kretprobe trampoline fixes

Recognize when a kretprobe trampoline was hit and continue with inexact stack dump.
Also some testsuite changes.

6 files changed, 111 insertions, 39 deletions

diff --git a/runtime/stack-i386.c b/runtime/stack-i386.c
index a86f94be..d7c2c201 100644
--- a/runtime/stack-i386.c
+++ b/runtime/stack-i386.c
@@ -43,7 +43,10 @@ static void __stp_stack_print (struct pt_regs *regs, int verbose, int levels)
 #endif /* STAPCONF_X86_UNIREGS */
 	
 	while (_stp_valid_stack_ptr(context, (unsigned long)ebp)) {
-		addr = *(unsigned long *)(ebp + 4);
+		if (unlikely(__stp_get_user(addr, (unsigned long *)(ebp + 4)))) {
+			/* cannot access stack.  give up. */
+			return;
+		}
 		if (verbose) {
 			_stp_print_char(' ');
 			_stp_symbol_print (addr);
@@ -55,18 +58,19 @@ static void __stp_stack_print (struct pt_regs *regs, int verbose, int levels)
 #else
 	struct unwind_frame_info info;
 	arch_unw_init_frame_info(&info, regs);
+	
 	while (!arch_unw_user_mode(&info)) {
 		int ret = unwind(&info);
 		dbug_unwind(1, "ret=%d PC=%lx SP=%lx\n", ret, UNW_PC(&info), UNW_SP(&info));
-		if (ret < 0) {
-			_stp_stack_print_fallback(context, UNW_SP(&info), verbose);
-			break;
+		if (ret == 0) {
+			_stp_func_print(UNW_PC(&info), verbose, 1);
+			continue;
 		}
-		if (ret)
-			break;
-		_stp_func_print(UNW_PC(&info), verbose, 1);
+		/* If an error happened or we hit a kretprobe trampoline, use fallback backtrace */
+		/* FIXME: is there a way to unwind across kretprobe trampolines? */
+		if (ret < 0 || (ret > 0 && UNW_PC(&info) == _stp_kretprobe_trampoline))
+			_stp_stack_print_fallback(UNW_SP(&info), verbose);
+		break;
 	}
-//	_stp_printf("***********************\n");
-//	_stp_stack_print_fallback(context, (unsigned long)stack, verbose);
 #endif /* CONFIG_FRAME_POINTER */
 }
diff --git a/runtime/stack-x86_64.c b/runtime/stack-x86_64.c
index e2eb4aa2..846653be 100644
--- a/runtime/stack-x86_64.c
+++ b/runtime/stack-x86_64.c
@@ -8,13 +8,12 @@
  * later version.
  */
 
-// todo: don't use unwinder  for kernel if CONFIG_FRAME
+// todo: don't use unwinder for kernel if CONFIG_FRAME
 
 /* DWARF unwinder failed.  Just dump intereting addresses on kernel stack. */
 static void _stp_stack_print_fallback(unsigned long stack, int verbose)
 {
 	unsigned long addr;
-
 	while (stack & (THREAD_SIZE - 1)) {
 		if (unlikely(__stp_get_user(addr, (unsigned long *)stack))) {
 			/* cannot access stack.  give up. */
@@ -33,12 +32,14 @@ static void __stp_stack_print(struct pt_regs *regs, int verbose, int levels)
 	while (!arch_unw_user_mode(&info)) {
 		int ret = unwind(&info);
 		dbug_unwind(1, "ret=%d PC=%lx SP=%lx\n", ret, UNW_PC(&info), UNW_SP(&info));
-		if (ret < 0) {
-			_stp_stack_print_fallback(UNW_SP(&info), verbose);
-			break;
+		if (ret == 0) {
+			_stp_func_print(UNW_PC(&info), verbose, 1);
+			continue;
 		}
-		if (ret)
-			break;
-		_stp_func_print(UNW_PC(&info), verbose, 1);
+		/* If an error happened or we hit a kretprobe trampoline, use fallback backtrace */
+		/* FIXME: is there a way to unwind across kretprobe trampolines? */
+		if (ret < 0 || (ret > 0 && UNW_PC(&info) == _stp_kretprobe_trampoline))
+			_stp_stack_print_fallback(UNW_SP(&info), verbose);
+		break;
 	}
 }
diff --git a/runtime/stack.c b/runtime/stack.c
index e338f587..eefdf715 100644
--- a/runtime/stack.c
+++ b/runtime/stack.c
@@ -58,12 +58,15 @@ void _stp_stack_print(struct pt_regs *regs, int verbose, struct kretprobe_instan
 			_stp_symbol_print((unsigned long)_stp_ret_addr_r(pi));
 		} else {
 			_stp_print_char(' ');
-			_stp_symbol_print (REG_IP(regs));
+			_stp_symbol_print(REG_IP(regs));
 		}
 		_stp_print_char('\n');
-	} else
-		_stp_printf ("%p ", (int64_t)REG_IP(regs));
-	__stp_stack_print (regs, verbose, 0);
+	} else if (pi)
+		_stp_printf("%p %p ", (int64_t) _stp_ret_addr_r(pi), (int64_t) REG_IP(regs));
+	else 
+		_stp_printf("%p ", (int64_t) REG_IP(regs));
+
+	__stp_stack_print(regs, verbose, 0);
 }
 
