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Commit b87a95ad609619482df0690320d5ace33ace8e7a

Authored by Oleg Nesterov
Committed by Linus Torvalds
1 parent 9afe33ada2
Exists in smarc-imx_3.14.28_1.0.0_ga and in 1 other branch imx_3.14.28_1.0.0_ga

ptrace/x86: ptrace_write_dr7() should create bp if !disabled 

Commit 24f1e32c60c4 ("hw-breakpoints: Rewrite the hw-breakpoints layer
on top of perf events") introduced the minor regression.  Before this
commit

	PTRACE_POKEUSER DR7, enableDR0
	PTRACE_POKEUSER DR0, address

was perfectly valid, now PTRACE_POKEUSER(DR7) fails if DR0 was not
previously initialized by PTRACE_POKEUSER(DR0).

Change ptrace_write_dr7() to do ptrace_register_breakpoint(addr => 0) if
!bp && !disabled.

This fixes watchpoint-zeroaddr from ptrace-tests, see

    https://bugzilla.redhat.com/show_bug.cgi?id=660204.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Jan Kratochvil <jan.kratochvil@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Michael Neuling <mikey@neuling.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 1 changed file with 10 additions and 7 deletions Side-by-side Diff

arch/x86/kernel/ptrace.c
Diff comments   View file @ b87a95a
... ... @@ -670,13 +670,16 @@
670 670 if (!bp) {
671 671 if (disabled)
672 672 continue;
673   - /*
674   - * We should have at least an inactive breakpoint at
675   - * this slot. It means the user is writing dr7 without
676   - * having written the address register first.
677   - */
678   - rc = -EINVAL;
679   - break;
  673 +
  674 + bp = ptrace_register_breakpoint(tsk,
  675 + len, type, 0, disabled);
  676 + if (IS_ERR(bp)) {
  677 + rc = PTR_ERR(bp);
  678 + break;
  679 + }
  680 +
  681 + thread->ptrace_bps[i] = bp;
  682 + continue;
680 683 }
681 684  
682 685 rc = ptrace_modify_breakpoint(bp, len, type, disabled);