On Sun, Oct 14, 2012 at 09:23:13PM +0200, Rabin Vincent wrote:
> Add basic uprobes support for ARM.
>
> perf probe --exec and SystemTap's userspace probing work. The ARM
> kprobes test code has also been run in a userspace harness to test the
> uprobe instruction decoding.
>
> Caveats:
>
> - Thumb is not supported
> - XOL abort/trap handling is not implemented
[...]
> diff --git a/arch/arm/kernel/uprobes.c b/arch/arm/kernel/uprobes.c
> new file mode 100644
> index 0000000..f25a4af
> --- /dev/null
> +++ b/arch/arm/kernel/uprobes.c
[...]
> +bool is_swbp_insn(uprobe_opcode_t *insn)
> +{
> + return (__mem_to_opcode_arm(*insn) & 0x0fffffff) == UPROBE_SWBP_INSN;
You should take care not to match any instruction whose top bits are
0xF0000000. That could be some completely different instruction.
[...]
> +static int uprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
> +{
> + unsigned long flags;
> +
> + local_irq_save(flags);
> + if ((instr & 0x0fffffff) == UPROBE_SWBP_INSN)
Is the check unnecessary here? I think the same comparison will
happen as a result of evaluating the associated undef_hook.
However, as above you must still check for and reject cases where
(instr & 0xF0000000) == 0xF0000000.
[...]
> +static struct undef_hook uprobes_arm_break_hook = {
> + .instr_mask = 0x0fffffff,
> + .instr_val = UPROBE_SWBP_INSN,
> + .cpsr_mask = MODE_MASK,
> + .cpsr_val = USR_MODE,
> + .fn = uprobe_trap_handler,
> +};
> +
> +static struct undef_hook uprobes_arm_ss_hook = {
> + .instr_mask = 0x0fffffff,
> + .instr_val = UPROBE_SS_INSN,
> + .cpsr_mask = MODE_MASK,
> + .cpsr_val = USR_MODE,
> + .fn = uprobe_trap_handler,
> +};
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