OpenBLAS

Also don't add br2_local by default, default params are insane.

README.adoc

@@ -2015,6 +2015,34 @@ External open source benchmarks. We will try to create Buildroot packages for th
 * http://parsec.cs.princeton.edu/ Mentioned on docs: http://gem5.org/PARSEC_benchmarks
 * http://www.m5sim.org/Splash_benchmarks
 
+===== BLAS
+
+Buildroot supports it, which makes everything just trivial:
+
+....
+printf 'BR2_PACKAGE_OPENBLAS=y\n' >> br2_local
+printf 'BR2_TARGET_ROOTFS_EXT2_SIZE="128M"\n' >> br2_local
+./build -a arm -g -i br2_local -- kernel_module-reconfigure
+....
+
+and then inside the guest run our test program:
+
+....
+/openblas.out
+....
+
+For x86, you also need:
+
+....
+printf 'BR2_PACKAGE_OPENBLAS_TARGET="NEHALEM"\n' >> br2_local
+....
+
+to overcome this bug: https://bugs.busybox.net/show_bug.cgi?id=10856
+
+....
+sgemm_kernel.o: No such file or directory
+....
+
 ===== PARSEC benchmark
 
 We have ported parts of the link:http://parsec.cs.princeton.edu[PARSEC benchmark] for cross compilation at: https://github.com/cirosantilli/parsec-benchmark See the documentation on that repo to find out which benchmarks have been ported. Furthermore, some of the benchmarks were are segfaulting, see link:parsec-benchmark/test.sh[]
@@ -2541,12 +2569,14 @@ dmesg
 
 We provide the following mechanisms:
 
-* `br2_local`: a gitignored file that gets appended to the `.config`. Get started with:
+* `./build -i br2_local`: append the file `br2_local` to a single build. Must be passed every time you run `./build`.
++
+For convenience, we already gitignore `br2_local` for you.
 +
 ....
 cp br2_local.off br2_local
 ....
-* `./build -i somefile`: append `somefile` to a single build. Must be passed every time you run `./build`.
++
 * `./build -c 'BR2_SOM_OPTION="myval"'`: append a single option to a single build.
 
 === ccache

build

@@ -57,9 +57,6 @@ while getopts 'a:c:Cgj:i:kK:lp:qS:v' OPT; do
 done
 shift $(($OPTIND - 1))
 extra_make_args="$extra_make_args $@"
-if [ -f br2_local ]; then
-  config_fragments="$config_fragments br2_local"
-fi
 case "$arch" in
   x86_64)
     defconfig=qemu_x86_64_defconfig

kernel_module/external.mk

@@ -8,8 +8,12 @@ KERNEL_MODULE_VERSION = 1.0
 KERNEL_MODULE_SITE = $(BR2_EXTERNAL_KERNEL_MODULE_PATH)
 KERNEL_MODULE_SITE_METHOD = local
 
+ifeq ($(BR2_PACKAGE_OPENBLAS),y)
+	KERNEL_MODULE_DEPENDENCIES += openblas
+endif
+
 define KERNEL_MODULE_BUILD_CMDS
-  $(MAKE) -C '$(@D)/user' CC="$(TARGET_CC)" LD="$(TARGET_LD)"
+  $(MAKE) -C '$(@D)/user' BR2_PACKAGE_OPENBLAS="$(BR2_PACKAGE_OPENBLAS)" CC="$(TARGET_CC)" LD="$(TARGET_LD)"
 endef
 
 define KERNEL_MODULE_INSTALL_TARGET_CMDS

kernel_module/user/Makefile

@@ -2,14 +2,20 @@
 
 CFLAGS_EXTRA ?= -ggdb3 -fopenmp -O0 -std=c99 -Wall -Werror -Wextra
 IN_EXT ?= .c
+LIBS :=
 OUT_EXT ?= .out
 
 OUTS := $(addsuffix $(OUT_EXT), $(basename $(wildcard *$(IN_EXT))))
+ifeq ($(BR2_PACKAGE_OPENBLAS),y)
+	LIBS += -lopenblas
+else
+	OUTS := $(filter-out openblas.out,$(OUTS))
+endif
 
 all: $(OUTS)
 
 %$(OUT_EXT): %$(IN_EXT)
-	$(CC) $(CFLAGS) $(CFLAGS_EXTRA) -o '$@' '$<'
+	$(CC) $(CFLAGS) $(CFLAGS_EXTRA) -o '$@' '$<' $(LIBS)
 
 clean:
 	rm -f *'$(OUT_EXT)'

kernel_module/user/openblas.c

@@ -0,0 +1,18 @@
+/*
+OpenBLAS hello world, initially adapted from:
+https://stackoverflow.com/questions/49227682/gem5-can-not-simulate-my-program-that-calls-openblas-functions-with-an-fatal-err
+*/
+
+#include <cblas.h>
+#include <stdio.h>
+
+int main() {
+	size_t i = 0;
+	double A[6] = {1.0,2.0,1.0,-3.0,4.0,-1.0};
+	double B[6] = {1.0,2.0,1.0,-3.0,4.0,-1.0};
+	double C[9] = {.5,.5,.5,.5,.5,.5,.5,.5,.5};
+	cblas_dgemm(CblasColMajor, CblasNoTrans, CblasTrans,3,3,2,1,A, 3, B, 3,2,C,3);
+	for(i = 0; i < 9; i++)
+		printf("%f ", C[i]);
+	printf("\n");
+}

run

@@ -70,6 +70,7 @@ fi
 root_dir="$(pwd)"
 buildroot_dir="${root_dir}/buildroot"
 out_dir="${root_dir}/buildroot/output.${arch_dir}~"
+images_dir="${out_dir}/images"
 
 if "$gem5"; then
   build_dir="${out_dir}/build/gem5-1.0"