linux-kernel - [PATCH 1/2] x86: Discard .note.gnu.property sections in vDSO

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Date:   Fri, 24 Jan 2020 10:18:18 -0800
From:   "H.J. Lu" <hjl.tools@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kees Cook <keescook@...omium.org>,
        Thomas Lendacky <Thomas.Lendacky@....com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [PATCH 1/2] x86: Discard .note.gnu.property sections in vDSO

With the command-line option, -mx86-used-note=yes, the x86 assembler
in binutils 2.32 and above generates a program property note in a note
section, .note.gnu.property, to encode used x86 ISAs and features.  X86
kernel vDSO linker script only contains a signle NOTE segment:

PHDRS
{
 text PT_LOAD FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
 dynamic PT_DYNAMIC FLAGS(4); /* PF_R */
 note PT_NOTE FLAGS(4); /* PF_R */
 eh_frame_hdr 0x6474e550;
}

which may not be incompatible with note.gnu.property sections.  Since
note.gnu.property section in vDSO is not used by dynamic linker, this
patch discards .note.gnu.property sections in vDSO by adding

/DISCARD/ : {
 *(.note.gnu.property)
}

before .notes sections.

Signed-off-by: H.J. Lu <hjl.tools@...il.com>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
---
 arch/x86/entry/vdso/vdso-layout.lds.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/entry/vdso/vdso-layout.lds.S b/arch/x86/entry/vdso/vdso-layout.lds.S
index 93c6dc7812d0..b604da6cc024 100644
--- a/arch/x86/entry/vdso/vdso-layout.lds.S
+++ b/arch/x86/entry/vdso/vdso-layout.lds.S
@@ -52,6 +52,10 @@ SECTIONS
 		*(.gnu.linkonce.b.*)
 	}						:text
 
+	/* .note.gnu.property sections should be discarded */
+	/DISCARD/ : {
+		*(.note.gnu.property)
+	}
 	.note		: { *(.note.*) }		:text	:note
 
 	.eh_frame_hdr	: { *(.eh_frame_hdr) }		:text	:eh_frame_hdr
-- 
2.24.1