 /** Writes stack backtrace to a string
@@ -72,7 +75,7 @@ void _stp_stack_print(struct pt_regs *regs, int verbose, struct kretprobe_instan
  * @param regs A pointer to the struct pt_regs.
  * @returns void
  */
-void _stp_stack_snprint (char *str, int size, struct pt_regs *regs, int verbose, struct kretprobe_instance *pi)
+void _stp_stack_snprint(char *str, int size, struct pt_regs *regs, int verbose, struct kretprobe_instance *pi)
 {
 	/* To get a string, we use a simple trick. First flush the print buffer, */
 	/* then call _stp_stack_print, then copy the result into the output string  */
@@ -84,19 +87,18 @@ void _stp_stack_snprint (char *str, int size, struct pt_regs *regs, int verbose,
 	pb->len = 0;
 }
 
-
 /** Prints the user stack backtrace
  * @param str string
  * @returns Same string as was input with trace info appended,
  * @note Currently limited to a depth of two. Works from jprobes and kprobes.
  */
 #if 0
-void _stp_ustack_print (char *str)
+void _stp_ustack_print(char *str)
 {
-	struct pt_regs *nregs = ((struct pt_regs *) (THREAD_SIZE + (unsigned long) current->thread_info)) - 1;
-	_stp_printf ("%p : [user]\n", (int64_t)REG_IP(nregs));
+	struct pt_regs *nregs = ((struct pt_regs *)(THREAD_SIZE + (unsigned long)current->thread_info)) - 1;
+	_stp_printf("%p : [user]\n", (int64_t) REG_IP(nregs));
 	if (REG_SP(nregs))
-		_stp_printf ("%p : [user]\n", (int64_t)(*(unsigned long *)REG_SP(nregs)));
+		_stp_printf("%p : [user]\n", (int64_t) (*(unsigned long *)REG_SP(nregs)));
 }
 #endif /* 0 */
 
diff --git a/runtime/sym.h b/runtime/sym.h
index 631a5bbf..0bb64c13 100644
--- a/runtime/sym.h
+++ b/runtime/sym.h
@@ -84,6 +84,7 @@ struct _stp_module *_stp_modules_by_addr[STP_MAX_MODULES];
 
 /* the number of modules in the arrays */
 int _stp_num_modules = 0;
+static unsigned long _stp_kretprobe_trampoline = 0;
 
 unsigned long _stp_module_relocate (const char *module, const char *section, unsigned long offset);
 static struct _stp_module *_stp_get_unwind_info (unsigned long addr);
diff --git a/runtime/transport/symbols.c b/runtime/transport/symbols.c
index a81e594f..83a3a635 100644
--- a/runtime/transport/symbols.c
+++ b/runtime/transport/symbols.c
@@ -200,6 +200,8 @@ static int _stp_init_kernel_symbols(void)
 	_stp_modules[0]->data = _stp_kallsyms_lookup_name("_etext");
 	_stp_modules[0]->text_size = _stp_modules[0]->data - _stp_modules[0]->text;
 	_stp_modules_by_addr[0] = _stp_modules[0];
+	
+	_stp_kretprobe_trampoline = _stp_kallsyms_lookup_name("kretprobe_trampoline");
 	return 0;
 }
 
diff --git a/runtime/unwind.c b/runtime/unwind.c
index 483c9345..e8cba72e 100644
--- a/runtime/unwind.c
+++ b/runtime/unwind.c
@@ -321,7 +321,7 @@ static unsigned long read_pointer(const u8 **pLoc, const void *end, signed ptrTy
 		return 0;
 	}
 	if ((ptrType & DW_EH_PE_indirect)
-	    && __stp_get_user(value, (unsigned long *)value))
+			&& __stp_get_user(value, (unsigned long *)value))
 		return 0;
 	*pLoc = ptr.p8;
 
