Merge patch series "riscv: Various text patching improvements"

Samuel Holland <samuel.holland@sifive.com> says:

Here are a few changes to minimize calls to stop_machine() and
flush_icache_*() in the various text patching functions, as well as
to simplify the code.

* b4-shazam-merge:
  riscv: Remove extra variable in patch_text_nosync()
  riscv: Use offset_in_page() in text patching functions
  riscv: Pass patch_text() the length in bytes
  riscv: Simplify text patching loops
  riscv: kprobes: Use patch_text_nosync() for insn slots
  riscv: jump_label: Simplify assembly syntax
  riscv: jump_label: Batch icache maintenance

Link: https://lore.kernel.org/r/20240327160520.791322-1-samuel.holland@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: palmer-dabbelt

arch/riscv/include/asm/jump_label.h

@@ -12,6 +12,8 @@
 #include <linux/types.h>
 #include <asm/asm.h>
 
+#define HAVE_JUMP_LABEL_BATCH
+
 #define JUMP_LABEL_NOP_SIZE 4
 
 static __always_inline bool arch_static_branch(struct static_key * const key,
@@ -44,7 +46,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
 		"	.option push				\n\t"
 		"	.option norelax				\n\t"
 		"	.option norvc				\n\t"
-		"1:	jal		zero, %l[label]		\n\t"
+		"1:	j		%l[label]		\n\t"
 		"	.option pop				\n\t"
 		"	.pushsection	__jump_table, \"aw\"	\n\t"
 		"	.align		" RISCV_LGPTR "		\n\t"

arch/riscv/include/asm/patch.h

@@ -9,7 +9,7 @@
 int patch_insn_write(void *addr, const void *insn, size_t len);
 int patch_text_nosync(void *addr, const void *insns, size_t len);
 int patch_text_set_nosync(void *addr, u8 c, size_t len);
-int patch_text(void *addr, u32 *insns, int ninsns);
+int patch_text(void *addr, u32 *insns, size_t len);
 
 extern int riscv_patch_in_stop_machine;
 

arch/riscv/kernel/jump_label.c

@@ -9,13 +9,14 @@
 #include <linux/memory.h>
 #include <linux/mutex.h>
 #include <asm/bug.h>
+#include <asm/cacheflush.h>
 #include <asm/patch.h>
 
 #define RISCV_INSN_NOP 0x00000013U
 #define RISCV_INSN_JAL 0x0000006fU
 
-void arch_jump_label_transform(struct jump_entry *entry,
-			       enum jump_label_type type)
+bool arch_jump_label_transform_queue(struct jump_entry *entry,
+				     enum jump_label_type type)
 {
 	void *addr = (void *)jump_entry_code(entry);
 	u32 insn;
@@ -24,7 +25,7 @@ void arch_jump_label_transform(struct jump_entry *entry,
 		long offset = jump_entry_target(entry) - jump_entry_code(entry);
 
 		if (WARN_ON(offset & 1 || offset < -524288 || offset >= 524288))
-			return;
+			return true;
 
 		insn = RISCV_INSN_JAL |
 			(((u32)offset & GENMASK(19, 12)) << (12 - 12)) |
@@ -36,6 +37,13 @@ void arch_jump_label_transform(struct jump_entry *entry,
 	}
 
 	mutex_lock(&text_mutex);
-	patch_text_nosync(addr, &insn, sizeof(insn));
+	patch_insn_write(addr, &insn, sizeof(insn));
 	mutex_unlock(&text_mutex);
+
+	return true;
+}
+
+void arch_jump_label_transform_apply(void)
+{
+	flush_icache_all();
 }

arch/riscv/kernel/patch.c

@@ -19,7 +19,7 @@
 struct patch_insn {
 	void *addr;
 	u32 *insns;
-	int ninsns;
+	size_t len;
 	atomic_t cpu_count;
 };
 
