On Fri, 10 Aug 2012, Cyril Chemparathy wrote:
> This patch adds basic sanity tests to ensure that the instruction patching
> results in valid instruction encodings. This is done by verifying the output
> of the patch process against a vector of assembler generated instructions at
> init time.
>
> Signed-off-by: Cyril Chemparathy <cy...@ti.com>
> ---
> arch/arm/Kconfig | 12 ++++++++++++
> arch/arm/kernel/runtime-patch.c | 41
> +++++++++++++++++++++++++++++++++++++++
> 2 files changed, 53 insertions(+)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index d0a04ad..7e552dc 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -211,6 +211,18 @@ config ARM_PATCH_PHYS_VIRT
> this feature (eg, building a kernel for a single machine) and
> you need to shrink the kernel to the minimal size.
>
> +config ARM_RUNTIME_PATCH_TEST
> + bool "Self test runtime patching mechanism" if ARM_RUNTIME_PATCH
> + default y
> + help
> + Select this to enable init time self checking for the runtime kernel
> + patching mechanism. This enables an ISA specific set of tests that
> + ensure that the instructions generated by the patch process are
> + consistent with those generated by the assembler at compile time.
> +
> + Only disable this option if you need to shrink the kernel to the
> + minimal size.
> +
> config NEED_MACH_IO_H
> bool
> help
> diff --git a/arch/arm/kernel/runtime-patch.c b/arch/arm/kernel/runtime-patch.c
> index fd37a2b..c471d8c 100644
> --- a/arch/arm/kernel/runtime-patch.c
> +++ b/arch/arm/kernel/runtime-patch.c
> @@ -163,6 +163,44 @@ static int apply_patch_imm8(const struct patch_info *p)
> return 0;
> }
>
> +#ifdef CONFIG_ARM_RUNTIME_PATCH_TEST
> +static void __init __used __naked __patch_test_code_imm8(void)
> +{
> + __asm__ __volatile__ (
> + " .irp shift1, 0, 6, 12, 18\n"
> + " .irp shift2, 0, 1, 2, 3, 4, 5\n"
> + " add r1, r2, #(0x41 << (\\shift1 + \\shift2))\n"
> + " .endr\n"
> + " .endr\n"
Maybe adding a "add r1, r2 #0x81 << 24" here might be a good thing since
this is the most used case but missing from the above.
> + " .word 0\n"
> + : : :
> + );
> +}
> +
> +static void __init test_patch_imm8(void)
> +{
> + u32 test_code_addr = (u32)(&__patch_test_code_imm8);
> + u32 *test_code = (u32 *)(test_code_addr & ~0x3);
Why this masking? With Thumb2 you may find functions starting at
halfword aligned addresses. Only the LSB (indicating thumb mode) should
be masked out.
> + int i, ret;
> + u32 ninsn, insn;
> +
> + insn = test_code[0];
> + for (i = 0; test_code[i]; i++) {
> + ret = do_patch_imm8(insn, 0x41 << i, &ninsn);
> + if (ret < 0)
> + pr_err("runtime patch (imm8): failed at shift %d\n", i);
> + else if (ninsn != test_code[i])
> + pr_err("runtime patch (imm8): failed, need %x got %x\n",
> + test_code[i], ninsn);
> + }
> +}
> +
> +static void __init runtime_patch_test(void)
> +{
> + test_patch_imm8();
> +}
> +#endif
> +
> int runtime_patch(const void *table, unsigned size)
> {
> const struct patch_info *p = table, *end = (table + size);
> @@ -185,5 +223,8 @@ void __init runtime_patch_kernel(void)
> const void *start = &__runtime_patch_table_begin;
> const void *end = &__runtime_patch_table_end;
>
> +#ifdef CONFIG_ARM_RUNTIME_PATCH_TEST
> + runtime_patch_test();
> +#endif
> BUG_ON(runtime_patch(start, end - start));
> }
> --
> 1.7.9.5
>
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