From fde03ae33d55b160a31a6c54946880dcdf8fd0d6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zolt=C3=A1n=20B=C3=B6sz=C3=B6rm=C3=A9nyi?=
 <zboszor@gmail.com>
Date: Fri, 28 Jul 2023 12:16:56 +0200
Subject: [PATCH] Allow setting platform macro settings externally (#2585)
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* Allow setting platform macro settings externally

By default, rpm installs a series of default platforms based on
the CPU architecture names in subdirectories called

    /usr/lib/platform/<arch>-<os>

This is enough for regular Linux distributions. However, some
distributions may use more specific platform names that refer to
particular computer systems, like SBCs or specific CPU tuning when
compiling.

If the platform subdirectory does not exist in /usr/lib/platform
then rpmbuild does not work.

Allow creating such custom platform subdirectory with feeding
the necessary data using external variables: RPM_CUSTOM_ARCH,
RPM_CUSTOM_ISANAME, RPM_CUSTOM_ISABITS, RPM_CUSTOM_CANONARCH
and RPM_CUSTOM_CANONCOLOR

Signed-off-by: Zoltán Böszörményi <zboszor@gmail.com>

---------

Signed-off-by: Zoltán Böszörményi <zboszor@gmail.com>
Co-authored-by: Florian Festi <ffesti@redhat.com>
---
 INSTALL         | 37 +++++++++++++++++++++++++++++++++++++
 installplatform |  9 ++++++++-
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/INSTALL b/INSTALL
index 0edbc32e7f..a057fd946a 100644
--- a/INSTALL
+++ b/INSTALL
@@ -143,6 +143,43 @@ and then install with:
 
     make install
 
+
+By default, rpm installs a series of default platforms based on the CPU
+architecture names in subdirectories called
+
+    /usr/lib/platform/<arch>-<os>
+
+This is enough for many distributions. However, some distributions
+may use more specific platform names that refer to particular computer
+systems, like SBCs or specific CPU tuning when compiling. Examples of such
+platform names are: "genericx86_64", "intel_skylake_64", "raspberrypi_armv7",
+"raspberrypi_armv8", etc.
+
+If the platform name is put into /etc/rpm/platform, then rpmbuild uses it
+and the only macros file rpmbuild looks for is
+
+    /usr/lib/platform/`cat /etc/rpm/platform`-<os>/macros
+
+If this file does not exist, many rpm macros will not have their expected
+values set and e.g. %configure will fail when trying to run rpmbuild.
+
+To allow creating the macros file for such a custom platform, the shell
+variables listed below must be set. If RPM_CUSTOM_ARCH is not set, the rest
+is ignored.
+
+    export RPM_CUSTOM_ARCH=genericx86_64
+    export RPM_CUSTOM_ISANAME=x86
+    export RPM_CUSTOM_ISABITS=64
+    export RPM_CUSTOM_CANONARCH=x86_64
+    export RPM_CUSTOM_CANONCOLOR=0 # to use /usr/lib for %_libdir
+    export RPM_CUSTOM_CANONCOLOR=3 # to use /usr/lib64 for %_libdir
+
+    make install 
+
+This also creates and installs the new platform file e.g.
+/usr/lib/platform/genericx86_64-linux/macros
+
+
 Rpm comes with an automated self-test suite. The test-suite requires
 autom4te from autoconf (https://www.gnu.org/software/autoconf/) and
 bwrap (https://github.com/containers/bubblewrap/). It is enabled by
diff --git a/installplatform b/installplatform
index c44055d9fc..ac9b616435 100755
--- a/installplatform
+++ b/installplatform
@@ -11,7 +11,7 @@ VENDOR="${4}"
 OS="${5}"
 RPMRC_GNU="${6}"
 
-for ARCH in noarch `grep ^arch_canon $RPMRC | cut -d: -f2`; do
+for ARCH in noarch `grep ^arch_canon $RPMRC | cut -d: -f2` ${RPM_CUSTOM_ARCH:+custom}; do
   RPMRC_OPTFLAGS="`sed -n 's/^optflags: '$ARCH' //p' $RPMRC`"
   RPMRC_OPTFLAGS="`echo $RPMRC_OPTFLAGS | sed -e 's, ,\ ,g'`"
   case $RPMRC_OPTFLAGS in
@@ -30,6 +30,13 @@ for ARCH in noarch `grep ^arch_canon $RPMRC | cut -d: -f2`; do
   CANONCOLOR=
   FILTER=cat
   case "${ARCH}" in
+    custom)
+	ARCH=$RPM_CUSTOM_ARCH
+	ISANAME=$RPM_CUSTOM_ISANAME
+	ISABITS=$RPM_CUSTOM_ISABITS
+	CANONARCH=$RPM_CUSTOM_CANONARCH
+	CANONCOLOR=$RPM_CUSTOM_CANONCOLOR
+    ;;
     sparc64*) 
 	ISANAME=sparc
 	ISABITS=64