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Merge pull request #71 from MaMazav/master
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README fixes: Replaced the block device instructions (which are no lo…
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palmer-dabbelt committed May 9, 2017
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Expand Up @@ -250,9 +250,39 @@ saying, "Hello world!". If not...

## <a name="help-it-doesnt-work"></a>"Help! It doesn't work!"

I know, I've been there too. Good luck!
Most of the errors below were seen when trying to build riscv-tools on CentOS linux distribution with nfs file-system.

### <a name="c++11-problem"></a>C++11 is not supported, although gcc is updated
This problem occured due to old OS installation repository.
A possible solution for CentOS distribution:

wget http://people.centos.org/tru/devtools-2/devtools-2.repo -O /etc/yum.repos.d/devtools-2.repo
sudo yum upgrade
sudo yum install devtoolset-2-gcc devtoolset-2-binutils devtoolset-2-gcc-c++
scl enable devtoolset-2 bash

Last operation will open a shell. Try to run .build.sh from within this shell.

### “error: Building GCC requires GMP 4.2+, MPFR 2.4.0+ and MPC 0.8.0+”
Try the following:

cd <riscv-tools>/riscv-gnu-toolchain/riscv-gcc
contrib/download_prerequisites
sudo yum install gmp gmp-devel mpfr mpfr-devel libmpc libmpc-devel

Also try to follow the instructions of [C++11 is not supported](#c++11-problem).

### Build script got stuck on "Installing project riscv-fesvr"
That's a very simple problem of output redirection. The solution is to open the <riscv-tools>/build.common file and change the following line:


$MAKE install >> build.log

to:

$MAKE install | tee install.log

Then when you run the build script, you will see requests to press y to continue which were hidden before. Just follow the instructions.


# <a name="linuxman"></a> The Linux/RISC-V Installation Manual
Expand Down Expand Up @@ -387,7 +417,7 @@ of resolving the references. Enter the newly-created riscv-tools directory and
instruct Git to update its submodules.

$ cd $TOP/riscv-tools
$ git submodule update --init
$ git submodule update --init --recursive

To build GCC, we will need several other packages, including
flex, bison, autotools, libmpc, libmpfr, and libgmp. Ubuntu distribution
Expand Down Expand Up @@ -513,21 +543,21 @@ We currently develop with BusyBox,
an unbelievably useful set of utilities that all compile into one multi-use
binary. We use BusyBox without source code modifications. You can obtain
the source at <a href="https://www.busybox.net">https://www.busybox.net</a>. In
our case, we will use BusyBox 1.21.1, but other versions should work fine.
our case, we will use BusyBox 1.26.2, but other versions should work fine.

Currently, we need it for its `init` and
`ash` applets, but with `bash` cross-compiled for RISC-V,
there is no longer a need for `ash`.

First, obtain and untar the source:

$ cd $TOP
$ curl -L https://busybox.net/downloads/busybox-1.21.1.tar.bz2 | tar -xj
$ curl -L http://busybox.net/downloads/busybox-1.26.2.tar.bz2 > busybox-1.26.2.tar.bz2
$ tar xvjf busybox-1.26.2.tar.bz2

Then, enter the directory and turn off every configuration
option:

$ cd busybox-1.21.1
$ cd busybox-1.26.2
$ make allnoconfig

We will need to change the cross-compiler, set the build to
Expand All @@ -541,7 +571,7 @@ Here are the configurations you will have to change:
* `CONFIG_STATIC=y`, listed as "Build
BusyBox as a static binary (no shared libs)" in BusyBox Settings
&rarr; Build Options
* `CONFIG_CROSS_COMPILER_PREFIX=riscv-linux-`,
* `CONFIG_CROSS_COMPILER_PREFIX=riscv64-unknown-linux-gnu-`,
listed as "Cross Compiler prefix" in BusyBox Settings &rarr; Build Options
* `CONFIG_FEATURE_INSTALLER=y`, listed as
"Support --install [-s] to install applet links at runtime" in BusyBox Settings
Expand All @@ -551,14 +581,7 @@ listed as "Cross Compiler prefix" in BusyBox Settings &rarr; Build Options
* `CONFIG_ASH_JOB_CONTROL=n`, listed as "Ash &rarr; Job control" in Shells
* `CONFIG_MOUNT=y`, listed as "mount" in Linux System Utilities

My configuration file used to create this example is located
here: [busybox-riscv.config](busybox-riscv.config). You
can also download it directly using this snippet of code:

$ curl -L http://riscv.org/install-guides/busybox-riscv.config > .config

Whether or not you want to use the file provided, enter the
configuration interface much in the same way as that of the Linux kernel:
Enter the configuration interface much in the same way as that of the Linux kernel:

O$ make menuconfig

Expand All @@ -581,49 +604,15 @@ back into the directory with the Linux sources.

