[gcc r13-881] [Ada] arm-qnx-7.1: unwind goes wrong after regs restore

[gcc r13-881] [Ada] arm-qnx-7.1: unwind goes wrong after regs restore

[Pierre-Marie de Rodat]

https://gcc.gnu.org/g:c97f3a7dc230dab0877d0c27b84eb06132cf7bf8

commit r13-881-gc97f3a7dc230dab0877d0c27b84eb06132cf7bf8
Author: Doug Rupp <rupp@adacore.com>
Date:   Thu Apr 14 10:59:37 2022 -0700

    [Ada] arm-qnx-7.1: unwind goes wrong after regs restore
    
    The usual increment of the pc to pc+2 for ARM is needed.
    
    gcc/ada/
    
            * init.c (QNX): __gnat_adjust_context_for_raise: New
            implementation for arm-qnx.

Diff:
---
 gcc/ada/init.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/gcc/ada/init.c b/gcc/ada/init.c
index 89f16a176d3..7322a54a4da 100644
--- a/gcc/ada/init.c
+++ b/gcc/ada/init.c
@@ -2560,6 +2560,29 @@ __gnat_install_handler (void)
 #include <errno.h>
 #include "sigtramp.h"
 
+#if defined (__ARMEL__) && !defined (__aarch64__)
+
+/* ARM-QNX case with arm unwinding exceptions */
+#define HAVE_GNAT_ADJUST_CONTEXT_FOR_RAISE
+
+#include <ucontext.h>
+#include <arm/cpu.h>
+#include <stdint.h>
+
+void
+__gnat_adjust_context_for_raise (int signo ATTRIBUTE_UNUSED,
+				 void *sc ATTRIBUTE_UNUSED)
+{
+  /* In case of ARM exceptions, the registers context have the PC pointing
+     to the instruction that raised the signal.  However the unwinder expects
+     the instruction to be in the range [PC+2,PC+3].  */
+  uintptr_t *pc_addr;
+  mcontext_t *mcontext = &((ucontext_t *) sc)->uc_mcontext;
+  pc_addr = (uintptr_t *)&mcontext->cpu.gpr [ARM_REG_PC];
+  *pc_addr += 2;
+}
+#endif /* ARMEL */
+
 void
 __gnat_map_signal (int sig,
 		   siginfo_t *si ATTRIBUTE_UNUSED,
@@ -2597,6 +2620,13 @@ __gnat_map_signal (int sig,
 static void
 __gnat_error_handler (int sig, siginfo_t *si, void *ucontext)
 {
+#ifdef HAVE_GNAT_ADJUST_CONTEXT_FOR_RAISE
+  /* We need to sometimes to adjust the PC in case of signals so that it
+     doesn't reference the exception that actually raised the signal but the
+     instruction before it.  */
+  __gnat_adjust_context_for_raise (sig, ucontext);
+#endif
+
   __gnat_sigtramp (sig, (void *) si, (void *) ucontext,
 		   (__sigtramphandler_t *)&__gnat_map_signal);
 }