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

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

>>>>> On Tue, 31 Aug 2004 15:59:45 +0200, Jakub Jelinek <jakub@redhat.com> said:

  Jakub> On Tue, Aug 31, 2004 at 09:14:20AM -0700, David Mosberger wrote:

  >> The only callers of __libc_longjmp() I found are:

  >> ./linuxthreads/sysdeps/pthread/ptlongjmp.c:  __libc_longjmp (env, val);
  >> ./nptl/sysdeps/pthread/pt-longjmp.c:  __libc_longjmp (env, val);
  >> ./nptl/unwind.c:    __libc_longjmp ((struct __jmp_buf_tag *) buf->cancel_jmp_buf, 1);
  >> ./nptl/unwind.c:  __libc_longjmp ((struct __jmp_buf_tag *) ibuf->cancel_jmp_buf, 1);

  >> so I think this would have the desired effect.

  Jakub> The first two should use the old longjmp implementation, the latter
  Jakub> two the sigaltstack-safe one.

OK, so how about this patch?  It introduces __libc_sigstack_longjmp()
for use by nptl/unwind.c.  By default, it's aliased to
__libc_siglongjmp(), but for ia64, I override it to the
sigstack-crossing-safe version of longjmp.

The patch passed my "make check" testing.

Please appy if there are no objections.

Thanks,

	--david

This patch introduces a glibc-internal function called
__libc_sigstack_longjmp() and changes nptl/unwind.c to use this routine
instead of __libc_siglongjmp().

The new routine is equivalent to __libc_siglongjmp() except that it
must be able to jump from an alternate signal stack back to the normal
stack.  For many platforms, the normal longjmp() can handle this
already, but on ia64 (and possibly other platforms), we need to
provide a separate implementation to satisfy the cross-stack jumping
requirement.

ChangeLog

2004-09-01  David Mosberger  <davidm@hpl.hp.com>

	* include/setjmp.h (__libc_sigstacklongjmp): Declare.
	* nptl/unwind.c (unwind_stop): Call __libc_sigstack_longjmp() instead
	of __libc_longjmp() since it may cross from sigstack to normal stack.
	(__pthread_unwind): Likewise.
	* setjmp/Versions: Mention __libc_sigstack_longjmp.
	* sysdeps/generic/longjmp.c: Make __libc_sigstack_longjmp a
	strong alias of __libc_siglongjmp.
	* sysdeps/unix/sysv/linux/ia64/Makefile (sysdep_routines): Mention
	__ia64_longjmp, sigstack_longjmp, and __sigstack_longjmp for
	setjmp directory.
	* sysdeps/unix/sysv/linux/ia64/__ia64_longjmp.S: New file.
	* sysdeps/unix/sysv/linux/ia64/__sigstack_longjmp.c: Likewise.
	* sysdeps/unix/sysv/linux/ia64/longjmp.c: Likewise.
	* sysdeps/unix/sysv/linux/ia64/sigstack_longjmp.c: Likewise.

Index: include/setjmp.h
--- include/setjmp.h
+++ include/setjmp.h
@@ -19,7 +19,10 @@
           __attribute__ ((noreturn));
 extern void __libc_longjmp (sigjmp_buf env, int val)
      __attribute__ ((noreturn));
+extern void __libc_sigstack_longjmp (sigjmp_buf env, int val)
+          __attribute__ ((noreturn));
 libc_hidden_proto (__libc_longjmp)
+libc_hidden_proto (__libc_sigstack_longjmp)
 
 libc_hidden_proto (_setjmp)
 libc_hidden_proto (__sigsetjmp)
Index: nptl/unwind.c
--- nptl/unwind.c
+++ nptl/unwind.c
@@ -93,7 +93,7 @@
     }
 
   if (do_longjump)
-    __libc_longjmp ((struct __jmp_buf_tag *) buf->cancel_jmp_buf, 1);
+    __libc_sigstack_longjmp ((struct __jmp_buf_tag *) buf->cancel_jmp_buf, 1);
 
   return _URC_NO_REASON;
 }
@@ -155,7 +155,7 @@
     }
 
   /* We simply jump to the registered setjmp buffer.  */
-  __libc_longjmp ((struct __jmp_buf_tag *) ibuf->cancel_jmp_buf, 1);
+  __libc_sigstack_longjmp ((struct __jmp_buf_tag *) ibuf->cancel_jmp_buf, 1);
 #endif
   /* NOTREACHED */
 
