Re: fix ia64 longjmp() to work from alternate signal-stack

[David Mosberger <davidm at napali dot hpl dot hp dot com>]

>>>>> On Thu, 02 Sep 2004 15:49:21 -0700, Ulrich Drepper <drepper@redhat.com> said:

  Uli> What I don't understand is why you have a separate longjmp
  Uli> implementation.  It seems identical to the generic version.
  Uli> And why is the new setjmp split out in two C files.  They
  Uli> should be merged.  Finally, since the code is only used in nptl
  Uli> there is no need to move the code to libc.so.

I  thought  you  wanted  to  have  the option  to  (easily)  make  the
stack-crossing longjmp the default.  If so, it would make sense to put
it in libc.

  Uli> To facilitate using the code I've added some changes to define
  Uli> a symbol __libc_unwind_longjmp.  For all archs it currently
  Uli> just points to __libc_longjmp.  For ia64 you should remove the
  Uli> macro definition and instead add a declaration.

Hmmh, I'm not sure I understand what you have in mind.  Is something
along the following lines closer to what you want?  The patch doesn't
actually work (I'm geting an unresolved reference for foo) and there
is also the problem that __sigaltstack() isn't exported, so I had to
use sigstack(), which is almost certainly wrong.  It might be easier
if you just put the stuff in the right place, since you know best what
you want and the code per se is there.