## <a name="creating-root-disk"></a> Creating a Root Disk Image

When we initially developed the kernel, we used an initramfs
to store our binaries ([BusyBox](https://www.busybox.net) in
particular). However, with our HTIF-enabled block device, we can boot off of a
root file system proper. (In fact, we still make use of the initramfs, but only
to set up devices and the symlink to `init`. See
`arch/riscv/initramfs.txt`.)
We use an initramfs to store our binaries ([BusyBox](https://www.busybox.net) in
particular).

Currently, we have a root file system pre-packaged
specifically for the RISC-V release. You can obtain it by heading to the index
of my website, [https://ocf.berkeley.edu/~qmn](https://ocf.berkeley.edu/~qmn), finding my
email, and contacting me.

To create your own root image, we need to create an ext2 disk
image. To create an empty disk image, use `dd`, setting the argument
to `count` to the size, in MiB, of your disk image. 64 MiB seems to
be good enough for our purposes.

$ dd if=/dev/zero of=root.bin bs=1M count=64

The file `root.bin` is just an empty chunk of
zeros and has no partitioning information. To format it as an ext2 disk, run
`mkfs.ext2` on it:

$ mkfs.ext2 -F root.bin

You can modify this filesystem if you mount it as writable
from within Linux/RISC-V. However, a better option, especially if you want to
copy big binaries, is to mount it on your host machine. _You will normally
need superuser privileges to do a mount._ Do so this way, assuming you want
to mount the disk image at `linux-3.14.33/mnt`:

$ mkdir mnt
$ sudo mount -o loop root.bin mnt

(Instructions for mounting provided courtesy of a_ou.)

If you cannot mount as root, you can use Filesystem in Userspace
(FUSE) instead. See [here](#using-fuse).

<a name="using-fuse-back"></a>

Once you've mounted the disk image, you can edit the files
inside. There are a few directories that you should have:
To create your own initramfs, there are a few directories that you should have:

* `/bin`
* `/dev`
Expand All @@ -636,13 +625,14 @@ inside. There are a few directories that you should have:

So create them:

$ cd mnt
$ mkdir root
$ cd root
$ mkdir -p bin etc dev lib proc sbin sys tmp usr usr/bin usr/lib usr/sbin

Then, place the BusyBox executable we just compiled in
`/bin`.

$ cp $TOP/busybox-1.21.1/busybox bin
$ cp $TOP/busybox-1.26.2/busybox bin

If you have built BusyBox statically, that will be all
that's needed. If you want to build BusyBox dynamically, you will need to follow
Expand Down Expand Up @@ -684,22 +674,41 @@ comment out line 4.
Also, we will need to create a symbolic link to `/bin/busybox` for `init` to work.

$ ln -s ../bin/busybox sbin/init
$ ln -s sbin/init init

We'll also need a character device for the console:

Add your final touches and binaries to your root disk image,
and then unmount the disk image.<p>
sudo mknod dev/console c 5 1

$ cd ..
$ sudo umount mnt
We are ready to create our initramfs:

find . | cpio --quiet -o -H newc > <riscv-linux>/rootfs.cpio

Configure linux to embed the created cpio archive. In the riscv-linux folder type

make ARCH=riscv menuconfig

Enter to General Setup, mark "Initial RAM filesystem and RAM disk". Then go to the option "Initramfs source file" and press enter to change it to "rootfs.cpio". Then Exit all the way back and save to .config.

Don't forget to rebuild riscv-linux and riscv-pk!

cd <riscv-linux>
make -j4 ARCH=riscv vmlinux
cd <riscv-pk>/build
rm -rf *
../configure --prefix=$RISCV --host=riscv64-unknown-linux-gnu --with-payload=<riscv-linux>/vmlinux
make
make install


Now, we're ready to boot a most basic kernel, with a shell.
Invoke `spike`, the RISC-V architectural simulator, named after the
[golden spike](https://www.nps.gov/gosp/index.htm) that joined the two
tracks of the Transcontinental Railroad, and considered to be the golden model of
execution. We will need to load in the root disk image through the
`+disk` argument to `spike` as well. The command looks
execution. The command looks
like this:

$ spike +disk=root.bin bbl vmlinux
$ spike bbl vmlinux

`vmlinux` is the name of the compiled Linux kernel binary.

