[PATCH] PA-RISC unwind updates

 - Update stale url to documentation

From: Kyle McMartin <kyle@parisc-linux.org>

 - Make unwinding from modules work, mostly
 - Fix unwinding from millicode
Signed-off-by: Randolph Chung <tausq@debian.org>
Signed-off-by: Matthew Wilcox <willy@parisc-linux.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/parisc/kernel/module.c

@@ -2,7 +2,7 @@
  *
  *    The best reference for this stuff is probably the Processor-
  *    Specific ELF Supplement for PA-RISC:
- *        http://ftp.parisc-linux.org/docs/elf-pa-hp.pdf
+ *        http://ftp.parisc-linux.org/docs/arch/elf-pa-hp.pdf
  *
  *    Linux/PA-RISC Project (http://www.parisc-linux.org/)
  *    Copyright (C) 2003 Randolph Chung <tausq at debian . org>
@@ -21,6 +21,23 @@
  *    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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ *
+ *    Notes:
+ *    - SEGREL32 handling
+ *      We are not doing SEGREL32 handling correctly. According to the ABI, we
+ *      should do a value offset, like this:
+ *			if (is_init(me, (void *)val))
+ *				val -= (uint32_t)me->module_init;
+ *			else
+ *				val -= (uint32_t)me->module_core;
+ *	However, SEGREL32 is used only for PARISC unwind entries, and we want
+ *	those entries to have an absolute address, and not just an offset.
+ *
+ *	The unwind table mechanism has the ability to specify an offset for 
+ *	the unwind table; however, because we split off the init functions into
+ *	a different piece of memory, it is not possible to do this using a 
+ *	single offset. Instead, we use the above hack for now.
  */
 
 #include <linux/moduleloader.h>
@@ -30,6 +47,8 @@
 #include <linux/string.h>
 #include <linux/kernel.h>
 
+#include <asm/unwind.h>
+
 #if 0
 #define DEBUGP printk
 #else
@@ -248,6 +267,10 @@ int module_frob_arch_sections(CONST Elf_Ehdr *hdr,
 		const Elf_Rela *rels = (void *)hdr + sechdrs[i].sh_offset;
 		unsigned long nrels = sechdrs[i].sh_size / sizeof(*rels);
 
+		if (strncmp(secstrings + sechdrs[i].sh_name,
+			    ".PARISC.unwind", 14) == 0)
+			me->arch.unwind_section = i;
+
 		if (sechdrs[i].sh_type != SHT_RELA)
 			continue;
 
@@ -499,7 +522,9 @@ int apply_relocate_add(Elf_Shdr *sechdrs,
 			break;
 		case R_PARISC_SEGREL32:
 			/* 32-bit segment relative address */
-			val -= (uint32_t)me->module_core;
+			/* See note about special handling of SEGREL32 at
+			 * the beginning of this file.
+			 */
 			*loc = fsel(val, addend); 
 			break;
 		case R_PARISC_DPREL21L:
@@ -651,7 +676,9 @@ int apply_relocate_add(Elf_Shdr *sechdrs,
 			break;
 		case R_PARISC_SEGREL32:
 			/* 32-bit segment relative address */
-			val -= (uint64_t)me->module_core;
+			/* See note about special handling of SEGREL32 at
+			 * the beginning of this file.
+			 */
 			*loc = fsel(val, addend); 
 			break;
 		case R_PARISC_FPTR64:
@@ -682,6 +709,32 @@ int apply_relocate_add(Elf_Shdr *sechdrs,
 }
 #endif
 
+static void
+register_unwind_table(struct module *me,
+		      const Elf_Shdr *sechdrs)
+{
+	unsigned char *table, *end;
+	unsigned long gp;
+
+	if (!me->arch.unwind_section)
+		return;
+
+	table = (unsigned char *)sechdrs[me->arch.unwind_section].sh_addr;
+	end = table + sechdrs[me->arch.unwind_section].sh_size;
+	gp = (Elf_Addr)me->module_core + me->arch.got_offset;
+
+	DEBUGP("register_unwind_table(), sect = %d at 0x%p - 0x%p (gp=0x%lx)\n",
+	       me->arch.unwind_section, table, end, gp);
+	me->arch.unwind = unwind_table_add(me->name, 0, gp, table, end);
+}
+
+static void
+deregister_unwind_table(struct module *me)
+{
+	if (me->arch.unwind)
+		unwind_table_remove(me->arch.unwind);
+}
+
 int module_finalize(const Elf_Ehdr *hdr,
 		    const Elf_Shdr *sechdrs,
 		    struct module *me)
@@ -711,6 +764,8 @@ int module_finalize(const Elf_Ehdr *hdr,
 	       me->arch.fdesc_count, me->arch.fdesc_max);
 #endif
 
