x86: Discard .note.gnu.property sections

When switching to kernel.org x86_64 gcc 11.1.0 toolchain, u-boot.rom
built from qemu-x86_defconfig no longer boots anymore. Investigation
shows that U-Boot fails at a very early stage during the boot process,
in fdtdec_prepare_fdt() where fdt_check_header() complains that there
is not a valid device tree found at gd->fdt_blob which points to _end.
Now _end points to an allocated section .note.gnu.property which of
course is wrong.

This issue is however not seen when using the default Ubuntu 20.04 gnu
toolchain (gcc 9.3.0 with binutils 2.34). Further investigation shows
that it is caused by a behavior change of binutils v2.36 which is part
of the kernel.org gcc 11.1.0 toolchain, via the following commit:

  939b95c77bf2 ("Linux/x86: Configure gas with --enable-x86-used-note by default")

In fact, there was already a regression bug report [1] for binutils two
months ago, but the binutils folks did not think it is a bug :(

To resolve this, there are several options:

* pass -Wa,-mx86-used-note=no to gas
* pass -R .note.gnu.property to objcopy
* discard the section in the linker script

Linux kernel uses the discard way [2], so let's do the same for U-Boot.

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=27753
[2] commit 4caffe6a28d3 ("x86/vdso: Discard .note.gnu.property sections in vDSO")

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

diff --git a/arch/x86/cpu/u-boot-64.lds b/arch/x86/cpu/u-boot-64.lds
index 98c7f8e9c53e9d78bea1e193fef10de59e1b85a6..ee0812aefbc2f2c6a6f132db5f2f540d844f050c 100644 (file)
--- a/arch/x86/cpu/u-boot-64.lds
+++ b/arch/x86/cpu/u-boot-64.lds
@@ -107,4 +107,5 @@ SECTIONS
        /DISCARD/ : { *(.plt*) }
        /DISCARD/ : { *(.interp*) }
        /DISCARD/ : { *(.gnu*) }
+       /DISCARD/ : { *(.note.gnu.property) }
 }

diff --git a/arch/x86/cpu/u-boot-spl.lds b/arch/x86/cpu/u-boot-spl.lds
index 4a655bf9b5980d8d862ca4bf369c3abc02946c7e..346f60bdac0b7039e5924c0cd45d1152ec0b5e40 100644 (file)
--- a/arch/x86/cpu/u-boot-spl.lds
+++ b/arch/x86/cpu/u-boot-spl.lds
@@ -82,6 +82,7 @@ SECTIONS
        /DISCARD/ : { *(.plt*) }
        /DISCARD/ : { *(.interp*) }
        /DISCARD/ : { *(.gnu*) }
+       /DISCARD/ : { *(.note.gnu.property) }
 
 #if defined(CONFIG_SPL_X86_16BIT_INIT) || defined(CONFIG_TPL_X86_16BIT_INIT)
        /*

diff --git a/arch/x86/cpu/u-boot.lds b/arch/x86/cpu/u-boot.lds
index a283c290eefd00fdc37ee166396b01eb0011d006..22fde01e7499e41defbf483437c1b3ca05cb2b1b 100644 (file)
--- a/arch/x86/cpu/u-boot.lds
+++ b/arch/x86/cpu/u-boot.lds
@@ -105,6 +105,7 @@ SECTIONS
        /DISCARD/ : { *(.plt*) }
        /DISCARD/ : { *(.interp*) }
        /DISCARD/ : { *(.gnu*) }
+       /DISCARD/ : { *(.note.gnu.property) }
 
 #ifdef CONFIG_X86_16BIT_INIT
        /*