From 219c27d420fe0abe5515cefc2513c6fe60aafdf9 Mon Sep 17 00:00:00 2001
From: Kimplul <kimi.h.kuparinen@gmail.com>
Date: Sun, 7 Jul 2024 21:47:14 +0300
Subject: add req_page back in as I realized it's useful

+ Can be used to pass contiguous memory regions to things like virtio
  block devices for implementing disk drivers etc.
---
 src/debug.c         |  5 ++++-
 src/uapi/dispatch.c |  1 +
 src/uapi/mem.c      | 28 ++++++++++++++++++++++++++++
 src/vmem.c          | 28 ++++++++++++++++++++++++++++
 4 files changed, 61 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/debug.c b/src/debug.c
index 9573bbc..567911b 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -753,7 +753,10 @@ void dbg(const char *fmt, ...)
 			if (is_set(flags, PRECS_FLAG))
 				i = precision;
 
-			chars_written += __puts(s);
+			for (; *s && i--;) {
+				__putchar(*s++);
+				chars_written++;
+			}
 			fmt++;
 			break;
 
diff --git a/src/uapi/dispatch.c b/src/uapi/dispatch.c
index 16a17d2..4135171 100644
--- a/src/uapi/dispatch.c
+++ b/src/uapi/dispatch.c
@@ -50,6 +50,7 @@ void handle_syscall(sys_arg_t syscall, sys_arg_t a, sys_arg_t b,
 	case SYS_PUTCH: sys_putch(t, a, b, c, d, e); break;
 	case SYS_REQ_MEM: sys_req_mem(t, a, b, c, d, e); break;
 	case SYS_REQ_PMEM: sys_req_pmem(t, a, b, c, d, e); break;
+	case SYS_REQ_PAGE: sys_req_page(t, a, b, c, d, e); break;
 	case SYS_REQ_FIXMEM: sys_req_fixmem(t, a, b, c, d, e); break;
 	case SYS_REQ_SHAREDMEM: sys_req_sharedmem(t, a, b, c, d, e); break;
 	case SYS_REF_SHAREDMEM: sys_ref_sharedmem(t, a, b, c, d, e); break;
diff --git a/src/uapi/mem.c b/src/uapi/mem.c
index 17823a1..49370fc 100644
--- a/src/uapi/mem.c
+++ b/src/uapi/mem.c
@@ -105,6 +105,34 @@ SYSCALL_DEFINE3(req_pmem)(struct tcb *t, sys_arg_t paddr, sys_arg_t size,
 	return_args2(t, OK, start);
 }
 
+/**
+ * Allocate some contiguous region in memory.
+ * Due to page allocation constraints, this is generally just one page that's
+ * larger than the \p size parameter. Should work fine for 4K - 2M allocations,
+ * which I assume is generally what is used, but we'll see if I have to
+ * implement an actually good page allocator at some point.
+ *
+ * @param t Current tcb.
+ * @param size Minimum size of mapping.
+ * @param flags Flags of mapping. Unsure why you'd want anything besides VM_W |
+ * VM_R, but eh.
+ *
+ * @return \see sys_req_page().
+ */
+SYSCALL_DEFINE2(req_page)(struct tcb *t, sys_arg_t size, sys_arg_t flags)
+{
+	struct tcb *r = get_cproc(t);
+
+	pm_t addr = 0;
+	vm_t start = 0;
+	size_t asize = 0;
+	flags = sanitize_uvflags(flags);
+	if (!(start = alloc_uvpage(r, size, flags, &addr, &asize)))
+		return_args1(t, ERR_OOMEM);
+
+	return_args4(t, OK, start, addr, asize);
+}
+
 /**
  * Request shared memory syscall handler.
  *
diff --git a/src/vmem.c b/src/vmem.c
index 27e1b2f..261ef42 100644
--- a/src/vmem.c
+++ b/src/vmem.c
@@ -279,6 +279,34 @@ vm_t map_fixed_uvmem(struct tcb *t, pm_t start, size_t size, vmflags_t flags)
 	return v + (start % BASE_PAGE_SIZE);
 }
 
+vm_t alloc_uvpage(struct tcb *t, size_t size, vmflags_t flags, pm_t *startp,
+                  size_t *sizep)
+{
+	enum mm_order order = nearest_order(size);
+	size = order_size(order);
+
+	const vm_t v = alloc_region(&t->uvmem.region, size, &size, flags);
+	if (!v)
+		return 0;
+
+	pm_t start = alloc_page(order);
+	if (!start) {
+		free_region(&t->uvmem.region, size);
+		return 0;
+	}
+
+	if (map_fixed_region(t->proc.vmem, v, start, size, flags)) {
+		unmap_region(t->proc.vmem, v, size);
+		free_region(&t->uvmem.region, v);
+		return NULL;
+	}
+
+	*startp = (pm_t)__pa(start);
+	*sizep = size;
+	return v;
+}
+
+
 /* free_shared_uvmem shouldn't be needed, likely to work with free_uvmem */
 vm_t alloc_shared_uvmem(struct tcb *s, size_t size, vmflags_t flags)
 {
-- 
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