From 17248ea0367465f4aaef728f6af661ed38e38cf1 Mon Sep 17 00:00:00 2001 From: Sven Schnelle Date: Wed, 15 Jan 2020 13:42:27 +0100 Subject: 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 75a0: R_390_PLT32DBL kmem_cache_free+0x2 75a4: a7 f4 00 01 j 75a6 00000000000075a8 : 75a8: c0 04 00 00 00 00 brcl 0,75a8 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: Heiko Carstens Signed-off-by: Sven Schnelle Signed-off-by: Vasily Gorbik --- arch/s390/kernel/pgm_check.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/s390/kernel/pgm_check.S') diff --git a/arch/s390/kernel/pgm_check.S b/arch/s390/kernel/pgm_check.S index 59dee9d3bebf..eee3a482195a 100644 --- a/arch/s390/kernel/pgm_check.S +++ b/arch/s390/kernel/pgm_check.S @@ -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 */ -- cgit v1.2.3