[OE-core][RFC PATCH 01/08] kernel.bbclass: map the kernel build directory to KERNEL_SRC_PATH

[bruce.ashfield@gmail.com]

From: Bruce Ashfield <bruce.ashfield@gmail.com>

kernel-arch's KERNEL_CC maps STAGING_KERNEL_DIR and
STAGING_KERNEL_BUILDDIR to KERNEL_SRC_PATH, but the kernel itself builds
in ${B}, which isn't mapped. Sources generated there (*.mod.c, asn1
parsers, data tables, etc) fall through to the generic debug prefix map,
so the kernel's debug info is split across two roots, and those files
are the only content of the kernel's ${PN}-src package.

Map ${B} to KERNEL_SRC_PATH too. All of the kernel's debug source paths
are then under /usr/src/kernel, and no ${PN}-src package is created
for the kernel.

The generated sources aren't packaged anywhere. They aren't needed to
debug the kernel, and those that are of any use can be regenerated from
the kernel source, where they land at the path the debug info expects.

This is only done in kernel.bbclass, since other kernel-arch users
(module-base, perf, make-mod-scripts) have their own mapping.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
---
 meta/classes-recipe/kernel.bbclass | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/meta/classes-recipe/kernel.bbclass b/meta/classes-recipe/kernel.bbclass
index 46da867a63..ab064bb085 100644
--- a/meta/classes-recipe/kernel.bbclass
+++ b/meta/classes-recipe/kernel.bbclass
@@ -246,6 +246,12 @@ UBOOT_LOADADDRESS ?= "${UBOOT_ENTRYPOINT}"
 # Some Linux kernel configurations need additional parameters on the command line
 KERNEL_EXTRA_ARGS ?= ""
 
+# The kernel builds out of tree in ${B}, which kernel-arch does not remap.
+# Map it to KERNEL_SRC_PATH as well, so generated sources are recorded under
+# the same root as the rest of the kernel and are not collected into a
+# ${PN}-src package. The last matching prefix map wins.
+KERNEL_CC:append = " -ffile-prefix-map=${B}=${KERNEL_SRC_PATH}"
+
 EXTRA_OEMAKE += ' ARCH="${@oe.kernel.map_kernel_arch(d)}"'
 EXTRA_OEMAKE += ' CC="${KERNEL_CC}" LD="${KERNEL_LD}" OBJCOPY="${KERNEL_OBJCOPY}" STRIP="${KERNEL_STRIP}"'
 EXTRA_OEMAKE += ' HOSTCC="${BUILD_CC}" HOSTCFLAGS="${BUILD_CFLAGS}" HOSTLDFLAGS="${BUILD_LDFLAGS}" HOSTCPP="${BUILD_CPP}"'
-- 
2.43.0