kernel.git/arch/powerpc/kernel/kprobes.c, branch linux-4.17.y

powerpc/kprobes: Fix call trace due to incorrect preempt count

2018-03-30T13:10:33Z

Michael Ellerman reported the following call trace when running ftracetest: BUG: using __this_cpu_write() in preemptible [00000000] code: ftracetest/6178 caller is opt_pre_handler+0xc4/0x110 CPU: 1 PID: 6178 Comm: ftracetest Not tainted 4.15.0-rc7-gcc6x-gb2cd1df #1 Call Trace: [c0000000f9ec39c0] [c000000000ac4304] dump_stack+0xb4/0x100 (unreliable) [c0000000f9ec3a00] [c00000000061159c] check_preemption_disabled+0x15c/0x170 [c0000000f9ec3a90] [c000000000217e84] opt_pre_handler+0xc4/0x110 [c0000000f9ec3af0] [c00000000004cf68] optimized_callback+0x148/0x170 [c0000000f9ec3b40] [c00000000004d954] optinsn_slot+0xec/0x10000 [c0000000f9ec3e30] [c00000000004bae0] kretprobe_trampoline+0x0/0x10 This is showing up since OPTPROBES is now enabled with CONFIG_PREEMPT. trampoline_probe_handler() considers itself to be a special kprobe handler for kretprobes. In doing so, it expects to be called from kprobe_handler() on a trap, and re-enables preemption before returning a non-zero return value so as to suppress any subsequent processing of the trap by the kprobe_handler(). However, with optprobes, we don't deal with special handlers (we ignore the return code) and just try to re-enable preemption causing the above trace. To address this, modify trampoline_probe_handler() to not be special. The only additional processing done in kprobe_handler() is to emulate the instruction (in this case, a 'nop'). We adjust the value of regs->nip for the purpose and delegate the job of re-enabling preemption and resetting current kprobe to the probe handlers (kprobe_handler() or optimized_callback()). Fixes: 8a2d71a3f273 ("powerpc/kprobes: Disable preemption before invoking probe handler for optprobes") Cc: stable@vger.kernel.org # v4.15+ Reported-by: Michael Ellerman Signed-off-by: Naveen N. Rao Acked-by: Ananth N Mavinakayanahalli Signed-off-by: Michael Ellerman

powerpc/kprobes: refactor kprobe_lookup_name for safer string operations

2017-11-12T12:51:43Z

Use safer string manipulation functions when dealing with a user-provided string in kprobe_lookup_name(). Reported-by: David Laight Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman

Merge branch 'fixes' into next

2017-11-10T09:55:03Z

We have some dependencies & conflicts between patches in fixes and things to go in next, both in the radix TLB flush code and the IMC PMU driver. So merge fixes into next.

powerpc/kprobes: Dereference function pointers only if the address does not belong to kernel text

2017-11-01T04:51:03Z

This makes the changes introduced in commit 83e840c770f2c5 ("powerpc64/elfv1: Only dereference function descriptor for non-text symbols") to be specific to the kprobe subsystem. We previously changed ppc_function_entry() to always check the provided address to confirm if it needed to be dereferenced. This is actually only an issue for kprobe blacklisted asm labels (through use of _ASM_NOKPROBE_SYMBOL) and can cause other issues with ftrace. Also, the additional checks are not really necessary for our other uses. As such, move this check to the kprobes subsystem. Fixes: 83e840c770f2 ("powerpc64/elfv1: Only dereference function descriptor for non-text symbols") Cc: stable@vger.kernel.org # v4.13+ Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman

powerpc/jprobes: Validate break handler invocation as being due to a jprobe_return()

2017-10-05T05:12:48Z

Fix a circa 2005 FIXME by implementing a check to ensure that we actually got into the jprobe break handler() due to the trap in jprobe_return(). Acked-by: Masami Hiramatsu Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman

powerpc/kprobes: Clean up jprobe detection in livepatch handler

2017-10-04T12:42:17Z

In commit c05b8c4474c03 ("powerpc/kprobes: Skip livepatch_handler() for jprobes"), we added a helper is_current_kprobe_addr() to help detect if the modified regs->nip was due to a jprobe or livepatch. Masami felt that the function name was not quite clear. To that end, this patch renames is_current_kprobe_addr() to __is_active_jprobe() and adds a comment to (hopefully) better clarify the purpose of this helper. The helper has also now been moved to kprobes-ftrace.c so that it is only available for KPROBES_ON_FTRACE. Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman

powerpc/kprobes: Do not suppress instruction emulation if a single run failed

2017-10-04T12:42:16Z

Currently, we disable instruction emulation if emulate_step() fails for any reason. However, such failures could be transient and specific to a particular run. Instead, only disable instruction emulation if we have never been able to emulate this. If we had emulated this instruction successfully at least once, then we single step only this probe hit and continue to try emulating the instruction in subsequent probe hits. Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman

powerpc/kprobes: Some cosmetic updates to try_to_emulate()

2017-10-04T12:42:12Z

1. This is only used in kprobes.c, so make it static. 2. Remove the un-necessary (ret == 0) comparison in the else clause. Reviewed-by: Masami Hiramatsu Reviewed-by: Kamalesh Babulal Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman

Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-07-09T17:49:47Z

Pull perf fixes from Thomas Gleixner: "A couple of fixes for perf and kprobes: - Add he missing exclude_kernel attribute for the precise_ip level so !CAP_SYS_ADMIN users get the proper results. - Warn instead of failing completely when perf has no unwind support for a particular architectiure built in. - Ensure that jprobes are at function entry and not at some random place" * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: kprobes: Ensure that jprobe probepoints are at function entry kprobes: Simplify register_jprobes() kprobes: Rename [arch_]function_offset_within_entry() to [arch_]kprobe_on_func_entry() perf unwind: Do not fail due to missing unwind support perf evsel: Set attr.exclude_kernel when probing max attr.precise_ip

kprobes: Rename [arch_]function_offset_within_entry() to [arch_]kprobe_on_func_entry()

2017-07-08T09:05:34Z

Rename function_offset_within_entry() to scope it to kprobe namespace by using kprobe_ prefix, and to also simplify it. Suggested-by: Ingo Molnar Suggested-by: Masami Hiramatsu Signed-off-by: Naveen N. Rao Cc: Ananth N Mavinakayanahalli Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/3aa6c7e2e4fb6e00f3c24fa306496a66edb558ea.1499443367.git.naveen.n.rao@linux.vnet.ibm.com Signed-off-by: Ingo Molnar