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

Yu-cheng Yu
2019-08-13T21:04:23Z

From: "H.J. Lu" <hjl.tools@gmail.com>

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 <hjl.tools@gmail.com>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
arch/x86/kernel/vmlinux.lds.S | 10 ++++++++++
1 file changed, 10 insertions(+)

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)
--
2.17.1