Its usage was removed in e2849500 but it wasn't removed as being
enabled.

asm!() and global_asm!() are now stabilized so they need to be used
instead of invoked via a feature flag.

Enhance README.md file with building instructions.  That way it
is easier for people new to the project to build the sample stand
alone oxerun binary.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Usage of llvm_asm!() has been superseded by a new asm!() macro.  This
patch removes the [naked] descriptor before function __impl_start().
Nowadays cargo demands that an asm!() block have a noreturn option,
which prevents anything after the asm!() block from being executed.

Removing the [naked] descriptor introduced a new "push rax" before
setting up the stack, which doesn't matter since we are never returning
from the sample application.  This is also in line with what is
done in the sample application of the bootloader crate.

Before:

_start:
        #APP
        mov     rbp, offset STACK_TOP
        mov     rsp, rbp

        #NO_APP
        call    hello_world
        call    poweroff
        ud2

After:

_start:
        push    rax
        mov     eax, offset STACK_TOP
        #APP

        mov     rbp, rax
        mov     rsp, rbp

        #NO_APP
        call    hello_world
        call    poweroff
        ud2

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Usage of llvm_asm!() has been superseded by a new asm!() macro.  No
change in functionality.

Before:

hypercall_2:
        mov     eax, edi
        shl     rax, 5
        lea     rax, [rax + HYPERCALL_PAGE]
        mov     rdi, rsi
        mov     rsi, rdx
        #APP
        call    rax
        #NO_APP
        ret

After:

hypercall_2:
        mov     rcx, rsi
        mov     eax, edi
        shl     rax, 5
        lea     rax, [rax + HYPERCALL_PAGE]
        mov     rsi, rdx
        mov     rdi, rcx
        #APP

        call    rax

        #NO_APP
        ret

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

It is much easier to look at generated assembler code when
rustc hasn't mangled function names.  As such add the no_mangle
directive.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Remove property "stack-probes" as it generates the following
compilation error:

$ rustc --version
rustc 1.57.0-nightly (5ecc8ad84 2021-09-19)
$
$ cargo build --target x86_64-xen-pv.json
error: failed to run `rustc` to learn about target-specific information

Caused by:
  process didn't exit successfully: `rustc - --crate-name ___ --print=file-names --target /home/mpoirier/work/stratos/xen/xen-sys/x86_64-xen-pv.json --crate-type bin --crate-type rlib --crate-type dylib --crate-type cdylib --crate-type staticlib --crate-type proc-macro --print=sysroot --print=cfg` (exit status: 1)
  --- stderr
  error: Error loading target specification: `Boolean(false)` is not a valid value for `stack-probes`: expected a JSON object. Run `rustc --print target-list` for a list of built-in targets

This issue has also been reported for another crate here[1].

[1]. https://github.com/o8vm/rust_dos/pull/5



Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Based on the recommendation of https://github.com/rust-osdev/cargo-xbuild/commit/07d65812e7cc1c2e5b14a11f781b23be8333252e, switch to using
https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#build-std
to compile the core for our custom Xen target.

Per RFC 2843, the asm!() macro was renamed to llvm_asm!().
https://rust-lang.github.io/rfcs/2843-llvm-asm.html

All assembly is now contained within the Rust code and the external
assembler is not necessary so these files aren't necessary.

The existing model of building a binary as a library and then linking
that with assembly to make the actual binary is not conducive going
forward. This moves the assembly code into a Rust macro and allows the
user to use a macro to declare an entry point which is then wrapped
appropriately to build a functioning Xen binary. This change allows code
to be compiled on any platform that has a functioning Rust compiler.

Include <public/elfnote.h> to be processed by bindgen.

eh_personality only needs to be defined when building a bare metal
target so only include it for the x86_64-xen-pv target.

This defines all the possible values to the shutdown hypercall and
moves the existing call sites into the xen crate.

Switch from hand-rolled defines for the hypercall code into code that is
using the bindgen bits for supporting hypercalls. Side effects of
changing the directory structure to make it clear what is platform
generic code and what is x86_64 specific code.

Use Xen 4.11.1 public headers on x86_64 to generate the necessary data
types.

Added makefile rule which will allow the ability to generate Rust from
the Xen headers so that all types are defined.

The target config was not being found for dependencies of xen and
xen-sys without being explicitly called. Change the display of xbuild so
that the user sees the target we are building for.

Switched from using the linker frok binutils to the Rust native lld
linker.

Switched to Rust Edition 2018

There is no target OS "pv" or "oxerun" in the Rust code base and this
should be reported as "none" for correctness.

The current target is really a 64-bit PV target so rename the target to
be more appropriate.

The clean rule wasn't updated after the build change to cargo-xbuild.

rustup respects the rust-toolchain file to set the default toolchain so
use that rather than asking people to set their toolchain to nightly.

This project aims to provide the ability to write bare metal unikernel
systems in Rust for Xen.

cargo-xbuild is a simpler fork of xargo which has entered maintenance
mode. With this change we do not need to specify rlibc which has been
retired in favor of compiler_intrinsics which cargo-xbuild supports out
of the box.

We aren't targetting x86_64-unknown-linux-gnu but instead bare metal so
target that appropriately.

The target spec for Rust changed to have the pre-link-args be per
linker.

RFC 2070 called out panic_implementation, which was renamed to
panic_handler which was stabilized.

https://doc.rust-lang.org/nightly/reference/runtime.html#the-panic_handler-attribute