Commit 05a68e89 authored by Ilya Leoshkevich's avatar Ilya Leoshkevich Committed by Heiko Carstens
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s390/kernel: expand exception table logic to allow new handling options 



This is a s390 port of commit 548acf19 ("x86/mm: Expand the
exception table logic to allow new handling options"), which is needed
for implementing BPF_PROBE_MEM on s390.

The new handler field is made 64-bit in order to allow pointing from
dynamically allocated entries to handlers in kernel text. Unlike on x86,
NULL is used instead of ex_handler_default. This is because exception
tables are used by boot/text_dma.S, and it would be a pain to preserve
ex_handler_default.

The new infrastructure is ignored in early_pgm_check_handler, since
there is no pt_regs.

Signed-off-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent 88aa8939

arch/s390/include/asm/extable.h

+47 −5
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#ifndef __S390_EXTABLE_H

#define __S390_EXTABLE_H



#include <asm/ptrace.h>

#include <linux/compiler.h>



/*

 * The exception table consists of pairs of addresses: the first is the

 * address of an instruction that is allowed to fault, and the second is

 * the address at which the program should continue.  No registers are

 * modified, so it is entirely up to the continuation code to figure out

 * what to do.

 * The exception table consists of three addresses:

 *

 * - Address of an instruction that is allowed to fault.

 * - Address at which the program should continue.

 * - Optional address of handler that takes pt_regs * argument and runs in

 *   interrupt context.

 *

 * No registers are modified, so it is entirely up to the continuation code

 * to figure out what to do.

 *

 * All the routines below use bits of fixup code that are out of line

 * with the main instruction path.  This means when everything is well,
@@ -17,6 +25,7 @@ 
struct exception_table_entry

{

	int insn, fixup;

	long handler;

};



extern struct exception_table_entry *__start_dma_ex_table;
@@ -29,6 +38,39 @@ static inline unsigned long extable_fixup(const struct exception_table_entry *x) 
	return (unsigned long)&x->fixup + x->fixup;

}



typedef bool (*ex_handler_t)(const struct exception_table_entry *,

			     struct pt_regs *);



static inline ex_handler_t

ex_fixup_handler(const struct exception_table_entry *x)

{

	if (likely(!x->handler))

		return NULL;

	return (ex_handler_t)((unsigned long)&x->handler + x->handler);

}



static inline bool ex_handle(const struct exception_table_entry *x,

			     struct pt_regs *regs)

{

	ex_handler_t handler = ex_fixup_handler(x);



	if (unlikely(handler))

		return handler(x, regs);

	regs->psw.addr = extable_fixup(x);

	return true;

}



#define ARCH_HAS_RELATIVE_EXTABLE



static inline void swap_ex_entry_fixup(struct exception_table_entry *a,

				       struct exception_table_entry *b,

				       struct exception_table_entry tmp,

				       int delta)

{

	a->fixup = b->fixup + delta;

	b->fixup = tmp.fixup - delta;

	a->handler = b->handler + delta;

	b->handler = tmp.handler - delta;

}



#endif

arch/s390/include/asm/linkage.h

+2 −1
Original line number Diff line number Diff line
@@ -14,9 +14,10 @@ 


#define __EX_TABLE(_section, _fault, _target)				\

	stringify_in_c(.section	_section,"a";)				\

	stringify_in_c(.align	4;)					\

	stringify_in_c(.align	8;)					\

	stringify_in_c(.long	(_fault) - .;)				\

	stringify_in_c(.long	(_target) - .;)				\

	stringify_in_c(.quad	0;)					\

	stringify_in_c(.previous)



#define EX_TABLE(_fault, _target)					\

arch/s390/kernel/kprobes.c

+1 −3
Original line number Diff line number Diff line
@@ -523,10 +523,8 @@ static int kprobe_trap_handler(struct pt_regs *regs, int trapnr) 
		 * zero, try to fix up.

		 */

		entry = s390_search_extables(regs->psw.addr);

		if (entry) {

			regs->psw.addr = extable_fixup(entry);

		if (entry && ex_handle(entry, regs))

			return 1;

		}



		/*

		 * fixup_exception() could not handle it,

arch/s390/kernel/traps.c

+2 −5
Original line number Diff line number Diff line
@@ -50,13 +50,10 @@ void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str) 
        } else {

                const struct exception_table_entry *fixup;

		fixup = s390_search_extables(regs->psw.addr);

                if (fixup)

			regs->psw.addr = extable_fixup(fixup);

		else {

		if (!fixup || !ex_handle(fixup, regs))

			die(regs, str);

        }

}

}



static void do_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)

{
@@ -251,7 +248,7 @@ void monitor_event_exception(struct pt_regs *regs) 
	case BUG_TRAP_TYPE_NONE:

		fixup = s390_search_extables(regs->psw.addr);

		if (fixup)

			regs->psw.addr = extable_fixup(fixup);

			ex_handle(fixup, regs);

		break;

	case BUG_TRAP_TYPE_WARN:

		break;

arch/s390/mm/fault.c

+1 −3
Original line number Diff line number Diff line
@@ -255,10 +255,8 @@ static noinline void do_no_context(struct pt_regs *regs) 


	/* Are we prepared to handle this kernel fault?  */

	fixup = s390_search_extables(regs->psw.addr);

	if (fixup) {

		regs->psw.addr = extable_fixup(fixup);

	if (fixup && ex_handle(fixup, regs))

		return;

	}



	/*

	 * Oops. The kernel tried to access some bad page. We'll have to

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