Implement the stat system call

A certain four-letters nineties game requires it.
29jm · Dec 8, 2020 · b5a6f09 · b5a6f09
1 parent 5b729d3
commit b5a6f09
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Showing 9 changed files with 84 additions and 7 deletions.
diff --git a/kernel/include/kernel/fs.h b/kernel/include/kernel/fs.h
@@ -45,7 +45,8 @@ typedef struct fs_t {
     /* TODO: require null termination of entries */
     sos_directory_entry_t* (*readdir)(struct fs_t*, uint32_t, uint32_t);
     inode_t* (*get_fs_inode)(struct fs_t*, uint32_t);
-    int32_t (*close)(fs_t*, uint32_t)
+    int32_t (*close)(fs_t*, uint32_t);
+    int32_t (*stat)(fs_t*, uint32_t, stat_t*);
 } fs_t;
 
 typedef inode_t* (*fs_get_fs_inode_t)(struct fs_t*, uint32_t);
@@ -56,6 +57,7 @@ typedef int32_t (*fs_unlink_t)(struct fs_t*, uint32_t, uint32_t);
 typedef int32_t (*fs_rename_t)(struct fs_t*, uint32_t, uint32_t, uint32_t);
 typedef uint32_t (*fs_create_t)(struct fs_t*, const char*, uint32_t, uint32_t);
 typedef int32_t (*fs_close_t)(struct fs_t*, uint32_t);
+typedef int32_t (*fs_stat_t)(struct fs_t*, uint32_t, stat_t*);
 
 void init_fs(fs_t* fs);
 void fs_mount(const char* mount_point, fs_t* fs);
@@ -67,4 +69,5 @@ int32_t fs_rename(const char* oldp, const char* newp);
 int32_t fs_close(inode_t* in);
 uint32_t fs_read(inode_t* in, uint32_t offset, uint8_t* buf, uint32_t size);
 uint32_t fs_write(inode_t* in, uint8_t* buf, uint32_t size);
-uint32_t fs_readdir(inode_t* in, uint32_t offset, sos_directory_entry_t* d_ent, uint32_t size);
+uint32_t fs_readdir(inode_t* in, uint32_t offset, sos_directory_entry_t* d_ent, uint32_t size);
+int32_t fs_stat(const char* path, stat_t* buf);
diff --git a/kernel/include/kernel/uapi/uapi_fs.h b/kernel/include/kernel/uapi/uapi_fs.h
@@ -30,4 +30,12 @@ typedef struct {
     uint8_t name_len_low;
     uint8_t type;
     char name[];
-} sos_directory_entry_t;
+} sos_directory_entry_t;
+
+typedef struct stat_t {
+    uint32_t st_dev;
+    uint32_t st_ino;
+    uint32_t st_mode;
+    uint32_t st_nlink;
+    uint32_t st_size;
+} stat_t;
diff --git a/kernel/include/kernel/uapi/uapi_syscall.h b/kernel/include/kernel/uapi/uapi_syscall.h
@@ -25,7 +25,8 @@
 #define SYS_UNLINK 19
 #define SYS_RENAME 20
 #define SYS_MAKETTY 21
-#define SYS_MAX 22 // First invalid syscall number
+#define SYS_STAT 22
+#define SYS_MAX 23 // First invalid syscall number
 
 #define SYS_INFO_UPTIME 1
 #define SYS_INFO_MEMORY 2

diff --git a/kernel/src/misc/ext2.c b/kernel/src/misc/ext2.c
@@ -161,7 +161,8 @@ uint32_t ext2_read(ext2_fs_t* fs, uint32_t inode, uint32_t offset, uint8_t* buf,
 uint32_t ext2_append(ext2_fs_t* fs, uint32_t inode, uint8_t* data, uint32_t size);
 sos_directory_entry_t* ext2_readdir(ext2_fs_t* fs, uint32_t inode, uint32_t offset);
 inode_t* ext2_get_fs_inode(ext2_fs_t* fs, uint32_t inode);
-int32_t ext2_close(fs_t* fs, uint32_t ino);
+int32_t ext2_close(ext2_fs_t* fs, uint32_t ino);
+int32_t ext2_stat(ext2_fs_t* fs, uint32_t ino, stat_t* stat);
 
 static void read_block(ext2_fs_t* fs, uint32_t block, uint8_t* buf);
 static void write_block(ext2_fs_t* fs, uint32_t block, uint8_t* buf);
@@ -212,6 +213,7 @@ fs_t* init_ext2(uint8_t* data, uint32_t len) {
     e2fs->fs.readdir = (fs_readdir_t) ext2_readdir;
     e2fs->fs.unlink = (fs_unlink_t) ext2_unlink;
     e2fs->fs.close = (fs_close_t) ext2_close;
+    e2fs->fs.stat = (fs_stat_t) ext2_stat;
 
     e2fs->fs.uid = e2fs->sb->id[0];
     e2fs->fs.root = (folder_inode_t*) ext2_get_fs_inode(e2fs, EXT2_ROOT_INODE);
@@ -463,13 +465,29 @@ inode_t* ext2_get_fs_inode(ext2_fs_t* fs, uint32_t inode) {
     return fs_in;
 }
 
