Add file removal, `rm`

build.sh

@@ -23,3 +23,4 @@ mcopy -i build/os.img@@"$((partition_offset * sector_size))" build/ls ::bin/ls
 mcopy -i build/os.img@@"$((partition_offset * sector_size))" build/cat ::bin/cat
 mcopy -i build/os.img@@"$((partition_offset * sector_size))" build/cp ::bin/cp
 mcopy -i build/os.img@@"$((partition_offset * sector_size))" build/mkdir ::bin/mkdir
+mcopy -i build/os.img@@"$((partition_offset * sector_size))" build/rm ::bin/rm

meson.build

@@ -388,3 +388,42 @@ custom_target(
   command: ['objcopy', '-O', 'binary', '@INPUT@', '@OUTPUT@'],
   build_by_default: true,
 )
+
+rm_start = custom_target(
+  'rm_start',
+  input:  'src/user/start.asm',
+  output: 'rm_start.o',
+  command: [nasm, '-f', 'elf64', '-o', '@OUTPUT@', '@INPUT@'],
+)
+
+rm_syscall = custom_target(
+  'rm_syscall',
+  input:  'src/user/syscall.asm',
+  output: 'rm_syscall.o',
+  command: [nasm, '-f', 'elf64', '-o', '@OUTPUT@', '@INPUT@'],
+)
+
+rm_elf = executable(
+  'rm.elf',
+  sources: [rm_start, rm_syscall, lib_sources, 'src/user/app/rm/rm.c'],
+  c_args: [
+    '-ffreestanding',
+    '-nostdlib',
+    '-fno-stack-protector',
+    '-mcmodel=large',
+    '-DVERSION="' + meson.project_version() + '"',
+  ],
+  link_args: [
+    '-T', meson.project_source_root() / 'src/user/linker.ld',
+    '-nostdlib',
+  ],
+  link_depends: 'src/user/linker.ld',
+)
+
+custom_target(
+  'rm',
+  input:  rm_elf,
+  output: 'rm',
+  command: ['objcopy', '-O', 'binary', '@INPUT@', '@OUTPUT@'],
+  build_by_default: true,
+)

src/kernel/fat16.c

@@ -42,21 +42,20 @@ typedef struct {
   uint32_t size;
   uint16_t dir_cluster;
   uint16_t dir_index;
-  uint8_t valid;
+  uint8_t removed;
 } fat16_inode_t;
 
 static fat16_inode_t inodes[MAX_INODES];
 
 static fat16_inode_t *inode_create(uint16_t first_cluster, uint32_t size, uint16_t dir_cluster, uint16_t dir_index) {
   for (uint64_t i = 0; i < MAX_INODES; i++) {
-    if (!inodes[i].valid) {
+    if (!inodes[i].refs) {
       inodes[i] = (fat16_inode_t){
           .refs = 1,
           .first_cluster = first_cluster,
           .size = size,
           .dir_cluster = dir_cluster,
           .dir_index = dir_index,
-          .valid = 1,
       };
       return &inodes[i];
     }
@@ -66,7 +65,7 @@ static fat16_inode_t *inode_create(uint16_t first_cluster, uint32_t size, uint16
 
 static fat16_inode_t *inode_get(uint32_t dir_cluster, uint16_t dir_index) {
   for (uint64_t i = 0; i < MAX_INODES; i++) {
-    if (inodes[i].valid && inodes[i].dir_cluster == dir_cluster && inodes[i].dir_index == dir_index) {
+    if (inodes[i].refs && inodes[i].dir_cluster == dir_cluster && inodes[i].dir_index == dir_index) {
       return &inodes[i];
     }
   }
@@ -84,14 +83,8 @@ static fat16_inode_t *inode_use(uint16_t first_cluster, uint32_t size, uint16_t
 }
 
 static void inode_free(fat16_inode_t *inode) {
-  inode->refs--;
-  if (!inode->refs) {
-    for (uint64_t i = 0; i < MAX_INODES; i++) {
-      if (&inodes[i] == inode) {
-        inodes[i].valid = 0;
-        break;
-      }
-    }
+  if (inode->refs) {
+    inode->refs--;
   }
 }
 