+	register_unwind_table(me, sechdrs);
+
 	/* haven't filled in me->symtab yet, so have to find it
 	 * ourselves */
 	for (i = 1; i < hdr->e_shnum; i++) {
@@ -763,4 +818,5 @@ int module_finalize(const Elf_Ehdr *hdr,
 
 void module_arch_cleanup(struct module *mod)
 {
+	deregister_unwind_table(mod);
 }

arch/parisc/kernel/unwind.c

@@ -36,8 +36,7 @@ static spinlock_t unwind_lock;
  * possible (before the slab allocator is initialized)
  */
 static struct unwind_table kernel_unwind_table;
-static struct unwind_table *unwind_tables, *unwind_tables_end;
-
+static LIST_HEAD(unwind_tables);
 
 static inline const struct unwind_table_entry *
 find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
@@ -65,14 +64,14 @@ find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
 static const struct unwind_table_entry *
 find_unwind_entry(unsigned long addr)
 {
-	struct unwind_table *table = unwind_tables;
+	struct unwind_table *table;
 	const struct unwind_table_entry *e = NULL;
 
 	if (addr >= kernel_unwind_table.start && 
 	    addr <= kernel_unwind_table.end)
 		e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
-	else
-		for (; table; table = table->next) {
+	else 
+		list_for_each_entry(table, &unwind_tables, list) {
 			if (addr >= table->start && 
 			    addr <= table->end)
 				e = find_unwind_entry_in_table(table, addr);
@@ -99,7 +98,7 @@ unwind_table_init(struct unwind_table *table, const char *name,
 	table->end = base_addr + end->region_end;
 	table->table = (struct unwind_table_entry *)table_start;
 	table->length = end - start + 1;
-	table->next = NULL;
+	INIT_LIST_HEAD(&table->list);
 
 	for (; start <= end; start++) {
 		if (start < end && 
@@ -112,33 +111,60 @@ unwind_table_init(struct unwind_table *table, const char *name,
 	}
 }
 
-void *
+static void
+unwind_table_sort(struct unwind_table_entry *start,
+		  struct unwind_table_entry *finish)
+{
+	struct unwind_table_entry el, *p, *q;
+
+	for (p = start + 1; p < finish; ++p) {
+		if (p[0].region_start < p[-1].region_start) {
+			el = *p;
+			q = p;
+			do {
+				q[0] = q[-1];
+				--q;
+			} while (q > start && 
+				 el.region_start < q[-1].region_start);
+			*q = el;
+		}
+	}
+}
+
+struct unwind_table *
 unwind_table_add(const char *name, unsigned long base_addr, 
 		 unsigned long gp,
                  void *start, void *end)
 {
 	struct unwind_table *table;
 	unsigned long flags;
+	struct unwind_table_entry *s = (struct unwind_table_entry *)start;
+	struct unwind_table_entry *e = (struct unwind_table_entry *)end;
+
+	unwind_table_sort(s, e);
 
 	table = kmalloc(sizeof(struct unwind_table), GFP_USER);
 	if (table == NULL)
 		return NULL;
 	unwind_table_init(table, name, base_addr, gp, start, end);
 	spin_lock_irqsave(&unwind_lock, flags);
-	if (unwind_tables)
-	{
-		unwind_tables_end->next = table;
-		unwind_tables_end = table;
-	}
-	else
-	{
-		unwind_tables = unwind_tables_end = table;
-	}
+	list_add_tail(&table->list, &unwind_tables);
 	spin_unlock_irqrestore(&unwind_lock, flags);
 
 	return table;
 }
 
+void unwind_table_remove(struct unwind_table *table)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&unwind_lock, flags);
+	list_del(&table->list);
+	spin_unlock_irqrestore(&unwind_lock, flags);
+
+	kfree(table);
+}
+
 /* Called from setup_arch to import the kernel unwind info */
 static int unwind_init(void)
 {
@@ -148,6 +174,8 @@ static int unwind_init(void)
 	start = (long)&__start___unwind[0];
 	stop = (long)&__stop___unwind[0];
 
