From 1c6ece7b5584aa1f9580cab3c918f6acfbdf8d1b Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Tue, 21 Apr 2026 21:15:27 +0100
Subject: [PATCH] libc: implement private/shared mapping support

---
 lib/libc/io/unistd/mmap.c | 18 ++++++++++++++++++
 lib/libc/malloc/heap.c    |  1 +
 2 files changed, 19 insertions(+)

diff --git a/lib/libc/io/unistd/mmap.c b/lib/libc/io/unistd/mmap.c
index 7845e17..43fa7d4 100644
--- a/lib/libc/io/unistd/mmap.c
+++ b/lib/libc/io/unistd/mmap.c
@@ -25,6 +25,21 @@ static vm_prot_t vm_prot_from_mmap_prot(int prot)
 	return vm_prot;
 }
 
+static vm_flags_t vm_flags_from_mmap_flags(int flags)
+{
+	vm_flags_t out = 0;
+
+	if (flags & MAP_PRIVATE) {
+		out |= VM_PRIVATE;
+	}
+
+	if (flags & (MAP_SHARED | MAP_SHARED_VALIDATE)) {
+		out |= VM_SHARED;
+	}
+
+	return out;
+}
+
 static int get_vmo_anon(
 	int fd,
 	int prot,
@@ -109,6 +124,7 @@ void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
 	kern_status_t status = KERN_OK;
 	kern_handle_t self = KERN_HANDLE_INVALID,
 		      address_space = KERN_HANDLE_INVALID;
+	vm_flags_t vm_flags = vm_flags_from_mmap_flags(flags);
 
 	status = task_self(&self);
 	if (status != KERN_OK) {
@@ -146,6 +162,7 @@ void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
 			vmo,
 			offset,
 			length,
+			vm_flags,
 			vm_prot,
 			&map_address);
 	} else {
@@ -155,6 +172,7 @@ void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
 			vmo,
 			offset,
 			length,
+			vm_flags,
 			vm_prot,
 			&map_address);
 	}
diff --git a/lib/libc/malloc/heap.c b/lib/libc/malloc/heap.c
index fc3f712..a117e40 100644
--- a/lib/libc/malloc/heap.c
+++ b/lib/libc/malloc/heap.c
@@ -79,6 +79,7 @@ static kern_status_t expand_heap(heap_t *heap)
 		vmo,
 		0,
 		HEAP_EXPAND_INCREMENT,
+		VM_PRIVATE,
 		VM_PROT_READ | VM_PROT_WRITE | VM_PROT_USER,
 		&base);