riscv: Disable text-data gap in flat binaries

uclibc/gcc combined with elf2flt riscv linker file fully resolve the
PC relative __global_pointer$ value at compile time and do not generate
a relocation entry to set a runtime gp value. As a result, if the
flatbin loader introduces a gap between the text and data sections, the
gp value becomes incorrect and prevent correct execution of a flatbin
executable.

Avoid this problem by enabling CONFIG_BINFMT_FLAT_NO_TEXT_DATA_GAP
automatically when CONFIG_RISCV is enabled and CONFIG_MMU disabled.

Signed-off-by: Damien Le Moal <damien.lemoal@....com>
---
 arch/riscv/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 0d0cf67359cb..6a85fbbd056e 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -33,6 +33,7 @@ config RISCV
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
+	select BINFMT_FLAT_NO_TEXT_DATA_GAP if !MMU
 	select CLONE_BACKWARDS
 	select CLINT_TIMER if !MMU
 	select COMMON_CLK
-- 
2.30.2