From 0da2d2102a026ab0a2f315045257c0c4886222c4 Mon Sep 17 00:00:00 2001
From: Daniel Bertalan <dani@danielbertalan.dev>
Date: Fri, 19 May 2023 12:12:27 +0200
Subject: [PATCH] Kernel/aarch64: Flatten `safe_{memset,strnlen,memcpy}()`

We want to detect if an access fault comes from within these operations,
so they cannot be calling out to the non-safe variants.
---
 Kernel/Arch/aarch64/SafeMem.cpp | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/Kernel/Arch/aarch64/SafeMem.cpp b/Kernel/Arch/aarch64/SafeMem.cpp
index 29e58668ee..c537dc95cd 100644
--- a/Kernel/Arch/aarch64/SafeMem.cpp
+++ b/Kernel/Arch/aarch64/SafeMem.cpp
@@ -9,23 +9,34 @@
 
 namespace Kernel {
 
-bool safe_memset(void* dest_ptr, int c, size_t n, void*&)
+bool safe_memset(void* dest_ptr, int c, size_t n, void*& fault_at)
 {
     // FIXME: Actually implement a safe memset.
-    memset(dest_ptr, c, n);
+    auto* dest = static_cast<u8*>(dest_ptr);
+    for (; n--;)
+        *dest++ = c;
+    fault_at = nullptr;
     return true;
 }
 
-ssize_t safe_strnlen(char const* str, unsigned long max_n, void*&)
+ssize_t safe_strnlen(char const* str, unsigned long max_n, void*& fault_at)
 {
     // FIXME: Actually implement a safe strnlen.
-    return strnlen(str, max_n);
+    size_t len = 0;
+    for (; len < max_n && *str; str++)
+        len++;
+    fault_at = nullptr;
+    return len;
 }
 
-bool safe_memcpy(void* dest_ptr, void const* src_ptr, unsigned long n, void*&)
+bool safe_memcpy(void* dest_ptr, void const* src_ptr, unsigned long n, void*& fault_at)
 {
     // FIXME: Actually implement a safe memcpy.
-    memcpy(dest_ptr, src_ptr, n);
+    auto* pd = static_cast<u8*>(dest_ptr);
+    auto const* ps = static_cast<u8 const*>(src_ptr);
+    for (; n--;)
+        *pd++ = *ps++;
+    fault_at = nullptr;
     return true;
 }