+	spin_lock_init(&unwind_lock);
+
 	printk("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n", 
 	    start, stop,
 	    (stop - start) / sizeof(struct unwind_table_entry));
@@ -239,9 +267,9 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
 		    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);
+		    "Save_RP = %d, Millicode = %d size = %u\n", 
+		    e->region_start, e->region_end, e->Save_SP, e->Save_RP, 
+		    e->Millicode, e->Total_frame_size);
 
 		looking_for_rp = e->Save_RP;
 
@@ -284,7 +312,9 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
 		}
 
 		info->prev_sp = info->sp - frame_size;
-		if (rpoffset)
+		if (e->Millicode)
+			info->rp = info->r31;
+		else if (rpoffset)
 			info->rp = *(unsigned long *)(info->prev_sp - rpoffset);
 		info->prev_ip = info->rp;
 		info->rp = 0;
@@ -296,13 +326,14 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
 }
 
 void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t, 
-		       unsigned long sp, unsigned long ip, unsigned long rp)
+		       struct pt_regs *regs)
 {
 	memset(info, 0, sizeof(struct unwind_frame_info));
 	info->t = t;
-	info->sp = sp;
-	info->ip = ip;
-	info->rp = rp;
+	info->sp = regs->gr[30];
+	info->ip = regs->iaoq[0];
+	info->rp = regs->gr[2];
+	info->r31 = regs->gr[31];
 
 	dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n", 
 	    t ? (int)t->pid : -1, info->sp, info->ip);
@@ -310,14 +341,22 @@ void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t,
 
 void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t)
 {
-	struct pt_regs *regs = &t->thread.regs;
-	unwind_frame_init(info, t, regs->ksp, regs->kpc, 0);
+	struct pt_regs *r = &t->thread.regs;
+	struct pt_regs *r2;
+
+	r2 = (struct pt_regs *)kmalloc(sizeof(struct pt_regs), GFP_KERNEL);
+	if (!r2)
+		return;
+	*r2 = *r;
+	r2->gr[30] = r->ksp;
+	r2->iaoq[0] = r->kpc;
+	unwind_frame_init(info, t, r2);
+	kfree(r2);
 }
 
 void unwind_frame_init_running(struct unwind_frame_info *info, struct pt_regs *regs)
 {
-	unwind_frame_init(info, current, regs->gr[30], regs->iaoq[0],
-			  regs->gr[2]);
+	unwind_frame_init(info, current, regs);
 }
 
 int unwind_once(struct unwind_frame_info *next_frame)

include/asm-parisc/module.h

@@ -17,12 +17,16 @@
 #define Elf_Rela Elf32_Rela
 #endif
 
+struct unwind_table;
+
 struct mod_arch_specific
 {
 	unsigned long got_offset, got_count, got_max;
 	unsigned long fdesc_offset, fdesc_count, fdesc_max;
 	unsigned long stub_offset, stub_count, stub_max;
 	unsigned long init_stub_offset, init_stub_count, init_stub_max;
+	int unwind_section;
+	struct unwind_table *unwind;
 };
 
 #endif /* _ASM_PARISC_MODULE_H */

include/asm-parisc/unwind.h

 #ifndef _UNWIND_H_
 #define _UNWIND_H_
 
+#include <linux/list.h>
+
 /* From ABI specifications */
 struct unwind_table_entry {
 	unsigned int region_start;
@@ -39,7 +41,7 @@ struct unwind_table_entry {
 };
 
 struct unwind_table {
-	struct unwind_table *next;
+	struct list_head list;
 	const char *name;
 	unsigned long gp;
 	unsigned long base_addr;
@@ -55,15 +57,18 @@ struct unwind_frame_info {
 	   available; but for now we only try to get the sp and ip for each
 	   frame */
 	/* struct pt_regs regs; */
-	unsigned long sp, ip, rp;
+	unsigned long sp, ip, rp, r31;
 	unsigned long prev_sp, prev_ip;
 };
 
-void * unwind_table_add(const char *name, unsigned long base_addr, 
-		 unsigned long gp,
-                 void *start, void *end);
+struct unwind_table *
+unwind_table_add(const char *name, unsigned long base_addr, 
+		 unsigned long gp, void *start, void *end);
+void
+unwind_table_remove(struct unwind_table *table);
+
 void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t, 
-		       unsigned long sp, unsigned long ip, unsigned long rp);
+		       struct pt_regs *regs);
 void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t);
 void unwind_frame_init_running(struct unwind_frame_info *info, struct pt_regs *regs);
 int unwind_once(struct unwind_frame_info *info);