	--david

Index: nptl/sysdeps/unix/sysv/linux/ia64/__ia64_longjmp.S
--- /dev/null
+++ nptl/sysdeps/unix/sysv/linux/ia64/__ia64_longjmp.S
@@ -0,0 +1,156 @@
+/* Copyright (C) 1999, 2000, 2001, 2004 Free Software Foundation, Inc.
+   Contributed by David Mosberger-Tang <davidm@hpl.hp.com>.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <sysdep.h>
+#include <features.h>
+
+LEAF(__ia64_flush_rbs)
+	flushrs
+	mov r9 = ar.rsc		// 12 cyc latency
+	;;
+	mov r8 = ar.bsp		// 12 cyc latency
+	;;
+	and r16 = ~0x3, r9	// clear ar.rsc.mode
+	;;
+	mov ar.rsc = r16	// put RSE into enforced-lazy mode
+	;;
+	mov r10 = ar.rnat	// 5 cyc latency
+	ret
+END(__ia64_flush_rbs)
+
+
+#	define	pPos	p6	/* is rotate count positive? */
+#	define	pNeg	p7	/* is rotate count negative? */
+
+/* __ia64_longjmp(__jmp_buf buf, int val, long rnat, long rsc)  */
+
+
+LEAF(__ia64_longjmp)
+	alloc r8=ar.pfs,4,0,0,0
+	add r2=0x98,in0		// r2 <- &jmpbuf.orig_jmp_buf_addr
+	add r3=0x88,in0		// r3 <- &jmpbuf.ar_bsp
+	;;
+	ld8 r8=[r2]		// r8 <- orig_jmp_buf_addr
+	ld8 r23=[r3],8		// r23 <- jmpbuf.ar_bsp
+	mov r2=in0
+	;;
+	//
+	// Note: we need to redo the "flushrs" here even though it's
+	// already been done by __ia64_flush_rbs.  It is needed to
+	// ensure that ar.bspstore == ar.bsp.
+	//
+	flushrs			// flush dirty regs to backing store
+	ld8 r25=[r3]		// r25 <- jmpbuf.ar_unat
+	sub r8=r8,in0		// r8 <- &orig_jmpbuf - &jmpbuf
+	;;
+	add r3=8,in0		// r3 <- &jmpbuf.r1
+	extr.u r8=r8,3,6	// r8 <- (&orig_jmpbuf - &jmpbuf)/8 & 0x3f
+	;;
+	cmp.lt pNeg,pPos=r8,r0
+	;;
+(pPos)	mov r16=r8
+(pNeg)	add r16=64,r8
+(pPos)	sub r17=64,r8
+(pNeg)	sub r17=r0,r8
+	;;
+	shr.u r8=r25,r16
+	shl r9=r25,r17
+	;;
+	or r25=r8,r9
+	;;
+	mov ar.unat=r25 // setup ar.unat (NaT bits for r1, r4-r7, and r12)
+	;;
+	ld8.fill.nta sp=[r2],16	// r12 (sp)
+	ld8.fill.nta gp=[r3],16 // r1 (gp)
+	dep r11=-1,r23,3,6	// r11 <- ia64_rse_rnat_addr(jmpbuf.ar_bsp)
+	;;
+	ld8.nta r16=[r2],16		// caller's unat
+	ld8.nta r17=[r3],16		// fpsr
+	;;
+	ld8.fill.nta r4=[r2],16		// r4
+	ld8.fill.nta r5=[r3],16		// r5 (gp)
+	;;
+	ld8.fill.nta r6=[r2],16		// r6
+	ld8.fill.nta r7=[r3],16		// r7
+	;;
+	mov ar.unat=r16			// restore caller's unat
+	mov ar.fpsr=r17			// restore fpsr
+	;;
+	ld8.nta r16=[r2],16		// b0
+	ld8.nta r17=[r3],16		// b1
+	;;
+	mov ar.bspstore=r23	// restore ar.bspstore
+	ld8.nta r18=[r2],16		// b2
+	;;
+	mov ar.rnat=in2		// restore ar.rnat
+	ld8.nta r19=[r3],16		// b3
+	;;
+	ld8.nta r20=[r2],16		// b4
+	ld8.nta r21=[r3],16		// b5
+	;;
+	ld8.nta r11=[r2],16		// ar.pfs
+	ld8.nta r22=[r3],56		// ar.lc
+	;;
+	ld8.nta r24=[r2],32		// pr
+	mov ar.rsc=in3		// restore ar.rsc
+	mov b0=r16
+	;;
+	ldf.fill.nta f2=[r2],32
+	ldf.fill.nta f3=[r3],32
+	mov b1=r17
+	;;
+	ldf.fill.nta f4=[r2],32
+	ldf.fill.nta f5=[r3],32
+	mov b2=r18
+	;;
+	ldf.fill.nta f16=[r2],32
+	ldf.fill.nta f17=[r3],32
+	mov b3=r19
+	;;
+	ldf.fill.nta f18=[r2],32
+	ldf.fill.nta f19=[r3],32
+	mov b4=r20
+	;;
+	ldf.fill.nta f20=[r2],32
+	ldf.fill.nta f21=[r3],32
+	mov b5=r21
+	;;
+	ldf.fill.nta f22=[r2],32
+	ldf.fill.nta f23=[r3],32
+	mov ar.lc=r22
+	;;
+	ldf.fill.nta f24=[r2],32
+	ldf.fill.nta f25=[r3],32
+	cmp.eq p8,p9=0,in1
+	;;
+	ldf.fill.nta f26=[r2],32
+	ldf.fill.nta f27=[r3],32
+	mov ar.pfs=r11
+	;;
+	ldf.fill.nta f28=[r2],32
+	ldf.fill.nta f29=[r3],32
+(p8)	mov r8=1
+	;;
+	ldf.fill.nta f30=[r2]
+	ldf.fill.nta f31=[r3]
+(p9)	mov r8=in1
+
+	invala			// virt. -> phys. regnum mapping may change
+	mov pr=r24,-1
+	ret
+END(__ia64_longjmp)
Index: nptl/sysdeps/unix/sysv/linux/ia64/__sigstack_longjmp.c
--- /dev/null
+++ nptl/sysdeps/unix/sysv/linux/ia64/__sigstack_longjmp.c
@@ -0,0 +1,171 @@
+/* Copyright (C) 2004 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by David Mosberger-Tang <davidm@hpl.hp.com>.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+/* The public __longjmp() implementation is limited to jumping within
+   the same stack.  That is, in general it is not possible to use this
+   __longjmp() implementation to cross from one stack to another.
+   In constrast, the __sigstack_longjmp() implemented here allows
+   crossing from the alternate signal stack to the normal stack
+   as a special case.  */
+
+#include <assert.h>
+#include <setjmp.h>
+#include <signal.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <sys/rse.h>
+
+#define JB_SP	0
+#define JB_BSP	17
+
+struct rbs_flush_values
+  {
