Uday Shankar a7c699d090 kbuild: rpm-pkg: build a debuginfo RPM
The rpm-pkg make target currently suffers from a few issues related to
debuginfo:
1. debuginfo for things built into the kernel (vmlinux) is not available
   in any RPM produced by make rpm-pkg. This makes using tools like
   systemtap against a make rpm-pkg kernel impossible.
2. debug source for the kernel is not available. This means that
   commands like 'disas /s' in gdb, which display source intermixed with
   assembly, can only print file names/line numbers which then must be
   painstakingly resolved to actual source in a separate editor.
3. debuginfo for modules is available, but it remains bundled with the
   .ko files that contain module code, in the main kernel RPM. This is a
   waste of space for users who do not need to debug the kernel (i.e.
   most users).

Address all of these issues by additionally building a debuginfo RPM
when the kernel configuration allows for it, in line with standard
patterns followed by RPM distributors. With these changes:
1. systemtap now works (when these changes are backported to 6.11, since
   systemtap lags a bit behind in compatibility), as verified by the
   following simple test script:

   # stap -e 'probe kernel.function("do_sys_open").call { printf("%s\n", $$parms); }'
   dfd=0xffffffffffffff9c filename=0x7fe18800b160 flags=0x88800 mode=0x0
   ...

2. disas /s works correctly in gdb, with source and disassembly
   interspersed:

   # gdb vmlinux --batch -ex 'disas /s blk_op_str'
   Dump of assembler code for function blk_op_str:
   block/blk-core.c:
   125     {
      0xffffffff814c8740 <+0>:     endbr64

   127
   128             if (op < ARRAY_SIZE(blk_op_name) && blk_op_name[op])
      0xffffffff814c8744 <+4>:     mov    $0xffffffff824a7378,%rax
      0xffffffff814c874b <+11>:    cmp    $0x23,%edi
      0xffffffff814c874e <+14>:    ja     0xffffffff814c8768 <blk_op_str+40>
      0xffffffff814c8750 <+16>:    mov    %edi,%edi

   126             const char *op_str = "UNKNOWN";
      0xffffffff814c8752 <+18>:    mov    $0xffffffff824a7378,%rdx

   127
   128             if (op < ARRAY_SIZE(blk_op_name) && blk_op_name[op])
      0xffffffff814c8759 <+25>:    mov    -0x7dfa0160(,%rdi,8),%rax

   126             const char *op_str = "UNKNOWN";
      0xffffffff814c8761 <+33>:    test   %rax,%rax
      0xffffffff814c8764 <+36>:    cmove  %rdx,%rax

   129                     op_str = blk_op_name[op];
   130
   131             return op_str;
   132     }
      0xffffffff814c8768 <+40>:    jmp    0xffffffff81d01360 <__x86_return_thunk>
   End of assembler dump.

3. The size of the main kernel package goes down substantially,
   especially if many modules are built (quite typical). Here is a
   comparison of installed size of the kernel package (configured with
   allmodconfig, dwarf4 debuginfo, and module compression turned off)
   before and after this patch:

   # rpm -qi kernel-6.13* | grep -E '^(Version|Size)'
   Version     : 6.13.0postpatch+
   Size        : 1382874089
   Version     : 6.13.0prepatch+
   Size        : 17870795887

   This is a ~92% size reduction.

Note that a debuginfo package can only be produced if the following
configs are set:
- CONFIG_DEBUG_INFO=y
- CONFIG_MODULE_COMPRESS=n
- CONFIG_DEBUG_INFO_SPLIT=n

The first of these is obvious - we can't produce debuginfo if the build
does not generate it. The second two requirements can in principle be
removed, but doing so is difficult with the current approach, which uses
a generic rpmbuild script find-debuginfo.sh that processes all packaged
executables. If we want to remove those requirements the best path
forward is likely to add some debuginfo extraction/installation logic to
the modules_install target (controllable by flags). That way, it's
easier to operate on modules before they're compressed, and the logic
can be reused by all packaging targets.

Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2025-04-06 06:22:01 +09:00

174 lines
6.0 KiB
RPMSpec

# _arch is undefined if /usr/lib/rpm/platform/*/macros was not included.
%{!?_arch: %define _arch dummy}
%{!?make: %define make make}
%define makeflags %{?_smp_mflags} ARCH=%{ARCH}
Name: kernel
Summary: The Linux Kernel
Version: %(echo %{KERNELRELEASE} | sed -e 's/-/_/g')
Release: %{pkg_release}
License: GPL
Group: System Environment/Kernel
Vendor: The Linux Community
URL: https://www.kernel.org
Source0: linux.tar.gz
Source1: config
Source2: diff.patch
Provides: kernel-%{KERNELRELEASE}
BuildRequires: bc binutils bison dwarves
BuildRequires: (elfutils-libelf-devel or libelf-devel) flex
BuildRequires: gcc make openssl openssl-devel perl python3 rsync
%description
The Linux Kernel, the operating system core itself
%package headers
Summary: Header files for the Linux kernel for use by glibc
Group: Development/System
Obsoletes: kernel-headers < %{version}
Provides: kernel-headers = %{version}
%description headers
Kernel-headers includes the C header files that specify the interface
between the Linux kernel and userspace libraries and programs. The
header files define structures and constants that are needed for
building most standard programs and are also needed for rebuilding the
glibc package.
%if %{with_devel}
%package devel
Summary: Development package for building kernel modules to match the %{version} kernel
Group: System Environment/Kernel
AutoReqProv: no
%description -n kernel-devel
This package provides kernel headers and makefiles sufficient to build modules
against the %{version} kernel package.
%endif
%if %{with_debuginfo}
# list of debuginfo-related options taken from distribution kernel.spec
# files
%undefine _include_minidebuginfo
%undefine _find_debuginfo_dwz_opts
%undefine _unique_build_ids
%undefine _unique_debug_names
%undefine _unique_debug_srcs
%undefine _debugsource_packages
%undefine _debuginfo_subpackages
%global _find_debuginfo_opts -r
%global _missing_build_ids_terminate_build 1
%global _no_recompute_build_ids 1
%{debug_package}
%endif
# some (but not all) versions of rpmbuild emit %%debug_package with
# %%install. since we've already emitted it manually, that would cause
# a package redefinition error. ensure that doesn't happen
%define debug_package %{nil}
# later, we make all modules executable so that find-debuginfo.sh strips
# them up. but they don't actually need to be executable, so remove the
# executable bit, taking care to do it _after_ find-debuginfo.sh has run
%define __spec_install_post \
%{?__debug_package:%{__debug_install_post}} \
%{__arch_install_post} \
%{__os_install_post} \
find %{buildroot}/lib/modules/%{KERNELRELEASE} -name "*.ko" -type f \\\
| xargs --no-run-if-empty chmod u-x
%prep
%setup -q -n linux
cp %{SOURCE1} .config
patch -p1 < %{SOURCE2}
%build
%{make} %{makeflags} KERNELRELEASE=%{KERNELRELEASE} KBUILD_BUILD_VERSION=%{release}
%install
mkdir -p %{buildroot}/lib/modules/%{KERNELRELEASE}
cp $(%{make} %{makeflags} -s image_name) %{buildroot}/lib/modules/%{KERNELRELEASE}/vmlinuz
