From 35ae8742a965a5851d010089e30a866d52255db2 Mon Sep 17 00:00:00 2001
From: kjhq <arvintro@gmail.com>
Date: Wed, 7 Oct 2026 10:41:01 +0000
Subject: [PATCH] feat(libkernel): implement POSIX mprotect

mprotect changes the protection of guest memory through the same path
as sceKernelMprotect and reports failures through errno: EINVAL for a
null or overflowing range or a range the allocation tracker rejects,
ENOMEM when allocation fails. A zero length succeeds.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 .../libkernel/DirectMemory/PosixMemory.cpp    | 19 +++++++++++++++++++
 core/libs/tests/GuestMemory.cpp               | 15 +++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/core/libs/prx/libkernel/DirectMemory/PosixMemory.cpp b/core/libs/prx/libkernel/DirectMemory/PosixMemory.cpp
index e3d2f1796..bac216bbc 100644
--- a/core/libs/prx/libkernel/DirectMemory/PosixMemory.cpp
+++ b/core/libs/prx/libkernel/DirectMemory/PosixMemory.cpp
@@ -78,4 +78,23 @@ int APS5_VABI munmap_nid_postfix(void* address, std::size_t length) noexcept {
     }
 }
 
+int APS5_VABI mprotect_nid_postfix(void* address, std::size_t length, int protection) noexcept {
+    const auto failed = [](int error) {
+        SetError(error);
+        return -1;
+    };
+    const auto start = reinterpret_cast<std::uintptr_t>(address);
+    if (length == 0) return 0;
+    if (start == 0 || length > std::numeric_limits<std::uintptr_t>::max() - start)
+        return failed(GuestInvalid);
+    try {
+        if (DoMprotect(address, length, protection) != 0) return failed(GuestInvalid);
+        return 0;
+    } catch (const std::bad_alloc&) {
+        return failed(GuestNoMemory);
+    } catch (const std::exception&) {
+        return failed(GuestInvalid);
+    }
+}
+
 }
diff --git a/core/libs/tests/GuestMemory.cpp b/core/libs/tests/GuestMemory.cpp
index 27908100c..e400e7e0a 100644
--- a/core/libs/tests/GuestMemory.cpp
+++ b/core/libs/tests/GuestMemory.cpp
@@ -36,6 +36,7 @@
 extern "C" {
 void* APS5_VABI mmap_nid_postfix(void*, std::size_t, int, int, int, std::int64_t) noexcept;
 int APS5_VABI munmap_nid_postfix(void*, std::size_t) noexcept;
+int APS5_VABI mprotect_nid_postfix(void*, std::size_t, int) noexcept;
 int* APS5_VABI __error_nid_postfix();
 int APS5_VABI sceKernelMapNamedFlexibleMemory(void**, std::size_t, int, int, const char*);
 int APS5_VABI sceKernelMapNamedFlexibleMemoryInternal(void**, std::size_t, int, int, const char*);
@@ -1099,6 +1100,20 @@ int main() {
         const auto range = mutation.Find(memory);
         Require(range.bytes == page * 3 && range.readable && range.writable);
     }
+    Require(mprotect_nid_postfix(memory, 0, 1) == 0);
+    Require(mprotect_nid_postfix(nullptr, page, 1) == -1 && *__error_nid_postfix() == 22);
+    Require(mprotect_nid_postfix(memory + 1, 1, 1) == 0);
+    {
+        GuestAllocations::Mutation mutation;
+        const auto range = mutation.Find(memory);
+        Require(range.readable && !range.writable);
+    }
+    Require(memory[0] == 42);
+    Require(mprotect_nid_postfix(memory, page, 3) == 0);
+    {
+        GuestAllocations::Mutation mutation;
+        Require(mutation.Find(memory).writable);
+    }
     Require(munmap_nid_postfix(memory + 1, page) == -1 && *__error_nid_postfix() == 22);
     Require(munmap_nid_postfix(memory, 0) == -1 && *__error_nid_postfix() == 22);
     Require(memory[0] == 42);