+    unsigned long bsp;
+    unsigned long rsc;
+    unsigned long rnat;
+  };
+
+extern struct rbs_flush_values __ia64_flush_rbs (void);
+extern void __ia64_longjmp (__jmp_buf buf, int val, long rnat, long rsc)
+     __attribute__ ((__noreturn__));
+
+static void
+copy_rbs (unsigned long *dst, unsigned long *dst_end, unsigned long dst_rnat,
+	  unsigned long *src, unsigned long *src_end,
+	  unsigned long current_rnat)
+{
+  unsigned long dst_slot, src_rnat = 0, src_slot, *src_rnat_addr, nat_bit;
+  int first_time = 1;
+
+  while (dst < dst_end)
+    {
+      dst_slot = ia64_rse_slot_num (dst);
+      if (dst_slot == 63)
+	{
+	  *dst++ = dst_rnat;
+	  dst_rnat = 0;
+	}
+      else
+	{
+	  /* read source value, including NaT bit: */
+	  src_slot = ia64_rse_slot_num (src);
+	  if (src_slot == 63)
+	    {
+	      /* skip src RNaT slot */
+	      ++src;
+	      src_slot = 0;
+	    }
+	  if (first_time || src_slot == 0)
+	    {
+	      first_time = 0;
+	      src_rnat_addr = ia64_rse_rnat_addr (src);
+	      if (src_rnat_addr < src_end)
+		src_rnat = *src_rnat_addr;
+	      else
+		src_rnat = current_rnat;
+	    }
+	  nat_bit = (src_rnat >> src_slot) & 1;
+
+	  assert (src < src_end);
+
+	  *dst++ = *src++;
+	  if (nat_bit)
+	    dst_rnat |=  (1UL << dst_slot);
+	  else
+	    dst_rnat &= ~(1UL << dst_slot);
+	}
+    }
+  dst_slot = ia64_rse_slot_num (dst);
+  if (dst_slot > 0)
+    *ia64_rse_rnat_addr (dst) = dst_rnat;
+}
+
+void
+__sigstack_longjmp (__jmp_buf buf, int val)
+{
+  unsigned long *rbs_base, *bsp, *bspstore, *jb_bsp, jb_sp, ss_sp;
+  unsigned long ndirty, rnat, load_rnat, *jb_rnat_addr;
+  struct sigcontext *sc;
+  stack_t stk;
+  struct rbs_flush_values c;
+
+  /* put RSE into enforced-lazy mode and return current bsp/rsc/rnat: */
+  c = __ia64_flush_rbs ();
+
+  jb_sp  = ((unsigned long *)  buf)[JB_SP];
+  jb_bsp = ((unsigned long **) buf)[JB_BSP];
+
+#if 0
+  /* Urgh, libc doesn't export __sigaltstack... */
+  __sigaltstack (NULL, &stk);
+#else
+  sigaltstack (NULL, &stk);
+#endif
+
+  ss_sp = (unsigned long) stk.ss_sp;
+  jb_rnat_addr = ia64_rse_rnat_addr (jb_bsp);
+
+  if ((stk.ss_flags & SS_ONSTACK) == 0 || jb_sp - ss_sp < stk.ss_size)
+    /* Normal non-stack-crossing longjmp; if the RNaT slot for the bsp
+       saved in the jump-buffer is the same as the one for the current
+       BSP, use the current AR.RNAT value, otherwise, load it from the
+       jump-buffer's RNaT-slot.  */
+    load_rnat = (ia64_rse_rnat_addr ((unsigned long *) c.bsp) != jb_rnat_addr);
+  else
+    {
+      /* If we are on the alternate signal-stack and the jump-buffer
+	 lies outside the signal-stack, we may need to copy back the
+	 dirty partition which was torn off and saved on the
+	 signal-stack when the signal was delivered.
+
+	 Caveat: we assume that the top of the alternate signal-stack
+		 stores the sigcontext structure of the signal that
+		 caused the switch to the signal-stack.	 This should
+		 be a fairly safe assumption but the kernel _could_
+		 do things differently.. */
+      sc = ((struct sigcontext *) ((ss_sp + stk.ss_size) & -16) - 1);
+
+      /* As a sanity-check, verify that the register-backing-store base
+	 of the alternate signal-stack is where we expect it.  */
+      rbs_base = (unsigned long *)
+	((ss_sp + sizeof (long) - 1) & -sizeof (long));
+
+      assert ((unsigned long) rbs_base == sc->sc_rbs_base);
+
+      ndirty = ia64_rse_num_regs (rbs_base, rbs_base + (sc->sc_loadrs >> 19));
+      bsp = (unsigned long *) sc->sc_ar_bsp;
+      bspstore = ia64_rse_skip_regs (bsp, -ndirty);
+
+      if (bspstore < jb_bsp)
+	/* AR.BSPSTORE at the time of the signal was below the value
+	   of AR.BSP saved in the jump-buffer => copy the missing
+	   portion from the torn off dirty partition which got saved
+	   on the alternate signal-stack.  */
+	copy_rbs (bspstore, jb_bsp, sc->sc_ar_rnat,
+		  rbs_base, (unsigned long *) c.bsp, c.rnat);
+
+      load_rnat = 1;
+    }
+  if (load_rnat)
+    rnat = *jb_rnat_addr;
+  else
+    rnat = c.rnat;
+  __ia64_longjmp (buf, val, rnat, c.rsc);
+}
Index: nptl/sysdeps/unix/sysv/linux/ia64/jmpbuf-unwind.h
--- nptl/sysdeps/unix/sysv/linux/ia64/jmpbuf-unwind.h
+++ nptl/sysdeps/unix/sysv/linux/ia64/jmpbuf-unwind.h
@@ -32,5 +32,9 @@
 #define _JMPBUF_UNWINDS_ADJ(_jmpbuf, _address, _adj) \
   ((uintptr_t)(_address) - (_adj) < (uintptr_t)(((long *)_jmpbuf)[0]) - (_adj))
 
