Add code for stepping over atomic instruction sequence on PPC

5 files changed, 275 insertions, 16 deletions

diff --git a/sysdeps/linux-gnu/ppc/arch.h b/sysdeps/linux-gnu/ppc/arch.h
index 711b4a3..64c1821 100644
--- a/sysdeps/linux-gnu/ppc/arch.h
+++ b/sysdeps/linux-gnu/ppc/arch.h
@@ -15,6 +15,7 @@
 
 /* Start of arch-specific functions.  */
 #define ARCH_HAVE_UMOVELONG
+#define ARCH_HAVE_ATOMIC_SINGLESTEP
 
 #define PPC_NOP { 0x60, 0x00, 0x00, 0x00 }
 #define PPC_NOP_LENGTH 4
diff --git a/sysdeps/linux-gnu/ppc/trace.c b/sysdeps/linux-gnu/ppc/trace.c
index 8642157..05993de 100644
--- a/sysdeps/linux-gnu/ppc/trace.c
+++ b/sysdeps/linux-gnu/ppc/trace.c
@@ -197,3 +197,85 @@ arch_umovelong (Process *proc, void *addr, long *result, arg_type_info *info) {
 	*result = pointed_to;
 	return 0;
 }
+
+/* The atomic skip code is mostly taken from GDB.  */
+
+/* Instruction masks used during single-stepping of atomic
+ * sequences.  This was lifted from GDB.  */
+#define LWARX_MASK 0xfc0007fe
+#define LWARX_INSTRUCTION 0x7c000028
+#define LDARX_INSTRUCTION 0x7c0000A8
+#define STWCX_MASK 0xfc0007ff
+#define STWCX_INSTRUCTION 0x7c00012d
+#define STDCX_INSTRUCTION 0x7c0001ad
+#define BC_MASK 0xfc000000
+#define BC_INSTRUCTION 0x40000000
+
+int
+arch_atomic_singlestep(struct Process *proc, Breakpoint *sbp,
+		       int (*add_cb)(void *addr, void *data),
+		       void *add_cb_data)
+{
+	void *addr = sbp->addr;
+	debug(1, "pid=%d addr=%p", proc->pid, addr);
+
+	/* If the original instruction was lwarx/ldarx, we can't
+	 * single-step over it, instead we have to execute the whole
+	 * atomic block at once.  */
+	union {
+		uint32_t insn;
+		char buf[4];
+	} u;
+	memcpy(u.buf, sbp->orig_value, BREAKPOINT_LENGTH);
+
+	if ((u.insn & LWARX_MASK) != LWARX_INSTRUCTION
+	    && (u.insn & LWARX_MASK) != LDARX_INSTRUCTION)
+		return 1;
+
+	int insn_count;
+	for (insn_count = 0; ; ++insn_count) {
+		addr += 4;
+		unsigned long l = ptrace(PTRACE_PEEKTEXT, proc->pid, addr, 0);
+		if (l == (unsigned long)-1 && errno)
+			return -1;
+		uint32_t insn;
+#ifdef __powerpc64__
+		insn = l >> 32;
+#else
+		insn = l;
+#endif
+
+		/* If we hit a branch instruction, give up.  The
+		 * computation could escape that way and we'd have to
+		 * treat that case specially.  */
+		if ((insn & BC_MASK) == BC_INSTRUCTION) {
+			debug(1, "pid=%d, found branch at %p, giving up",
+			      proc->pid, addr);
+			return -1;
+		}
+
+		if ((insn & STWCX_MASK) == STWCX_INSTRUCTION
+		    || (insn & STWCX_MASK) == STDCX_INSTRUCTION) {
+			debug(1, "pid=%d, found end of atomic block at %p",
+			      proc->pid, addr);
+			break;
+		}
+
+		/* Arbitrary cut-off.  If we didn't find the
+		 * terminating instruction by now, just give up.  */
+		if (insn_count > 16) {
+			debug(1, "pid=%d, couldn't find end of atomic block",
+			      proc->pid);
+			return -1;
+		}
+	}
+
+	/* Put the breakpoint to the next instruction.  */
+	addr += 4;
+	if (add_cb(addr, add_cb_data) < 0)
+		return -1;
+
+	debug(1, "PTRACE_CONT");
+	ptrace(PTRACE_CONT, proc->pid, 0, 0);
+	return 0;
+}
diff --git a/sysdeps/linux-gnu/trace.c b/sysdeps/linux-gnu/trace.c
index 9ecea1e..d962048 100644
--- a/sysdeps/linux-gnu/trace.c
+++ b/sysdeps/linux-gnu/trace.c
@@ -249,6 +249,9 @@ struct process_stopping_handler
 	/* The pointer being re-enabled.  */
 	Breakpoint * breakpoint_being_enabled;
 