@@ -54,7 +54,7 @@ static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
 	BUG_ON(!page);
 
 	return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
-					 (uintaddr & ~PAGE_MASK));
+					 offset_in_page(addr));
 }
 
 static void patch_unmap(int fixmap)
@@ -65,8 +65,8 @@ NOKPROBE_SYMBOL(patch_unmap);
 
 static int __patch_insn_set(void *addr, u8 c, size_t len)
 {
+	bool across_pages = (offset_in_page(addr) + len) > PAGE_SIZE;
 	void *waddr = addr;
-	bool across_pages = (((uintptr_t)addr & ~PAGE_MASK) + len) > PAGE_SIZE;
 
 	/*
 	 * Only two pages can be mapped at a time for writing.
@@ -102,8 +102,8 @@ NOKPROBE_SYMBOL(__patch_insn_set);
 
 static int __patch_insn_write(void *addr, const void *insn, size_t len)
 {
+	bool across_pages = (offset_in_page(addr) + len) > PAGE_SIZE;
 	void *waddr = addr;
-	bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE;
 	int ret;
 
 	/*
@@ -163,69 +163,70 @@ NOKPROBE_SYMBOL(__patch_insn_write);
 
 static int patch_insn_set(void *addr, u8 c, size_t len)
 {
-	size_t patched = 0;
 	size_t size;
-	int ret = 0;
+	int ret;
 
 	/*
 	 * __patch_insn_set() can only work on 2 pages at a time so call it in a
 	 * loop with len <= 2 * PAGE_SIZE.
 	 */
-	while (patched < len && !ret) {
-		size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched);
-		ret = __patch_insn_set(addr + patched, c, size);
-
-		patched += size;
+	while (len) {
+		size = min(len, PAGE_SIZE * 2 - offset_in_page(addr));
+		ret = __patch_insn_set(addr, c, size);
+		if (ret)
+			return ret;
+
+		addr += size;
+		len -= size;
 	}
 
-	return ret;
+	return 0;
 }
 NOKPROBE_SYMBOL(patch_insn_set);
 
 int patch_text_set_nosync(void *addr, u8 c, size_t len)
 {
-	u32 *tp = addr;
 	int ret;
 
-	ret = patch_insn_set(tp, c, len);
-
+	ret = patch_insn_set(addr, c, len);
 	if (!ret)
-		flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len);
+		flush_icache_range((uintptr_t)addr, (uintptr_t)addr + len);
 
 	return ret;
 }
 NOKPROBE_SYMBOL(patch_text_set_nosync);
 
 int patch_insn_write(void *addr, const void *insn, size_t len)
 {
-	size_t patched = 0;
 	size_t size;
-	int ret = 0;
+	int ret;
 
 	/*
 	 * Copy the instructions to the destination address, two pages at a time
 	 * because __patch_insn_write() can only handle len <= 2 * PAGE_SIZE.
 	 */
-	while (patched < len && !ret) {
-		size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched);
-		ret = __patch_insn_write(addr + patched, insn + patched, size);
-
-		patched += size;
+	while (len) {
+		size = min(len, PAGE_SIZE * 2 - offset_in_page(addr));
+		ret = __patch_insn_write(addr, insn, size);
+		if (ret)
+			return ret;
+
+		addr += size;
+		insn += size;
+		len -= size;
 	}
 
-	return ret;
+	return 0;
 }
 NOKPROBE_SYMBOL(patch_insn_write);
 
 int patch_text_nosync(void *addr, const void *insns, size_t len)
 {
-	u32 *tp = addr;
 	int ret;
 
-	ret = patch_insn_write(tp, insns, len);
-
+	ret = patch_insn_write(addr, insns, len);
 	if (!ret)
-		flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len);
+		flush_icache_range((uintptr_t)addr, (uintptr_t)addr + len);
 
 	return ret;
 }
@@ -234,14 +235,10 @@ NOKPROBE_SYMBOL(patch_text_nosync);
 static int patch_text_cb(void *data)
 {
 	struct patch_insn *patch = data;
-	unsigned long len;
-	int i, ret = 0;
+	int ret = 0;
 
 	if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
-		for (i = 0; ret == 0 && i < patch->ninsns; i++) {
-			len = GET_INSN_LENGTH(patch->insns[i]);
-			ret = patch_insn_write(patch->addr + i * len, &patch->insns[i], len);
-		}
+		ret = patch_insn_write(patch->addr, patch->insns, patch->len);
 		/*
 		 * Make sure the patching store is effective *before* we
 		 * increment the counter which releases all waiting CPUs
@@ -261,13 +258,13 @@ static int patch_text_cb(void *data)
 }
 NOKPROBE_SYMBOL(patch_text_cb);
 
