Merge #299

299: Expose __syscall and add new bootstrap method r=jonas-schievink a=adamgreig

We added `__syscall` in the new inline asm, but did not expose it in the crate API, and the cortex-m-semihosting crate can't use it directly because the pre-built binaries would contain duplicate symbols (#271). This PR renames it to `__sh_syscall` (since we could imagine other different syscalls; this one is explicitly semihosting with the `bkpt 0xAB`) and exposes it in `cortex_m::asm::sh_syscall`.

This PR also adds the new methods discussed in #297 to permit sound bootstrapping, either from an MSP and RV or a vector table address.

Co-authored-by: Adam Greig <adam@adamgreig.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/asm/lib.rs b/asm/lib.rs
index b57642e..fc8ddc8 100644
--- a/asm/lib.rs
+++ b/asm/lib.rs
@@ -69,10 +69,11 @@ shims! {
     fn __psp_r() -> u32;
     fn __psp_w(val: u32);
     fn __sev();
-    fn __udf();
+    fn __udf() -> !;
     fn __wfe();
     fn __wfi();
-    fn __syscall(nr: u32, arg: u32) -> u32;
+    fn __sh_syscall(nr: u32, arg: u32) -> u32;
+    fn __bootstrap(msp: u32, rv: u32) -> !;
 }
 
 // v7m *AND* v8m.main, but *NOT* v8m.base