svn commit: r298358 - in head: contrib/gdb/gdb gnu/usr.bin/gdb/kgdb

Wojciech Macek wma at FreeBSD.org
Wed Apr 20 17:58:14 UTC 2016


Author: wma
Date: Wed Apr 20 17:58:13 2016
New Revision: 298358
URL: https://svnweb.freebsd.org/changeset/base/298358

Log:
  Fix KGDB backtrace on ARM
  
  Modify trapframe decoding to properly analyze trapframe.
  
  Provide method for fixup_pc. It happens, that in some kernel
  functions, the GDB stack frame decoder cannot determine both
  func name and frame size. This is because these functions
  either contain invalid instruction, or their format does
  not match standard schema. Detect that scenarios and move
  PC accordingly to jump into known function schema, which
  GDB is able to parse.
  
  Obtained from:         Semihalf
  Sponsored by:          Juniper Networks
  Reviewed by:           kib, zbb
  Differential Revision: https://reviews.freebsd.org/D5976

Modified:
  head/contrib/gdb/gdb/arm-tdep.c
  head/contrib/gdb/gdb/frame.c
  head/contrib/gdb/gdb/frame.h
  head/gnu/usr.bin/gdb/kgdb/kgdb.h
  head/gnu/usr.bin/gdb/kgdb/main.c
  head/gnu/usr.bin/gdb/kgdb/trgt_arm.c

Modified: head/contrib/gdb/gdb/arm-tdep.c
==============================================================================
--- head/contrib/gdb/gdb/arm-tdep.c	Wed Apr 20 17:54:53 2016	(r298357)
+++ head/contrib/gdb/gdb/arm-tdep.c	Wed Apr 20 17:58:13 2016	(r298358)
@@ -678,6 +678,9 @@ arm_scan_prologue (struct frame_info *ne
   cache->framesize = 0;
   cache->frameoffset = 0;
 
+  if (frame_tdep_pc_fixup)
+  	frame_tdep_pc_fixup(&prev_pc);
+
   /* Check for Thumb prologue.  */
   if (arm_pc_is_thumb (prev_pc))
     {
@@ -914,7 +917,6 @@ arm_make_prologue_cache (struct frame_in
   cache->saved_regs = trad_frame_alloc_saved_regs (next_frame);
 
   arm_scan_prologue (next_frame, cache);
-
   unwound_fp = frame_unwind_register_unsigned (next_frame, cache->framereg);
   if (unwound_fp == 0)
     return cache;

Modified: head/contrib/gdb/gdb/frame.c
==============================================================================
--- head/contrib/gdb/gdb/frame.c	Wed Apr 20 17:54:53 2016	(r298357)
+++ head/contrib/gdb/gdb/frame.c	Wed Apr 20 17:58:13 2016	(r298358)
@@ -136,6 +136,7 @@ static int frame_debug;
 static int backtrace_past_main;
 static unsigned int backtrace_limit = UINT_MAX;
 
+int (*frame_tdep_pc_fixup)(CORE_ADDR *pc);
 
 void
 fprint_frame_id (struct ui_file *file, struct frame_id id)
@@ -2010,6 +2011,9 @@ frame_unwind_address_in_block (struct fr
   /* A draft address.  */
   CORE_ADDR pc = frame_pc_unwind (next_frame);
 
+  if ((frame_tdep_pc_fixup != NULL) && (frame_tdep_pc_fixup(&pc) == 0))
+  	return pc;
+
   /* If THIS frame is not inner most (i.e., NEXT isn't the sentinel),
      and NEXT is `normal' (i.e., not a sigtramp, dummy, ....) THIS
      frame's PC ends up pointing at the instruction fallowing the

Modified: head/contrib/gdb/gdb/frame.h
==============================================================================
--- head/contrib/gdb/gdb/frame.h	Wed Apr 20 17:54:53 2016	(r298357)
+++ head/contrib/gdb/gdb/frame.h	Wed Apr 20 17:58:13 2016	(r298358)
@@ -702,4 +702,6 @@ extern struct frame_info *deprecated_fra
    code.  */
 extern int legacy_frame_p (struct gdbarch *gdbarch);
 
+extern int (*frame_tdep_pc_fixup)(CORE_ADDR *pc);
+
 #endif /* !defined (FRAME_H)  */

Modified: head/gnu/usr.bin/gdb/kgdb/kgdb.h
==============================================================================
--- head/gnu/usr.bin/gdb/kgdb/kgdb.h	Wed Apr 20 17:54:53 2016	(r298357)
+++ head/gnu/usr.bin/gdb/kgdb/kgdb.h	Wed Apr 20 17:58:13 2016	(r298358)
@@ -75,4 +75,7 @@ CORE_ADDR kgdb_parse_1(const char *, int
 #define	kgdb_parse(exp)		kgdb_parse_1((exp), 0)
 #define	kgdb_parse_quiet(exp)	kgdb_parse_1((exp), 1)
 
+extern int (*arm_tdep_pc_fixup)(CORE_ADDR *pc);
+int kgdb_trgt_pc_fixup(CORE_ADDR *pc);
+
 #endif /* _KGDB_H_ */

Modified: head/gnu/usr.bin/gdb/kgdb/main.c
==============================================================================
--- head/gnu/usr.bin/gdb/kgdb/main.c	Wed Apr 20 17:54:53 2016	(r298357)
+++ head/gnu/usr.bin/gdb/kgdb/main.c	Wed Apr 20 17:58:13 2016	(r298358)
@@ -474,7 +474,9 @@ main(int argc, char *argv[])
 	add_arg(&args, NULL);
 
 	init_ui_hook = kgdb_init;
-
+#if TARGET_CPUARCH == arm
+	frame_tdep_pc_fixup = kgdb_trgt_pc_fixup;
+#endif
 	kgdb_sniffer_kluge = kgdb_trgt_trapframe_sniffer;
 
 	return (gdb_main(&args));