@@ -263,6 +256,10 @@ fs_node_t *fat16_open_by(const fs_node_t *directory, const char *name, uint64_t
     return NUL;
   }
 
+  if (((fat16_node_t *)directory)->inode->removed) {
+    return NUL;
+  }
+
   uint16_t dir_cluster = ((fat16_node_t *)directory)->inode->first_cluster;
 
   char name_8_3[12];
@@ -350,6 +347,10 @@ fs_node_t *fat16_open_at(const fs_node_t *directory, uint16_t index, uint64_t fl
     return NUL;
   }
 
+  if (((fat16_node_t *)directory)->inode->removed) {
+    return NUL;
+  }
+
   uint16_t dir_cluster = ((fat16_node_t *)directory)->inode->first_cluster;
 
   fat16_dir_entry_t *entries;
@@ -403,6 +404,10 @@ uint64_t fat16_read(const fs_node_t *file, uint32_t offset, uint32_t bytes, void
     return (uint64_t)-1;
   }
 
+  if (fat_file->inode->removed) {
+    return 0;
+  }
+
   if (offset >= fat_file->inode->size) {
     return 0;
   }
@@ -460,6 +465,10 @@ uint64_t fat16_write(fs_node_t *file, uint32_t offset, const void *from, uint32_
     return (uint64_t)-1;
   }
 
+  if (fat_file->inode->removed) {
+    return 0;
+  }
+
   ensure_fat();
 
   if (!fat_file->inode->first_cluster) {
@@ -540,6 +549,10 @@ uint64_t fat16_truncate(fs_node_t *file, uint32_t size) {
     return (uint64_t)-1;
   }
 
+  if (fat_file->inode->removed) {
+    return 0;
+  }
+
   if (file->size == size) {
     return size;
   } else if (file->size < size) {
@@ -585,6 +598,57 @@ uint64_t fat16_truncate(fs_node_t *file, uint32_t size) {
   return (uint64_t)-1;
 }
 
+uint64_t fat16_remove(fs_node_t *file) {
+  fat16_node_t *fat_file = (fat16_node_t *)file;
+
+  if (fat_file->base.type != FAT16) {
+    return (uint64_t)-1;
+  }
+
+  if (fat_file->inode->removed) {
+    return 0;
+  }
+
+  if (file->is_dir) {
+    fat16_dir_entry_t *subentries;
+    uint16_t subentries_count = read_directory(fat_file->inode->first_cluster, &subentries);
+    uint16_t ei = 0, vi = 0;
+    while (ei < subentries_count && subentries[ei].name[0]) {
+      if ((uint8_t)subentries[ei].name[0] != 0xE5 && (uint8_t)subentries[ei].attributes != 0x0F) {
+        vi++;
+      }
+      ei++;
+    }
+    memory_free(subentries);
+    if (vi > 2) {
+      return (uint64_t)-1;
+    }
+  }
+
+  fat_file->inode->removed = 1;
+
+  if (fat_file->inode->first_cluster) {
+    ensure_fat();
+    uint64_t next_cluster = fat_file->inode->first_cluster;
+    do {
+      uint32_t swap = fat[next_cluster];
+      fat[next_cluster] = 0;
+      next_cluster = swap;
+    } while (next_cluster < 0xFFF8);
+    flush_fat();
+  }
+
+  fat16_dir_entry_t *entries;
+  uint16_t entries_count = read_directory(fat_file->inode->dir_cluster, &entries);
+  entries[fat_file->inode->dir_index].name[0] = 0xE5;
+  entries[fat_file->inode->dir_index].first_cluster = 0;
+  entries[fat_file->inode->dir_index].size = 0;
+  write_directory(fat_file->inode->dir_cluster, entries, entries_count);
+  memory_free(entries);
+
+  return 1;
+}
+
 typedef struct {
   stream_t stream;
   fs_node_t *node;

src/kernel/fat16.h

@@ -21,6 +21,8 @@ uint64_t fat16_write(fs_node_t *file, uint32_t offset, const void *from, uint32_
 
 uint64_t fat16_truncate(fs_node_t *file, uint32_t size);
 
+uint64_t fat16_remove(fs_node_t *file);
+
 void fat16_close(fs_node_t *node);
 
 void fat16_unmount(fs_node_t *fs);

src/kernel/fs.c

@@ -33,6 +33,10 @@ void fs_truncate(fs_node_t *file, uint32_t size) {
   fat16_truncate(file, size);
 }
 
