From 2db69d0f24e962c4eaaa41dc998159d330ab8bc6 Mon Sep 17 00:00:00 2001
From: Dominique Martinet <dominique.martinet@cea.fr>
Date: Thu, 21 Sep 2017 17:35:13 +0900
Subject: [PATCH] process/vm: implement access_ok()

---
 kernel/include/process.h |  4 ++++
 kernel/process.c         | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/kernel/include/process.h b/kernel/include/process.h
index 2295757a..5e9499ab 100644
--- a/kernel/include/process.h
+++ b/kernel/include/process.h
@@ -834,4 +834,8 @@ void copy_fp_regs(struct thread *from, struct thread *to);
 void restore_fp_regs(struct thread *proc);
 void clear_fp_regs(void);
 
+#define VERIFY_READ 0
+#define VERIFY_WRITE 1
+int access_ok(struct process_vm *vm, int type, uintptr_t addr, size_t len);
+
 #endif
diff --git a/kernel/process.c b/kernel/process.c
index 36a8bd33..be5313aa 100644
--- a/kernel/process.c
+++ b/kernel/process.c
@@ -3607,3 +3607,35 @@ debug_log(unsigned long arg)
 		break;
 	}
 }
+
+int access_ok(struct process_vm *vm, int type, uintptr_t addr, size_t len) {
+	struct vm_range *range, *next;
+
+	range = lookup_process_memory_range(vm, addr, addr + len);
+
+	while (range) {
+		if ((type == VERIFY_WRITE && !(range->flag & VR_PROT_WRITE)) ||
+		    (type == VERIFY_READ && !(range->flag & VR_PROT_READ))) {
+			kprintf("%s: 0x%llx - 0x%llx does not have prot %s (request was %0x%llx-0x%llx %zu)\n",
+				__FUNCTION__, range->start, range->end,
+				type == VERIFY_WRITE ? "write" : "ready",
+				addr, addr+len, len);
+			return -EACCES;
+		}
+
+		if (addr + len < range->end)
+			break;
+
+		next = next_process_memory_range(vm, range);
+		if (range->end != next->start) {
+			kprintf("%s: 0x%llx - 0x%llx and 0x%llx - 0x%llx are not adjacent (request was %0x%llx-0x%llx %zu)\n",
+				__FUNCTION__, range->start, range->end,
+				next->start, next->end,
+				addr, addr+len, len);
+			return -EFAULT;
+		}
+		range = next;
+	}
+
+	return 0;
+}