parisc: Add vDSO support

Add minimal vDSO support, which provides the signal trampoline helpers,
but none of the userspace syscall helpers like time wrappers.

The big benefit of this vDSO implementation is, that we now don't need
an executeable stack any longer. PA-RISC is one of the last
architectures where an executeable stack was needed in oder to implement
the signal trampolines by putting assembly instructions on the stack
which then gets executed. Instead the kernel will provide the relevant
code in the vDSO page and only put the pointers to the signal
information on the stack.

By dropping the need for executable stacks we avoid running into issues
with applications which want non executable stacks for security reasons.
Additionally, alternative stacks on memory areas without exec
permissions are supported too.

This code is based on an initial implementation by Randolph Chung from 2006:
https://lore.kernel.org/linux-parisc/4544A34A.6080700@tausq.org/

I did the porting and lifted the code to current code base. Dave fixed
the unwind code so that gdb and glibc are able to backtrace through the
code. An additional patch to gdb will be pushed upstream by Dave.

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Dave Anglin <dave.anglin@bell.net>
Cc: Randolph Chung <randolph@tausq.org>
Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 104 insertions, 121 deletions

diff --git a/arch/parisc/kernel/signal.c b/arch/parisc/kernel/signal.c
index 46b1050640b8..24443908f905 100644
--- a/arch/parisc/kernel/signal.c
+++ b/arch/parisc/kernel/signal.c
@@ -1,16 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- *  linux/arch/parisc/kernel/signal.c: Architecture-specific signal
- *  handling support.
+ *  PA-RISC architecture-specific signal handling support.
  *
  *  Copyright (C) 2000 David Huggins-Daines <dhd@debian.org>
  *  Copyright (C) 2000 Linuxcare, Inc.
+ *  Copyright (C) 2000-2022 Helge Deller <deller@gmx.de>
+ *  Copyright (C) 2022 John David Anglin <dave.anglin@bell.net>
  *
  *  Based on the ia64, i386, and alpha versions.
- *
- *  Like the IA-64, we are a recent enough port (we are *starting*
- *  with glibc2.2) that we do not need to support the old non-realtime
- *  Linux signals.  Therefore we don't.
  */
 
 #include <linux/sched.h>
@@ -32,6 +29,7 @@
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>
 #include <asm/asm-offsets.h>
+#include <asm/vdso.h>
 
 #ifdef CONFIG_COMPAT
 #include "signal32.h"
@@ -59,14 +57,6 @@
  * Do a signal return - restore sigcontext.
  */
 
-/* Trampoline for calling rt_sigreturn() */
-#define INSN_LDI_R25_0	 0x34190000 /* ldi  0,%r25 (in_syscall=0) */
-#define INSN_LDI_R25_1	 0x34190002 /* ldi  1,%r25 (in_syscall=1) */
-#define INSN_LDI_R20	 0x3414015a /* ldi  __NR_rt_sigreturn,%r20 */
-#define INSN_BLE_SR2_R0  0xe4008200 /* be,l 0x100(%sr2,%r0),%sr0,%r31 */
-/* For debugging */
-#define INSN_DIE_HORRIBLY 0x68000ccc /* stw %r0,0x666(%sr0,%r0) */
-
 static long
 restore_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
 {
@@ -77,9 +67,9 @@ restore_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
 	err |= __copy_from_user(regs->iaoq, sc->sc_iaoq, sizeof(regs->iaoq));
 	err |= __copy_from_user(regs->iasq, sc->sc_iasq, sizeof(regs->iasq));
 	err |= __get_user(regs->sar, &sc->sc_sar);
-	DBG(2,"restore_sigcontext: iaoq is %#lx / %#lx\n",
-			regs->iaoq[0],regs->iaoq[1]);
-	DBG(2,"restore_sigcontext: r28 is %ld\n", regs->gr[28]);
+	DBG(2, "%s: iaoq is %#lx / %#lx\n",
+			__func__, regs->iaoq[0], regs->iaoq[1]);
+	DBG(2, "%s: r28 is %ld\n", __func__, regs->gr[28]);
 	return err;
 }
 