Modified: head/gnu/usr.bin/gdb/kgdb/trgt_arm.c
==============================================================================
--- head/gnu/usr.bin/gdb/kgdb/trgt_arm.c	Wed Apr 20 17:54:53 2016	(r298357)
+++ head/gnu/usr.bin/gdb/kgdb/trgt_arm.c	Wed Apr 20 17:58:13 2016	(r298358)
@@ -96,6 +96,7 @@ kgdb_trgt_new_objfile(struct objfile *ob
 struct kgdb_frame_cache {
 	CORE_ADDR	fp;
 	CORE_ADDR	sp;
+	CORE_ADDR	pc;
 };
 
 static int kgdb_trgt_frame_offset[26] = {
@@ -135,6 +136,7 @@ kgdb_trgt_frame_cache(struct frame_info 
 		frame_unwind_register(next_frame, ARM_FP_REGNUM, buf);
 		cache->fp = extract_unsigned_integer(buf,
 		    register_size(current_gdbarch, ARM_FP_REGNUM));
+		cache->pc = frame_func_unwind(next_frame);
 	}
 	return (cache);
 }
@@ -148,7 +150,7 @@ kgdb_trgt_trapframe_this_id(struct frame
 	struct kgdb_frame_cache *cache;
 
 	cache = kgdb_trgt_frame_cache(next_frame, this_cache);
-	*this_id = frame_id_build(cache->fp, 0);
+	*this_id = frame_id_build(cache->sp, cache->pc);
 }
 
 static void
@@ -159,7 +161,7 @@ kgdb_trgt_trapframe_prev_register(struct
 	char dummy_valuep[MAX_REGISTER_SIZE];
 	struct kgdb_frame_cache *cache;
 	int ofs, regsz;
-	int is_undefined = 0;
+	CORE_ADDR sp;
 
 	regsz = register_size(current_gdbarch, regnum);
 
@@ -177,24 +179,12 @@ kgdb_trgt_trapframe_prev_register(struct
 		return;
 
 	cache = kgdb_trgt_frame_cache(next_frame, this_cache);
+	sp = cache->sp;
 
-	if (is_undef && (regnum == ARM_SP_REGNUM || regnum == ARM_PC_REGNUM)) {
-		*addrp = cache->sp + offsetof(struct trapframe, tf_spsr);
-		target_read_memory(*addrp, valuep, regsz);
-		is_undefined = 1;
-		ofs = kgdb_trgt_frame_offset[ARM_SP_REGNUM];
-
-	}
-	*addrp = cache->sp + ofs;
+	ofs = kgdb_trgt_frame_offset[regnum];
+	*addrp = sp + ofs;
 	*lvalp = lval_memory;
 	target_read_memory(*addrp, valuep, regsz);
-
-	if (is_undefined) {
-		*addrp = *(unsigned int *)valuep + (regnum == ARM_SP_REGNUM ?
-		    0 : 8);
-		target_read_memory(*addrp, valuep, regsz);
-
-	}
 }
 
 static const struct frame_unwind kgdb_trgt_trapframe_unwind = {
@@ -233,3 +223,64 @@ kgdb_trgt_trapframe_sniffer(struct frame
 #endif
 	return (NULL);
 }
+
+/*
+ * This function ensures, that the PC is inside the
+ * function section which is understood by GDB.
+ *
+ * Return 0 when fixup is necessary, -1 otherwise.
+ */
+int
+kgdb_trgt_pc_fixup(CORE_ADDR *pc)
+{
+#ifndef CROSS_DEBUGGER
+	struct minimal_symbol *msymbol;
+	int valpc;
+
+	/*
+	 * exception_exit and swi_exit are special. These functions
+	 * are artificially injected into the stack to be executed
+	 * as the last entry in calling chain when all functions exit.
+	 * Treat them differently.
+	 */
+	msymbol = lookup_minimal_symbol_by_pc(*pc);
+	if (msymbol != NULL) {
+		if (strcmp(DEPRECATED_SYMBOL_NAME(msymbol), "exception_exit") == 0)
+			return (0);
+		if (strcmp(DEPRECATED_SYMBOL_NAME(msymbol), "swi_exit") == 0)
+			return (0);
+	}
+
+	/*
+	 * kdb_enter contains an invalid instruction which is supposed
+	 * to generate a trap. BFD does not understand it and treats
+	 * this part of function as a separate function. Move PC
+	 * two instruction earlier to be inside kdb_enter section.
+	 */
+	target_read_memory(*pc - 4, (char*)&valpc, 4);
+	if (valpc == 0xe7ffffff) {
+		*pc = *pc - 8;
+		return (0);
+	}
+
+	/*
+	 * When the panic/vpanic is the last (noreturn) function,
+	 * the bottom of the calling function looks as below.
+	 *   mov lr, pc
+	 *   b panic
+	 * Normally, GDB is not able to detect function boundaries,
+	 * so move the PC two instruction earlier where it can deal
+	 * with it.
+	 * Match this pair of instructions: mov lr, pc followed with
+	 * non-linked branch.
+	 */
+	if ((valpc & 0xff000000) == 0xea000000) {
+		target_read_memory(*pc - 8, (char*)&valpc, 4);
+		if (valpc == 0xe1a0e00f) {
+			*pc -= 8;
+			return (0);
+		}
+	}
+#endif
+	return (-1);
+}


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