kernel.git/arch/arm64/kernel/probes, branch linux-4.9.y

arm64: debug: Ensure debug handlers check triggering exception level

2019-04-05T20:29:03Z

commit 6bd288569b50bc89fa5513031086746968f585cb upstream. Debug exception handlers may be called for exceptions generated both by user and kernel code. In many cases, this is checked explicitly, but in other cases things either happen to work by happy accident or they go slightly wrong. For example, executing 'brk #4' from userspace will enter the kprobes code and be ignored, but the instruction will be retried forever in userspace instead of delivering a SIGTRAP. Fix this issue in the most stable-friendly fashion by simply adding explicit checks of the triggering exception level to all of our debug exception handlers. Cc: Reviewed-by: Mark Rutland Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Greg Kroah-Hartman

arm64: kprobe: Always blacklist the KVM world-switch code

2019-03-13T21:04:57Z

[ Upstream commit f2b3d8566d81deaca31f4e3163def0bea7746e11 ] On systems with VHE the kernel and KVM's world-switch code run at the same exception level. Code that is only used on a VHE system does not need to be annotated as __hyp_text as it can reside anywhere in the kernel text. __hyp_text was also used to prevent kprobes from patching breakpoint instructions into this region, as this code runs at a different exception level. While this is no longer true with VHE, KVM still switches VBAR_EL1, meaning a kprobe's breakpoint executed in the world-switch code will cause a hyp-panic. Move the __hyp_text check in the kprobes blacklist so it applies on VHE systems too, to cover the common code and guest enter/exit assembly. Fixes: 888b3c8720e0 ("arm64: Treat all entry code as non-kprobe-able") Reviewed-by: Christoffer Dall Signed-off-by: James Morse Acked-by: Masami Hiramatsu Signed-off-by: Will Deacon Signed-off-by: Sasha Levin

kprobes/arm64: Fix %p uses in error messages

2018-09-05T07:20:05Z

commit 0722867dcbc28cc9b269b57acd847c7c1aa638d6 upstream. Fix %p uses in error messages by removing it because those are redundant or meaningless. Signed-off-by: Masami Hiramatsu Acked-by: Will Deacon Cc: Ananth N Mavinakayanahalli Cc: Anil S Keshavamurthy Cc: Arnd Bergmann Cc: David Howells Cc: David S . Miller Cc: Heiko Carstens Cc: Jon Medhurst Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Thomas Richter Cc: Tobin C . Harding Cc: acme@kernel.org Cc: akpm@linux-foundation.org Cc: brueckner@linux.vnet.ibm.com Cc: linux-arch@vger.kernel.org Cc: rostedt@goodmis.org Cc: schwidefsky@de.ibm.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/lkml/152491908405.9916.12425053035317241111.stgit@devbox Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

arm64: migrate exception table users off module.h and onto extable.h

2016-09-20T08:36:21Z

These files were only including module.h for exception table related functions. We've now separated that content out into its own file "extable.h" so now move over to that and avoid all the extra header content in module.h that we don't really need to compile these files. Cc: Catalin Marinas Acked-by: Catalin Marinas Cc: Will Deacon Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Paul Gortmaker Signed-off-by: Will Deacon

arm64: Improve kprobes test for atomic sequence

2016-09-15T07:33:46Z

Kprobes searches backwards a finite number of instructions to determine if there is an attempt to probe a load/store exclusive sequence. It stops when it hits the maximum number of instructions or a load or store exclusive. However this means it can run up past the beginning of the function and start looking at literal constants. This has been shown to cause a false positive and blocks insertion of the probe. To fix this, further limit the backwards search to stop if it hits a symbol address from kallsyms. The presumption is that this is the entry point to this code (particularly for the common case of placing probes at the beginning of functions). This also improves efficiency by not searching code that is not part of the function. There may be some possibility that the label might not denote the entry path to the probed instruction but the likelihood seems low and this is just another example of how the kprobes user really needs to be careful about what they are doing. Acked-by: Masami Hiramatsu Signed-off-by: David A. Long Signed-off-by: Will Deacon

arm64: Create sections.h

2016-08-25T17:00:29Z

Each time new section markers are added, kernel/vmlinux.ld.S is updated, and new extern char __start_foo[] definitions are scattered through the tree. Create asm/include/sections.h to collect these definitions (and include the existing asm-generic version). Signed-off-by: James Morse Reviewed-by: Mark Rutland Tested-by: Mark Rutland Reviewed-by: Catalin Marinas Signed-off-by: Will Deacon

