[RFC,13/15] riscv: probes: sort out endian-ness

Commit Message

Ben Dooks Dec. 20, 2024, 3:57 p.m. UTC

Updated {k,u}probe code to deal with big endian mode where
the instruction stream is always in little endian.

Signed-off-by: Ben Dooks <[e-mail]>
---
 arch/riscv/kernel/probes/decode-insn.c |  2 +-
 arch/riscv/kernel/probes/decode-insn.h |  5 +++++
 arch/riscv/kernel/probes/kprobes.c     | 30 ++++++++++++++++----------
 arch/riscv/kernel/probes/uprobes.c     | 10 ++++-----
 4 files changed, 30 insertions(+), 17 deletions(-)

Patch

diff --git a/arch/riscv/kernel/probes/decode-insn.c b/arch/riscv/kernel/probes/decode-insn.c
index 65d9590bfb9f..5f30c10f7d8d 100644
--- a/arch/riscv/kernel/probes/decode-insn.c
+++ b/arch/riscv/kernel/probes/decode-insn.c
@@ -16,7 +16,7 @@ 
 enum probe_insn __kprobes
 riscv_probe_decode_insn(probe_opcode_t *addr, struct arch_probe_insn *api)
 {
-	probe_opcode_t insn = *addr;
+	probe_opcode_t insn = le32_to_cpu(*addr);
 
 	/*
 	 * Reject instructions list:
diff --git a/arch/riscv/kernel/probes/decode-insn.h b/arch/riscv/kernel/probes/decode-insn.h
index 42269a7d676d..0515deb204b5 100644
--- a/arch/riscv/kernel/probes/decode-insn.h
+++ b/arch/riscv/kernel/probes/decode-insn.h
@@ -15,4 +15,9 @@  enum probe_insn {
 enum probe_insn __kprobes
 riscv_probe_decode_insn(probe_opcode_t *addr, struct arch_probe_insn *asi);
 
+static inline int read_insn_length(void *ptr)
+{
+	return GET_INSN_LENGTH(le16_to_cpu(*(__le16 *)ptr));
+}
+
 #endif /* _RISCV_KERNEL_KPROBES_DECODE_INSN_H */
diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
index 474a65213657..aba684938284 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c
@@ -24,13 +24,13 @@  post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *);
 
 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
 {
-	size_t len = GET_INSN_LENGTH(p->opcode);
-	u32 insn = __BUG_INSN_32;
+	size_t len = read_insn_length(&p->opcode);
+	u32 insn = cpu_to_le32(__BUG_INSN_32);
 
 	p->ainsn.api.restore = (unsigned long)p->addr + len;
 
 	patch_text_nosync(p->ainsn.api.insn, &p->opcode, len);
-	patch_text_nosync(p->ainsn.api.insn + len, &insn, GET_INSN_LENGTH(insn));
+	patch_text_nosync((void *)p->ainsn.api.insn + len, &insn, GET_INSN_LENGTH(__BUG_INSN_32));
 }
 
 static void __kprobes arch_prepare_simulate(struct kprobe *p)
@@ -58,7 +58,7 @@  static bool __kprobes arch_check_kprobe(struct kprobe *p)
 		if (tmp == addr)
 			return true;
 
-		tmp += GET_INSN_LENGTH(*(u16 *)tmp);
+		tmp += read_insn_length((u16 *)tmp);
 	}
 
 	return false;
@@ -75,9 +75,9 @@  int __kprobes arch_prepare_kprobe(struct kprobe *p)
 		return -EILSEQ;
 
 	/* copy instruction */
-	p->opcode = (kprobe_opcode_t)(*insn++);
-	if (GET_INSN_LENGTH(p->opcode) == 4)
-		p->opcode |= (kprobe_opcode_t)(*insn) << 16;
+	*((u16 *)&p->opcode) = (*insn++);
+	if (read_insn_length(&p->opcode) == 4)
+		p->opcode = (kprobe_opcode_t)(*(u32 *)p->addr);
 
 	/* decode instruction */
 	switch (riscv_probe_decode_insn(p->addr, &p->ainsn.api)) {
@@ -107,16 +107,24 @@  int __kprobes arch_prepare_kprobe(struct kprobe *p)
 /* install breakpoint in text */
 void __kprobes arch_arm_kprobe(struct kprobe *p)
 {
-	size_t len = GET_INSN_LENGTH(p->opcode);
-	u32 insn = len == 4 ? __BUG_INSN_32 : __BUG_INSN_16;
+	size_t len = read_insn_length(&p->opcode);
+	u32 insn;
+
+	if (len == 4)
+		insn = cpu_to_le32(__BUG_INSN_32);
+	else {
+		insn = cpu_to_le16(__BUG_INSN_16);
+		insn |= cpu_to_le16(__BUG_INSN_16) << 16;
+	}
 
+	pr_info("%s: patching %px (%d bytes)\n", __func__, p->addr, (int)len);
 	patch_text(p->addr, &insn, len);
 }
 
 /* remove breakpoint from text */
 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 {
-	size_t len = GET_INSN_LENGTH(p->opcode);
+	size_t len = read_insn_length(&p->opcode);
 
 	patch_text(p->addr, &p->opcode, len);
 }
@@ -336,7 +344,7 @@  kprobe_single_step_handler(struct pt_regs *regs)
 	struct kprobe *cur = kprobe_running();
 
 	if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) &&
-	    ((unsigned long)&cur->ainsn.api.insn[0] + GET_INSN_LENGTH(cur->opcode) == addr)) {
+	    ((unsigned long)&cur->ainsn.api.insn[0] + read_insn_length(&cur->opcode) == addr)) {
 		kprobes_restore_local_irqflag(kcb, regs);
 		post_kprobe_handler(cur, kcb, regs);
 		return true;
diff --git a/arch/riscv/kernel/probes/uprobes.c b/arch/riscv/kernel/probes/uprobes.c
index 4b3dc8beaf77..e31c1dd337d5 100644
--- a/arch/riscv/kernel/probes/uprobes.c
+++ b/arch/riscv/kernel/probes/uprobes.c
@@ -12,9 +12,9 @@ 
 bool is_swbp_insn(uprobe_opcode_t *insn)
 {
 #ifdef CONFIG_RISCV_ISA_C
-	return (*insn & 0xffff) == UPROBE_SWBP_INSN;
+	return (*(u16 *)insn) == cpu_to_le16(UPROBE_SWBP_INSN);
 #else
-	return *insn == UPROBE_SWBP_INSN;
+	return *insn == cpu_to_le32(UPROBE_SWBP_INSN);
 #endif
 }
 
@@ -35,7 +35,7 @@  int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
 
 	opcode = *(probe_opcode_t *)(&auprobe->insn[0]);
 
-	auprobe->insn_size = GET_INSN_LENGTH(opcode);
+	auprobe->insn_size = GET_INSN_LENGTH(le32_to_cpu(opcode));
 
 	switch (riscv_probe_decode_insn(&opcode, &auprobe->api)) {
 	case INSN_REJECTED:
@@ -172,8 +172,8 @@  void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
 
 	/* Add ebreak behind opcode to simulate singlestep */
 	if (vaddr) {
-		dst += GET_INSN_LENGTH(*(probe_opcode_t *)src);
-		*(uprobe_opcode_t *)dst = __BUG_INSN_32;
+		dst += read_insn_length(src);
+		*(uprobe_opcode_t *)dst = cpu_to_le32(__BUG_INSN_32);
 	}
 
 	kunmap_atomic(kaddr);