Commit 17248ea0 authored by Sven Schnelle's avatar Sven Schnelle Committed by Vasily Gorbik
Browse files

s390: fix __EMIT_BUG() macro 



Setting a kprobe on getname_flags() failed:

$ echo 'p:tmr1 getname_flags +0(%r2):ustring' > kprobe_events
-bash: echo: write error: Invalid argument

Debugging the kprobes code showed that the address of
getname_flags() is contained in the __bug_table. Kprobes
doesn't allow to set probes at BUG() locations.

$ objdump -j  __bug_table -x build/fs/namei.o
[..]
0000000000000108 R_390_PC32        .text+0x00000000000075a8
000000000000010c R_390_PC32        .L223+0x0000000000000004

I was expecting getname_flags() to start with a BUG(), but:

7598:       e3 20 10 00 00 04       lg      %r2,0(%r1)
759e:       c0 f4 00 00 00 00       jg      759e <putname+0x7e>
75a0: R_390_PLT32DBL    kmem_cache_free+0x2
75a4:       a7 f4 00 01             j       75a6 <putname+0x86>

00000000000075a8 <getname_flags>:
75a8:       c0 04 00 00 00 00       brcl    0,75a8 <getname_flags>
75ae:       eb 6f f0 48 00 24       stmg    %r6,%r15,72(%r15)
75b4:       b9 04 00 ef             lgr     %r14,%r15
75b8:       e3 f0 ff a8 ff 71       lay     %r15,-88(%r15)

So the BUG() is actually the last opcode of the previous function.
Fix this by switching to using the MONITOR CALL (MC) instruction,
and set the entry in __bug_table to the beginning of that MC.

Reviewed-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarSven Schnelle <svens@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 45f7a0da

arch/s390/boot/head.S

+1 −1
Original line number Diff line number Diff line
@@ -329,7 +329,7 @@ ENTRY(startup_kdump) 
	.quad	.Lduct			# cr5: primary-aste origin

	.quad	0			# cr6:	I/O interrupts

	.quad	0			# cr7:	secondary space segment table

	.quad	0			# cr8:	access registers translation

	.quad	0x0000000000008000	# cr8:	access registers translation

	.quad	0			# cr9:	tracing off

	.quad	0			# cr10: tracing off

	.quad	0			# cr11: tracing off

arch/s390/include/asm/bug.h

+7 −9
Original line number Diff line number Diff line
@@ -10,15 +10,14 @@ 


#define __EMIT_BUG(x) do {					\

	asm_inline volatile(					\

		"0:	j	0b+2\n"				\

		"1:\n"						\

		"0:	mc	0,0\n"				\

		".section .rodata.str,\"aMS\",@progbits,1\n"	\

		"2:	.asciz	\""__FILE__"\"\n"		\

		"1:	.asciz	\""__FILE__"\"\n"		\

		".previous\n"					\

		".section __bug_table,\"awM\",@progbits,%2\n"	\

		"3:	.long	1b-3b,2b-3b\n"			\

		"2:	.long	0b-2b,1b-2b\n"			\

		"	.short	%0,%1\n"			\

		"	.org	3b+%2\n"			\

		"	.org	2b+%2\n"			\

		".previous\n"					\

		: : "i" (__LINE__),				\

		    "i" (x),					\
@@ -29,12 +28,11 @@ 


#define __EMIT_BUG(x) do {					\

	asm_inline volatile(					\

		"0:	j	0b+2\n"				\

		"1:\n"						\

		"0:	mc	0,0\n"				\

		".section __bug_table,\"awM\",@progbits,%1\n"	\

		"2:	.long	1b-2b\n"			\

		"1:	.long	0b-1b\n"			\

		"	.short	%0\n"				\

		"	.org	2b+%1\n"			\

		"	.org	1b+%1\n"			\

		".previous\n"					\

		: : "i" (x),					\

		    "i" (sizeof(struct bug_entry)));		\

arch/s390/kernel/entry.h

+1 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ void specification_exception(struct pt_regs *regs); 
void transaction_exception(struct pt_regs *regs);

void translation_exception(struct pt_regs *regs);

void vector_exception(struct pt_regs *regs);

void monitor_event_exception(struct pt_regs *regs);



void do_per_trap(struct pt_regs *regs);

void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str);

arch/s390/kernel/pgm_check.S

+1 −1
Original line number Diff line number Diff line
@@ -81,7 +81,7 @@ PGM_CHECK_DEFAULT /* 3c */ 
PGM_CHECK_DEFAULT			/* 3d */

PGM_CHECK_DEFAULT			/* 3e */

PGM_CHECK_DEFAULT			/* 3f */

PGM_CHECK_DEFAULT			/* 40 */

PGM_CHECK(monitor_event_exception)	/* 40 */

PGM_CHECK_DEFAULT			/* 41 */

PGM_CHECK_DEFAULT			/* 42 */

PGM_CHECK_DEFAULT			/* 43 */

arch/s390/kernel/traps.c

+36 −5
Original line number Diff line number Diff line
@@ -53,11 +53,6 @@ void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str) 
                if (fixup)

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

		else {

			enum bug_trap_type btt;



			btt = report_bug(regs->psw.addr, regs);

			if (btt == BUG_TRAP_TYPE_WARN)

				return;

			die(regs, str);

		}

        }
@@ -245,6 +240,27 @@ void space_switch_exception(struct pt_regs *regs) 
	do_trap(regs, SIGILL, ILL_PRVOPC, "space switch event");

}



void monitor_event_exception(struct pt_regs *regs)

{

	const struct exception_table_entry *fixup;



	if (user_mode(regs))

		return;



	switch (report_bug(regs->psw.addr - (regs->int_code >> 16), regs)) {

	case BUG_TRAP_TYPE_NONE:

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

		if (fixup)

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

		break;

	case BUG_TRAP_TYPE_WARN:

		break;

	case BUG_TRAP_TYPE_BUG:

		die(regs, "monitor event");

		break;

	}

}



void kernel_stack_overflow(struct pt_regs *regs)

{

	bust_spinlocks(1);
@@ -255,8 +271,23 @@ void kernel_stack_overflow(struct pt_regs *regs) 
}

NOKPROBE_SYMBOL(kernel_stack_overflow);



static void test_monitor_call(void)

{

	int val = 1;



	asm volatile(

		"	mc	0,0\n"

		"0:	xgr	%0,%0\n"

		"1:\n"

		EX_TABLE(0b,1b)

		: "+d" (val));

	if (!val)

		panic("Monitor call doesn't work!\n");

}



void __init trap_init(void)

{

	sort_extable(__start_dma_ex_table, __stop_dma_ex_table);

	local_mcck_enable();

	test_monitor_call();

}