-/* We use the normal lobngjmp for unwinding.  */
-#define __libc_unwind_longjmp(buf, val) __libc_longjmp (buf, val)
+/* We use a longjmp() which can cross from the alternate signal-stack
+   to the normal stack.  */
+#define __libc_unwind_longjmp(buf, val) __libc_sigstack_longjmp (buf, val)
+extern void __libc_sigstack_longjmp (sigjmp_buf env, int val)
+          __attribute__ ((noreturn));
+hidden_proto (__libc_sigstack_longjmp)
Index: nptl/sysdeps/unix/sysv/linux/ia64/sigstack_longjmp.c
--- /dev/null
+++ nptl/sysdeps/unix/sysv/linux/ia64/sigstack_longjmp.c
@@ -0,0 +1,44 @@
+/* Copyright (C) 1991,92,94,95,97,98,2000,02,04 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <stddef.h>
+#include <setjmp.h>
+#include <signal.h>
+#include <pthreadP.h>
+#include <jmpbuf-unwind.h>
+
+extern void __sigstack_longjmp (__jmp_buf, int)
+     __attribute__ ((noreturn));
+
+/* Like __libc_siglongjmp(), but safe for crossing from alternate
+   signal stack to normal stack.  Needed by NPTL.  */
+void
+__libc_sigstack_longjmp (sigjmp_buf env, int val)
+{
+  /* Perform any cleanups needed by the frames being unwound.  */
+  __pthread_cleanup_upto (env->__jmpbuf, CURRENT_STACK_FRAME);
+
+  if (env[0].__mask_was_saved)
+    /* Restore the saved signal mask.  */
+    (void) __sigprocmask (SIG_SETMASK, &env[0].__saved_mask,
+			  (sigset_t *) NULL);
+
+  /* Call the machine-dependent function to restore machine state.  */
+  __sigstack_longjmp (env[0].__jmpbuf, val ?: 1);
+}
+hidden_def (__libc_sigstack_longjmp)