From e0f86d4dc09865956afef3277299a00a9136918d Mon Sep 17 00:00:00 2001
From: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Date: Tue, 13 Apr 2021 11:55:32 +0200
Subject: [PATCH] d/s390fw.mak: retain boot rom debuginfo

Currently we have stripped roms which can be non-useful in some debugging cases:
s390-ccw.img:     ELF 64-bit MSB pie executable, IBM S/390, version 1 (SYSV),
  dynamically linked, interpreter /lib/ld64.so.1,
  BuildID[sha1]=13d565dd0aaed9c6b14f1c406a7d069c19013bce, stripped
s390-netboot.img: ELF 64-bit MSB pie executable, IBM S/390, version 1 (SYSV),
  dynamically linked, interpreter /lib/ld64.so.1,
  BuildID[sha1]=7f9b1ec0a9343bc907335ba7978881354a843a30, stripped

They appear as linked objects with a build-id (strange right).

I've learned that for bootloader debugging you'd ant to load that debug
data. If you had debuginfo example steps are:
1. use qemu with gdbserver
   https://wiki.qemu.org/Features/gdbstub
2. attach to gdbserver
   gdb /usr/bin/qemu-system-s390x -ex "target remote localhost:1234"
3. add-symbol-file "path-to-bios" -o 0x7fe00000
   # because this is the guest address the bios is loaded to

Note: in the s390x case as a bonus some of it is EBSDIC encoded. So you
might also want to use `set target-charset  ...`

Developers are used to debuginfo being stored by buildid as it is
done in dh_strip. Also the FHS kind of implies this path, therefore this
fillows those usual paths.

In dh_strip the path is split and due to that
    Build ID: e65a23729d5a540c689b725703e095c961ff72c1
Becomes
    /usr/lib/debug/.build-id/e6/5a23729d5a540c689b725703e095c961ff72c1.debug

The calls it uses are:
objcopy --only-keep-debug --compress-debug-sections infile outfile
strip --remove-section=.comment --remove-section=.note" --strip-unneeded infile

This implements the same in debian/s390fw.mak for our s390x FW builds.
In regard to size we talk about 14k+18k, so IMHO an extra
qemu-system-data-dbgsym isn't needed, but could be created if preferred.

Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
---
 debian/rom-strip  | 16 ++++++++++++++++
 debian/rules      |  4 +++-
 debian/s390fw.mak |  4 ++--
 3 files changed, 21 insertions(+), 3 deletions(-)
 create mode 100755 debian/rom-strip

diff --git a/debian/rom-strip b/debian/rom-strip
new file mode 100755
index 0000000000..21d0bc0f70
--- /dev/null
+++ b/debian/rom-strip
@@ -0,0 +1,16 @@
+#!/bin/sh
+set -uxe
+CROSSPFX=${1}
+IMAGE=${2}
+DEBUGPATH="b/s390fw/usr/lib/debug/.build-id"
+
+BUILDID1=$(readelf -n ${IMAGE} | grep '^\s*Build ID:' | cut -c 15-16)
+BUILDID2=$(readelf -n ${IMAGE} | grep '^\s*Build ID:' | cut -c 17-)
+
+mkdir -p "${DEBUGPATH}/${BUILDID1}"
+
+${CROSSPFX}objcopy --only-keep-debug --compress-debug-sections \
+    "${IMAGE}" "${DEBUGPATH}/${BUILDID1}/${BUILDID2}.debug"
+
+${CROSSPFX}strip --remove-section=.comment --remove-section=.note \
+    --strip-unneeded "${IMAGE}"
diff --git a/debian/rules b/debian/rules
index 9d9f18f740..7031395acf 100755
--- a/debian/rules
+++ b/debian/rules
@@ -38,7 +38,8 @@ enable_linux_user = $(if $(filter qemu-user,${BUILD_PACKAGES}),enable,disable)
 FIRMWAREPATH = /usr/share/qemu:/usr/share/seabios:/usr/lib/ipxe/qemu
 PKGVERSION = Debian ${DEB_VERSION}
 SAVEMODDIR = /run/qemu/$(shell echo -n "${PKGVERSION}" | tr --complement '[:alnum:]+-.~' '_')
-sysdatadir = debian/qemu-system-data/usr/share/qemu
+sysdatabase = debian/qemu-system-data
+sysdatadir = ${sysdatabase}/usr/share/qemu
 
 ALPHAEV67_CROSSPFX = alpha-linux-gnu-
 PPC64_CROSSPFX = powerpc64-linux-gnu-
@@ -488,6 +489,7 @@ b/s390fw/built:
 	touch $@
 install-s390x-fw: build-s390x-fw
 	install -m 0644 -t "${sysdatadir}" b/s390fw/s390*.img
+	cp -av b/s390fw/usr debian/qemu-system-data
 sysdata-components += s390x-fw
 
 ### hppa-firmware (roms/seabios-hppa)
diff --git a/debian/s390fw.mak b/debian/s390fw.mak
index 64fab0f2c0..7061db7e56 100644
--- a/debian/s390fw.mak
+++ b/debian/s390fw.mak
@@ -20,7 +20,7 @@ CCW_FSRCS = $(addprefix pc-bios/s390-ccw/,${CCW_SRCS})
 
 ${OUT}s390-ccw.img: $(CCW_FSRCS)
 	${S390X_CROSSPFX}gcc -o $@ ${LDFLAGS} $^
-	${S390X_CROSSPFX}strip --strip-unneeded $@
+	./debian/rom-strip $(S390X_CROSSPFX) $@
 	chmod -x $@
 
 NETBOOT_SRCS = start.S sclp.c cio.c virtio.c virtio-net.c jump2ipl.c netmain.c
@@ -45,5 +45,5 @@ ${OUT}s390-netboot.img: ${NETBOOT_FSRCS} ${SLOF_LIBSRCS}
 	${S390X_CROSSPFX}gcc -o $@ ${LDFLAGS} -Ttext=0x7800000 \
 	  -nostdinc -I${SLOFLIB}include -I${SLOF}/lib/libnet -DDHCPARCH=0x1F \
 	  $^
-	${S390X_CROSSPFX}strip --strip-unneeded $@
+	./debian/rom-strip $(S390X_CROSSPFX) $@
 	chmod -x $@
-- 
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