@@ -102,7 +92,7 @@ sys_rt_sigreturn(struct pt_regs *regs, int in_syscall)
 	/* Unwind the user stack to get the rt_sigframe structure. */
 	frame = (struct rt_sigframe __user *)
 		(usp - sigframe_size);
-	DBG(2,"sys_rt_sigreturn: frame is %p\n", frame);
+	DBG(2, "%s: frame is %p pid %d\n", __func__, frame, task_pid_nr(current));
 
 	regs->orig_r28 = 1; /* no restarts for sigreturn */
 
@@ -110,7 +100,6 @@ sys_rt_sigreturn(struct pt_regs *regs, int in_syscall)
 	compat_frame = (struct compat_rt_sigframe __user *)frame;
 	
 	if (is_compat_task()) {
-		DBG(2,"sys_rt_sigreturn: ELF32 process.\n");
 		if (get_compat_sigset(&set, &compat_frame->uc.uc_sigmask))
 			goto give_sigsegv;
 	} else
@@ -125,25 +114,25 @@ sys_rt_sigreturn(struct pt_regs *regs, int in_syscall)
 	/* Good thing we saved the old gr[30], eh? */
 #ifdef CONFIG_64BIT
 	if (is_compat_task()) {
-		DBG(1,"sys_rt_sigreturn: compat_frame->uc.uc_mcontext 0x%p\n",
-				&compat_frame->uc.uc_mcontext);
+		DBG(1, "%s: compat_frame->uc.uc_mcontext 0x%p\n",
+				__func__, &compat_frame->uc.uc_mcontext);
 // FIXME: Load upper half from register file
 		if (restore_sigcontext32(&compat_frame->uc.uc_mcontext, 
 					&compat_frame->regs, regs))
 			goto give_sigsegv;
-		DBG(1,"sys_rt_sigreturn: usp %#08lx stack 0x%p\n", 
-				usp, &compat_frame->uc.uc_stack);
+		DBG(1, "%s: usp %#08lx stack 0x%p\n",
+				__func__, usp, &compat_frame->uc.uc_stack);
 		if (compat_restore_altstack(&compat_frame->uc.uc_stack))
 			goto give_sigsegv;
 	} else
 #endif
 	{
-		DBG(1,"sys_rt_sigreturn: frame->uc.uc_mcontext 0x%p\n",
-				&frame->uc.uc_mcontext);
+		DBG(1, "%s: frame->uc.uc_mcontext 0x%p\n",
+				__func__, &frame->uc.uc_mcontext);
 		if (restore_sigcontext(&frame->uc.uc_mcontext, regs))
 			goto give_sigsegv;
-		DBG(1,"sys_rt_sigreturn: usp %#08lx stack 0x%p\n", 
-				usp, &frame->uc.uc_stack);
+		DBG(1, "%s: usp %#08lx stack 0x%p\n",
+				__func__, usp, &frame->uc.uc_stack);
 		if (restore_altstack(&frame->uc.uc_stack))
 			goto give_sigsegv;
 	}
@@ -155,14 +144,11 @@ sys_rt_sigreturn(struct pt_regs *regs, int in_syscall)
 	 */
 	if (in_syscall)
 		regs->gr[31] = regs->iaoq[0];
-#if DEBUG_SIG
-	DBG(1,"sys_rt_sigreturn: returning to %#lx, DUMPING REGS:\n", regs->iaoq[0]);
-	show_regs(regs);
-#endif
+
 	return;
 
 give_sigsegv:
-	DBG(1,"sys_rt_sigreturn: Sending SIGSEGV\n");
+	DBG(1, "%s: Sending SIGSEGV\n", __func__);
 	force_sig(SIGSEGV);
 	return;
 }
@@ -177,15 +163,15 @@ get_sigframe(struct k_sigaction *ka, unsigned long sp, size_t frame_size)
 	/*FIXME: ELF32 vs. ELF64 has different frame_size, but since we
 	  don't use the parameter it doesn't matter */
 
-	DBG(1,"get_sigframe: ka = %#lx, sp = %#lx, frame_size = %#lx\n",
-			(unsigned long)ka, sp, frame_size);
+	DBG(1, "%s: ka = %#lx, sp = %#lx, frame_size = %zu\n",
+			__func__, (unsigned long)ka, sp, frame_size);
 	
 	/* Align alternate stack and reserve 64 bytes for the signal
 	   handler's frame marker.  */
 	if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! sas_ss_flags(sp))
 		sp = (current->sas_ss_sp + 0x7f) & ~0x3f; /* Stacks grow up! */
 
