More asm comments, riscv32-unknown-elf support, action cleanup, stack align fix.
diff --git a/.github/workflows/mac_os.yml b/.github/workflows/mac_os.yml
index 3124b35..79bb1f2 100644
--- a/.github/workflows/mac_os.yml
+++ b/.github/workflows/mac_os.yml
@@ -18,17 +18,10 @@
steps:
# Clones a single commit from the libtock-rs repository. The commit cloned
# is a merge commit between the PR's target branch and the PR's source.
- # Note that we checkout submodules so that we can invoke Tock's CI setup
- # scripts, but we do not recursively checkout submodules as we need Tock's
- # makefile to set up the qemu submodule itself.
- name: Clone repository
uses: actions/checkout@v2.3.0
- with:
- submodules: true
- # Install the toolchains we need, the run the Makefile's test action. We
- # let the makefile do most of the work because the makefile can be tested
- # locally. Using -j2 because the Actions VMs have 2 cores.
+ # Install the toolchains we need, then run `cargo build`.
- name: Build and Test
run: |
brew tap riscv/riscv
diff --git a/core/runtime/asm/asm_riscv32.S b/core/runtime/asm/asm_riscv32.S
index d95ca12..db1036e 100644
--- a/core/runtime/asm/asm_riscv32.S
+++ b/core/runtime/asm/asm_riscv32.S
@@ -1,3 +1,31 @@
+/* rt_header is defined by the general linker script (libtock_layout.ld). It has
+ * the following layout:
+ *
+ * Field | Offset
+ * ------------------------------------
+ * Address of the start symbol | 0
+ * Initial process break | 4
+ * Top of the stack | 8
+ * Size of .data | 12
+ * Start of .data in flash | 16
+ * Start of .data in ram | 20
+ * Size of .bss | 24
+ * Start of .bss in ram | 28
+ */
+
+/* start is the entry point -- the first code executed by the kernel. The kernel
+ * passes arguments through 4 registers:
+ *
+ * a0 Pointer to beginning of the process binary's code. The linker script
+ * locates rt_header at this address.
+ *
+ * a1 Address of the beginning of the process's usable memory region.
+ * a2 Size of the process' allocated memory region (including grant region)
+ * a3 Process break provided by the kernel.
+ *
+ * We currently only use the value in a0. It is copied into a5 early on because
+ * a0-a4 are needed to invoke system calls.
+ */
.section .start, "ax"
.globl start
start:
diff --git a/core/runtime/extern_asm.rs b/core/runtime/extern_asm.rs
index 1f9419a..d0488f8 100644
--- a/core/runtime/extern_asm.rs
+++ b/core/runtime/extern_asm.rs
@@ -12,14 +12,21 @@
let build_configs = match arch.as_str() {
"riscv32" => &[
// First try riscv64-unknown-elf, as it is the toolchain used by
- // libtock-c.
+ // libtock-c and the toolchain used in the CI environment.
AsmBuildConfig {
triple: "riscv64-unknown-elf",
as_extra_args: &["-march=rv32imc"],
strip: true,
},
- // Second try riscv64-linux-gnu, as riscv64-unknown-elf is
- // unavailable on Debian 10.
+ // Second try riscv32-unknown-elf. This is the best match for Tock's
+ // risc-v targets, but is not as widely available (and has not been
+ // tested with libtock-rs yet).
+ AsmBuildConfig {
+ triple: "riscv32-unknown-elf",
+ as_extra_args: &[],
+ strip: false, // Untested, may need to change.
+ },
+ // Last try riscv64-linux-gnu, as it is the only option on Debian 10
AsmBuildConfig {
triple: "riscv64-linux-gnu",
as_extra_args: &["-march=rv32imc"],
diff --git a/core/runtime/libtock_layout.ld b/core/runtime/libtock_layout.ld
index 38624a0..fcff09a 100644
--- a/core/runtime/libtock_layout.ld
+++ b/core/runtime/libtock_layout.ld
@@ -34,6 +34,10 @@
* the process break.
*/
+/* TODO: Should TBF_HEADER_SIZE be configured via a similar mechanism to the
+ * stack size? We should see if that is possible.
+ */
+
/* GNU LD looks for `start` as an entry point by default, while LLVM's LLD looks
* for `_start`. To be compatible with both, we manually specify an entry point.
*/
@@ -88,7 +92,8 @@
*/
.stack (NOLOAD) : {
KEEP(*(.stack_buffer))
- _stack_top = ALIGN(16); /* Used in rt_header */
+ . = ALIGN(16);
+ _stack_top = .; /* Used in rt_header */
} > RAM
/* Read-write data section. This is deployed as part of FLASH but is copied