+void fs_remove(fs_node_t *file) {
+  fat16_remove(file);
+}
+
 void fs_close(fs_node_t *node) {
   fat16_close(node);
 }

src/kernel/fs.h

@@ -27,6 +27,8 @@ void fs_write(fs_node_t *file, uint32_t offset, const void *from, uint32_t bytes
 
 void fs_truncate(fs_node_t *file, uint32_t size);
 
+void fs_remove(fs_node_t *file);
+
 void fs_close(fs_node_t *node);
 
 void fs_unmount(fs_node_t *fs);

src/kernel/path.c

@@ -74,3 +74,12 @@ void path_close(path_t *path) {
   }
   memory_free(path);
 }
+
+void path_remove(const fs_node_t *root, const path_t *source, const char *path) {
+  path_t *p = path_open(root, source, path, OPEN_FILE | OPEN_DIRECTORY);
+  if (!p || !p->depth) {
+    return;
+  }
+  fs_remove(p->stack[p->depth - 1]);
+  path_close(p);
+}

src/kernel/path.h

@@ -17,3 +17,5 @@ fs_node_t *path_open_node(const fs_node_t *root, const path_t *source, const cha
 stream_t *path_open_stream(const fs_node_t *root, const path_t *source, const char *path, uint64_t flags);
 
 void path_close(path_t *path);
+
+void path_remove(const fs_node_t *root, const path_t *source, const char *path);

src/kernel/syscall.c

@@ -185,6 +185,11 @@ static uint64_t truncate(uint64_t fd, uint64_t size) {
   return current_process->fds[fd]->truncate(current_process->fds[fd], size);
 }
 
+static uint64_t remove(const char *path) {
+  path_remove(current_process->root, current_process->cwd, path);
+  return 0;
+}
+
 static void exit(exit_code_t code) {
   current_process->state = PROCESS_ZOMBIE;
   current_process->code = code;
@@ -219,6 +224,8 @@ uint64_t syscall_dispatch(uint64_t func, uint64_t arg1, uint64_t arg2, uint64_t
     return close(arg1);
   case SYSCALL_TRUNCATE:
     return truncate(arg1, arg2);
+  case SYSCALL_REMOVE:
+    return remove((char *)arg1);
   case SYSCALL_EXIT:
     exit(arg1);
     return 0;

src/lib/syscall.h

@@ -7,6 +7,7 @@
 #define SYSCALL_OPEN 6
 #define SYSCALL_CLOSE 7
 #define SYSCALL_TRUNCATE 8
+#define SYSCALL_REMOVE 9
 #define SYSCALL_EXIT 60
 
 #define OPEN_CREATE 0b0001

src/user/app/rm/rm.c

@@ -0,0 +1,26 @@
+#include "src/lib/syscall.h"
+#include "src/lib/util.h"
+#include "src/user/syscall.h"
+
+#define BLOCK_SIZE 65536
+
+#define PRINT_S(s) write(1, s, sizeof(s) - 1);
+#define PRINT_D(s) write(1, s, string_length(s));
+
+exit_code_t main(uint64_t argc, const char **argv) {
+  if (argc < 2) {
+    PRINT_S("rm: requires one or more arguments\n");
+    return EXIT_CODE_GENERAL_FAILURE;
+  }
+
+  uint64_t code = EXIT_CODE_OK;
+  for (uint64_t i = 1; i < argc; i++) {
+    exit_code_t c = remove(argv[i]);
+    if (c != EXIT_CODE_OK) {
+      PRINT_S("rm: coult not remove file\n");
+      code = c;
+    }
+  }
+
+  return code;
+}

src/user/syscall.asm

@@ -54,6 +54,12 @@ truncate:
     syscall
     ret
 
+global remove
+remove:
+    mov rax, 9
+    syscall
+    ret
+
 global exit
 exit:
     mov rax, 60

src/user/syscall.h

@@ -20,4 +20,6 @@ uint64_t close(uint64_t fd);
 
 uint64_t truncate(uint64_t fd, uint64_t size);
 
+uint64_t remove(const char *path);
+
 void exit(exit_code_t code);