-	DBG(1,"get_sigframe: Returning sp = %#lx\n", (unsigned long)sp);
+	DBG(1, "%s: Returning sp = %#lx\n", __func__, (unsigned long)sp);
 	return (void __user *) sp; /* Stacks grow up.  Fun. */
 }
 
@@ -205,20 +191,20 @@ setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, int in_sysc
 		err |= __put_user(regs->gr[31]+4, &sc->sc_iaoq[1]);
 		err |= __put_user(regs->sr[3], &sc->sc_iasq[0]);
 		err |= __put_user(regs->sr[3], &sc->sc_iasq[1]);
-		DBG(1,"setup_sigcontext: iaoq %#lx / %#lx (in syscall)\n",
-			regs->gr[31], regs->gr[31]+4);
+		DBG(1, "%s: iaoq %#lx / %#lx (in syscall)\n",
+			__func__, regs->gr[31], regs->gr[31]+4);
 	} else {
 		err |= __copy_to_user(sc->sc_iaoq, regs->iaoq, sizeof(regs->iaoq));
 		err |= __copy_to_user(sc->sc_iasq, regs->iasq, sizeof(regs->iasq));
-		DBG(1,"setup_sigcontext: iaoq %#lx / %#lx (not in syscall)\n", 
-			regs->iaoq[0], regs->iaoq[1]);
+		DBG(1, "%s: iaoq %#lx / %#lx (not in syscall)\n",
+			__func__, regs->iaoq[0], regs->iaoq[1]);
 	}
 
 	err |= __put_user(flags, &sc->sc_flags);
 	err |= __copy_to_user(sc->sc_gr, regs->gr, sizeof(regs->gr));
 	err |= __copy_to_user(sc->sc_fr, regs->fr, sizeof(regs->fr));
 	err |= __put_user(regs->sar, &sc->sc_sar);
-	DBG(1,"setup_sigcontext: r28 is %ld\n", regs->gr[28]);
+	DBG(1, "%s: r28 is %ld\n", __func__, regs->gr[28]);
 
 	return err;
 }
@@ -230,7 +216,7 @@ setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs,
 	struct rt_sigframe __user *frame;
 	unsigned long rp, usp;
 	unsigned long haddr, sigframe_size;
-	unsigned long start, end;
+	unsigned long start;
 	int err = 0;
 #ifdef CONFIG_64BIT
 	struct compat_rt_sigframe __user * compat_frame;
@@ -247,8 +233,7 @@ setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs,
 #endif
 	frame = get_sigframe(&ksig->ka, usp, sigframe_size);
 
-	DBG(1,"SETUP_RT_FRAME: START\n");
-	DBG(1,"setup_rt_frame: frame %p info %p\n", frame, ksig->info);
+	DBG(1, "%s: frame %p info %p\n", __func__, frame, &ksig->info);
 
 	start = (unsigned long) frame;
 	if (start >= user_addr_max() - sigframe_size)
@@ -259,11 +244,12 @@ setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs,
 	compat_frame = (struct compat_rt_sigframe __user *)frame;
 	
 	if (is_compat_task()) {
-		DBG(1,"setup_rt_frame: frame->info = 0x%p\n", &compat_frame->info);
+		DBG(1, "%s: frame->info = 0x%p\n", __func__, &compat_frame->info);
 		err |= copy_siginfo_to_user32(&compat_frame->info, &ksig->info);
 		err |= __compat_save_altstack( &compat_frame->uc.uc_stack, regs->gr[30]);
-		DBG(1,"setup_rt_frame: frame->uc = 0x%p\n", &compat_frame->uc);
-		DBG(1,"setup_rt_frame: frame->uc.uc_mcontext = 0x%p\n", &compat_frame->uc.uc_mcontext);
+		DBG(1, "%s: frame->uc = 0x%p\n", __func__, &compat_frame->uc);
+		DBG(1, "%s: frame->uc.uc_mcontext = 0x%p\n",
+			__func__, &compat_frame->uc.uc_mcontext);
 		err |= setup_sigcontext32(&compat_frame->uc.uc_mcontext, 
 					&compat_frame->regs, regs, in_syscall);
 		err |= put_compat_sigset(&compat_frame->uc.uc_sigmask, set,
@@ -271,11 +257,12 @@ setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs,
 	} else
 #endif
 	{	
-		DBG(1,"setup_rt_frame: frame->info = 0x%p\n", &frame->info);
+		DBG(1, "%s: frame->info = 0x%p\n", __func__, &frame->info);
 		err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 		err |= __save_altstack(&frame->uc.uc_stack, regs->gr[30]);
-		DBG(1,"setup_rt_frame: frame->uc = 0x%p\n", &frame->uc);
-		DBG(1,"setup_rt_frame: frame->uc.uc_mcontext = 0x%p\n", &frame->uc.uc_mcontext);
+		DBG(1, "%s: frame->uc = 0x%p\n", __func__, &frame->uc);
+		DBG(1, "%s: frame->uc.uc_mcontext = 0x%p\n",
+			__func__, &frame->uc.uc_mcontext);
 		err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, in_syscall);
 		/* FIXME: Should probably be converted as well for the compat case */
 		err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
@@ -284,32 +271,15 @@ setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs,
 	if (err)
 		return -EFAULT;
 
