[PATCH] parisc: unwind fixes

- fix unwind table search so it works reliably
- add special case handling for ret_from_kernel_thread and _switch_to_ret
- tidy up the code a bit
- Fix sp falling in an unmapped kernel page
- Sparse annotations
Committed-by: Randolph Chung <tausq@parisc-linux.org>

arch/parisc/kernel/unwind.c

@@ -12,8 +12,10 @@
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/slab.h>
+#include <linux/kallsyms.h>
 
 #include <asm/uaccess.h>
+#include <asm/assembly.h>
 
 #include <asm/unwind.h>
 
@@ -40,25 +42,27 @@ static struct unwind_table *unwind_tables, *unwind_tables_end;
 static inline const struct unwind_table_entry *
 find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
 {
-	const struct unwind_table_entry *e = 0;
+	const struct unwind_table_entry *e = NULL;
 	unsigned long lo, hi, mid;
 
-	for (lo = 0, hi = table->length; lo < hi; )
-	{
-		mid = (lo + hi) / 2;
+	lo = 0; 
+	hi = table->length - 1; 
+	
+	while (lo <= hi) {
+		mid = (hi - lo) / 2 + lo;
 		e = &table->table[mid];
 		if (addr < e->region_start)
-			hi = mid;
+			hi = mid - 1;
 		else if (addr > e->region_end)
 			lo = mid + 1;
 		else
-			break;
+			return e;
 	}
 
-	return e;
+	return NULL;
 }
 
-static inline const struct unwind_table_entry *
+static const struct unwind_table_entry *
 find_unwind_entry(unsigned long addr)
 {
 	struct unwind_table *table = unwind_tables;
@@ -68,8 +72,7 @@ find_unwind_entry(unsigned long addr)
 	    addr <= kernel_unwind_table.end)
 		e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
 	else
-		for (; table; table = table->next)
-		{
+		for (; table; table = table->next) {
 			if (addr >= table->start && 
 			    addr <= table->end)
 				e = find_unwind_entry_in_table(table, addr);
@@ -99,6 +102,11 @@ unwind_table_init(struct unwind_table *table, const char *name,
 	table->next = NULL;
 
 	for (; start <= end; start++) {
+		if (start < end && 
+		    start->region_end > (start+1)->region_start) {
+			printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1);
+		}
+
 		start->region_start += base_addr;
 		start->region_end += base_addr;
 	}
@@ -114,7 +122,7 @@ unwind_table_add(const char *name, unsigned long base_addr,
 
 	table = kmalloc(sizeof(struct unwind_table), GFP_USER);
 	if (table == NULL)
-		return 0;
+		return NULL;
 	unwind_table_init(table, name, base_addr, gp, start, end);
 	spin_lock_irqsave(&unwind_lock, flags);
 	if (unwind_tables)
@@ -170,12 +178,40 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
 	int looking_for_rp, rpoffset = 0;
 
 	e = find_unwind_entry(info->ip);
-	if (!e) {
+	if (e == NULL) {
 		unsigned long sp;
 		extern char _stext[], _etext[];
 
 		dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip);
 
+#ifdef CONFIG_KALLSYMS
+		/* Handle some frequent special cases.... */
+		{
+			char symname[KSYM_NAME_LEN+1];
+			char *modname;
+			unsigned long symsize, offset;
+
+			kallsyms_lookup(info->ip, &symsize, &offset,
+					&modname, symname);
+
+			dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname);
+
+			if (strcmp(symname, "_switch_to_ret") == 0) {
+				info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
+				info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
+				dbg("_switch_to_ret @ %lx - setting "
+				    "prev_sp=%lx prev_ip=%lx\n", 
+				    info->ip, info->prev_sp, 
+				    info->prev_ip);
+				return;
+			} else if (strcmp(symname, "ret_from_kernel_thread") == 0 ||
+				   strcmp(symname, "syscall_exit") == 0) {
+				info->prev_ip = info->prev_sp = 0;
+				return;
+			}
+		}
+#endif
+
 		/* Since we are doing the unwinding blind, we don't know if
 		   we are adjusting the stack correctly or extracting the rp
 		   correctly. The rp is checked to see if it belongs to the
@@ -185,30 +221,33 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
 		   modules. */
 		sp = info->sp & ~63;
 		do {
-			info->prev_sp = sp - 64;
-
-			/* FIXME: what happens if we unwind too far so that 
-			   sp no longer falls in a mapped kernel page? */
-#ifndef __LP64__
-			info->prev_ip = *(unsigned long *)(info->prev_sp - 20);
-#else
-			info->prev_ip = *(unsigned long *)(info->prev_sp - 16);
-#endif
+			unsigned long tmp;
 
+			info->prev_sp = sp - 64;
+			info->prev_ip = 0;
+			if (get_user(tmp, (unsigned long *)(info->prev_sp - RP_OFFSET))) 
+				break;
+			info->prev_ip = tmp;
 			sp = info->prev_sp;
 		} while (info->prev_ip < (unsigned long)_stext ||
 			 info->prev_ip > (unsigned long)_etext);
 
-		dbg("analyzing func @ %lx with no unwind info, setting prev_sp=%lx prev_ip=%lx\n", info->ip, info->prev_sp, info->prev_ip);
-	} else {
+		info->rp = 0;
 
-		dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, Save_RP = %d size = %u\n",
-				e->region_start, e->region_end, e->Save_SP, e->Save_RP, e->Total_frame_size);
+		dbg("analyzing func @ %lx with no unwind info, setting "
+		    "prev_sp=%lx prev_ip=%lx\n", info->ip, 
+		    info->prev_sp, info->prev_ip);
+	} else {
+		dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, "
+		    "Save_RP = %d size = %u\n", e->region_start, 
+		    e->region_end, e->Save_SP, e->Save_RP, 
+		    e->Total_frame_size);
 
 		looking_for_rp = e->Save_RP;
 
 		for (npc = e->region_start; 
-		     (frame_size < (e->Total_frame_size << 3) || looking_for_rp) && 
+		     (frame_size < (e->Total_frame_size << 3) || 
+		      looking_for_rp) && 
 		     npc < info->ip; 
 		     npc += 4) {
 