Expand All @@ -722,7 +731,91 @@ symbolic links to BusyBox applets. Otherwise, it will generate several

## <a name="help-it-doesnt-work-linux"></a> "Help! It doesn't work!"

I know, I've been there too. Good luck!
First take a look at the [Newlib problem list](#help-it-doesnt-work) which are also relevant to here.
Here are some more problems that can occur in the linux build:

### Problems with "flock"

Some filesystems don't support flock, e.g. nfs (you can check your filesystem by `df -Th`). Look for
"+flock $(SYSROOT)/.lock" in the following files and delete them:

riscv-tools/riscv-gnu-toolchain/Makefile
riscv-tools/riscv-gnu-toolchain/Makefile.in
riscv-tools/riscv-gnu-toolchain/build/Makefile

Avoid building with concurrency (i.e. avoid running make with the -j flag).

### "These critical programs are missing or too old: make"

Not sure why, but gmake doesn't work well for the riscv-tools build in some platforms.
In order to use make instead of gmake, open the file `<riscv-tools>/riscv-gnu-toolchain/riscv-glibc/configure`
and replace the following line:

for ac_prog in gnumake gmake make

with:

for ac_prog in gnumake make gmake


### "Operation not permitted" when trying to create character device

This may occur when running the following command:

sudo mknod dev/console c 5 1

Even if you have sudo permissions, you may still see this message in some filesystem (e.g. nfs). You can create
a virtual drive by:

dd if=/dev/zero of=root.bin bs=1M count=64
mkfs.ext2 -F root.bin
chmod 777 root.bin
mkdir mnt
sudo mount -o loop root.bin mnt

If the `mkfs.ext2` command not found, try instead:

/sbin/mkfs.ext2 -F root.bin

Copy the contents in the above created root directory into the new mnt directory and continue to create the cpio
archive with the mnt directory instead of the root directory.

When finished, you may unmount by:

cd ..
sudo umount root.bin

### compiler-gcc6.h not found

Use newer linux version for RISC-V. You can find it in https://github.com/riscv/riscv-linux
Notice that similar problems as detailed here may occur, so don't forget to check this problem list in case of problems.


### Error on build about "mcmodel=medany"

Such error may occur in one of the stages that requires the RISC-V gcc compiler. Some build stages use the default
x86 gcc compiler installed on the x86 machine to compile if the RISC-V gcc not found. Some possible cases for that:

* RISC-V compiler is not built.
* $RISCV/bin is not in $PATH (Use "setenv PATH $RISCV/bin" or similar export command to add it to path).
* RISC-V compiler has been built but for the wrong variant (built for newlib and not for linux, 32/64 bit variant issue...).
* gcc path is wrong. For example, if "CONFIG_CROSS_COMPILER_PREFIX=riscv-linux-" is used in the Busybox build configuration
instead of "CONFIG_CROSS_COMPILER_PREFIX=riscv64-unknown-linux-gnu-" but the RISC-V compiler is built into
riscv64-unknown-linux-gnu-gcc, the busybox configurator will not find the correct gcc and will use the x86 as default.
Similar problem may occur when compiling https://github.com/riscv/riscv-pk with a wrong --host argument.


### Spike exits immediately with "This is bbl's dummy_payload" message

https://github.com/riscv/riscv-pk should be rebuilt with --with-payload flag points to the compiled vmlinux (replace the
riscv-pk and riscv-linux below with the appropriate repository paths):

cd <riscv-pk>/build
rm -rf *
../configure --prefix=$RISCV --host=riscv64-unknown-linux-gnu --with-payload=<riscv-linux>/vmlinux
make
make install


## <a name="optional-commands"></a> Optional Commands

Expand Down Expand Up @@ -821,14 +914,14 @@ BusyBox as a static binary (no shared libs)" in BusyBox Settings
To make things a little faster, I've used a bit of
`sed` magic instead.

O$ cd $TOP/busybox-1.21.1
O$ cd $TOP/busybox-1.26.2
O$ sed -i 's/CONFIG_STATIC=y/# CONFIG_STATIC is not set/' .config

Then, rebuild and reinstall BusyBox into `mnt/bin`.

O$ make -j16
O$ cd $TOP/linux-3.14.33/mnt
O$ cp $TOP/busybox-1.21.1/busybox bin
O$ cp $TOP/busybox-1.26.2/busybox bin

[Return to text.](#dynamic-busybox-back)

Expand Down

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