[openwrt/openwrt] build: add option KERNEL_DEBUG_INFO_BTF

[LEDE Commits]

stintel pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/531e0399cd7fca9e1a88520b817ac036da204c1c

commit 531e0399cd7fca9e1a88520b817ac036da204c1c
Author: Tony Ambardar <itugrok at yahoo.com>
AuthorDate: Sun Jul 26 07:51:34 2020 -0700

    build: add option KERNEL_DEBUG_INFO_BTF
    
    Generate BTF (BPF Type Format) information from DWARF debug info. This is
    embedded in the kernel and exported via sysfs as /sys/kernel/btf/vmlinux.
    BTF data enhances kernel portability and introspection for BPF programs.
    
    Selecting this also enables the dwarves host package which provides the
    pahole tool used for BTF encoding.
    
    Test using: "bpftool btf dump file /sys/kernel/btf/vmlinux format c"
    
    This needs to depend on KERNEL_DEBUG_INFO_REDUCED not being set,
    otherwise we can enable both KERNEL_DEBUG_INFO_BTF and
    KERNEL_DEBUG_INFO_REDUCED, which will result in undefined behaviour.
    
    Signed-off-by: Tony Ambardar <itugrok at yahoo.com>
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
    [split DEBUG_INFO_REDUCED into separate commit, add dependency]
    Signed-off-by: Stijn Tintel <stijn at linux-ipv6.be>
---
 config/Config-kernel.in | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/config/Config-kernel.in b/config/Config-kernel.in
index e146107148..1a3f6a8bdc 100644
--- a/config/Config-kernel.in
+++ b/config/Config-kernel.in
@@ -373,6 +373,20 @@ config KERNEL_DEBUG_INFO
 	help
 	  This will compile your kernel and modules with debug information.
 
+config KERNEL_DEBUG_INFO_BTF
+
+	bool "Enable additional BTF type information"
+	default n
+	depends on !HOST_OS_MACOS
+	depends on KERNEL_DEBUG_INFO && !KERNEL_DEBUG_INFO_REDUCED
+	select DWARVES
+	help
+	  Generate BPF Type Format (BTF) information from DWARF debug info.
+	  Turning this on expects presence of pahole tool, which will convert
+	  DWARF type info into equivalent deduplicated BTF type info.
+
+	  Required to run BPF CO-RE applications.
+
 config KERNEL_DEBUG_INFO_REDUCED
 	bool "Reduce debugging information"
 	default y