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Sender: Emil Renner Berthing <emil.renner.berthing@gmail.com>
From:   Emil Renner Berthing <kernel@esmil.dk>
To:     linux-riscv@lists.infradead.org
Cc:     Emil Renner Berthing <kernel@esmil.dk>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Peter Zijlstra <peterz@infradead.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Jason Baron <jbaron@akamai.com>,
        Ard Biesheuvel <ardb@kernel.org>,
        Jisheng Zhang <jszhang@kernel.org>,
        Alexandre Ghiti <alex@ghiti.fr>, linux-kernel@vger.kernel.org
Subject: [PATCH v3 8/8] riscv: Use asm/insn.h for dynamic ftrace
Date:   Thu, 24 Feb 2022 16:24:56 +0100
Message-Id: <20220224152456.493365-9-kernel@esmil.dk>
In-Reply-To: <20220224152456.493365-1-kernel@esmil.dk>
References: <20220224152456.493365-1-kernel@esmil.dk>
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This converts kernel/ftrace.c to use asm/insn.h to generate the
instructions for dynamic ftrace. This also converts the make_call macro
into a regular static function.

Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
---
 arch/riscv/kernel/ftrace.c | 69 ++++++++++++--------------------------
 1 file changed, 22 insertions(+), 47 deletions(-)

diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index 2cc15dc45ce0..7dd3aafa17aa 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -9,6 +9,7 @@
 #include <linux/uaccess.h>
 #include <linux/memory.h>
 #include <asm/cacheflush.h>
+#include <asm/insn.h>
 #include <asm/patch.h>
 
 #ifdef CONFIG_DYNAMIC_FTRACE
@@ -21,31 +22,13 @@
  * Dynamic ftrace generates probes to call sites, so we must deal with
  * both auipc and jalr at the same time.
  */
+static void make_call(unsigned long caller, unsigned long callee, unsigned int call[2])
+{
+	u32 offset = callee - caller;
 
-#define JALR_SIGN_MASK		(0x00000800)
-#define JALR_OFFSET_MASK	(0x00000fff)
-#define AUIPC_OFFSET_MASK	(0xfffff000)
-#define AUIPC_PAD		(0x00001000)
-#define JALR_SHIFT		20
-#define JALR_BASIC		(0x000080e7)
-#define AUIPC_BASIC		(0x00000097)
-#define NOP4			(0x00000013)
-
-#define make_call(caller, callee, call)					\
-do {									\
-	call[0] = to_auipc_insn((unsigned int)((unsigned long)callee -	\
-				(unsigned long)caller));		\
-	call[1] = to_jalr_insn((unsigned int)((unsigned long)callee -	\
-			       (unsigned long)caller));			\
-} while (0)
-
-#define to_jalr_insn(offset)						\
-	(((offset & JALR_OFFSET_MASK) << JALR_SHIFT) | JALR_BASIC)
-
-#define to_auipc_insn(offset)						\
-	((offset & JALR_SIGN_MASK) ?					\
-	(((offset & AUIPC_OFFSET_MASK) + AUIPC_PAD) | AUIPC_BASIC) :	\
-	((offset & AUIPC_OFFSET_MASK) | AUIPC_BASIC))
+	call[0] = RISCV_INSN_AUIPC | RISCV_INSN_RD_RA | riscv_insn_u_imm(offset + 0x800);
+	call[1] = RISCV_INSN_JALR  | RISCV_INSN_RD_RA | RISCV_INSN_RS1_RA | riscv_insn_i_imm(offset);
+}
 
 int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
 {
@@ -63,7 +46,7 @@ static int ftrace_check_current_call(unsigned long hook_pos,
 				     unsigned int *expected)
 {
 	unsigned int replaced[2];
-	unsigned int nops[2] = {NOP4, NOP4};
+	unsigned int nops[2] = { RISCV_INSN_NOP, RISCV_INSN_NOP };
 
 	/* we expect nops at the hook position */
 	if (!expected)
@@ -95,7 +78,7 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
 				bool enable)
 {
 	unsigned int call[2];
-	unsigned int nops[2] = {NOP4, NOP4};
+	unsigned int nops[2] = { RISCV_INSN_NOP, RISCV_INSN_NOP };
 
 	make_call(hook_pos, target, call);
 
@@ -108,39 +91,31 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
 }
 
 /*
- * Put 5 instructions with 16 bytes at the front of function within
+ * Put 4 instructions with 16 bytes at the front of function within
  * patchable function entry nops' area.
  *
  * 0: REG_S  ra, -SZREG(sp)
- * 1: auipc  ra, 0x?
- * 2: jalr   -?(ra)
+ * 1: auipc  ra, ?
+ * 2: jalr   ra, ra, ?
  * 3: REG_L  ra, -SZREG(sp)
- *
- * So the opcodes is:
- * 0: 0xfe113c23 (sd)/0xfe112e23 (sw)
- * 1: 0x???????? -> auipc
- * 2: 0x???????? -> jalr
- * 3: 0xff813083 (ld)/0xffc12083 (lw)
  */
-#if __riscv_xlen == 64
-#define INSN0	0xfe113c23
-#define INSN3	0xff813083
-#elif __riscv_xlen == 32
-#define INSN0	0xfe112e23
-#define INSN3	0xffc12083
-#endif
-
 #define FUNC_ENTRY_SIZE	16
 #define FUNC_ENTRY_JMP	4
 
 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
-	unsigned int call[4] = {INSN0, 0, 0, INSN3};
+	unsigned int call[4] = {
+		RISCV_INSN_REG_S | RISCV_INSN_RS2_RA | RISCV_INSN_RS1_SP |
+			riscv_insn_s_imm(-RISCV_INSN_SZREG),
+		0,
+		0,
+		RISCV_INSN_REG_L | RISCV_INSN_RD_RA  | RISCV_INSN_RS1_SP |
+			riscv_insn_i_imm(-RISCV_INSN_SZREG),
+	};
 	unsigned long target = addr;
 	unsigned long caller = rec->ip + FUNC_ENTRY_JMP;
 
-	call[1] = to_auipc_insn((unsigned int)(target - caller));
-	call[2] = to_jalr_insn((unsigned int)(target - caller));
+	make_call(caller, target, &call[1]);
 
 	if (patch_text_nosync((void *)rec->ip, call, FUNC_ENTRY_SIZE))
 		return -EPERM;
@@ -151,7 +126,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 		    unsigned long addr)
 {
-	unsigned int nops[4] = {NOP4, NOP4, NOP4, NOP4};
+	unsigned int nops[4] = { RISCV_INSN_NOP, RISCV_INSN_NOP, RISCV_INSN_NOP, RISCV_INSN_NOP };
 
 	if (patch_text_nosync((void *)rec->ip, nops, FUNC_ENTRY_SIZE))
 		return -EPERM;
-- 
2.35.1