The core kprobes code uses kprobe_opcode_t for the in-memory representation of an instruction, using 'kprobe_opcode_t *' for XOL slots. As arm64 instructions are always little-endian 32-bit values, kprobes_opcode_t should be __le32, but at the moment kprobe_opcode_t is typedef'd to u32.
Today there is no functional issue as we convert values via cpu_to_le32() and le32_to_cpu() where necessary, but these conversions are inconsistent with the types used, causing sparse warnings:
| CHECK arch/arm64/kernel/probes/kprobes.c | arch/arm64/kernel/probes/kprobes.c:102:21: warning: cast to restricted __le32 | CHECK arch/arm64/kernel/probes/decode-insn.c | arch/arm64/kernel/probes/decode-insn.c:122:46: warning: cast to restricted __le32 | arch/arm64/kernel/probes/decode-insn.c:124:50: warning: cast to restricted __le32 | arch/arm64/kernel/probes/decode-insn.c:136:31: warning: cast to restricted __le32
Improve this by making kprobes_opcode_t a typedef for __le32 and consistently using this for pointers to executable instructions. With this change we can rely on the type system to tell us where conversions are necessary.
Since kprobe::opcode is changed from u32 to __le32, the existing le32_to_cpu() converion moves from the point this is initialized (in arch_prepare_kprobe()) to the points this is consumed when passed to a handler or text patching function. As kprobe::opcode isn't altered or consumed elsewhere, this shouldn't result in a functional change.
Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will@kernel.org --- arch/arm64/include/asm/probes.h | 4 ++-- arch/arm64/kernel/probes/decode-insn.c | 2 +- arch/arm64/kernel/probes/kprobes.c | 9 +++++---- 3 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/arch/arm64/include/asm/probes.h b/arch/arm64/include/asm/probes.h index 4aa54322794da..11e809733b7d9 100644 --- a/arch/arm64/include/asm/probes.h +++ b/arch/arm64/include/asm/probes.h @@ -16,10 +16,10 @@ struct arch_probe_insn { probes_handler_t *handler; }; #ifdef CONFIG_KPROBES -typedef u32 kprobe_opcode_t; +typedef __le32 kprobe_opcode_t; struct arch_specific_insn { struct arch_probe_insn api; - probe_opcode_t *xol_insn; + kprobe_opcode_t *xol_insn; /* restore address after step xol */ unsigned long xol_restore; }; diff --git a/arch/arm64/kernel/probes/decode-insn.c b/arch/arm64/kernel/probes/decode-insn.c index 3496d6169e59b..147d6ddf3a4c9 100644 --- a/arch/arm64/kernel/probes/decode-insn.c +++ b/arch/arm64/kernel/probes/decode-insn.c @@ -134,7 +134,7 @@ arm_kprobe_decode_insn(kprobe_opcode_t *addr, struct arch_specific_insn *asi) { enum probe_insn decoded; probe_opcode_t insn = le32_to_cpu(*addr); - probe_opcode_t *scan_end = NULL; + kprobe_opcode_t *scan_end = NULL; unsigned long size = 0, offset = 0; struct arch_probe_insn *api = &asi->api;
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index 222419a41a400..48d88e07611d4 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -64,7 +64,7 @@ static void __kprobes arch_prepare_ss_slot(struct kprobe *p) * the BRK exception handler, so it is unnecessary to generate * Contex-Synchronization-Event via ISB again. */ - aarch64_insn_patch_text_nosync(addr, p->opcode); + aarch64_insn_patch_text_nosync(addr, le32_to_cpu(p->opcode)); aarch64_insn_patch_text_nosync(addr + 1, BRK64_OPCODE_KPROBES_SS);
/* @@ -85,7 +85,7 @@ static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs) struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
if (p->ainsn.api.handler) - p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs); + p->ainsn.api.handler(le32_to_cpu(p->opcode), (long)p->addr, regs);
/* single step simulated, now go for post processing */ post_kprobe_handler(p, kcb, regs); @@ -99,7 +99,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) return -EINVAL;
/* copy instruction */ - p->opcode = le32_to_cpu(*p->addr); + p->opcode = *p->addr;
if (search_exception_tables(probe_addr)) return -EINVAL; @@ -142,8 +142,9 @@ void __kprobes arch_arm_kprobe(struct kprobe *p) void __kprobes arch_disarm_kprobe(struct kprobe *p) { void *addr = p->addr; + u32 insn = le32_to_cpu(p->opcode);
- aarch64_insn_patch_text(&addr, &p->opcode, 1); + aarch64_insn_patch_text(&addr, &insn, 1); }
void __kprobes arch_remove_kprobe(struct kprobe *p)