[PATCH v2 2/3] riscv: traps: make insn fetch common in unknown instruction

[Ben Dooks]

Add the trapped instruction (insn) as the second argument to
riscv_v_first_use_handler() from the trap handler so when we
add more handlers we can do the fetch of the instruction just
once.

Signed-off-by: Ben Dooks <ben.dooks at codethink.co.uk>
---
- fixed wording of patch from rfc
v2:
  - fixed todo by going to illegal instruction error if get_user fails
  - added pointer print for failed read
  - fixed issues with rebasing onto main branch
---
 arch/riscv/include/asm/vector.h |  4 ++--
 arch/riscv/kernel/traps.c       | 14 +++++++++++++-
 arch/riscv/kernel/vector.c      | 11 +----------
 3 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h
index c7c023afbacd..9ec2473c1b73 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -22,7 +22,7 @@
 extern unsigned long riscv_v_vsize;
 int riscv_v_setup_vsize(void);
 bool insn_is_vector(u32 insn_buf);
-bool riscv_v_first_use_handler(struct pt_regs *regs);
+bool riscv_v_first_use_handler(struct pt_regs *regs, u32 insn);
 void kernel_vector_begin(void);
 void kernel_vector_end(void);
 void get_cpu_vector_context(void);
@@ -270,7 +270,7 @@ struct pt_regs;
 static inline int riscv_v_setup_vsize(void) { return -EOPNOTSUPP; }
 static __always_inline bool has_vector(void) { return false; }
 static __always_inline bool insn_is_vector(u32 insn_buf) { return false; }
-static inline bool riscv_v_first_use_handler(struct pt_regs *regs) { return false; }
+static inline bool riscv_v_first_use_handler(struct pt_regs *regs, u32 insn) { return false; }
 static inline bool riscv_v_vstate_query(struct pt_regs *regs) { return false; }
 static inline bool riscv_v_vstate_ctrl_user_allowed(void) { return false; }
 #define riscv_v_vsize (0)
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 51ebfd23e007..9662138ba45c 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -172,11 +172,23 @@ asmlinkage __visible __trap_section void do_trap_insn_illegal(struct pt_regs *re
 	bool handled;
 
 	if (user_mode(regs)) {
+		u32 __user *epc = (u32 __user *)regs->epc;
+		u32 insn = (u32)regs->badaddr;
+
 		irqentry_enter_from_user_mode(regs);
 
 		local_irq_enable();
 
-		handled = riscv_v_first_use_handler(regs);
+		if (!insn) {
+			if (__get_user(insn, epc)) {
+				printk_ratelimited(KERN_ERR "traps: failed to read instruction at user %px\n", epc);
+				handled = false;
+				insn = 0;
+			}
+		}
+
+		if (insn)
+			handled = riscv_v_first_use_handler(regs, insn);
 
 		local_irq_disable();
 
diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
index 821818886fab..08164a9121fe 100644
--- a/arch/riscv/kernel/vector.c
+++ b/arch/riscv/kernel/vector.c
@@ -168,11 +168,8 @@ bool riscv_v_vstate_ctrl_user_allowed(void)
 }
 EXPORT_SYMBOL_GPL(riscv_v_vstate_ctrl_user_allowed);
 
-bool riscv_v_first_use_handler(struct pt_regs *regs)
+bool riscv_v_first_use_handler(struct pt_regs *regs, u32 insn)
 {
-	u32 __user *epc = (u32 __user *)regs->epc;
-	u32 insn = (u32)regs->badaddr;
-
 	if (!has_vector())
 		return false;
 
@@ -184,12 +181,6 @@ bool riscv_v_first_use_handler(struct pt_regs *regs)
 	if (riscv_v_vstate_query(regs))
 		return false;
 
-	/* Get the instruction */
-	if (!insn) {
-		if (__get_user(insn, epc))
-			return false;
-	}
-
 	/* Filter out non-V instructions */
 	if (!insn_is_vector(insn))
 		return false;
-- 
2.37.2.352.g3c44437643