# DEPMOD=true makes depmod no-op. We do not package depmod-generated files.
%{make} %{makeflags} INSTALL_MOD_PATH=%{buildroot} DEPMOD=true modules_install
%{make} %{makeflags} INSTALL_HDR_PATH=%{buildroot}/usr headers_install
cp System.map %{buildroot}/lib/modules/%{KERNELRELEASE}
cp .config %{buildroot}/lib/modules/%{KERNELRELEASE}/config
if %{make} %{makeflags} run-command KBUILD_RUN_COMMAND='test -d ${srctree}/arch/${SRCARCH}/boot/dts' 2>/dev/null; then
%{make} %{makeflags} INSTALL_DTBS_PATH=%{buildroot}/lib/modules/%{KERNELRELEASE}/dtb dtbs_install
fi
ln -fns /usr/src/kernels/%{KERNELRELEASE} %{buildroot}/lib/modules/%{KERNELRELEASE}/build
%if %{with_devel}
%{make} %{makeflags} run-command KBUILD_RUN_COMMAND='${srctree}/scripts/package/install-extmod-build %{buildroot}/usr/src/kernels/%{KERNELRELEASE}'
%endif
{
echo "/lib/modules/%{KERNELRELEASE}"
for x in alias alias.bin builtin.alias.bin builtin.bin dep dep.bin \
devname softdep symbols symbols.bin weakdep; do
echo "%ghost /lib/modules/%{KERNELRELEASE}/modules.${x}"
done
for x in System.map config vmlinuz; do
echo "%ghost /boot/${x}-%{KERNELRELEASE}"
done
if [ -d "%{buildroot}/lib/modules/%{KERNELRELEASE}/dtb" ];then
find "%{buildroot}/lib/modules/%{KERNELRELEASE}/dtb" -printf "%%%ghost /boot/dtb-%{KERNELRELEASE}/%%P\n"
fi
echo "%exclude /lib/modules/%{KERNELRELEASE}/build"
} > %{buildroot}/kernel.list
# make modules executable so that find-debuginfo.sh strips them. this
# will be undone later in %%__spec_install_post
find %{buildroot}/lib/modules/%{KERNELRELEASE} -name "*.ko" -type f \
| xargs --no-run-if-empty chmod u+x
%if %{with_debuginfo}
# copying vmlinux directly to the debug directory means it will not get
# stripped (but its source paths will still be collected + fixed up)
mkdir -p %{buildroot}/usr/lib/debug/lib/modules/%{KERNELRELEASE}
cp vmlinux %{buildroot}/usr/lib/debug/lib/modules/%{KERNELRELEASE}
%endif
%clean
rm -rf %{buildroot}
rm -f debugfiles.list debuglinks.list debugsourcefiles.list debugsources.list \
elfbins.list
%post
if [ -x /usr/bin/kernel-install ]; then
/usr/bin/kernel-install add %{KERNELRELEASE} /lib/modules/%{KERNELRELEASE}/vmlinuz
fi
for file in vmlinuz System.map config; do
if ! cmp --silent "/lib/modules/%{KERNELRELEASE}/${file}" "/boot/${file}-%{KERNELRELEASE}"; then
cp "/lib/modules/%{KERNELRELEASE}/${file}" "/boot/${file}-%{KERNELRELEASE}"
fi
done
if [ -d "/lib/modules/%{KERNELRELEASE}/dtb" ] && \
! diff -rq "/lib/modules/%{KERNELRELEASE}/dtb" "/boot/dtb-%{KERNELRELEASE}" >/dev/null 2>&1; then
rm -rf "/boot/dtb-%{KERNELRELEASE}"
cp -r "/lib/modules/%{KERNELRELEASE}/dtb" "/boot/dtb-%{KERNELRELEASE}"
fi
if [ ! -e "/lib/modules/%{KERNELRELEASE}/modules.dep" ]; then
/usr/sbin/depmod %{KERNELRELEASE}
fi
%preun
if [ -x /usr/bin/kernel-install ]; then
kernel-install remove %{KERNELRELEASE}
fi
%files -f %{buildroot}/kernel.list
%defattr (-, root, root)
%exclude /kernel.list
%files headers
%defattr (-, root, root)
/usr/include
%if %{with_devel}
%files devel
%defattr (-, root, root)
/usr/src/kernels/%{KERNELRELEASE}
/lib/modules/%{KERNELRELEASE}/build
%endif