Replace all setjmp()/longjmp() with sigsetjmp()/siglongjmp()

The setjmp() function doesn't specify whether signal masks are saved and
restored; on Linux they are not, but on BSD (including MacOSX) they are.
We want to have consistent behaviour across platforms, so we should
always use "don't save/restore signal mask" (this is also generally
going to be faster). This also works around a bug in MacOSX where the
signal-restoration on longjmp() affects the signal mask for a completely
different thread, not just the mask for the thread which did the longjmp.
The most visible effect of this was that ctrl-C was ignored on MacOSX
because the CPU thread did a longjmp which resulted in its signal mask
being applied to every thread, so that all threads had SIGINT and SIGTERM
blocked.

The POSIX-sanctioned portable way to do a jump without affecting signal
masks is to siglongjmp() to a sigjmp_buf which was created by calling
sigsetjmp() with a zero savemask parameter, so change all uses of
setjmp()/longjmp() accordingly. [Technically POSIX allows sigsetjmp(buf, 0)
to save the signal mask; however the following siglongjmp() must not
restore the signal mask, so the pair can be effectively considered as
"sigjmp/longjmp which don't touch the mask".]

For Windows we provide a trivial sigsetjmp/siglongjmp in terms of
setjmp/longjmp -- this is OK because no user will ever pass a non-zero
savemask.

The setjmp() uses in tests/tcg/test-i386.c and tests/tcg/linux-test.c
are left untouched because these are self-contained singlethreaded
test programs intended to be run under QEMU's Linux emulation, so they
have neither the portability nor the multithreading issues to deal with.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Tested-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

2 files changed, 9 insertions, 8 deletions

diff --git a/disas/i386.c b/disas/i386.c
index dbecf1ffb5..73cc06f1c3 100644
--- a/disas/i386.c
+++ b/disas/i386.c
@@ -226,7 +226,7 @@ struct dis_private {
   bfd_byte the_buffer[MAX_MNEM_SIZE];
   bfd_vma insn_start;
   int orig_sizeflag;
-  jmp_buf bailout;
+  sigjmp_buf bailout;
 };
 
 enum address_mode
@@ -303,7 +303,7 @@ fetch_data2(struct disassemble_info *info, bfd_byte *addr)
 	 STATUS.  */
       if (priv->max_fetched == priv->the_buffer)
 	(*info->memory_error_func) (status, start, info);
-      longjmp (priv->bailout, 1);
+      siglongjmp(priv->bailout, 1);
     }
   else
     priv->max_fetched = addr;
@@ -3661,7 +3661,7 @@ print_insn (bfd_vma pc, disassemble_info *info)
   start_codep = priv.the_buffer;
   codep = priv.the_buffer;
 
-  if (setjmp (priv.bailout) != 0)
+  if (sigsetjmp(priv.bailout, 0) != 0)
     {
       const char *name;
 
diff --git a/disas/m68k.c b/disas/m68k.c
index c950241f79..cc0db96cae 100644
--- a/disas/m68k.c
+++ b/disas/m68k.c
@@ -624,7 +624,7 @@ struct private
   bfd_byte *max_fetched;
   bfd_byte the_buffer[MAXLEN];
   bfd_vma insn_start;
-  jmp_buf bailout;
+  sigjmp_buf bailout;
 };
 
 /* Make sure that bytes from INFO->PRIVATE_DATA->BUFFER (inclusive)
@@ -644,7 +644,7 @@ fetch_data2(struct disassemble_info *info, bfd_byte *addr)
   if (status != 0)
     {
       (*info->memory_error_func) (status, start, info);
-      longjmp (priv->bailout, 1);
+      siglongjmp(priv->bailout, 1);
     }
   else
     priv->max_fetched = addr;
@@ -1912,9 +1912,10 @@ print_insn_m68k (bfd_vma memaddr, disassemble_info *info)
   priv.max_fetched = priv.the_buffer;
   priv.insn_start = memaddr;
 
-  if (setjmp (priv.bailout) != 0)
-    /* Error return.  */
-    return -1;
+  if (sigsetjmp(priv.bailout, 0) != 0) {
+      /* Error return.  */
+      return -1;
+  }
 
   switch (info->mach)
     {