[kernel] Change VMA syscall addr param to inout

This change allows the `vma_map` and `vma_create_map` syscalls to map to
addresses other than the one specified, and therefore makes the address
parameter to those syscalls `inout` in order to return the mapped
address.

Also add the `exact` flag for specifying that mapping needs to be done
at the exact address given. If the mapping collides with another, the
new `j6_err_collision` error is returned.

src/libraries/j6/channel.cpp

@@ -56,7 +56,7 @@ channel::create(size_t size)
     channel_addr += size * 2; // account for ring buffer virtual space doubling
     lock.release();
 
-    result = j6_vma_create_map(&vma, size, addr, j6_vm_flag_write|j6_vm_flag_ring);
+    result = j6_vma_create_map(&vma, size, &addr, j6_vm_flag_write|j6_vm_flag_ring);
     if (result != j6_status_ok) {
         syslog("Failed to create channel VMA. Error: %lx", result);
         return nullptr;
@@ -77,7 +77,7 @@ channel::open(j6_handle_t vma)
     util::scoped_lock lock {addr_spinlock};
     uintptr_t addr = channel_addr;
 
-    result = j6_vma_map(vma, 0, addr);
+    result = j6_vma_map(vma, 0, &addr, 0);
     if (result != j6_status_ok) {
         syslog("Failed to map channel VMA. Error: %lx", result);
         return nullptr;

src/libraries/j6/include/j6/errors.h

@@ -24,4 +24,5 @@
 #define j6_err_insufficient         j6_err(0x0005)
 #define j6_err_timed_out            j6_err(0x0006)
 #define j6_err_denied               j6_err(0x0007)
+#define j6_err_collision            j6_err(0x0008)
 

src/libraries/j6/include/j6/flags.h

@@ -12,5 +12,5 @@ enum j6_vm_flags {
 enum j6_flags {
     j6_flag_block = 0x01,
 
-    j6_flags_COUNT // custom per-type flags should start here
+    j6_flags_MAX // custom per-type flags should start here
 };

src/libraries/j6/include/j6/tables/vm_flags.inc

@@ -1,10 +1,15 @@
 VM_FLAG( none,            0x00000000 )
+
 VM_FLAG( write,           0x00000001 )
 VM_FLAG( exec,            0x00000002 )
-VM_FLAG( contiguous,      0x00000020 )
-VM_FLAG( large_pages,     0x00000100 )
-VM_FLAG( huge_pages,      0x00000200 )
-VM_FLAG( write_combine,   0x00001000 )
-VM_FLAG( ring,            0x00002000 )
 
-VM_FLAG( mmio,            0x00010000 )
+VM_FLAG( contiguous,      0x00000010 )
+VM_FLAG( large_pages,     0x00000020 )
+VM_FLAG( huge_pages,      0x00000040 )
+
+VM_FLAG( write_combine,   0x00000100 )
+
+VM_FLAG( mmio,            0x00001000 )
+
+VM_FLAG( exact,           0x00010000 )
+VM_FLAG( ring,            0x00020000 )

src/libraries/j6/include/j6/thread.hh

@@ -19,22 +19,25 @@ template <typename Proc>
 class thread
 {
 public:
+    static constexpr uintptr_t stack_base_start = 0x7f0'0000'0000;
+
     /// Constructor. Create a thread and its stack space, but
     /// do not start executing the thread.
     /// \arg p           The function where the thread will begin execution
     /// \arg stack_top   The address where the top of this thread's stack should be mapped
-    /// \arg stack_size  Size of the stack, in bytes (default 64KiB)
-    thread(Proc p, uintptr_t stack_top, size_t stack_size = 0x10000) :
+    /// \arg stack_size  Size of the stack, in bytes (default 16MiB)
+    thread(Proc p, size_t stack_size = 0x100'0000) :
         m_stack {j6_handle_invalid},
         m_thread {j6_handle_invalid},
-        m_stack_top {stack_top},
         m_proc {p}
     {
-        uintptr_t stack_base = stack_top - stack_size;
-        m_status = j6_vma_create_map(&m_stack, stack_size, stack_base, j6_vm_flag_write);
+        uintptr_t stack_base = stack_base_start;
+        m_status = j6_vma_create_map(&m_stack, stack_size, &stack_base, j6_vm_flag_write);
         if (m_status != j6_status_ok)
             return;
 
+        m_stack_top = stack_base + stack_size;
+
         static constexpr size_t zeros_size = 0x10;
         m_stack_top -= zeros_size; // Sentinel
         memset(reinterpret_cast<void*>(m_stack_top), 0, zeros_size);