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authorMasami Hiramatsu <mhiramat@kernel.org>2018-06-20 01:15:45 +0900
committerIngo Molnar <mingo@kernel.org>2018-06-21 12:33:19 +0200
commitcce188bd58cfbd603b904dbce75f34de2eff959a (patch)
tree745abbdf6e0b9587c114ae48f3504bd085238b6c /arch/powerpc/kernel/kprobes-ftrace.c
parentd5ad85b6d9ac286ae7fa8718a8a1c28561349c07 (diff)
downloadlinux-cce188bd58cfbd603b904dbce75f34de2eff959a.tar.bz2
bpf/error-inject/kprobes: Clear current_kprobe and enable preempt in kprobe
Clear current_kprobe and enable preemption in kprobe even if pre_handler returns !0. This simplifies function override using kprobes. Jprobe used to require to keep the preemption disabled and keep current_kprobe until it returned to original function entry. For this reason kprobe_int3_handler() and similar arch dependent kprobe handers checks pre_handler result and exit without enabling preemption if the result is !0. After removing the jprobe, Kprobes does not need to keep preempt disabled even if user handler returns !0 anymore. But since the function override handler in error-inject and bpf is also returns !0 if it overrides a function, to balancing the preempt count, it enables preemption and reset current kprobe by itself. That is a bad design that is very buggy. This fixes such unbalanced preempt-count and current_kprobes setting in kprobes, bpf and error-inject. Note: for powerpc and x86, this removes all preempt_disable from kprobe_ftrace_handler because ftrace callbacks are called under preempt disabled. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: David S. Miller <davem@davemloft.net> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: James Hogan <jhogan@kernel.org> Cc: Josef Bacik <jbacik@fb.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Rich Felker <dalias@libc.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Tony Luck <tony.luck@intel.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: linux-arch@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-ia64@vger.kernel.org Cc: linux-mips@linux-mips.org Cc: linux-s390@vger.kernel.org Cc: linux-sh@vger.kernel.org Cc: linux-snps-arc@lists.infradead.org Cc: linuxppc-dev@lists.ozlabs.org Cc: sparclinux@vger.kernel.org Link: https://lore.kernel.org/lkml/152942494574.15209.12323837825873032258.stgit@devbox Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/powerpc/kernel/kprobes-ftrace.c')
-rw-r--r--arch/powerpc/kernel/kprobes-ftrace.c19
1 files changed, 6 insertions, 13 deletions
diff --git a/arch/powerpc/kernel/kprobes-ftrace.c b/arch/powerpc/kernel/kprobes-ftrace.c
index 070d1d862444..e4a49c051325 100644
--- a/arch/powerpc/kernel/kprobes-ftrace.c
+++ b/arch/powerpc/kernel/kprobes-ftrace.c
@@ -32,11 +32,9 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
struct kprobe *p;
struct kprobe_ctlblk *kcb;
- preempt_disable();
-
p = get_kprobe((kprobe_opcode_t *)nip);
if (unlikely(!p) || kprobe_disabled(p))
- goto end;
+ return;
kcb = get_kprobe_ctlblk();
if (kprobe_running()) {
@@ -60,18 +58,13 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
kcb->kprobe_status = KPROBE_HIT_SSDONE;
p->post_handler(p, regs, 0);
}
- __this_cpu_write(current_kprobe, NULL);
- } else {
- /*
- * If pre_handler returns !0, it sets regs->nip and
- * resets current kprobe. In this case, we should not
- * re-enable preemption.
- */
- return;
}
+ /*
+ * If pre_handler returns !0, it changes regs->nip. We have to
+ * skip emulating post_handler.
+ */
+ __this_cpu_write(current_kprobe, NULL);
}
-end:
- preempt_enable_no_resched();
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);