+	/* Artificial atomic skip breakpoint, if any needed.  */
+	void *atomic_skip_bp_addr;
+
 	enum {
 		/* We are waiting for everyone to land in t/T.  */
 		psh_stopping = 0,
@@ -612,12 +615,84 @@ all_stops_accountable(struct pid_set * pids)
 	return 1;
 }
 
-static void
-singlestep(Process * proc)
+/* The protocol is: 0 for success, negative for failure, positive if
+ * default singlestep is to be used.  */
+int arch_atomic_singlestep(struct Process *proc, Breakpoint *sbp,
+			   int (*add_cb)(void *addr, void *data),
+			   void *add_cb_data);
+
+#ifndef ARCH_HAVE_ATOMIC_SINGLESTEP
+int
+arch_atomic_singlestep(struct Process *proc, Breakpoint *sbp,
+		       int (*add_cb)(void *addr, void *data),
+		       void *add_cb_data)
+{
+	return 1;
+}
+#endif
+
+static int
+atomic_singlestep_add_bp(void *addr, void *data)
+{
+	struct process_stopping_handler *self = data;
+	struct Process *proc = self->task_enabling_breakpoint;
+
+	/* Only support single address as of now.  */
+	assert(self->atomic_skip_bp_addr == NULL);
+
+	self->atomic_skip_bp_addr = addr + 4;
+	insert_breakpoint(proc->leader, self->atomic_skip_bp_addr, NULL, 1);
+
+	return 0;
+}
+
+static int
+singlestep(struct process_stopping_handler *self)
 {
+	struct Process *proc = self->task_enabling_breakpoint;
+
+	int status = arch_atomic_singlestep(self->task_enabling_breakpoint,
+					    self->breakpoint_being_enabled,
+					    &atomic_singlestep_add_bp, self);
+
+	/* Propagate failure and success.  */
+	if (status <= 0)
+		return status;
+
+	/* Otherwise do the default action: singlestep.  */
 	debug(1, "PTRACE_SINGLESTEP");
-	if (ptrace(PTRACE_SINGLESTEP, proc->pid, 0, 0))
+	if (ptrace(PTRACE_SINGLESTEP, proc->pid, 0, 0)) {
 		perror("PTRACE_SINGLESTEP");
+		return -1;
+	}
+	return 0;
+}
+
+static void
+post_singlestep(struct process_stopping_handler *self, Event **eventp)
+{
+	continue_for_sigstop_delivery(&self->pids);
+
+	if ((*eventp)->type == EVENT_BREAKPOINT)
+		*eventp = NULL; // handled
+
+	if (self->atomic_skip_bp_addr != 0)
+		delete_breakpoint(self->task_enabling_breakpoint->leader,
+				  self->atomic_skip_bp_addr);
+
+	self->breakpoint_being_enabled = NULL;
+}
+
+static void
+singlestep_error(struct process_stopping_handler *self, Event **eventp)
+{
+	struct Process *teb = self->task_enabling_breakpoint;
+	Breakpoint *sbp = self->breakpoint_being_enabled;
+	fprintf(stderr, "%d couldn't singlestep over %s (%p)\n",
+		teb->pid, sbp->libsym != NULL ? sbp->libsym->name : NULL,
+		sbp->addr);
+	delete_breakpoint(teb->leader, sbp->addr);
+	post_singlestep(self, eventp);
 }
 
 /* This event handler is installed when we are in the process of
@@ -670,7 +745,11 @@ process_stopping_on_event(Event_Handler * super, Event * event)
 			      teb->pid);
 			if (sbp->enabled)
 				disable_breakpoint(teb, sbp);
-			singlestep(teb);
+			if (singlestep(self) < 0) {
+				singlestep_error(self, &event);
+				goto psh_sinking;
+			}
+
 			self->state = state = psh_singlestep;
 		}
 		break;
@@ -682,7 +761,10 @@ process_stopping_on_event(Event_Handler * super, Event * event)
 
