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path: root/arch/arm/kernel/kprobes-common.c
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2011-07-13ARM: kprobes: Add alu_write_pc()Jon Medhurst
This writes a new value to PC which was obtained as the result of an ARM ALU instruction. For ARMv7 and later this performs interworking. On ARM kernels we shouldn't encounter any ALU instructions trying to switch to Thumb mode so support for this isn't strictly necessary. However, the approach taken in all other instruction decoding is for us to avoid unpredictable modification of the PC for security reasons. This is usually achieved by rejecting insertion of probes on problematic instruction, but for ALU instructions we can't do this as it depends on the contents of the CPU registers at the time the probe is hit. So, as we require some form of run-time checking to trap undesirable PC modification, we may as well simulate the instructions correctly, i.e. in the way they would behave in the absence of a probe. Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
2011-07-13ARM: kprobes: Optimise emulation of LDM and STMJon Medhurst
This patch improves the performance of LDM and STM instruction emulation. This is desirable because. - jprobes and kretprobes probe the first instruction in a function and, when the frame pointer is omitted, this instruction is often a STM used to push registers onto the stack. - The STM and LDM instructions are common in the body and tail of functions. - At the same time as being a common instruction form, they also have one of the slowest and most complicated simulation routines. The approach taken to optimisation is to use emulation rather than simulation, that is, a modified form of the instruction is run with an appropriate register context. Benchmarking on an OMAP3530 shows the optimised emulation is between 2 and 3 times faster than the simulation routines. On a Kirkwood based device the relative performance was very significantly better than this. Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
2011-07-13ARM: kprobes: Add common decoding function for LDM and STMJon Medhurst
The encoding of these instructions is substantially the same for both ARM and Thumb, so we can have common decoding and simulation functions. This patch moves the simulation functions from kprobes-arm.c to kprobes-common.c. It also adds a new simulation function (simulate_ldm1_pc) for the case where we load into PC because this may need to interwork. The instruction decoding is done by a custom function (kprobe_decode_ldmstm) rather than just relying on decoding table entries because we will later be adding optimisation code. Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
2011-07-13ARM: kprobes: Add load_write_pc()Jon Medhurst
This writes a value to PC which was obtained as the result of a LDR or LDM instruction. For ARMv5T and later this must perform interworking. Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
2011-07-13ARM: kprobes: Decode 16-bit Thumb hint instructionsJon Medhurst
For hints which may have observable effects, like SEV (send event), we use kprobe_emulate_none which emulates the hint by executing the original instruction. For NOP we simulate the instruction using kprobe_simulate_nop, which does nothing. As probes execute with interrupts disabled this is also used for hints which may block for an indefinite time, like WFE (wait for event). Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
2011-07-13ARM: kprobes: Infrastructure for table driven decoding of CPU instructionsJon Medhurst
The existing ARM instruction decoding functions are a mass of if/else code. Rather than follow this pattern for Thumb instruction decoding this patch implements an infrastructure for a new table driven scheme. This has several advantages: - Reduces the kernel size by approx 2kB. (The ARM instruction decoding will eventually have -3.1kB code, +1.3kB data; with similar or better estimated savings for Thumb decoding.) - Allows programmatic checking of decoding consistency and test case coverage. - Provides more uniform source code and is therefore, arguably, clearer. For a detailed explanation of how decoding tables work see the in-source documentation in kprobes.h, and also for kprobe_decode_insn(). Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
2011-07-13ARM: kprobes: Make str_pc_offset a constant on ARMv7Jon Medhurst
The str_pc_offset value is architecturally defined on ARMv7 onwards so we can make it a compile time constant. This means on Thumb kernels the runtime checking code isn't needed, which saves us from having to fix it to work for Thumb. Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
2011-07-13ARM: kprobes: Move find_str_pc_offset into kprobes-common.cJon Medhurst
Move str_pc_offset into kprobes-common.c as it will be needed by common code later. Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
2011-07-13ARM: kprobes: Add kprobes-common.cJon Medhurst
This file will contain the instruction decoding and emulation code which is common to both ARM and Thumb instruction sets. For now, we will just move over condition_checks from kprobes-arm.c This table is also renamed to kprobe_condition_checks to avoid polluting the public namespace with a too generic name. Signed-off-by: Jon Medhurst <tixy@yxit.co.uk> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>