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 | 75 +++++++++++++++++++++++++++++++++++++++
2 files changed, 87 insertions(+)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 98a3a1a..5bfaa20 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -205,6 +205,18 @@ 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 28a6367..0be9ef3 100644
--- a/arch/arm/kernel/runtime-patch.c
+++ b/arch/arm/kernel/runtime-patch.c
@@ -168,6 +168,78 @@ static int apply_patch_imm8(const struct patch_info *p)
return 0;
}
+#ifdef CONFIG_ARM_RUNTIME_PATCH_TEST
+
+struct patch_test_imm8 {
+ u16 imm;
+ u16 shift;
+ u32 insn;
+};
+
+static void __init __used __naked __patch_test_code_imm8(void)
+{
+ __asm__ __volatile__ (
+
+ /* a single test case */
+ " .macro test_one, imm, sft\n"
+ " .hword \\imm\n"
+ " .hword \\sft\n"
+ " add r1, r2, #(\\imm << \\sft)\n"
+ " .endm\n"
+
+ /* a sequence of tests at 'inc' increments of shift */
+ " .macro test_seq, imm, sft, max, inc\n"
+ " test_one \\imm, \\sft\n"
+ " .if \\sft < \\max\n"
+ " test_seq \\imm, (\\sft + \\inc), \\max, \\inc\n"
+ " .endif\n"
+ " .endm\n"
+
+ /* an empty record to mark the end */
+ " .macro test_end\n"
+ " .hword 0, 0\n"
+ " .word 0\n"
+ " .endm\n"
+
+ /* finally generate the test sequences */
+ " test_seq 0x41, 0, 24, 1\n"
+ " test_seq 0x81, 0, 24, 2\n"
+ " test_end\n"
+ : : : "r1", "r2", "cc");
+}
+
+static void __init test_patch_imm8(void)
+{
+ u32 test_code_addr = (u32)(&__patch_test_code_imm8);
+ struct patch_test_imm8 *test = (void *)(test_code_addr & ~1);
+ u32 ninsn, insn, patched_insn;
+ int i, err;
+
+ insn = test[0].insn;
+ for (i = 0; test[i].insn; i++) {
+ err = do_patch_imm8(insn, test[i].imm << test[i].shift, &ninsn);
+ __patch_text(&patched_insn, ninsn);
+
+ if (err) {
+ pr_err("rtpatch imm8: failed at imm %x, shift %d\n",
+ test[i].imm, test[i].shift);
+ } else if (patched_insn != test[i].insn) {
+ pr_err("rtpatch imm8: failed, need %x got %x\n",
+ test[i].insn, patched_insn);
+ } else {
+ pr_debug("rtpatch imm8: imm %x, shift %d, %x -> %x\n",
+ test[i].imm, test[i].shift, insn,
+ patched_insn);
+ }
+ }
+}
+
+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);
@@ -189,5 +261,8 @@ 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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