From d3107640858a93a639129eed634da722514deb96 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Sat, 10 Aug 2024 22:41:29 -0300
Subject: [PATCH] vmm: VMM_FLAGS_REPLACE

---
 kernel-src/mm/vmm.c            | 25 ++++++++++++++++++-------
 kernel-src/sys/syscalls/mmap.c |  3 +--
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/kernel-src/mm/vmm.c b/kernel-src/mm/vmm.c
index 7acf7dc1..cd96d8d0 100644
--- a/kernel-src/mm/vmm.c
+++ b/kernel-src/mm/vmm.c
@@ -482,10 +482,22 @@ void *vmm_map(void *addr, volatile size_t size, int flags, mmuflags_t mmuflags,
 	if (range == NULL)
 		goto cleanup;
 
-	range->start = start;
-	range->size = size;
-	range->flags = VMM_PERMANENT_FLAGS_MASK & flags;
-	range->mmuflags = mmuflags;
+	if (flags & VMM_FLAGS_REPLACE) {
+		__assert(addr);
+		retaddr = addr;
+		range->start = addr;
+		range->size = size;
+		range->flags = VMM_PERMANENT_FLAGS_MASK & flags;
+		range->mmuflags = mmuflags;
+		__assert((flags & (VMM_FLAGS_ALLOCATE | VMM_FLAGS_PHYSICAL)) == 0);
+		unmap(space, addr, size);
+	} else {
+		retaddr = start;
+		range->start = start;
+		range->size = size;
+		range->flags = VMM_PERMANENT_FLAGS_MASK & flags;
+		range->mmuflags = mmuflags;
+	}
 
 	if (flags & VMM_FLAGS_FILE) {
 		// XXX make sure that writes can't happen to executable memory mapped files and check file permissions
@@ -503,6 +515,7 @@ void *vmm_map(void *addr, volatile size_t size, int flags, mmuflags_t mmuflags,
 				for (uintmax_t j = 0; j < size; j += PAGE_SIZE)
 					arch_mmu_unmap(_cpu()->vmmctx->pagetable, (void *)((uintptr_t)start + j));
 
+				retaddr = NULL;
 				goto cleanup;
 			}
 		}
@@ -526,6 +539,7 @@ void *vmm_map(void *addr, volatile size_t size, int flags, mmuflags_t mmuflags,
 						}
 				}
 
+				retaddr = NULL;
 				goto cleanup;
 			}
 			memset(MAKE_HHDM(allocated), 0, PAGE_SIZE);
@@ -533,9 +547,6 @@ void *vmm_map(void *addr, volatile size_t size, int flags, mmuflags_t mmuflags,
 	}
 
 	insertrange(space, range);
-
-	retaddr = start;
-
 	cleanup:
 	if (start == NULL && range)
 		freerange(range);
diff --git a/kernel-src/sys/syscalls/mmap.c b/kernel-src/sys/syscalls/mmap.c
index 4cfbb1c4..d0b0fd02 100644
--- a/kernel-src/sys/syscalls/mmap.c
+++ b/kernel-src/sys/syscalls/mmap.c
@@ -44,9 +44,8 @@ syscallret_t syscall_mmap(context_t *context, void *hint, size_t len, int prot,
 	bool isfile = (flags & MAP_ANONYMOUS) == 0;
 	int vmmflags = 0;
 
-	// XXX this isn't the correct behaviour for MAP_FIXED
 	if (flags & MAP_FIXED)
-		vmmflags |= VMM_FLAGS_EXACT;
+		vmmflags |= VMM_FLAGS_REPLACE;
 
 	if ((flags & MAP_ANONYMOUS) == 0)
 		vmmflags |= VMM_FLAGS_FILE;