[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/kernel/kernel_main.cpp

@@ -100,7 +100,7 @@ load_init_server(bootproto::program &program, uintptr_t modules_address)
             ((sect.type && section_flags::write) ? vm_flags::write : vm_flags::none);
 
         obj::vm_area *vma = new obj::vm_area_fixed(sect.phys_addr, sect.size, flags);
-        space.add(sect.virt_addr, vma);
+        space.add(sect.virt_addr, vma, obj::vm_flags::exact);
     }
 
     uint64_t iopl = (3ull << 12);

src/kernel/memory_bootstrap.cpp

@@ -102,8 +102,8 @@ memory_initialize_pre_ctors(bootproto::args &kargs)
     obj::vm_area *heap_map = new (&g_kernel_heapmap_area)
         obj::vm_area_untracked(mem::heapmap_size, vm_flags::write);
 
-    vm.add(mem::heap_offset, heap);
-    vm.add(mem::heapmap_offset, heap_map);
+    vm.add(mem::heap_offset, heap, vm_flags::exact);
+    vm.add(mem::heapmap_offset, heap_map, vm_flags::exact);
 
     new (&g_kernel_heap) heap_allocator {mem::heap_offset, mem::heap_size, mem::heapmap_offset};
 
@@ -111,7 +111,7 @@ memory_initialize_pre_ctors(bootproto::args &kargs)
     size_t log_buffer_size = log::log_pages * arch::frame_size;
     obj::vm_area *logs = new (&g_kernel_log_area)
         obj::vm_area_ring(log_buffer_size, vm_flags::write);
-    vm.add(mem::logs_offset, logs);
+    vm.add(mem::logs_offset, logs, vm_flags::exact);
 
     new (&g_logger) log::logger(
             util::buffer::from(mem::logs_offset, log_buffer_size));
@@ -120,7 +120,7 @@ memory_initialize_pre_ctors(bootproto::args &kargs)
     obj::vm_area *caps = new (&g_cap_table_area)
         obj::vm_area_untracked(mem::caps_size, vm_flags::write);
 
-    vm.add(mem::caps_offset, caps);
+    vm.add(mem::caps_offset, caps, vm_flags::exact);
 
     new (&g_cap_table) cap_table {mem::caps_offset};
 
@@ -129,7 +129,7 @@ memory_initialize_pre_ctors(bootproto::args &kargs)
         mem::kernel_stack_pages,
         mem::stacks_size,
         vm_flags::write};
-    vm.add(mem::stacks_offset, &g_kernel_stacks);
+    vm.add(mem::stacks_offset, &g_kernel_stacks, vm_flags::exact);
 
     // Clean out any remaning bootloader page table entries
     for (unsigned i = 0; i < arch::kernel_root_index; ++i)
@@ -140,7 +140,7 @@ void
 memory_initialize_post_ctors(bootproto::args &kargs)
 {
     vm_space &vm = vm_space::kernel_space();
-    vm.add(mem::buffers_offset, &g_kernel_buffers);
+    vm.add(mem::buffers_offset, &g_kernel_buffers, vm_flags::exact);
 
     g_frame_allocator.free(
         get_physical_page(kargs.page_tables.pointer),

src/kernel/smp.cpp

@@ -58,7 +58,7 @@ start(cpu_data &bsp, void *kpml4)
     uintptr_t addr = 0x8000; // TODO: find a valid address, rewrite addresses
     isr vector = static_cast<isr>(addr >> 12);
     obj::vm_area *vma = new obj::vm_area_fixed(addr, 0x1000, vm_flags::write);
-    vm_space::kernel_space().add(addr, vma);
+    vm_space::kernel_space().add(addr, vma, obj::vm_flags::exact);
     memcpy(
         reinterpret_cast<void*>(addr),
         reinterpret_cast<void*>(&ap_startup),

src/kernel/syscalls/vm_area.cpp

@@ -23,7 +23,7 @@ vma_create(j6_handle_t *self, size_t size, uint32_t flags)
 }
 
 j6_status_t
-vma_create_map(j6_handle_t *self, size_t size, uintptr_t base, uint32_t flags)
+vma_create_map(j6_handle_t *self, size_t size, uintptr_t *base, uint32_t flags)
 {
     vm_area *a = nullptr;
     vm_flags f = vm_flags::user_mask & flags;
@@ -32,16 +32,17 @@ vma_create_map(j6_handle_t *self, size_t size, uintptr_t base, uint32_t flags)
     else
         a = construct_handle<vm_area_open>(self, size, f);
 
-    process::current().space().add(base, a);
-    return j6_status_ok;
+    *base = process::current().space().add(*base, a, f);
+    return *base ? j6_status_ok : j6_err_collision;
 }
 
 j6_status_t
-vma_map(vm_area *self, process *proc, uintptr_t base)
+vma_map(vm_area *self, process *proc, uintptr_t *base, uint32_t flags)
 {
     vm_space &space = proc ? proc->space() : process::current().space();
-    space.add(base, self);
-    return j6_status_ok;
+    vm_flags f = vm_flags::user_mask & flags;
+    *base = space.add(*base, self, f);
+    return *base ? j6_status_ok : j6_err_collision;
 }
 
 j6_status_t

src/kernel/vm_space.cpp

@@ -57,7 +57,7 @@ vm_space::vm_space() :
             sizeof(system_config),
             vm_flags::none);
 
