refactor: move mcontext_restore to arch_context

runtime/include/arch/aarch64/context.h

@@ -4,6 +4,8 @@
 #include <unistd.h>
 #include <ucontext.h>
 
+#include "arch_context.h"
+
 #define ARCH_NREGS       (2)   /* SP + PC only */
 #define ARCH_SIG_JMP_OFF 0x100 /* Based on code generated! */
 
@@ -18,7 +20,6 @@ struct arch_context {
 	mcontext_t mctx;
 };
 
-extern void __attribute__((noreturn)) worker_thread_mcontext_restore(void);
 extern __thread struct arch_context worker_thread_base_context;
 
 /* Initialized a context, zeroing out registers and setting the Instruction and Stack pointers */
@@ -104,7 +105,7 @@ arch_context_switch(struct arch_context *ca, struct arch_context *na)
 	             ".align 8\n\t"
 	             "exit%=:\n\t"
 	             :
-	             : [ curr ] "r"(cr), [ next ] "r"(nr), [ slowpath ] "r"(&worker_thread_mcontext_restore)
+	             : [ curr ] "r"(cr), [ next ] "r"(nr), [ slowpath ] "r"(&arch_context_mcontext_restore)
 	             : "memory", "cc", "x0", "x1", "x2", "x3", "x4", "x5", "x6", "x7", "x8", "x9", "x10", "x11", "x12",
 	               "x13", "x14", "x15", "x16", "x17", "x18", "x19", "x20", "x21", "x22", "x23", "x24", "x25", "x26",
 	               "d8", "d9", "d10", "d11", "d12", "d13", "d14", "d15");

runtime/include/arch/x86_64/context.h

@@ -7,6 +7,7 @@
 #include <ucontext.h>
 #include <unistd.h>
 
+#include "arch_context.h"
 #include "software_interrupt.h"
 
 #define ARCH_SIG_JMP_OFF 8
@@ -31,7 +32,6 @@ struct arch_context {
 	mcontext_t mctx;
 };
 
-extern void __attribute__((noreturn)) worker_thread_mcontext_restore(void);
 extern __thread struct arch_context worker_thread_base_context;
 
 static void __attribute__((noinline)) arch_context_init(struct arch_context *actx, reg_t ip, reg_t sp)
@@ -162,11 +162,11 @@ arch_context_switch(struct arch_context *current, struct arch_context *next)
 	   * Slow Path
 	   * If the stack pointer equaled 0, that means the sandbox was preempted and we need to
 	   * fallback to a full mcontext-based context switch. We do this by invoking
-	   * worker_thread_mcontext_restore,  which fires a SIGUSR1 signal. The SIGUSR1 signal handler
+	   * arch_context_mcontext_restore,  which fires a SIGUSR1 signal. The SIGUSR1 signal handler
 	   * executes the mcontext-based context switch.
 	   */
 	  "1:\n\t"
-	  "call worker_thread_mcontext_restore\n\t"
+	  "call arch_context_mcontext_restore\n\t"
 	  ".align 8\n\t"
 
 	  /*

runtime/include/arch_context.h

@@ -0,0 +1 @@
+void __attribute__((noinline)) __attribute__((noreturn)) arch_context_mcontext_restore(void);

runtime/include/sandbox.h

@@ -86,7 +86,6 @@ extern __thread struct arch_context *worker_thread_next_context;
 extern void worker_thread_block_current_sandbox(void);
 extern void worker_thread_on_sandbox_exit(struct sandbox *sandbox);
 extern void worker_thread_process_io(void);
-extern void __attribute__((noreturn)) worker_thread_mcontext_restore(void);
 extern void worker_thread_wakeup_sandbox(struct sandbox *sandbox);
 
 /***************************

runtime/src/arch_context.c

@@ -0,0 +1,18 @@
+#include <signal.h>
+#include <pthread.h>
+
+#include "types.h"
+
+/**
+ * Called by the inline assembly in arch_context_switch to send a SIGUSR1 in order to restore a previously preempted
+ * thread. The only way to restore all of the mcontext registers of a preempted sandbox is to send ourselves a signal,
+ * then update the registers we should return to, then sigreturn (by returning from the handler). This returns to the
+ * control flow restored from the mcontext
+ */
+void __attribute__((noinline)) __attribute__((noreturn)) arch_context_mcontext_restore(void)
+{
+	debuglog("Thread %lu | Signaling SIGUSR1 on self to initiate mcontext restore...\n", pthread_self());
+	pthread_kill(pthread_self(), SIGUSR1);
+
+	assert(false); /* should not get here.. */
+}

runtime/src/worker_thread.c

@@ -142,19 +142,6 @@ worker_thread_process_io(void)
 #endif
 }
 
-/**
- * We need to switch back to a previously preempted thread. The only way to restore all of its registers is to use
- * sigreturn. To get to sigreturn, we need to send ourselves a signal, then update the registers we should return to,
- * then sigreturn (by returning from the handler).
- */
-void __attribute__((noinline)) __attribute__((noreturn)) worker_thread_mcontext_restore(void)
-{
-	debuglog("Thread %lu | Signaling SIGUSR1 on self to initiate mcontext restore...\n", pthread_self());
-	pthread_kill(pthread_self(), SIGUSR1);
-
-	assert(false); /* should not get here.. */
-}
-
 /**
  * Run all outstanding events in the local thread's libuv event loop
  */