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/include/asm/bug.h | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) (limited to 'arch/s390/include/asm/bug.h') diff --git a/arch/s390/include/asm/bug.h b/arch/s390/include/asm/bug.h index a2b11ac00f60..7725f8006fdf 100644 --- a/arch/s390/include/asm/bug.h +++ b/arch/s390/include/asm/bug.h @@ -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))); \ -- cgit v1.2.3