-int32_t ext2_close(fs_t* fs, uint32_t ino) {
+int32_t ext2_close(ext2_fs_t* fs, uint32_t ino) {
     UNUSED(fs);
     UNUSED(ino);
 
     return 0;
 }
 
+int32_t ext2_stat(ext2_fs_t* fs, uint32_t ino, stat_t* stat) {
+    ext2_inode_t* in = get_inode(fs, ino);
+
+    if (!in) {
+        return -1;
+    }
+
+    stat->st_dev = fs->fs.uid;
+    stat->st_ino = ino;
+    stat->st_mode = in->type_perms;
+    stat->st_nlink = in->hardlinks_count;
+    stat->st_size = in->size_lower;
+
+    return 0;
+}
+
 /* Utility functions */
 
 /* Reads the content of the given block.

diff --git a/kernel/src/misc/fs.c b/kernel/src/misc/fs.c
@@ -333,6 +333,17 @@ int32_t fs_rename(const char* oldp, const char* newp) {
     return 0;
 }
 
+int32_t fs_stat(const char* path, stat_t* buf) {
+    printk("stat: %s", path);
+    inode_t* in = fs_open(path, O_RDONLY);
+
+    if (!in) {
+        return -1;
+    }
+
+    return FS(in)->stat(FS(in), in->inode_no, buf);
+}
+
 /* A process has released its grip on a file: notify the fs.
  */
 int32_t fs_close(inode_t* in) {

diff --git a/kernel/src/sys/syscall.c b/kernel/src/sys/syscall.c
@@ -38,6 +38,7 @@ static void syscall_getcwd(registers_t* regs);
 static void syscall_unlink(registers_t* regs);
 static void syscall_rename(registers_t* regs);
 static void syscall_maketty(registers_t* regs);
+static void syscall_stat(registers_t* regs);
 
 handler_t syscall_handlers[SYSCALL_NUM] = { 0 };
 
@@ -65,6 +66,7 @@ void init_syscall() {
     syscall_handlers[SYS_UNLINK] = syscall_unlink;
     syscall_handlers[SYS_RENAME] = syscall_rename;
     syscall_handlers[SYS_MAKETTY] = syscall_maketty;
+    syscall_handlers[SYS_STAT] = syscall_stat;
 }
 
 static void syscall_handler(registers_t* regs) {
@@ -275,4 +277,11 @@ static void syscall_maketty(registers_t* regs) {
     proc_add_fd(entry);
 
     regs->eax = 0;
+}
+
+static void syscall_stat(registers_t* regs) {
+    const char* path = (const char*) regs->ebx;
+    stat_t* buf = (stat_t*) regs->ecx;
+
+    regs->eax = fs_stat(path, buf);
 }
diff --git a/libc/include/sys/stat.h b/libc/include/sys/stat.h
@@ -4,6 +4,15 @@
 
 typedef uint32_t mode_t;
 
+struct stat {
+    uint32_t st_dev;
+    uint32_t st_ino;
+    uint32_t st_mode;
+    uint32_t st_nlink;
+    uint32_t st_size;
+};
+
 #ifndef _KERNEL_
 int mkdir(const char* pathname, mode_t mode);
+int stat(const char* path, struct stat* buf);
 #endif
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
@@ -1,8 +1,9 @@
 #pragma once
 
-#include <stddef.h>
 #include <kernel/uapi/uapi_fs.h>
 
+#include <stddef.h>
+
 #define STDOUT_FILENO FS_STDOUT_FILENO
 
 #ifndef _KERNEL_

diff --git a/libc/src/unix/stat.c b/libc/src/unix/stat.c
@@ -31,4 +31,21 @@ int unlink(const char* path) {
     return syscall1(SYS_UNLINK, (uintptr_t) path);
 }
 
+int stat(const char* path, struct stat* buf) {
+    stat_t statbuf;
+    int ret = syscall2(SYS_STAT, (uintptr_t) path, (uintptr_t) &statbuf);
+
+    if (ret) {
+        return ret;
+    }
+
+    buf->st_dev = statbuf.st_dev;
+    buf->st_ino = statbuf.st_ino;
+    buf->st_mode = statbuf.st_mode;
+    buf->st_nlink = statbuf.st_nlink;
+    buf->st_size = statbuf.st_size;
+
+    return 0;
+}
+
 #endif