[v8,13/14] x86: Discard .note.gnu.property sections

Commit Message

Yu-cheng Yu Aug. 13, 2019, 8:53 p.m. UTC

From: "H.J. Lu" <[e-mail]>

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.
To exclude .note.gnu.property sections from NOTE segment in x86 kernel
linker script:

PHDRS {
 text PT_LOAD FLAGS(5);
 data PT_LOAD FLAGS(6);
 percpu PT_LOAD FLAGS(6);
 init PT_LOAD FLAGS(7);
 note PT_NOTE FLAGS(0);
}
SECTIONS
{
...
 .notes : AT(ADDR(.notes) - 0xffffffff80000000) { __start_notes = .; KEEP(*(.not
e.*)) __stop_notes = .; } :text :note
...
}

this patch discards .note.gnu.property sections in kernel linker script
by adding

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

before .notes sections.  Since .exit.text and .exit.data sections are
discarded at runtime, it undefines EXIT_TEXT and EXIT_DATA to exclude
.exit.text and .exit.data sections from default discarded sections.

Signed-off-by: H.J. Lu <[e-mail]>
Signed-off-by: Yu-cheng Yu <[e-mail]>
---
 arch/x86/kernel/vmlinux.lds.S | 10 ++++++++++
 1 file changed, 10 insertions(+)

Patch

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index e2feacf921a0..5ef137493a85 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -146,6 +146,10 @@  SECTIONS
 		_etext = .;
 	} :text = 0x9090
 
+	/* .note.gnu.property sections should be discarded */
+	/DISCARD/ : {
+		*(.note.gnu.property)
+	}
 	NOTES :text :note
 
 	EXCEPTION_TABLE(16) :text = 0x9090
@@ -415,6 +419,12 @@  SECTIONS
 	STABS_DEBUG
 	DWARF_DEBUG
 
+	/* Sections to be discarded.  EXIT_TEXT and EXIT_DATA discard at
+	 * runtime, not link time. */
+#undef EXIT_TEXT
+#define EXIT_TEXT
+#undef EXIT_DATA
+#define EXIT_DATA
 	DISCARDS
 	/DISCARD/ : {
 		*(.eh_frame)