-	/* Set up to return from userspace.  If provided, use a stub
-	   already in userspace. The first words of tramp are used to
-	   save the previous sigrestartblock trampoline that might be
-	   on the stack. We start the sigreturn trampoline at 
-	   SIGRESTARTBLOCK_TRAMP+X. */
-	err |= __put_user(in_syscall ? INSN_LDI_R25_1 : INSN_LDI_R25_0,
-			&frame->tramp[SIGRESTARTBLOCK_TRAMP+0]);
-	err |= __put_user(INSN_LDI_R20, 
-			&frame->tramp[SIGRESTARTBLOCK_TRAMP+1]);
-	err |= __put_user(INSN_BLE_SR2_R0, 
-			&frame->tramp[SIGRESTARTBLOCK_TRAMP+2]);
-	err |= __put_user(INSN_NOP, &frame->tramp[SIGRESTARTBLOCK_TRAMP+3]);
-
-	start = (unsigned long) &frame->tramp[0];
-	end = (unsigned long) &frame->tramp[TRAMP_SIZE];
-	flush_user_dcache_range_asm(start, end);
-	flush_user_icache_range_asm(start, end);
-
-	/* TRAMP Words 0-4, Length 5 = SIGRESTARTBLOCK_TRAMP
-	 * TRAMP Words 5-9, Length 4 = SIGRETURN_TRAMP
-	 * So the SIGRETURN_TRAMP is at the end of SIGRESTARTBLOCK_TRAMP
-	 */
-	rp = (unsigned long) &frame->tramp[SIGRESTARTBLOCK_TRAMP];
+#ifdef CONFIG_64BIT
+	if (!is_compat_task())
+		rp = VDSO64_SYMBOL(current, sigtramp_rt);
+	else
+#endif
+		rp = VDSO32_SYMBOL(current, sigtramp_rt);
 
-	if (err)
-		return -EFAULT;
+	if (in_syscall)
+		rp += 4*4; /* skip 4 instructions and start at ldi 1,%r25 */
 
 	haddr = A(ksig->ka.sa.sa_handler);
 	/* The sa_handler may be a pointer to a function descriptor */
@@ -340,8 +310,8 @@ setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs,
 		
 		haddr = fdesc.addr;
 		regs->gr[19] = fdesc.gp;
-		DBG(1,"setup_rt_frame: 64 bit signal, exe=%#lx, r19=%#lx, in_syscall=%d\n",
-		     haddr, regs->gr[19], in_syscall);
+		DBG(1, "%s: 64 bit signal, exe=%#lx, r19=%#lx, in_syscall=%d\n",
+		     __func__, haddr, regs->gr[19], in_syscall);
 	}
 #endif
 
@@ -351,7 +321,7 @@ setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs,
 		regs->gr[31] = haddr;
 #ifdef CONFIG_64BIT
 		if (!test_thread_flag(TIF_32BIT))
-			sigframe_size |= 1;
+			sigframe_size |= 1; /* XXX ???? */
 #endif
 	} else {
 		unsigned long psw = USER_PSW;
@@ -373,11 +343,11 @@ setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs,
 		}
 
 		regs->gr[0] = psw;
-		regs->iaoq[0] = haddr | 3;
+		regs->iaoq[0] = haddr | PRIV_USER;
 		regs->iaoq[1] = regs->iaoq[0] + 4;
 	}
 
-	regs->gr[2]  = rp;                /* userland return pointer */
+	regs->gr[2]  = rp;			/* userland return pointer */
 	regs->gr[26] = ksig->sig;               /* signal number */
 	
