[libc-commits] [libc] [llvm] [libc] Add bare-metal Hexagon port (PR #217528)

[Brian Cain via libc-commits]

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@@ -0,0 +1,99 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the startup code for bare-metal Hexagon targets.
+//===----------------------------------------------------------------------===//
+
+#include "hdr/stdint_proxy.h"
+#include "src/__support/macros/config.h"
+#include "src/stdlib/atexit.h"
+#include "src/stdlib/exit.h"
+#include "src/string/memcpy.h"
+#include "src/string/memset.h"
+#include "startup/baremetal/fini.h"
+#include "startup/baremetal/init.h"
+
+extern "C" {
+int main(int argc, char **argv);
+void _start();
+
+// Semihosting library initialisation if applicable. Required for printf, etc.
+[[gnu::weak]] void _platform_init() {}
+
+// These symbols are provided by the linker. The exact names are not defined by
+// a standard.
+extern uintptr_t __stack;
+extern uintptr_t __data_source[];
+extern uintptr_t __data_start[];
+extern uintptr_t __data_size[];
+extern uintptr_t __bss_start[];
+extern uintptr_t __bss_size[];
+} // extern "C"
+
+namespace LIBC_NAMESPACE_DECL {
+
+[[noreturn]] void do_start() {
+  // TODO: This startup code is the MVP for running under the Hexagon
+  // simulator with semihosting. It does not configure the MMU or caches.
+
+  // Clear the Supervisor Status Register so that a subsequent trap0
+  // semihosting call is serviced by the monitor.
+  asm volatile("ssr = %0" : : "r"(0));
+
+  // Perform the equivalent of scatterloading
+  LIBC_NAMESPACE::memcpy(__data_start, __data_source,
+                         reinterpret_cast<uintptr_t>(__data_size));
+  LIBC_NAMESPACE::memset(__bss_start, '\0',
+                         reinterpret_cast<uintptr_t>(__bss_size));
+  __libc_init_array();
+
+  _platform_init();
+  LIBC_NAMESPACE::atexit(&__libc_fini_array);
+  LIBC_NAMESPACE::exit(main(0, 0));
+}
+} // namespace LIBC_NAMESPACE_DECL
+
+extern "C" {
+[[gnu::section(".text.init.enter"), gnu::naked]]
+void _start() {
+  // Setup event vector base (needed for semihosting trap handling).
+  asm volatile("r0 = ##__llvm_libc_hexagon_event_vectors\n\t"
+               "evb = r0");
----------------
androm3da wrote:

This points the evb to the table below, which seems reasonable but the reset vector is set to spin there.

Is there another vector table somewhere else that allowed us to handle the original reset vector?  And if so, maybe the table below could be used there instead?

https://github.com/llvm/llvm-project/pull/217528