[Buildroot] [PATCH] qemu/riscv32-virt: Fix missing linux-headers patch

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

Hello Francis,

+Yann in Cc.

First of all, my apologies for breaking the build with my change.

On Thu, 20 Jun 2019 10:56:48 -0700
Alistair Francis <alistair.francis@wdc.com> wrote:

> Commit f9993797959 "configs/qemu_riscv32_virt: update to 5.1 kernel"
> broke the qemu/riscv32-virt machine build as the BR2_LINUX_KERNEL_PATCH
> mechanism was replaced with the BR2_GLOBAL_PATCH_DIR mechanism when the
> patch was applied. This results in the linux-headers not having the
> patch applied which causes a glibc build failure.
> 
> Add a symbolic link to ensure the linux patch is applied to linux and
> linux-headers.
> 
> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
> ---
>  board/qemu/riscv32-virt/patches/linux-headers | 1 +
>  1 file changed, 1 insertion(+)
>  create mode 120000 board/qemu/riscv32-virt/patches/linux-headers
> 
> diff --git a/board/qemu/riscv32-virt/patches/linux-headers b/board/qemu/riscv32-virt/patches/linux-headers
> new file mode 120000
> index 0000000000..9c52cb36f4
> --- /dev/null
> +++ b/board/qemu/riscv32-virt/patches/linux-headers
> @@ -0,0 +1 @@
> +linux
> \ No newline at end of file

I understand the problem, but I am not sure it is the right solution.
Indeed, when the option BR2_KERNEL_HEADERS_AS_KERNEL is enabled, we
really expect that linux-headers will use the same source code as the
kernel, including all patches. The linux-headers.mk is already doing
some effort to achieve this, but it does not do it entirely due do
BR2_GLOBAL_PATCH_DIR patches.

So what I would propose instead is this:

diff --git a/package/linux-headers/linux-headers.mk b/package/linux-headers/linux-headers.mk
index 95432ade83..46f270a0e1 100644
--- a/package/linux-headers/linux-headers.mk
+++ b/package/linux-headers/linux-headers.mk
@@ -60,7 +60,8 @@ endif # LINUX_HEADERS_CUSTOM_TARBALL
 # Apply any necessary patches if we are using the headers from a kernel
 # build.
 ifeq ($(BR2_KERNEL_HEADERS_AS_KERNEL),y)
-LINUX_HEADERS_PATCHES = $(call qstrip,$(BR2_LINUX_KERNEL_PATCH))
+LINUX_HEADERS_PATCHES = $(call qstrip,$(BR2_LINUX_KERNEL_PATCH)) \
+       $(wildcard $(addsuffix /linux,$(call qstrip,$(BR2_GLOBAL_PATCH_DIR))))
 
 # We rely on the generic package infrastructure to download and apply
 # remote patches (downloaded from ftp, http or https). For local

Yann, what do you think of this ?

However, Francis & Mark: it is not normal that we can't build a RISC-V
32 toolchain out of the box, as I reported separately. So while this
linux-headers/linux patch consistency issue is real, I think we need
something better for RISC-V 32. Indeed a user who would build a RISC-V
32 system, but not for Qemu, would not use this defconfig, and would
therefore not have this patch. Do you expect this issue to be resolved
in the near future on the kernel side ?

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com