 #ifdef CONFIG_64BIT
@@ -391,15 +361,15 @@ setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs,
 		regs->gr[24] = A(&frame->uc);   /* ucontext pointer */
 	}
 	
-	DBG(1,"setup_rt_frame: making sigreturn frame: %#lx + %#lx = %#lx\n",
+	DBG(1, "%s: making sigreturn frame: %#lx + %#lx = %#lx\n", __func__,
 	       regs->gr[30], sigframe_size,
 	       regs->gr[30] + sigframe_size);
 	/* Raise the user stack pointer to make a proper call frame. */
 	regs->gr[30] = (A(frame) + sigframe_size);
 
 
-	DBG(1,"setup_rt_frame: sig deliver (%s,%d) frame=0x%p sp=%#lx iaoq=%#lx/%#lx rp=%#lx\n",
-	       current->comm, current->pid, frame, regs->gr[30],
+	DBG(1, "%s: sig deliver (%s,%d) frame=0x%p sp=%#lx iaoq=%#lx/%#lx rp=%#lx\n",
+	       __func__, current->comm, current->pid, frame, regs->gr[30],
 	       regs->iaoq[0], regs->iaoq[1], rp);
 
 	return 0;
@@ -415,8 +385,8 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs, int in_syscall)
 	int ret;
 	sigset_t *oldset = sigmask_to_save();
 
-	DBG(1,"handle_signal: sig=%ld, ka=%p, info=%p, oldset=%p, regs=%p\n",
-	       ksig->sig, ksig->ka, ksig->info, oldset, regs);
+	DBG(1, "%s: sig=%d, ka=%p, info=%p, oldset=%p, regs=%p\n",
+	       __func__, ksig->sig, &ksig->ka, &ksig->info, oldset, regs);
 	
 	/* Set up the stack frame */
 	ret = setup_rt_frame(ksig, oldset, regs, in_syscall);
@@ -424,8 +394,8 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs, int in_syscall)
 	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP) ||
 			  test_thread_flag(TIF_BLOCKSTEP));
 
-	DBG(1,KERN_DEBUG "do_signal: Exit (success), regs->gr[28] = %ld\n",
-		regs->gr[28]);
+	DBG(1, "%s: Exit (success), regs->gr[28] = %ld\n",
+		__func__, regs->gr[28]);
 }
 
 /*
@@ -483,21 +453,27 @@ syscall_restart(struct pt_regs *regs, struct k_sigaction *ka)
 	if (regs->orig_r28)
 		return;
 	regs->orig_r28 = 1; /* no more restarts */
+
+	DBG(1, "%s:  orig_r28 = %ld  pid %d  r20 %ld\n",
+		__func__, regs->orig_r28, task_pid_nr(current), regs->gr[20]);
+
 	/* Check the return code */
 	switch (regs->gr[28]) {
 	case -ERESTART_RESTARTBLOCK:
 	case -ERESTARTNOHAND:
-		DBG(1,"ERESTARTNOHAND: returning -EINTR\n");
+		DBG(1, "%s: ERESTARTNOHAND: returning -EINTR\n", __func__);
 		regs->gr[28] = -EINTR;
 		break;
 	case -ERESTARTSYS:
 		if (!(ka->sa.sa_flags & SA_RESTART)) {
-			DBG(1,"ERESTARTSYS: putting -EINTR\n");
+			DBG(1, "%s: ERESTARTSYS: putting -EINTR pid %d\n",
+				__func__, task_pid_nr(current));
 			regs->gr[28] = -EINTR;
 			break;
 		}
 		fallthrough;
 	case -ERESTARTNOINTR:
+		DBG(1, "%s: %ld\n", __func__, regs->gr[28]);
 		check_syscallno_in_delay_branch(regs);
 		break;
 	}
@@ -509,50 +485,52 @@ insert_restart_trampoline(struct pt_regs *regs)
 	if (regs->orig_r28)
 		return;
 	regs->orig_r28 = 1; /* no more restarts */
-	switch(regs->gr[28]) {
+
+	DBG(2, "%s: gr28 = %ld pid %d\n",
+		__func__, regs->gr[28], task_pid_nr(current));
+
+	switch (regs->gr[28]) {
 	case -ERESTART_RESTARTBLOCK: {
 		/* Restart the system call - no handlers present */
 		unsigned int *usp = (unsigned int *)regs->gr[30];
-		unsigned long start = (unsigned long) &usp[2];
-		unsigned long end  = (unsigned long) &usp[5];
+		unsigned long rp;
 		long err = 0;
 