Index: setjmp/Versions
--- setjmp/Versions
+++ setjmp/Versions
@@ -11,6 +11,6 @@
   }
   GLIBC_PRIVATE {
     # helper functions
-    __libc_longjmp; __libc_siglongjmp;
+    __libc_longjmp; __libc_siglongjmp; __libc_sigstack_longjmp;
   }
 }
Index: sysdeps/generic/longjmp.c
--- sysdeps/generic/longjmp.c
+++ sysdeps/generic/longjmp.c
@@ -44,3 +44,6 @@
 weak_alias (__libc_siglongjmp, _longjmp)
 weak_alias (__libc_siglongjmp, longjmp)
 weak_alias (__libc_siglongjmp, siglongjmp)
+
+strong_alias (__libc_siglongjmp, __libc_sigstack_longjmp)
+libc_hidden_def (__libc_sigstack_longjmp)
Index: sysdeps/unix/sysv/linux/ia64/Makefile
--- sysdeps/unix/sysv/linux/ia64/Makefile
+++ sysdeps/unix/sysv/linux/ia64/Makefile
@@ -7,6 +7,10 @@
 gen-as-const-headers += sigcontext-offsets.sym
 endif
 
+ifeq ($(subdir),setjmp)
+sysdep_routines += __ia64_longjmp sigstack_longjmp __sigstack_longjmp
+endif
+
 ifeq ($(subdir),misc)
 sysdep_headers += sys/io.h
 sysdep_routines += ioperm clone2
Index: sysdeps/unix/sysv/linux/ia64/__ia64_longjmp.S
--- /dev/null
+++ 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: sysdeps/unix/sysv/linux/ia64/__sigstack_longjmp.c
--- /dev/null
+++ sysdeps/unix/sysv/linux/ia64/__sigstack_longjmp.c
@@ -0,0 +1,166 @@
+/* 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];
+
+  __sigaltstack (NULL, &stk);
+
+  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: sysdeps/unix/sysv/linux/ia64/longjmp.c
--- /dev/null
+++ sysdeps/unix/sysv/linux/ia64/longjmp.c
@@ -0,0 +1,46 @@
+/* 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>
+
+
+/* Set the signal mask to the one specified in ENV, and jump
+   to the position specified in ENV, causing the setjmp
+   call there to return VAL, or 1 if VAL is 0.  */
+void
+__libc_siglongjmp (sigjmp_buf env, int val)
+{
+  /* Perform any cleanups needed by the frames being unwound.  */
+  _longjmp_unwind (env, val);
+
+  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.  */
+  __longjmp (env[0].__jmpbuf, val ?: 1);
+}
+
+strong_alias (__libc_siglongjmp, __libc_longjmp)
+libc_hidden_def (__libc_longjmp)
+weak_alias (__libc_siglongjmp, _longjmp)
+weak_alias (__libc_siglongjmp, longjmp)
+weak_alias (__libc_siglongjmp, siglongjmp)
Index: sysdeps/unix/sysv/linux/ia64/sigstack_longjmp.c
--- /dev/null
+++ sysdeps/unix/sysv/linux/ia64/sigstack_longjmp.c
@@ -0,0 +1,41 @@
+/* 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>
+
+/* 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)
+{
+  extern void __sigstack_longjmp (__jmp_buf, int);
+
+  /* Perform any cleanups needed by the frames being unwound.  */
+  _longjmp_unwind (env, val);
+
+  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);
+}
+libc_hidden_def (__libc_sigstack_longjmp)