feat(kernel): add int 0x80 syscall dispatch table

include/syscall.h

@@ -0,0 +1,19 @@
+#ifndef FROSTBYTE_SYSCALL_H
+#define FROSTBYTE_SYSCALL_H
+
+#define sysExit     0
+#define sysWrite    1
+#define sysRead     2
+#define sysYield    3
+#define sysGetpid   4
+#define sysSbrk     5
+#define sysSleep    6
+#define sysOpen     7
+#define sysClose    8
+#define sysLseek    9
+#define sysStat     10
+#define sysGetdents 11
+#define sysMkdir    12
+#define sysUnlink   13
+
+#endif

src/syscall.c

@@ -0,0 +1,129 @@
+#include "syscall.h"
+#include "isr.h"
+#include "console.h"
+#include "sched.h"
+#include "vfs.h"
+#include "fs.h"
+#include "string.h"
+
+#define userSpaceMin 0x0000000040000000ull
+#define userSpaceMax 0x0000800000000000ull
+
+static bool userRangeOk(uint64 pointer, uint64 length)
+{
+    if (pointer < userSpaceMin)
+        return false;
+    if (pointer + length < pointer)
+        return false;
+    if (pointer + length > userSpaceMax)
+        return false;
+    return true;
+}
+
+static bool copyUserPath(uint64 pointer, char* dst, uint64 max)
+{
+    if (pointer < userSpaceMin || pointer >= userSpaceMax)
+        return false;
+    const char* src = (const char*)pointer;
+    for (uint64 i = 0; i < max; i++) {
+        dst[i] = src[i];
+        if (src[i] == 0)
+            return true;
+    }
+    dst[max - 1] = 0;
+    return true;
+}
+
+static int64 doWrite(uint64 fd, uint64 buffer, uint64 length)
+{
+    if (!userRangeOk(buffer, length))
+        return -1;
+    return vfsWrite((int)fd, (const void*)buffer, length);
+}
+
+static int64 doRead(uint64 fd, uint64 buffer, uint64 length)
+{
+    if (!userRangeOk(buffer, length))
+        return -1;
+    return vfsRead((int)fd, (void*)buffer, length);
+}
+
+uint64 syscallDispatch(Registers* regs)
+{
+    switch (regs->rax) {
+    case sysWrite:
+        regs->rax = (uint64)doWrite(regs->rdi, regs->rsi, regs->rdx);
+        return (uint64)regs;
+    case sysRead:
+        regs->rax = (uint64)doRead(regs->rdi, regs->rsi, regs->rdx);
+        return (uint64)regs;
+    case sysGetpid:
+        regs->rax = currentThreadId();
+        return (uint64)regs;
+    case sysSbrk:
+        regs->rax = currentThreadSbrk((int64)regs->rdi);
+        return (uint64)regs;
+    case sysYield:
+        regs->rax = 0;
+        return schedule((uint64)regs);
+    case sysSleep:
+        threadSleep(regs->rdi);
+        regs->rax = 0;
+        return schedule((uint64)regs);
+    case sysExit:
+        threadExit(regs->rdi);
+        return schedule((uint64)regs);
+    case sysOpen: {
+        char path[256];
+        if (!copyUserPath(regs->rdi, path, sizeof(path)))
+            regs->rax = (uint64)-1;
+        else
+            regs->rax = (uint64)(int64)vfsOpen(path, (uint32)regs->rsi);
+        return (uint64)regs;
+    }
+    case sysClose:
+        regs->rax = (uint64)(int64)vfsClose((int)regs->rdi);
+        return (uint64)regs;
+    case sysLseek:
+        regs->rax = (uint64)vfsLseek((int)regs->rdi, (int64)regs->rsi, (int)regs->rdx);
+        return (uint64)regs;
+    case sysStat: {
+        char path[256];
+        FbStat st;
+        if (copyUserPath(regs->rdi, path, sizeof(path)) &&
+            userRangeOk(regs->rsi, sizeof(FbStat)) &&
+            vfsStat(path, &st) == 0) {
+            memcpy((void*)regs->rsi, &st, sizeof(FbStat));
+            regs->rax = 0;
+        } else {
+            regs->rax = (uint64)-1;
+        }
+        return (uint64)regs;
+    }
+    case sysGetdents:
+        if (!userRangeOk(regs->rsi, regs->rdx))
+            regs->rax = (uint64)-1;
+        else
+            regs->rax = (uint64)vfsGetdents((int)regs->rdi, (void*)regs->rsi, regs->rdx);
+        return (uint64)regs;
+    case sysMkdir: {
+        char path[256];
+        if (!copyUserPath(regs->rdi, path, sizeof(path)))
+            regs->rax = (uint64)-1;
+        else
+            regs->rax = (uint64)(int64)vfsMkdir(path);
+        return (uint64)regs;
+    }
+    case sysUnlink: {
+        char path[256];
+        if (!copyUserPath(regs->rdi, path, sizeof(path)))
+            regs->rax = (uint64)-1;
+        else
+            regs->rax = (uint64)(int64)vfsUnlink(path);
+        return (uint64)regs;
+    }
+    default:
+        regs->rax = (uint64)-1;
+        return (uint64)regs;
+    }
+}