 		/* check that we don't exceed the stack */
 		if (A(&usp[0]) >= user_addr_max() - 5 * sizeof(int))
 			return;
 
-		/* Setup a trampoline to restart the syscall
-		 * with __NR_restart_syscall
+		/* Call trampoline in vdso to restart the syscall
+		 * with __NR_restart_syscall.
+		 * Original return addresses are on stack like this:
 		 *
 		 *  0: <return address (orig r31)>
 		 *  4: <2nd half for 64-bit>
-		 *  8: ldw 0(%sp), %r31
-		 * 12: be 0x100(%sr2, %r0)
-		 * 16: ldi __NR_restart_syscall, %r20
 		 */
 #ifdef CONFIG_64BIT
-		err |= put_user(regs->gr[31] >> 32, &usp[0]);
-		err |= put_user(regs->gr[31] & 0xffffffff, &usp[1]);
-		err |= put_user(0x0fc010df, &usp[2]);
-#else
-		err |= put_user(regs->gr[31], &usp[0]);
-		err |= put_user(0x0fc0109f, &usp[2]);
+		if (!is_compat_task()) {
+			err |= put_user(regs->gr[31] >> 32, &usp[0]);
+			err |= put_user(regs->gr[31] & 0xffffffff, &usp[1]);
+			rp = VDSO64_SYMBOL(current, restart_syscall);
+		} else
 #endif
-		err |= put_user(0xe0008200, &usp[3]);
-		err |= put_user(0x34140000, &usp[4]);
-
+		{
+			err |= put_user(regs->gr[31], &usp[0]);
+			rp = VDSO32_SYMBOL(current, restart_syscall);
+		}
 		WARN_ON(err);
 
-		/* flush data/instruction cache for new insns */
-		flush_user_dcache_range_asm(start, end);
-		flush_user_icache_range_asm(start, end);
-
-		regs->gr[31] = regs->gr[30] + 8;
+		regs->gr[31] = rp;
+		DBG(1, "%s: ERESTART_RESTARTBLOCK\n", __func__);
 		return;
 	}
+	case -EINTR:
+		/* ok, was handled before and should be returned. */
+		break;
 	case -ERESTARTNOHAND:
 	case -ERESTARTSYS:
 	case -ERESTARTNOINTR:
+		DBG(1, "%s: Type %ld\n", __func__, regs->gr[28]);
 		check_syscallno_in_delay_branch(regs);
 		return;
 	default:
@@ -567,30 +545,35 @@ insert_restart_trampoline(struct pt_regs *regs)
  * registers).  As noted below, the syscall number gets restored for
  * us due to the magic of delayed branching.
  */
-asmlinkage void
-do_signal(struct pt_regs *regs, long in_syscall)
+static void do_signal(struct pt_regs *regs, long in_syscall)
 {
 	struct ksignal ksig;
+	int restart_syscall;
+	bool has_handler;
 
-	DBG(1,"\ndo_signal: regs=0x%p, sr7 %#lx, in_syscall=%d\n",
-	       regs, regs->sr[7], in_syscall);
+	has_handler = get_signal(&ksig);
 
-	if (get_signal(&ksig)) {
-		DBG(3,"do_signal: signr = %d, regs->gr[28] = %ld\n", signr, regs->gr[28]);
+	restart_syscall = 0;
+	if (in_syscall)
+		restart_syscall = 1;
+
+	if (has_handler) {
 		/* Restart a system call if necessary. */
-		if (in_syscall)
+		if (restart_syscall)
 			syscall_restart(regs, &ksig.ka);
 
 		handle_signal(&ksig, regs, in_syscall);
+		DBG(1, "%s: Handled signal pid %d\n",
+			__func__, task_pid_nr(current));
 		return;
 	}
 
-	/* Did we come from a system call? */
-	if (in_syscall)
+	/* Do we need to restart the system call? */
+	if (restart_syscall)
 		insert_restart_trampoline(regs);
 	
-	DBG(1,"do_signal: Exit (not delivered), regs->gr[28] = %ld\n", 
-		regs->gr[28]);
+	DBG(1, "%s: Exit (not delivered), regs->gr[28] = %ld  orig_r28 = %ld  pid %d\n",
+		__func__, regs->gr[28], regs->orig_r28, task_pid_nr(current));
 
 	restore_saved_sigmask();
 }