-    add(sysconf_user_address, sysc);
+    add(sysconf_user_address, sysc, vm_flags::exact);
 }
 
 vm_space::~vm_space()
@@ -80,14 +80,34 @@ vm_space::kernel_space()
     return obj::process::kernel_process().space();
 }
 
-bool
-vm_space::add(uintptr_t base, obj::vm_area *area)
+uintptr_t
+vm_space::add(uintptr_t base, obj::vm_area *area, obj::vm_flags flags)
 {
-    //TODO: check for collisions
+    if (!base)
+        base = min_auto_address;
+
+    uintptr_t end = base + area->size();
+
+    //TODO: optimize find/insert
+    bool exact = util::bits::has(flags, j6_vm_flag_exact);
+    for (size_t i = 0; i < m_areas.count(); ++i) {
+        const vm_space::area &a = m_areas[i];
+        uintptr_t aend = a.base + a.area->size();
+        if (base >= aend)
+            continue;
+
+        if (end <= a.base)
+            break;
+        else if (exact)
+            return 0;
+        else
+            base = aend;
+    }
+
     m_areas.sorted_insert({base, area});
     area->add_to(this);
     area->handle_retain();
-    return true;
+    return base;
 }
 
 void

src/kernel/vm_space.h

@@ -4,23 +4,27 @@
 
 #include <stdint.h>
 
+#include <j6/flags.h>
 #include <util/enum_bitfields.h>
 #include <util/spinlock.h>
 #include <util/vector.h>
 
+#include "objects/vm_area.h"
 #include "page_table.h"
 
 struct TCB;
 
 namespace obj {
     class process;
-    class vm_area;
 }
 
 /// Tracks a region of virtual memory address space
 class vm_space
 {
 public:
+    /// Never map below this address unless explicitly asked.
+    static constexpr uintptr_t min_auto_address = 16 * 1024 * 1024; // 16 MiB
+
     /// Constructor for the kernel address space
     /// \arg pml4   The existing kernel PML4
     vm_space(page_table *pml4);
@@ -33,8 +37,9 @@ public:
     /// Add a virtual memorty area to this address space
     /// \arg base  The starting address of the area
     /// \arg area  The area to add
-    /// \returns   True if the add succeeded
-    bool add(uintptr_t base, obj::vm_area *area);
+    /// \arg flags Flags for the operation (exact, clobber, etc)
+    /// \returns   The base address the area was added at
+    uintptr_t add(uintptr_t base, obj::vm_area *area, obj::vm_flags flags);
 
     /// Remove a virtual memory area from this address space
     /// \arg area  The area to remove

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);

src/libraries/libc/__j6libc/increase_core.cpp

@@ -1,26 +1,17 @@
 #include <stddef.h>
 #include <stdint.h>
+#include <j6/errors.h>
+#include <j6/syscalls.h>
 
 namespace __j6libc {
 
-using j6_status_t = uint64_t;
-using j6_handle_t = uint64_t;
-
-constexpr j6_handle_t j6_handle_invalid = -1ull;
-constexpr j6_status_t j6_status_ok = 0;
-
 static j6_handle_t core_handle = j6_handle_invalid;
 static intptr_t core_size = 0;
 
-static const uintptr_t core_base = 0x1c0000000;
+static uintptr_t core_base = 0x1c0000000;
 
 static const void *error_val = (void*)-1;
 
-extern "C" {
-    j6_status_t j6_vma_create_map(j6_handle_t *, size_t, uintptr_t, unsigned);
-    j6_status_t j6_vma_resize(j6_handle_t, size_t *);
-}
-
 void * increase_core(intptr_t i)
 {
 	if (i == 0)
@@ -30,7 +21,7 @@ void * increase_core(intptr_t i)
 		if (i < 0)
 			return (void*)-1;
 
-		j6_status_t result = j6_vma_create_map(&core_handle, i, core_base, 1);
+		j6_status_t result = j6_vma_create_map(&core_handle, i, &core_base, 1);
 		if (result != j6_status_ok)
 			return (void*)-1;
 

src/user/drv.uefi_fb/main.cpp

@@ -55,7 +55,7 @@ main(int argc, const char **argv, const char **env)
         return s;
     }
 
-    s = j6_vma_map(fb_handle, 0, lfb_addr);
+    s = j6_vma_map(fb_handle, 0, &lfb_addr, j6_vm_flag_exact);
     if (s != j6_status_ok) {
         return s;
     }

src/user/srv.init/initfs.cpp

@@ -10,7 +10,6 @@
 
 static uint64_t initfs_running = 1;
 static constexpr size_t buffer_size = 2048;
-static constexpr uintptr_t load_addr = 0xf00000000;
 
 j6_status_t
 handle_load_request(j6romfs::fs &fs, const char *path, j6_handle_t &vma)
@@ -21,7 +20,8 @@ handle_load_request(j6romfs::fs &fs, const char *path, j6_handle_t &vma)
         return j6_status_ok;
     }
 