@@ -621,15 +621,62 @@ static u32 *_stp_search_unwind_hdr(unsigned long pc, struct _stp_module *m)
 	return fde;
 }
 
+#ifdef DEBUG_UNWIND
+static const char *_stp_enc_hi_name[] = {
+	"",
+	"DW_EH_PE_pcrel",
+	"DW_EH_PE_textrel",
+	"DW_EH_PE_datarel",
+	"DW_EH_PE_funcrel",
+	"DW_EH_PE_aligned"
+};
+static const char *_stp_enc_lo_name[] = {
+	"DW_EH_PE_absptr",
+	"DW_EH_PE_uleb128",
+	"DW_EH_PE_udata2",
+	"DW_EH_PE_udata4",
+	"DW_EH_PE_udata8",
+	"DW_EH_PE_sleb128",
+	"DW_EH_PE_sdata2",
+	"DW_EH_PE_sdata4",
+	"DW_EH_PE_sdata8"
+};
+char *_stp_eh_enc_name(signed type)
+{
+	static char buf[64];
+	int hi, low;
+	if (type == DW_EH_PE_omit)
+		return "DW_EH_PE_omit";
+
+	hi = (type & DW_EH_PE_ADJUST) >> 4;
+	low = type & DW_EH_PE_FORM;
+	if (hi > 5 || low > 4 || (low == 0 && (type & DW_EH_PE_signed))) {
+		sprintf(buf, "ERROR:encoding=0x%x", type);
+		return buf;
+	}
+
+	buf[0] = 0;
+	if (type & DW_EH_PE_indirect)
+		strlcpy(buf, "DW_EH_PE_indirect|", sizeof(buf));
+	if (hi)
+		strlcat(buf, _stp_enc_hi_name[hi], sizeof(buf));
+
+	if (type & DW_EH_PE_signed)
+		low += 4;
+	strlcat(buf, _stp_enc_lo_name[low], sizeof(buf));
+	return buf;
+}
+#endif /* DEBUG_UNWIND */
+
 /* Unwind to previous to frame.  Returns 0 if successful, negative
- * number in case of an error.  A positive return means unwinding is finished; */
-/* don't try to fallback to dumping addresses on the stack. */
+ * number in case of an error.  A positive return means unwinding is finished; 
+ * don't try to fallback to dumping addresses on the stack. */
 int unwind(struct unwind_frame_info *frame)
 {
 #define FRAME_REG(r, t) (((t *)frame)[reg_info[r].offs])
 	const u32 *fde, *cie = NULL;
 	const u8 *ptr = NULL, *end = NULL;
-	unsigned long pc = UNW_PC(frame) - frame->call_frame;
+	unsigned long pc = UNW_PC(frame);
 	unsigned long tableSize, startLoc = 0, endLoc = 0, cfa;
 	unsigned i;
 	signed ptrType = -1;
@@ -637,6 +684,15 @@ int unwind(struct unwind_frame_info *frame)
 	struct _stp_module *m;
 	struct unwind_state state;
 
+	if (pc != _stp_kretprobe_trampoline)
+		pc -= frame->call_frame;
+	else {
+		unsigned long a1, a2, *addr = (unsigned long *)UNW_SP(frame);
+		__stp_get_user(a1, addr);
+		__stp_get_user(a2, addr+1);
+		dbug_unwind(1, "TRAMPOLINE: SP=%lx *SP=%lx  *(SP+1)=%lx\n", UNW_SP(frame), a1, a2);
+		return -EINVAL;
+	}
 	dbug_unwind(1, "pc=%lx, %lx", pc, UNW_PC(frame));
 
