@@ -6,7 +6,7 @@
* *
* Asm Implementation File *
* *
- * Copyright (C) 2015-2022, Free Software Foundation, Inc. *
+ * Copyright (C) 2011-2022, Free Software Foundation, Inc. *
* *
* GNAT is free software; you can redistribute it and/or modify it under *
* terms of the GNU General Public License as published by the Free Soft- *
@@ -33,49 +33,44 @@
* ARM-QNX version of the __gnat_sigtramp service *
**************************************************/
+#include <signal.h>
#include <ucontext.h>
#include "sigtramp.h"
/* See sigtramp.h for a general explanation of functionality. */
-/* ----------------------
- -- General comments --
- ----------------------
+/* -------------------------------------------
+ -- Prototypes for our internal asm stubs --
+ -------------------------------------------
- Stubs are generated from toplevel asms,
- The general idea is to establish CFA as the sigcontext
- and state where to find the registers as offsets from there.
+ Eventhough our symbols will remain local, the prototype claims "extern"
+ and not "static" to prevent compiler complaints about a symbol used but
+ never defined. */
- Note that the registers we "restore" here are those to which we have
- direct access through the system sigcontext structure, which includes
- only a partial set of the non-volatiles ABI-wise. */
+/* sigtramp stub providing ARM unwinding info for common registers. */
-/* -----------------------------------------
- -- Protypes for our internal asm stubs --
- -----------------------------------------
-
- The registers are expected to be at SIGCONTEXT + 12 (reference the
- sicontext structure in asm/sigcontext.h which describes the first
- 3 * 4byte fields.) Even though our symbols will remain local, the
- prototype claims "extern" and not "static" to prevent compiler complaints
- about a symbol used but never defined. */
+extern void __gnat_sigtramp_common
+(int signo, void *siginfo, void *sigcontext,
+ __sigtramphandler_t * handler, void * sc_pregs);
-/* sigtramp stub providing unwind info for common registers. */
+/* -------------------------------------
+ -- Common interface implementation --
+ -------------------------------------
-extern void __gnat_sigtramp_common
- (int signo, void *siginfo, void *sigcontext,
- __sigtramphandler_t * handler);
+ We enforce optimization to minimize the overhead of the extra layer. */
void __gnat_sigtramp (int signo, void *si, void *sc,
- __sigtramphandler_t * handler)
+ __sigtramphandler_t * handler)
__attribute__((optimize(2)));
-void __gnat_sigtramp (int signo, void *si, void *ucontext,
- __sigtramphandler_t * handler)
+void __gnat_sigtramp (int signo, void *si, void *sc,
+ __sigtramphandler_t * handler)
{
- struct sigcontext *mcontext = &((ucontext_t *) ucontext)->uc_mcontext;
+ mcontext_t *mcontext = &((ucontext_t *) sc)->uc_mcontext;
- __gnat_sigtramp_common (signo, si, mcontext, handler);
+ /* Pass MCONTEXT in the fifth position so that the assembly code can find
+ it at the same stack location as SC_PREGS. */
+ __gnat_sigtramp_common (signo, si, mcontext, handler, &mcontext->cpu);
}
/* asm string construction helpers. */
@@ -98,27 +93,25 @@ void __gnat_sigtramp (int signo, void *si, void *ucontext,
/* Trampoline body block
--------------------- */
+/* The 5 arguments passed to __gnat_sigtramp_common are located in:
+ - r0-r2: arguments to pass on to the actual handler
+ - r3: the actual handler
+ - sp: the address of the reg set to restore
+ All we have to do then is to instruct the unwinder to restore the registers
+ from the value in VSP. Unwinder instructions are executed backwards, so we
+ 1- instruct to pop r2 from the VSP (.save {r2})
+ 2- move the VSP to the address pointed to by r2 (.movsp r2)
+ 3- restore all registers from there. (.save {r0-r15})
+ Once the unwinding instructions are set, we just need to call the handler
+ as r0-r2 are already properly set.
+*/
#define SIGTRAMP_BODY \
CR("") \
-TCR("# Allocate frame and also save r2 which is the argument register") \
-TCR("# containing the sigcontext, so that we can restore it during") \
-TCR("# unwinding and thereby load the rest of the desired context.") \
-TCR("stmfd sp!, {r2, r3, lr}") \
-TCR("# The unwinder undo's these operations in reverse order so starting") \
-TCR("# from bottom, restore r2 from the current vsp location, move r2 into") \
-TCR("# the vsp, add 12 bytes to get the start of the register save area") \
-TCR("# then restore the 15 general purpose registers of the frame which") \
-TCR("# raised the signal.") \
TCR(".save {r0-r15}") \
-TCR(".pad #12") \
TCR(".movsp r2") \
TCR(".save {r2}") \
-TCR("# Call the real handler. The signo, siginfo and sigcontext") \
-TCR("# arguments are the same as those we received in r0, r1 and r2.") \
TCR("blx r3") \
-TCR("# Restore our callee-saved items, release our frame and return") \
-TCR("# (should never get here!).") \
-TCR("ldmfd sp, {r2, r3, pc}")
+TCR("# No return here.")
/* Symbol definition block
----------------------- */