@@ -219,22 +258,28 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
 				/* ldo X(sp), sp, or stwm X,D(sp) */
 				frame_size += (insn & 0x1 ? -1 << 13 : 0) | 
 					((insn & 0x3fff) >> 1);
-				dbg("analyzing func @ %lx, insn=%08x @ %lx, frame_size = %ld\n", info->ip, insn, npc, frame_size);
-			} else if ((insn & 0xffe00008) == 0x7ec00008) {
+				dbg("analyzing func @ %lx, insn=%08x @ "
+				    "%lx, frame_size = %ld\n", info->ip,
+				    insn, npc, frame_size);
+			} else if ((insn & 0xffe00008) == 0x73c00008) {
 				/* std,ma X,D(sp) */
 				frame_size += (insn & 0x1 ? -1 << 13 : 0) | 
 					(((insn >> 4) & 0x3ff) << 3);
-				dbg("analyzing func @ %lx, insn=%08x @ %lx, frame_size = %ld\n", info->ip, insn, npc, frame_size);
+				dbg("analyzing func @ %lx, insn=%08x @ "
+				    "%lx, frame_size = %ld\n", info->ip,
+				    insn, npc, frame_size);
 			} else if (insn == 0x6bc23fd9) { 
 				/* stw rp,-20(sp) */
 				rpoffset = 20;
 				looking_for_rp = 0;
-				dbg("analyzing func @ %lx, insn=stw rp,-20(sp) @ %lx\n", info->ip, npc);
+				dbg("analyzing func @ %lx, insn=stw rp,"
+				    "-20(sp) @ %lx\n", info->ip, npc);
 			} else if (insn == 0x0fc212c1) {
 				/* std rp,-16(sr0,sp) */
 				rpoffset = 16;
 				looking_for_rp = 0;
-				dbg("analyzing func @ %lx, insn=std rp,-16(sp) @ %lx\n", info->ip, npc);
+				dbg("analyzing func @ %lx, insn=std rp,"
+				    "-16(sp) @ %lx\n", info->ip, npc);
 			}
 		}
 
@@ -244,7 +289,9 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
 		info->prev_ip = info->rp;
 		info->rp = 0;
 
-		dbg("analyzing func @ %lx, setting prev_sp=%lx prev_ip=%lx\n", info->ip, info->prev_sp, info->prev_ip);
+		dbg("analyzing func @ %lx, setting prev_sp=%lx "
+		    "prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp, 
+		    info->prev_ip, npc);
 	}
 }
 
@@ -257,7 +304,8 @@ void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t,
 	info->ip = ip;
 	info->rp = rp;
 
-	dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n", t ? (int)t->pid : 0, info->sp, info->ip);
+	dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n", 
+	    t ? (int)t->pid : -1, info->sp, info->ip);
 }
 
 void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t)
@@ -285,7 +333,9 @@ int unwind_once(struct unwind_frame_info *next_frame)
 	next_frame->prev_sp = 0;
 	next_frame->prev_ip = 0;
 
-	dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n", (int)next_frame->t->pid, next_frame->sp, next_frame->ip);
+	dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n", 
+	    next_frame->t ? (int)next_frame->t->pid : -1, 
+	    next_frame->sp, next_frame->ip);
 
 	return 0;
 }

include/asm-parisc/assembly.h

@@ -29,6 +29,7 @@
 #define STREGM	std,ma
 #define RP_OFFSET	16
 #define FRAME_SIZE	128
+#define CALLEE_SAVE_FRAME_SIZE	144
 #else
 #define LDREG	ldw
 #define STREG	stw
@@ -37,6 +38,7 @@
 #define STREGM	stwm
 #define RP_OFFSET	20
 #define FRAME_SIZE	64
+#define CALLEE_SAVE_FRAME_SIZE	128
 #endif
 
 #ifdef CONFIG_PA20
@@ -292,7 +294,7 @@
 
 #ifdef __LP64__
 	.macro	callee_save
-	std,ma	  %r3,	144(%r30)
+	std,ma	  %r3,	CALLEE_SAVE_FRAME_SIZE(%r30)
 	mfctl	  %cr27, %r3
 	std	  %r4,	-136(%r30)
 	std	  %r5,	-128(%r30)
@@ -330,13 +332,13 @@
 	ldd	-128(%r30),    %r5
 	ldd	-136(%r30),    %r4
 	mtctl	%r3, %cr27
-	ldd,mb	-144(%r30),    %r3
+	ldd,mb	-CALLEE_SAVE_FRAME_SIZE(%r30),    %r3
 	.endm
 
 #else /* ! __LP64__ */
 
 	.macro	callee_save
-	stw,ma	 %r3,	128(%r30)
+	stw,ma	 %r3,	CALLEE_SAVE_FRAME_SIZE(%r30)
 	mfctl	 %cr27, %r3
 	stw	 %r4,	-124(%r30)
 	stw	 %r5,	-120(%r30)
@@ -374,7 +376,7 @@
 	ldw	-120(%r30),   %r5
 	ldw	-124(%r30),   %r4
 	mtctl	%r3, %cr27
-	ldw,mb	-128(%r30),   %r3
+	ldw,mb	-CALLEE_SAVE_FRAME_SIZE(%r30),   %r3
 	.endm
 #endif /* ! __LP64__ */