 			/* This is not the singlestep that we are waiting for.  */
 			if (event->type == EVENT_SIGNAL) {
-				singlestep(task);
+				if (singlestep(self) < 0) {
+					singlestep_error(self, &event);
+					goto psh_sinking;
+				}
 				break;
 			}
 
@@ -692,18 +774,13 @@ process_stopping_on_event(Event_Handler * super, Event * event)
 			if (sbp->enabled)
 				enable_breakpoint(teb, sbp);
 
-			continue_for_sigstop_delivery(&self->pids);
-
-			self->breakpoint_being_enabled = NULL;
-			self->state = state = psh_sinking;
-
-			if (event->type == EVENT_BREAKPOINT)
-				event = NULL; // handled
-		} else
-			break;
-
-		/* fall-through */
+			post_singlestep(self, &event);
+			goto psh_sinking;
+		}
+		break;
 
+	psh_sinking:
+		state = self->state = psh_sinking;
 	case psh_sinking:
 		if (await_sigstop_delivery(&self->pids, task_info, event))
 			process_stopping_done(self, leader);
diff --git a/testsuite/ltrace.torture/ppc-lwarx.c b/testsuite/ltrace.torture/ppc-lwarx.c
new file mode 100644
index 0000000..0716407
--- /dev/null
+++ b/testsuite/ltrace.torture/ppc-lwarx.c
@@ -0,0 +1,44 @@
+/*
+ * This file is part of ltrace.
+ * Copyright (C) 2012 Petr Machata, Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#include <stdint.h>
+
+__attribute__((noinline, optimize(3))) void
+atomic_add(uint32_t *a, uint32_t b)
+{
+	__asm__ volatile("lwarx 9,0,%0\n"
+			 "add 9,9,%2\n"
+			 "stwcx. 9,0,%0\n"
+			 "bne- atomic_add\n"
+			 : "=r"(a)
+			 : "0"(a), "r"(b)
+			 : "%r9");
+}
+
+uint32_t a = 0;
+
+__attribute__((optimize(0))) int
+main(int argc, char **argv)
+{
+	atomic_add(&a, 5);
+	atomic_add(&a, 10);
+	atomic_add(&a, 15);
+	return a;
+}
diff --git a/testsuite/ltrace.torture/ppc-lwarx.exp b/testsuite/ltrace.torture/ppc-lwarx.exp
new file mode 100644
index 0000000..bc2eba4
--- /dev/null
+++ b/testsuite/ltrace.torture/ppc-lwarx.exp
@@ -0,0 +1,55 @@
+# This file is part of ltrace.
+# Copyright (C) 2012 Petr Machata, Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation; either version 2 of the
+# License, or (at your option) any later version.
+#
+# This program 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
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+# 02110-1301 USA
+
+set testfile "ppc-lwarx"
+set srcfile ${testfile}.c
+set binfile ${testfile}
+
+if [get_compiler_info $binfile] {
+  return -1
+}
+
+if { [istarget powerpc*-*] } then {
+    verbose "compiling source file now....."
+    if { [ltrace_compile $srcdir/$subdir/$srcfile $objdir/$subdir/$binfile executable {debug} ] != "" } {
+	 send_user "Testcase compile failed, so all tests in this file will automatically fail\n."
+    }
+
+    # set options for ltrace.
+    ltrace_options "-x" "atomic_add" "-e" "!atoi"
+
+    # Run PUT for ltarce.
+    set exec_output [ltrace_runtest $objdir/$subdir $objdir/$subdir/$binfile]
+
+    # Check the output of this program.
+    verbose "ltrace runtest output: $exec_output\n"
+    if [regexp {ELF from incompatible architecture} $exec_output] {
+	    fail "32-bit ltrace can not perform on 64-bit PUTs and rebuild ltrace in 64 bit mode!"
+	    return 
+    } elseif [ regexp {Couldn't get .hash data} $exec_output ] {
+	    fail "Couldn't get .hash data!"
+	    return
+    }
+
+    set pattern "atomic_add(.*, 5,.*)"
+    ltrace_verify_output ${objdir}/${subdir}/${testfile}.ltrace $pattern 1
+    set pattern "atomic_add(.*, 10,.*)"
+    ltrace_verify_output ${objdir}/${subdir}/${testfile}.ltrace $pattern 1
+    set pattern "atomic_add(.*, 15,.*)"
+    ltrace_verify_output ${objdir}/${subdir}/${testfile}.ltrace $pattern 1
+}