riscv: user: Force LINUX_HEADERS on hwprobe

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/arch/riscv/user/hwprobe/README.md b/arch/riscv/user/hwprobe/README.md
new file mode 100644
index 0000000..58f09c1
--- /dev/null
+++ b/arch/riscv/user/hwprobe/README.md
@@ -0,0 +1,36 @@
+The RISC-V support for the Linux kernel has a new system call which is specific
+to it, called `hwprobe`. With this system call you can check which features,
+extensions, etc. are available on the current machine.
+
+In order to build this example you need Linux headers for the RISC-V
+architecture. You can achieve this in two ways:
+
+1. Simply install the Linux headers from your distribution if you are already
+   using a RISC-V machine.
+2. Build the Linux kernel and use the `LINUX_HEADERS` environment variable to
+   point to the headers directory (i.e. the directory produced by `make
+   headers_install`)
+
+After that, build it and run it. On a QEMU machine I got the following:
+
+```
+Supports base extensions I, M, A? yes
+
+We got back this bit map: 0000001110001101001010000001000100100000000000000000000011111011; which means:
+
+F, D: OK
+C: OK
+ZBA: OK
+ZBB: OK
+ZBS: OK
+ZICBOZ: OK
+ZBC: OK
+ZIHINTNTL: OK
+ZFA: OK
+ZIHINTPAUSE: OK
+ZCA: OK
+ZCD: OK
+ZAWRS: OK
+ZICNTR: OK
+ZIHPM: OK
+```