-    j6_vma_create_map(&vma, in->size, load_addr, j6_vm_flag_write);
+    uintptr_t load_addr = 0;
+    j6_vma_create_map(&vma, in->size, &load_addr, j6_vm_flag_write);
     util::buffer dest = util::buffer::from(load_addr, in->size);
     fs.load_inode_data(in, dest);
     j6_vma_unmap(vma, 0);

src/user/srv.init/loader.cpp

@@ -16,10 +16,9 @@
 
 using bootproto::module;
 
-static uintptr_t load_addr = 0xf'000'0000;
-static constexpr size_t stack_size = 0x10000;
-static constexpr uintptr_t stack_top = 0x80000000000;
 static constexpr size_t MiB = 0x10'0000ull;
+static constexpr size_t stack_size = 16 * MiB;
+static constexpr uintptr_t stack_top = 0x7f0'0000'0000;
 
 inline uintptr_t align_up(uintptr_t a) { return ((a-1) & ~(MiB-1)) + MiB; }
 
@@ -31,7 +30,7 @@ map_phys(j6_handle_t sys, uintptr_t phys, size_t len, j6_vm_flags flags)
     if (res != j6_status_ok)
         return j6_handle_invalid;
 
-    res = j6_vma_map(vma, 0, phys);
+    res = j6_vma_map(vma, 0, &phys, j6_vm_flag_exact);
     if (res != j6_status_ok)
         return j6_handle_invalid;
 
@@ -72,8 +71,7 @@ load_program_into(j6_handle_t proc, elf::file &file, uintptr_t image_base, const
         if (seg.type != elf::segment_type::load)
             continue;
 
-        uintptr_t addr = load_addr;
-        load_addr = align_up(load_addr + seg.mem_size);
+        uintptr_t addr = 0;
 
         // TODO: way to remap VMA as read-only if there's no write flag on
         // the segment
@@ -86,7 +84,7 @@ load_program_into(j6_handle_t proc, elf::file &file, uintptr_t image_base, const
         size_t epilogue = seg.mem_size - seg.file_size;
 
         j6_handle_t sub_vma = j6_handle_invalid;
-        j6_status_t res = j6_vma_create_map(&sub_vma, seg.mem_size+prologue, addr, flags);
+        j6_status_t res = j6_vma_create_map(&sub_vma, seg.mem_size+prologue, &addr, flags);
         if (res != j6_status_ok) {
             j6::syslog("  ** error loading ELF '%s': creating sub vma: %lx", path, res);
             return 0;
@@ -102,9 +100,9 @@ load_program_into(j6_handle_t proc, elf::file &file, uintptr_t image_base, const
         if (eos > eop)
             eop = eos;
 
-        uintptr_t start_addr = (image_base + seg.vaddr);
+        uintptr_t start_addr = (image_base + seg.vaddr) & ~0xfffull;
         j6::syslog("Mapping segment from %s at %012lx - %012lx", path, start_addr, start_addr+seg.mem_size);
-        res = j6_vma_map(sub_vma, proc, start_addr & ~0xfffull);
+        res = j6_vma_map(sub_vma, proc, &start_addr, j6_vm_flag_exact);
         if (res != j6_status_ok) {
             j6::syslog("  ** error loading ELF '%s': mapping sub vma to child: %lx", path, res);
             return 0;
@@ -193,10 +191,9 @@ load_program(
     if (!eop)
         return false;
 
-    uintptr_t stack_addr = load_addr;
-    load_addr = align_up(load_addr + stack_size);
+    uintptr_t stack_addr = 0;
     j6_handle_t stack_vma = j6_handle_invalid;
-    j6_status_t res = j6_vma_create_map(&stack_vma, stack_size, stack_addr, j6_vm_flag_write);
+    j6_status_t res = j6_vma_create_map(&stack_vma, stack_size, &stack_addr, j6_vm_flag_write);
     if (res != j6_status_ok) {
         j6::syslog("  ** error loading program '%s': creating stack vma: %lx", path, res);
         return false;
@@ -223,9 +220,8 @@ load_program(
         const elf::file_header *h = program_elf.header();
         loader_arg->image_base = program_image_base;
         loader_arg->phdr = h->ph_offset;
-        loader_arg->phdr_size = h->ph_entsize;
         loader_arg->phdr_count = h->ph_num;
-        loader_arg->entrypoint = program_elf.entrypoint();
+        loader_arg->entrypoint = entrypoint;
 
         j6_arg_handles *handles_arg = stack_push<j6_arg_handles>(stack, 2 * sizeof(j6_arg_handle_entry));
         handles_arg->nhandles = 1;
@@ -258,7 +254,8 @@ load_program(
         }
     }
 
-    res = j6_vma_map(stack_vma, proc, stack_top-stack_size);
+    uintptr_t stack_base = stack_top-stack_size;
+    res = j6_vma_map(stack_vma, proc, &stack_base, j6_vm_flag_exact);
     if (res != j6_status_ok) {
         j6::syslog("  ** error loading program '%s': mapping stack vma: %lx", path, res);
         return false;