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From: Fangrui Song <maskray@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org, Bill Wendling <morbo@google.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Fangrui Song <maskray@google.com>
Subject: [PATCH] arm64: lds: move .got section out of .text
Date: Fri, 28 Apr 2023 05:04:42 +0000	[thread overview]
Message-ID: <20230428050442.180913-1-maskray@google.com> (raw)

Currently, the .got section is placed within the output section .text.
However, when .got is non-empty, the SHF_WRITE flag is set when linked
by lld. GNU ld recognizes .text as a special section and ignores the
SHF_WRITE flag. By renaming .text, we can also get the SHF_WRITE flag.

Conventionally, the .got section is placed just before .got.plt (which
should be empty and omitted in the kernel). Therefore, we move the .got
section to a conventional location (between .text and .data) and remove
the unneeded `. = ALIGN(16)`.

Signed-off-by: Fangrui Song <maskray@google.com>
---
 arch/arm64/kernel/vmlinux.lds.S | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index b9202c2ee18e..2bcb3b30db41 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -181,18 +181,8 @@ SECTIONS
 			KPROBES_TEXT
 			HYPERVISOR_TEXT
 			*(.gnu.warning)
-		. = ALIGN(16);
-		*(.got)			/* Global offset table		*/
 	}
 
-	/*
-	 * Make sure that the .got.plt is either completely empty or it
-	 * contains only the lazy dispatch entries.
-	 */
-	.got.plt : { *(.got.plt) }
-	ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18,
-	       "Unexpected GOT/PLT entries detected!")
-
 	. = ALIGN(SEGMENT_ALIGN);
 	_etext = .;			/* End of text section */
 
@@ -247,6 +237,16 @@ SECTIONS
 
 	. = ALIGN(SEGMENT_ALIGN);
 	__inittext_end = .;
+
+	.got : { *(.got) }
+	/*
+	 * Make sure that the .got.plt is either completely empty or it
+	 * contains only the lazy dispatch entries.
+	 */
+	.got.plt : { *(.got.plt) }
+	ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18,
+	       "Unexpected GOT/PLT entries detected!")
+
 	__initdata_begin = .;
 
 	init_idmap_pg_dir = .;
-- 
2.40.1.495.gc816e09b53d-goog


             reply	other threads:[~2023-04-28  5:05 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-04-28  5:04 Fangrui Song [this message]
2023-04-28  7:29 ` Ard Biesheuvel
2023-04-28 18:58   ` Fangrui Song
2023-04-28 19:11     ` Ard Biesheuvel
2023-04-28 21:06       ` Fangrui Song
2023-04-28 21:25         ` Ard Biesheuvel
2023-04-28 22:29           ` Fangrui Song
2023-04-29  6:13             ` Ard Biesheuvel
2023-04-29  7:51               ` Fangrui Song
2023-04-29  8:14                 ` Ard Biesheuvel

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