 	if (UNW_PC(frame) == 0)
@@ -659,16 +715,16 @@ int unwind(struct unwind_frame_info *frame)
 	/* found the fde, now set startLoc and endLoc */
 	if (fde != NULL) {
 		cie = cie_for_fde(fde, m);
-		ptr = (const u8 *)(fde + 2);
 		if (likely(cie != NULL && cie != &bad_cie && cie != &not_fde)) {
+			ptr = (const u8 *)(fde + 2);
 			ptrType = fde_pointer_type(cie);
 			startLoc = read_pointer(&ptr, (const u8 *)(fde + 1) + *fde, ptrType);
+			dbug_unwind(2, "startLoc=%lx, ptrType=%s", startLoc, _stp_eh_enc_name(ptrType));
 			if (!(ptrType & DW_EH_PE_indirect))
 				ptrType &= DW_EH_PE_FORM | DW_EH_PE_signed;
 			endLoc = startLoc + read_pointer(&ptr, (const u8 *)(fde + 1) + *fde, ptrType);
 			if (pc > endLoc) {
-				dbug_unwind(1, "pc (%lx) > endLoc(%x)\n", pc, endLoc);
-				/* finished? */
+				dbug_unwind(1, "pc (%lx) > endLoc(%lx)\n", pc, endLoc);
 				goto done;
 			}
 		} else {
@@ -676,6 +732,8 @@ int unwind(struct unwind_frame_info *frame)
 			fde = NULL;
 		}
 	}
+
+	/* did not a good fde find with binary search, so do slow linear search */
 	if (fde == NULL) {
 		for (fde = m->unwind_data, tableSize = m->unwind_data_len; cie = NULL, tableSize > sizeof(*fde)
 		     && tableSize - sizeof(*fde) >= *fde; tableSize -= sizeof(*fde) + *fde, fde += 1 + *fde / sizeof(*fde)) {
@@ -690,13 +748,13 @@ int unwind(struct unwind_frame_info *frame)
 
 			ptr = (const u8 *)(fde + 2);
 			startLoc = read_pointer(&ptr, (const u8 *)(fde + 1) + *fde, ptrType);
-			dbug_unwind(3, "startLoc=%p\n", (u64)startLoc);
+			dbug_unwind(2, "startLoc=%lx, ptrType=%s", startLoc, _stp_eh_enc_name(ptrType));
 			if (!startLoc)
 				continue;
 			if (!(ptrType & DW_EH_PE_indirect))
 				ptrType &= DW_EH_PE_FORM | DW_EH_PE_signed;
 			endLoc = startLoc + read_pointer(&ptr, (const u8 *)(fde + 1) + *fde, ptrType);
-			dbug_unwind(3, "endLoc=%p\n", (u64)endLoc);
+			dbug_unwind(3, "endLoc=%lx\n", endLoc);
 			if (pc >= startLoc && pc < endLoc)
 				break;
 		}
@@ -729,6 +787,7 @@ int unwind(struct unwind_frame_info *frame)
 				case 'R':
 					continue;
 				case 'S':
+					dbug_unwind(1, "This is a signal frame\n");
 					frame->call_frame = 0;
 					continue;
 				default:
@@ -785,7 +844,6 @@ int unwind(struct unwind_frame_info *frame)
 		goto err;
 
 	/* update frame */
-	dbug_unwind(1, "cie=%lx fde=%lx\n", cie, fde);
 #ifndef CONFIG_AS_CFI_SIGNAL_FRAME
 	if (frame->call_frame && !UNW_DEFAULT_RA(state.regs[retAddrReg], state.dataAlign))
 		frame->call_frame = 0;
@@ -793,11 +851,11 @@ int unwind(struct unwind_frame_info *frame)
 	cfa = FRAME_REG(state.cfa.reg, unsigned long) + state.cfa.offs;
 	startLoc = min((unsigned long)UNW_SP(frame), cfa);
 	endLoc = max((unsigned long)UNW_SP(frame), cfa);
-	dbug_unwind(1, "cfa=%lx SP startLoc=%lx, endLoc=%lx\n", cfa, startLoc, endLoc);
+	dbug_unwind(1, "cfa=%lx startLoc=%lx, endLoc=%lx\n", cfa, startLoc, endLoc);
 	if (STACK_LIMIT(startLoc) != STACK_LIMIT(endLoc)) {
 		startLoc = min(STACK_LIMIT(cfa), cfa);
 		endLoc = max(STACK_LIMIT(cfa), cfa);
-		dbug_unwind(1, "SP startLoc=%p, endLoc=%p\n", (u64)startLoc, (u64)endLoc);
+		dbug_unwind(1, "cfa startLoc=%p, endLoc=%p\n", (u64)startLoc, (u64)endLoc);
 	}
 #ifndef CONFIG_64BIT
 # define CASES CASE(8); CASE(16); CASE(32)
@@ -898,7 +956,11 @@ copy_failed:
 err:
 	read_unlock(&m->lock);
 	return -EIO;
+	
 done:
+	/* PC was in a range convered by a module but no unwind info */
+	/* found for the specific PC. This seems to happen only for kretprobe */
+	/* trampolines and at the end of interrupt backtraces. */
 	read_unlock(&m->lock);
 	return 1;
 #undef CASES