Revert "x86/mm: Expand the exception table logic to allow new handling options"

This reverts commit fcf5e5198b447969ed2a56ec335dae3c695a6b46 which is
548acf19234dbda5a52d5a8e7e205af46e9da840 upstream.

Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 29 insertions, 73 deletions

diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 9dd7e4b7fcde..903ec1e9c326 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -3,9 +3,6 @@
 #include <linux/sort.h>
 #include <asm/uaccess.h>
 
-typedef bool (*ex_handler_t)(const struct exception_table_entry *,
-			    struct pt_regs *, int);
-
 static inline unsigned long
 ex_insn_addr(const struct exception_table_entry *x)
 {
@@ -16,56 +13,11 @@ ex_fixup_addr(const struct exception_table_entry *x)
 {
 	return (unsigned long)&x->fixup + x->fixup;
 }
-static inline ex_handler_t
-ex_fixup_handler(const struct exception_table_entry *x)
-{
-	return (ex_handler_t)((unsigned long)&x->handler + x->handler);
-}
-
-bool ex_handler_default(const struct exception_table_entry *fixup,
-		       struct pt_regs *regs, int trapnr)
-{
-	regs->ip = ex_fixup_addr(fixup);
-	return true;
-}
-EXPORT_SYMBOL(ex_handler_default);
-
-bool ex_handler_fault(const struct exception_table_entry *fixup,
-		     struct pt_regs *regs, int trapnr)
-{
-	regs->ip = ex_fixup_addr(fixup);
-	regs->ax = trapnr;
-	return true;
-}
-EXPORT_SYMBOL_GPL(ex_handler_fault);
-
-bool ex_handler_ext(const struct exception_table_entry *fixup,
-		   struct pt_regs *regs, int trapnr)
-{
-	/* Special hack for uaccess_err */
-	current_thread_info()->uaccess_err = 1;
-	regs->ip = ex_fixup_addr(fixup);
-	return true;
-}
-EXPORT_SYMBOL(ex_handler_ext);
-
-bool ex_has_fault_handler(unsigned long ip)
-{
-	const struct exception_table_entry *e;
-	ex_handler_t handler;
-
-	e = search_exception_tables(ip);
-	if (!e)
-		return false;
-	handler = ex_fixup_handler(e);
-
-	return handler == ex_handler_fault;
-}
 
-int fixup_exception(struct pt_regs *regs, int trapnr)
+int fixup_exception(struct pt_regs *regs)
 {
-	const struct exception_table_entry *e;
-	ex_handler_t handler;
+	const struct exception_table_entry *fixup;
+	unsigned long new_ip;
 
 #ifdef CONFIG_PNPBIOS
 	if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
@@ -81,34 +33,42 @@ int fixup_exception(struct pt_regs *regs, int trapnr)
 	}
 #endif
 
-	e = search_exception_tables(regs->ip);
-	if (!e)
-		return 0;
+	fixup = search_exception_tables(regs->ip);
+	if (fixup) {
+		new_ip = ex_fixup_addr(fixup);
+
+		if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
+			/* Special hack for uaccess_err */
+			current_thread_info()->uaccess_err = 1;
+			new_ip -= 0x7ffffff0;
+		}
+		regs->ip = new_ip;
+		return 1;
+	}
 
-	handler = ex_fixup_handler(e);
-	return handler(e, regs, trapnr);
+	return 0;
 }
 
 /* Restricted version used during very early boot */
 int __init early_fixup_exception(unsigned long *ip)
 {
-	const struct exception_table_entry *e;
+	const struct exception_table_entry *fixup;
 	unsigned long new_ip;
-	ex_handler_t handler;
 
-	e = search_exception_tables(*ip);
-	if (!e)
-		return 0;
+	fixup = search_exception_tables(*ip);
+	if (fixup) {
+		new_ip = ex_fixup_addr(fixup);
 
-	new_ip  = ex_fixup_addr(e);
-	handler = ex_fixup_handler(e);
+		if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
+			/* uaccess handling not supported during early boot */
+			return 0;
+		}
 
-	/* special handling not supported during early boot */
-	if (handler != ex_handler_default)
-		return 0;
+		*ip = new_ip;
+		return 1;
+	}
 
-	*ip = new_ip;
-	return 1;
+	return 0;
 }
 
 /*
@@ -173,8 +133,6 @@ void sort_extable(struct exception_table_entry *start,
 		i += 4;
 		p->fixup += i;
 		i += 4;
-		p->handler += i;
-		i += 4;
 	}
 
 	sort(start, finish - start, sizeof(struct exception_table_entry),
@@ -187,8 +145,6 @@ void sort_extable(struct exception_table_entry *start,
 		i += 4;
 		p->fixup -= i;
 		i += 4;
-		p->handler -= i;
-		i += 4;
 	}
 }
 
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 03898aea6e0f..e830c71a1323 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -663,7 +663,7 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 	int sig;
 
 	/* Are we prepared to handle this kernel fault? */
-	if (fixup_exception(regs, X86_TRAP_PF)) {
+	if (fixup_exception(regs)) {
 		/*
 		 * Any interrupt that takes a fault gets the fixup. This makes
 		 * the below recursive fault logic only apply to a faults from