Expose __syscall and add new bootstrap method

1 files changed, 41 insertions, 0 deletions

diff --git a/src/asm.rs b/src/asm.rs
index 8f23aa9..a546fe1 100644
--- a/src/asm.rs
+++ b/src/asm.rs
@@ -164,3 +164,44 @@ pub fn ttat(addr: *mut u32) -> u32 {
 pub unsafe fn bx_ns(addr: u32) {
     call_asm!(__bxns(addr: u32));
 }
+
+/// Semihosing syscall.
+///
+/// This method is used by cortex-m-semihosting to provide semihosting syscalls.
+#[inline]
+pub unsafe fn sh_syscall(nr: u32, arg: u32) -> u32 {
+    call_asm!(__sh_syscall(nr: u32, arg: u32) -> u32)
+}
+
+/// Bootstrap.
+///
+/// Sets the active stack to the main stack, updates the main stack pointer to `msp`,
+/// then jumps execution to the address in `rv`.
+/// Writes `msp` to the MSP special register, then jumps to the address in `rv`.
+#[inline]
+pub unsafe fn bootstrap(msp: *const u32, rv: *const u32) -> ! {
+    let msp = msp as u32;
+    let rv = rv as u32;
+    call_asm!(__bootstrap(msp: u32, rv: u32));
+    core::hint::unreachable_unchecked();
+}
+
+/// Bootload.
+///
+/// Reads the initial stack pointer value and reset vector from
+/// the provided vector table address, sets the active stack to
+/// the main stack, sets the main stack pointer to the new initial
+/// stack pointer view, then jumps to the reset vector.
+///
+/// # Safety
+///
+/// The provided `vector_table` must point to a valid vector
+/// table, with a valid stack pointer as the first word and
+/// a valid reset vector (in thumb mode, with the least significant
+/// bit cleared) as the second word.
+#[inline]
+pub unsafe fn bootload(vector_table: *const u32) -> ! {
+    let msp = core::ptr::read_volatile(vector_table);
+    let rv = core::ptr::read_volatile(vector_table.offset(1));
+    bootstrap(msp as *const u32, rv as *const u32);
+}