[bug#70962] [PATCH 12/14] gnu: linux-libre: Enable BTF debug info.

[Maxim Cournoyer]

This is needed for software making use of eBPF programs, such as the sysdig
utility, among others.  For more information about BPF, see:
<https://brendangregg.com/blog/2020-11-04/bpf-co-re-btf-libbpf.html>.

* gnu/packages/linux.scm (%default-extra-linux-options): Enable
CONFIG_DEBUG_INFO, CONFIG_DEBUG_INFO_BTF,
CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT, CONFIG_BPF_JIT,
CONFIG_BPF_JIT_ALWAYS_ON, CONFIG_BPF_SYSCALL and BPF_UNPRIV_DEFAULT_OFF.
Disable CONFIG_DEBUG_INFO_REDUCED.
(make-linux-libre*) [native-inputs]: Add dwarves, python-wrapper and zlib.

Change-Id: Idfc64f82aa404e86168bffcf721a325f9e807f75
---

 gnu/packages/linux.scm | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/gnu/packages/linux.scm b/gnu/packages/linux.scm
index eaa9f66d74..d2b9344296 100644
--- a/gnu/packages/linux.scm
+++ b/gnu/packages/linux.scm
@@ -829,6 +829,24 @@ (define (default-extra-linux-options version)
   `(;; Make the kernel config available at /proc/config.gz
     ("CONFIG_IKCONFIG" . #t)
     ("CONFIG_IKCONFIG_PROC" . #t)
+    ;; Debugging options.
+    ("CONFIG_DEBUG_INFO" . #t)          ;required by BTF
+    ,@(if (version>=? version "5.1")
+          '(("CONFIG_DEBUG_INFO_BTF" . #t))
+          '())
+    ,@(if (version>=? version "5.12")
+          '(("CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT" . #t))
+          '())
+    ("CONFIG_DEBUG_INFO_REDUCED" . #f)  ;incompatible with BTF
+    ;; Tracing and related options.
+    ,@(if (version>=? version "5.1")
+          '(("CONFIG_BPF_JIT" . #t)
+            ("CONFIG_BPF_JIT_ALWAYS_ON" . #t)
+            ("CONFIG_BPF_SYSCALL" . #t))
+          '())
+    ,@(if (version>=? version "5.13")
+          '(("BPF_UNPRIV_DEFAULT_OFF" . #t))
+          '())
     ;; Some very mild hardening.
     ("CONFIG_SECURITY_DMESG_RESTRICT" . #t)
     ;; All kernels should have NAMESPACES options enabled
@@ -1107,7 +1125,12 @@ (define* (make-linux-libre* version gnu-revision source 
supported-systems
            ;; These are needed to compile the GCC plugins.
            gmp
            mpfr
-           mpc))
+           mpc
+           ;; These are needed when building with the CONFIG_DEBUG_INFO_BTF
+           ;; support.
+           dwarves                      ;for pahole
+           python-wrapper
+           zlib))
     (home-page "https://www.gnu.org/software/linux-libre/";)
     (synopsis "100% free redistribution of a cleaned Linux kernel")
     (description "GNU Linux-Libre is a free (as in freedom) variant of the
-- 
2.41.0