kernel.git/arch/arm64/include/asm/debug-monitors.h, branch linux-5.12.y

arm64: kprobes: Use BRK instead of single-step when executing instructions out-of-line

2020-11-03T14:03:38Z

Commit 36dadef23fcc ("kprobes: Init kprobes in early_initcall") enabled using kprobes from early_initcall. Unfortunately at this point the hardware debug infrastructure is not operational. The OS lock may still be locked, and the hardware watchpoints may have unknown values when kprobe enables debug monitors to single-step instructions. Rather than using hardware single-step, append a BRK instruction after the instruction to be executed out-of-line. Fixes: 36dadef23fcc ("kprobes: Init kprobes in early_initcall") Suggested-by: Will Deacon Signed-off-by: Jean-Philippe Brucker Acked-by: Masami Hiramatsu Link: https://lore.kernel.org/r/20201103134900.337243-1-jean-philippe@linaro.org Signed-off-by: Will Deacon

arm64: ptrace: Override SPSR.SS when single-stepping is enabled

2020-07-16T10:41:21Z

Luis reports that, when reverse debugging with GDB, single-step does not function as expected on arm64: | I've noticed, under very specific conditions, that a PTRACE_SINGLESTEP | request by GDB won't execute the underlying instruction. As a consequence, | the PC doesn't move, but we return a SIGTRAP just like we would for a | regular successful PTRACE_SINGLESTEP request. The underlying problem is that when the CPU register state is restored as part of a reverse step, the SPSR.SS bit is cleared and so the hardware single-step state can transition to the "active-pending" state, causing an unexpected step exception to be taken immediately if a step operation is attempted. In hindsight, we probably shouldn't have exposed SPSR.SS in the pstate accessible by the GPR regset, but it's a bit late for that now. Instead, simply prevent userspace from configuring the bit to a value which is inconsistent with the TIF_SINGLESTEP state for the task being traced. Cc: Cc: Mark Rutland Cc: Keno Fischer Link: https://lore.kernel.org/r/1eed6d69-d53d-9657-1fc9-c089be07f98c@linaro.org Reported-by: Luis Machado Tested-by: Luis Machado Signed-off-by: Will Deacon

arm64: Call debug_traps_init() from trap_init() to help early kgdb

2020-05-18T16:51:20Z

A new kgdb feature will soon land (kgdb_earlycon) that lets us run kgdb much earlier. In order for everything to work properly it's important that the break hook is setup by the time we process "kgdbwait". Right now the break hook is setup in debug_traps_init() and that's called from arch_initcall(). That's a bit too late since kgdb_earlycon really needs things to be setup by the time the system calls dbg_late_init(). We could fix this by adding call_break_hook() into early_brk64() and that works fine. However, it's a little ugly. Instead, let's just add a call to debug_traps_init() straight from trap_init(). There's already a documented dependency between trap_init() and debug_traps_init() and this makes the dependency more obvious rather than just relying on a comment. NOTE: this solution isn't early enough to let us select the "ARCH_HAS_EARLY_DEBUG" KConfig option that is introduced by the kgdb_earlycon patch series. That would only be set if we could do breakpoints when early params are parsed. This patch only enables "late early" breakpoints, AKA breakpoints when dbg_late_init() is called. It's expected that this should be fine for most people. It should also be noted that if you crash you can still end up in kgdb earlier than debug_traps_init(). Since you don't need breakpoints to debug a crash that's fine. Suggested-by: Will Deacon Signed-off-by: Douglas Anderson Acked-by: Will Deacon Cc: Catalin Marinas Cc: Will Deacon Link: https://lore.kernel.org/r/20200513160501.1.I0b5edf030cc6ebef6ab4829f8867cdaea42485d8@changeid Signed-off-by: Will Deacon

arm64: remove pointless KERNEL guards

2019-08-05T10:06:33Z

For a number of years, UAPI headers have been split from kernel-internal headers. The latter are never exposed to userspace, and always built with __KERNEL__ defined. Most headers under arch/arm64 don't have __KERNEL__ guards, but there are a few stragglers lying around. To make things more consistent, and to set a good example going forward, let's remove these redundant __KERNEL__ guards. In a couple of cases, a trailing #endif lacked a comment describing its corresponding #if or #ifdef, so these are fixes up at the same time. Guards in auto-generated crypto code are left as-is, as these guards are generated by scripting imported from the upstream openssl project scripts. Guards in UAPI headers are left as-is, as these can be included by userspace or the kernel. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland Cc: Ard Biesheuvel Cc: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234

