From: Sven Schnelle svens@linux.ibm.com
[ Upstream commit 17248ea0367465f4aaef728f6af661ed38e38cf1 ]
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: Heiko Carstens heiko.carstens@de.ibm.com Signed-off-by: Sven Schnelle svens@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/boot/head.S | 2 +- arch/s390/include/asm/bug.h | 16 ++++++-------- arch/s390/kernel/entry.h | 1 + arch/s390/kernel/pgm_check.S | 2 +- arch/s390/kernel/traps.c | 41 +++++++++++++++++++++++++++++++----- 5 files changed, 46 insertions(+), 16 deletions(-)
diff --git a/arch/s390/boot/head.S b/arch/s390/boot/head.S index 4b86a8d3c1219..dae10961d0724 100644 --- a/arch/s390/boot/head.S +++ b/arch/s390/boot/head.S @@ -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 diff --git a/arch/s390/include/asm/bug.h b/arch/s390/include/asm/bug.h index a2b11ac00f607..7725f8006fdfb 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))); \ diff --git a/arch/s390/kernel/entry.h b/arch/s390/kernel/entry.h index b2956d49b6ad7..1d3927e01a5fd 100644 --- a/arch/s390/kernel/entry.h +++ b/arch/s390/kernel/entry.h @@ -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); diff --git a/arch/s390/kernel/pgm_check.S b/arch/s390/kernel/pgm_check.S index 59dee9d3bebf1..eee3a482195a6 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 */ diff --git a/arch/s390/kernel/traps.c b/arch/s390/kernel/traps.c index 164c0282b41ae..dc75588d78943 100644 --- a/arch/s390/kernel/traps.c +++ b/arch/s390/kernel/traps.c @@ -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(); }