-int patch_text(void *addr, u32 *insns, int ninsns)
+int patch_text(void *addr, u32 *insns, size_t len)
 {
 	int ret;
 	struct patch_insn patch = {
 		.addr = addr,
 		.insns = insns,
-		.ninsns = ninsns,
+		.len = len,
 		.cpu_count = ATOMIC_INIT(0),
 	};
 

arch/riscv/kernel/probes/kprobes.c

@@ -24,14 +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;
-	unsigned long offset = GET_INSN_LENGTH(p->opcode);
 
-	p->ainsn.api.restore = (unsigned long)p->addr + offset;
+	p->ainsn.api.restore = (unsigned long)p->addr + len;
 
-	patch_text(p->ainsn.api.insn, &p->opcode, 1);
-	patch_text((void *)((unsigned long)(p->ainsn.api.insn) + offset),
-		   &insn, 1);
+	patch_text_nosync(p->ainsn.api.insn, &p->opcode, len);
+	patch_text_nosync(p->ainsn.api.insn + len, &insn, GET_INSN_LENGTH(insn));
 }
 
 static void __kprobes arch_prepare_simulate(struct kprobe *p)
@@ -108,16 +107,18 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 /* install breakpoint in text */
 void __kprobes arch_arm_kprobe(struct kprobe *p)
 {
-	u32 insn = (p->opcode & __INSN_LENGTH_MASK) == __INSN_LENGTH_32 ?
-		   __BUG_INSN_32 : __BUG_INSN_16;
+	size_t len = GET_INSN_LENGTH(p->opcode);
+	u32 insn = len == 4 ? __BUG_INSN_32 : __BUG_INSN_16;
 
-	patch_text(p->addr, &insn, 1);
+	patch_text(p->addr, &insn, len);
 }
 
 /* remove breakpoint from text */
 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 {
-	patch_text(p->addr, &p->opcode, 1);
+	size_t len = GET_INSN_LENGTH(p->opcode);
+
+	patch_text(p->addr, &p->opcode, len);
 }
 
 void __kprobes arch_remove_kprobe(struct kprobe *p)

arch/riscv/net/bpf_jit_comp64.c

@@ -16,6 +16,7 @@
 #include "bpf_jit.h"
 
 #define RV_FENTRY_NINSNS 2
+#define RV_FENTRY_NBYTES (RV_FENTRY_NINSNS * 4)
 
 #define RV_REG_TCC RV_REG_A6
 #define RV_REG_TCC_SAVED RV_REG_S6 /* Store A6 in S6 if program do calls */
@@ -672,7 +673,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
 	if (ret)
 		return ret;
 
-	if (memcmp(ip, old_insns, RV_FENTRY_NINSNS * 4))
+	if (memcmp(ip, old_insns, RV_FENTRY_NBYTES))
 		return -EFAULT;
 
 	ret = gen_jump_or_nops(new_addr, ip, new_insns, is_call);
@@ -681,8 +682,8 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
 
 	cpus_read_lock();
 	mutex_lock(&text_mutex);
-	if (memcmp(ip, new_insns, RV_FENTRY_NINSNS * 4))
-		ret = patch_text(ip, new_insns, RV_FENTRY_NINSNS);
+	if (memcmp(ip, new_insns, RV_FENTRY_NBYTES))
+		ret = patch_text(ip, new_insns, RV_FENTRY_NBYTES);
 	mutex_unlock(&text_mutex);
 	cpus_read_unlock();