2019-06-19T15:09:07Z

Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details you should have received a copy of the gnu general public license along with this program if not see http www gnu org licenses extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 503 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Alexios Zavras Reviewed-by: Allison Randal Reviewed-by: Enrico Weigelt Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190602204653.811534538@linutronix.de Signed-off-by: Greg Kroah-Hartman

arm64: probes: Move magic BRK values into brk-imm.h

2019-04-09T10:21:13Z

kprobes and uprobes reserve some BRK immediates for installing their probes. Define these along with the other reservations in brk-imm.h and rename the ESR definitions to be consistent with the others that we already have. Reviewed-by: Mark Rutland Signed-off-by: Will Deacon

arm64: debug: Separate debug hooks based on target exception level

2019-04-09T10:21:13Z

Mixing kernel and user debug hooks together is highly error-prone as it relies on all of the hooks to figure out whether the exception came from kernel or user, and then to act accordingly. Make our debug hook code a little more robust by maintaining separate hook lists for user and kernel, with separate registration functions to force callers to be explicit about the exception levels that they care about. Reviewed-by: Mark Rutland Signed-off-by: Will Deacon

arm64: Add uprobe support

2016-11-07T18:15:21Z

This patch adds support for uprobe on ARM64 architecture. Unit tests for following have been done so far and they have been found working 1. Step-able instructions, like sub, ldr, add etc. 2. Simulation-able like ret, cbnz, cbz etc. 3. uretprobe 4. Reject-able instructions like sev, wfe etc. 5. trapped and abort xol path 6. probe at unaligned user address. 7. longjump test cases Currently it does not support aarch32 instruction probing. Signed-off-by: Pratyush Anand Signed-off-by: Catalin Marinas

arm64: kgdb: handle read-only text / modules

2016-09-23T10:25:01Z

Handle read-only cases when CONFIG_DEBUG_RODATA (4.0) or CONFIG_DEBUG_SET_MODULE_RONX (3.18) are enabled by using aarch64_insn_write() instead of probe_kernel_write() as introduced by commit 2f896d586610 ("arm64: use fixmap for text patching") in 4.0. Fixes: 11d91a770f1f ("arm64: Add CONFIG_DEBUG_SET_MODULE_RONX support") Signed-off-by: AKASHI Takahiro Reviewed-by: Mark Rutland Cc: Will Deacon Cc: Jason Wessel Signed-off-by: Catalin Marinas

arm64: Kprobes with single stepping support

2016-07-19T14:03:20Z

Add support for basic kernel probes(kprobes) and jump probes (jprobes) for ARM64. Kprobes utilizes software breakpoint and single step debug exceptions supported on ARM v8. A software breakpoint is placed at the probe address to trap the kernel execution into the kprobe handler. ARM v8 supports enabling single stepping before the break exception return (ERET), with next PC in exception return address (ELR_EL1). The kprobe handler prepares an executable memory slot for out-of-line execution with a copy of the original instruction being probed, and enables single stepping. The PC is set to the out-of-line slot address before the ERET. With this scheme, the instruction is executed with the exact same register context except for the PC (and DAIF) registers. Debug mask (PSTATE.D) is enabled only when single stepping a recursive kprobe, e.g.: during kprobes reenter so that probed instruction can be single stepped within the kprobe handler -exception- context. The recursion depth of kprobe is always 2, i.e. upon probe re-entry, any further re-entry is prevented by not calling handlers and the case counted as a missed kprobe). Single stepping from the x-o-l slot has a drawback for PC-relative accesses like branching and symbolic literals access as the offset from the new PC (slot address) may not be ensured to fit in the immediate value of the opcode. Such instructions need simulation, so reject probing them. Instructions generating exceptions or cpu mode change are rejected for probing. Exclusive load/store instructions are rejected too. Additionally, the code is checked to see if it is inside an exclusive load/store sequence (code from Pratyush). System instructions are mostly enabled for stepping, except MSR/MRS accesses to "DAIF" flags in PSTATE, which are not safe for probing. This also changes arch/arm64/include/asm/ptrace.h to use include/asm-generic/ptrace.h. Thanks to Steve Capper and Pratyush Anand for several suggested Changes. Signed-off-by: Sandeepa Prabhu Signed-off-by: David A. Long Signed-off-by: Pratyush Anand Acked-by: Masami Hiramatsu Signed-off-by: Catalin Marinas