arm64: kprobe: Always clear pstate.D in breakpoint exception handler

2016-08-25T17:00:20Z

Whenever we are hitting a kprobe from a none-kprobe debug exception handler, we hit an infinite occurrences of "Unexpected kernel single-step exception at EL1" PSTATE.D is debug exception mask bit. It is set whenever we enter into an exception mode. When it is set then Watchpoint, Breakpoint, and Software Step exceptions are masked. However, software Breakpoint Instruction exceptions can never be masked. Therefore, if we ever execute a BRK instruction, irrespective of D-bit setting, we will be receiving a corresponding breakpoint exception. For example: - We are executing kprobe pre/post handler, and kprobe has been inserted in one of the instruction of a function called by handler. So, it executes BRK instruction and we land into the case of KPROBE_REENTER. (This case is already handled by current code) - We are executing uprobe handler or any other BRK handler such as in WARN_ON (BRK BUG_BRK_IMM), and we trace that path using kprobe.So, we enter into kprobe breakpoint handler,from another BRK handler.(This case is not being handled currently) In all such cases kprobe breakpoint exception will be raised when we were already in debug exception mode. SPSR's D bit (bit 9) shows the value of PSTATE.D immediately before the exception was taken. So, in above example cases we would find it set in kprobe breakpoint handler. Single step exception will always be followed by a kprobe breakpoint exception.However, it will only be raised gracefully if we clear D bit while returning from breakpoint exception. If D bit is set then, it results into undefined exception and when it's handler enables dbg then single step exception is generated, however it will never be handled(because address does not match and therefore treated as unexpected). This patch clears D-flag unconditionally in setup_singlestep, so that we can always get single step exception correctly after returning from breakpoint exception. Additionally, it also removes D-flag set statement for KPROBE_REENTER return path, because debug exception for KPROBE_REENTER will always take place in a debug exception state. So, D-flag will already be set in this case. Acked-by: Sandeepa Prabhu Acked-by: Masami Hiramatsu Signed-off-by: Pratyush Anand Signed-off-by: Will Deacon

arm64: Remove stack duplicating code from jprobes

2016-08-11T16:38:16Z

Because the arm64 calling standard allows stacked function arguments to be anywhere in the stack frame, do not attempt to duplicate the stack frame for jprobes handler functions. Documentation changes to describe this issue have been broken out into a separate patch in order to simultaneously address them in other architecture(s). Signed-off-by: David A. Long Acked-by: Masami Hiramatsu Acked-by: Marc Zyngier Signed-off-by: Catalin Marinas

arm64: kprobes: Add KASAN instrumentation around stack accesses

2016-07-21T10:47:53Z

This patch disables KASAN around the memcpy from/to the kernel or IRQ stacks to avoid warnings like below: BUG: KASAN: stack-out-of-bounds in setjmp_pre_handler+0xe4/0x170 at addr ffff800935cbbbc0 Read of size 128 by task swapper/0/1 page:ffff7e0024d72ec0 count:0 mapcount:0 mapping: (null) index:0x0 flags: 0x1000000000000000() page dumped because: kasan: bad access detected CPU: 4 PID: 1 Comm: swapper/0 Not tainted 4.7.0-rc4+ #1 Hardware name: ARM Juno development board (r0) (DT) Call trace: [] dump_backtrace+0x0/0x280 [] show_stack+0x14/0x20 [] dump_stack+0xa4/0xc8 [] kasan_report_error+0x4fc/0x528 [] kasan_report+0x40/0x48 [] check_memory_region+0x144/0x1a0 [] memcpy+0x34/0x68 [] setjmp_pre_handler+0xe4/0x170 [] kprobe_breakpoint_handler+0xec/0x1d8 [] brk_handler+0x5c/0xa0 [] do_debug_exception+0xa0/0x138 Signed-off-by: Catalin Marinas

arm64: kprobes: Cleanup jprobe_return

2016-07-21T10:47:52Z

jprobe_return seems to have aged badly. Comments referring to non-existent behaviours, and a dangerous habit of messing with registers without telling the compiler. This patches applies the following remedies: - Fix the comments to describe the actual behaviour - Tidy up the asm sequence to directly assign the stack pointer without clobbering extra registers - Mark the rest of the function as unreachable() so that the compiler knows that there is no need for an epilogue - Stop making jprobe_return_break a global function (you really don't want to call that guy, and it isn't even a function). Tested with tcp_probe. Signed-off-by: Marc Zyngier Signed-off-by: Catalin Marinas