Merge pull request #1149 from zqb-all/read-write-cross-page

riscv: fix read/write virtual memory across page boundaries
riscv-collab · Oct 28, 2024 · 9ff272e · 9ff272e
2 parents 7b4ad6f + 92d7a57
commit 9ff272e
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Showing 2 changed files with 78 additions and 28 deletions.
diff --git a/src/target/riscv/riscv.c b/src/target/riscv/riscv.c
@@ -3086,32 +3086,28 @@ static int riscv_virt2phys(struct target *target, target_addr_t virtual, target_
 			virtual, physical);
 }
 
+static int check_virt_memory_access(struct target *target, target_addr_t address,
+			uint32_t size, uint32_t count, bool is_write)
+{
+	const bool is_misaligned = address % size != 0;
+	// TODO: This assumes that size of each page is 4 KiB, which is not necessarily the case.
+	const bool crosses_page_boundary = RISCV_PGBASE(address + size * count - 1) != RISCV_PGBASE(address);
+	if (is_misaligned && crosses_page_boundary) {
+		LOG_TARGET_ERROR(target, "Mis-aligned memory %s (address=0x%" TARGET_PRIxADDR ", size=%d, count=%d)"
+			" would access an element across page boundary. This is not supported.",
+			is_write ? "write" : "read", address, size, count);
+		return ERROR_FAIL;
+	}
+	return ERROR_OK;
+}
+
 static int riscv_read_phys_memory(struct target *target, target_addr_t phys_address,
 			uint32_t size, uint32_t count, uint8_t *buffer)
 {
 	RISCV_INFO(r);
 	return r->read_memory(target, phys_address, size, count, buffer, size);
 }
 
-static int riscv_read_memory(struct target *target, target_addr_t address,
-		uint32_t size, uint32_t count, uint8_t *buffer)
-{
-	if (count == 0) {
-		LOG_TARGET_WARNING(target, "0-length read from 0x%" TARGET_PRIxADDR, address);
-		return ERROR_OK;
-	}
-
-	target_addr_t physical_addr;
-	int result = target->type->virt2phys(target, address, &physical_addr);
-	if (result != ERROR_OK) {
-		LOG_TARGET_ERROR(target, "Address translation failed.");
-		return result;
-	}
-
-	RISCV_INFO(r);
-	return r->read_memory(target, physical_addr, size, count, buffer, size);
-}
-
 static int riscv_write_phys_memory(struct target *target, target_addr_t phys_address,
 			uint32_t size, uint32_t count, const uint8_t *buffer)
 {
@@ -3121,25 +3117,76 @@ static int riscv_write_phys_memory(struct target *target, target_addr_t phys_add
 	return tt->write_memory(target, phys_address, size, count, buffer);
 }
 
-static int riscv_write_memory(struct target *target, target_addr_t address,
-		uint32_t size, uint32_t count, const uint8_t *buffer)
+static int riscv_rw_memory(struct target *target, target_addr_t address, uint32_t size,
+		uint32_t count, uint8_t *read_buffer, const uint8_t *write_buffer)
 {
+	/* Exactly one of the buffers must be set, the other must be NULL */
+	assert(!!read_buffer != !!write_buffer);
+
+	const bool is_write = write_buffer ? true : false;
 	if (count == 0) {
-		LOG_TARGET_WARNING(target, "0-length write to 0x%" TARGET_PRIxADDR, address);
+		LOG_TARGET_WARNING(target, "0-length %s 0x%" TARGET_PRIxADDR,
+				is_write ? "write to" : "read from", address);
 		return ERROR_OK;
 	}
 
-	target_addr_t physical_addr;
-	int result = target->type->virt2phys(target, address, &physical_addr);
-	if (result != ERROR_OK) {
-		LOG_TARGET_ERROR(target, "Address translation failed.");
+	int mmu_enabled;
+	int result = riscv_mmu(target, &mmu_enabled);
+	if (result != ERROR_OK)
 		return result;
-	}
 
+	RISCV_INFO(r);
 	struct target_type *tt = get_target_type(target);
 	if (!tt)
 		return ERROR_FAIL;
-	return tt->write_memory(target, physical_addr, size, count, buffer);
+
+	if (!mmu_enabled) {
+		if (is_write)
+			return tt->write_memory(target, address, size, count, write_buffer);
+		else
+			return r->read_memory(target, address, size, count, read_buffer, size);
+	}
+
+	result = check_virt_memory_access(target, address, size, count, is_write);
+	if (result != ERROR_OK)
+		return result;
+
+	uint32_t current_count = 0;
+	while (current_count < count) {
+		target_addr_t physical_addr;
+		result = target->type->virt2phys(target, address, &physical_addr);
+		if (result != ERROR_OK) {
+			LOG_TARGET_ERROR(target, "Address translation failed.");
+			return result;
+		}
+
+		/* TODO: For simplicity, this algorithm assumes the worst case - the smallest possible page size,
+		 * which is  4 KiB. The algorithm can be improved to detect the real page size, and allow to use larger
+		 * memory transfers and avoid extra unnecessary virt2phys address translations. */
+		uint32_t chunk_count = MIN(count - current_count, (RISCV_PGSIZE - RISCV_PGOFFSET(address)) / size);
+		if (is_write)
+			result = tt->write_memory(target, physical_addr, size, chunk_count, write_buffer + current_count * size);
+		else
+			result = r->read_memory(target, physical_addr, size, chunk_count, read_buffer + current_count * size, size);
+		if (result != ERROR_OK)
+			return result;
+
+		current_count += chunk_count;
+		address += chunk_count * size;
+	}
+	return ERROR_OK;
+}
+
+static int riscv_read_memory(struct target *target, target_addr_t address,
+		uint32_t size, uint32_t count, uint8_t *buffer)
+{
+	return riscv_rw_memory(target, address, size, count, buffer, NULL);
+}
+
+static int riscv_write_memory(struct target *target, target_addr_t address,
+		uint32_t size, uint32_t count, const uint8_t *buffer)
+{
+	return riscv_rw_memory(target, address, size, count, NULL, buffer);
 }
 
 static const char *riscv_get_gdb_arch(const struct target *target)

diff --git a/src/target/riscv/riscv.h b/src/target/riscv/riscv.h
@@ -29,6 +29,9 @@ struct riscv_program;
 #define RISCV_HGATP_MODE(xlen)  ((xlen) == 32 ? HGATP32_MODE : HGATP64_MODE)
 #define RISCV_HGATP_PPN(xlen)  ((xlen) == 32 ? HGATP32_PPN : HGATP64_PPN)
 #define RISCV_PGSHIFT 12
+#define RISCV_PGSIZE BIT(RISCV_PGSHIFT)
+#define RISCV_PGBASE(addr) ((addr) & ~(RISCV_PGSIZE - 1))
+#define RISCV_PGOFFSET(addr) ((addr) & (RISCV_PGSIZE - 1))
 
 #define PG_MAX_LEVEL 5