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: 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>
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@ -329,7 +329,7 @@ ENTRY(startup_kdump)
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.quad .Lduct # cr5: primary-aste origin
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.quad 0 # cr6: I/O interrupts
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.quad 0 # cr7: secondary space segment table
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.quad 0 # cr8: access registers translation
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.quad 0x0000000000008000 # cr8: access registers translation
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.quad 0 # cr9: tracing off
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.quad 0 # cr10: tracing off
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.quad 0 # cr11: tracing off
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@ -10,15 +10,14 @@
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#define __EMIT_BUG(x) do { \
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asm_inline volatile( \
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"0: j 0b+2\n" \
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"1:\n" \
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"0: mc 0,0\n" \
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".section .rodata.str,\"aMS\",@progbits,1\n" \
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"2: .asciz \""__FILE__"\"\n" \
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"1: .asciz \""__FILE__"\"\n" \
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".previous\n" \
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".section __bug_table,\"awM\",@progbits,%2\n" \
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"3: .long 1b-3b,2b-3b\n" \
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"2: .long 0b-2b,1b-2b\n" \
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" .short %0,%1\n" \
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" .org 3b+%2\n" \
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" .org 2b+%2\n" \
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".previous\n" \
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: : "i" (__LINE__), \
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"i" (x), \
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@ -29,12 +28,11 @@
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#define __EMIT_BUG(x) do { \
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asm_inline volatile( \
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"0: j 0b+2\n" \
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"1:\n" \
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"0: mc 0,0\n" \
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".section __bug_table,\"awM\",@progbits,%1\n" \
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"2: .long 1b-2b\n" \
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"1: .long 0b-1b\n" \
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" .short %0\n" \
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" .org 2b+%1\n" \
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" .org 1b+%1\n" \
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".previous\n" \
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: : "i" (x), \
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"i" (sizeof(struct bug_entry))); \
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@ -45,6 +45,7 @@ void specification_exception(struct pt_regs *regs);
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void transaction_exception(struct pt_regs *regs);
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void translation_exception(struct pt_regs *regs);
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void vector_exception(struct pt_regs *regs);
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void monitor_event_exception(struct pt_regs *regs);
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void do_per_trap(struct pt_regs *regs);
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void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str);
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@ -81,7 +81,7 @@ PGM_CHECK_DEFAULT /* 3c */
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PGM_CHECK_DEFAULT /* 3d */
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PGM_CHECK_DEFAULT /* 3e */
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PGM_CHECK_DEFAULT /* 3f */
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PGM_CHECK_DEFAULT /* 40 */
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PGM_CHECK(monitor_event_exception) /* 40 */
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PGM_CHECK_DEFAULT /* 41 */
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PGM_CHECK_DEFAULT /* 42 */
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PGM_CHECK_DEFAULT /* 43 */
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@ -53,11 +53,6 @@ void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)
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if (fixup)
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regs->psw.addr = extable_fixup(fixup);
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else {
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enum bug_trap_type btt;
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btt = report_bug(regs->psw.addr, regs);
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if (btt == BUG_TRAP_TYPE_WARN)
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return;
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die(regs, str);
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}
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}
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@ -245,6 +240,27 @@ void space_switch_exception(struct pt_regs *regs)
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do_trap(regs, SIGILL, ILL_PRVOPC, "space switch event");
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}
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void monitor_event_exception(struct pt_regs *regs)
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{
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const struct exception_table_entry *fixup;
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if (user_mode(regs))
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return;
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switch (report_bug(regs->psw.addr - (regs->int_code >> 16), regs)) {
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case BUG_TRAP_TYPE_NONE:
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fixup = s390_search_extables(regs->psw.addr);
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if (fixup)
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regs->psw.addr = extable_fixup(fixup);
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break;
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case BUG_TRAP_TYPE_WARN:
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break;
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case BUG_TRAP_TYPE_BUG:
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die(regs, "monitor event");
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break;
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}
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}
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void kernel_stack_overflow(struct pt_regs *regs)
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{
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bust_spinlocks(1);
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@ -255,8 +271,23 @@ void kernel_stack_overflow(struct pt_regs *regs)
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}
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NOKPROBE_SYMBOL(kernel_stack_overflow);
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static void test_monitor_call(void)
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{
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int val = 1;
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asm volatile(
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" mc 0,0\n"
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"0: xgr %0,%0\n"
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"1:\n"
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EX_TABLE(0b,1b)
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: "+d" (val));
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if (!val)
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panic("Monitor call doesn't work!\n");
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}
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void __init trap_init(void)
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{
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sort_extable(__start_dma_ex_table, __stop_dma_ex_table);
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local_mcck_enable();
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test_monitor_call();
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}
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