From 3dfa5a54f4d668a1a5a7141ff6ad5b79af7067c8 Mon Sep 17 00:00:00 2001
From: Mark <alnyan@airmail.cc>
Date: Sun, 13 Oct 2019 18:25:22 +0300
Subject: [PATCH] Fix syscalls

---
 etc/make/amd64/platform.mk |  3 ++-
 sys/amd64/sys/sched.c      | 28 ++++++++++++++++++++--
 sys/amd64/syscall.c        |  6 +++++
 sys/amd64/syscall_s.S      | 49 +++++++++++++++++++++++++++++++-------
 4 files changed, 75 insertions(+), 11 deletions(-)
 create mode 100644 sys/amd64/syscall.c

diff --git a/etc/make/amd64/platform.mk b/etc/make/amd64/platform.mk
index e41400e..2fede30 100644
--- a/etc/make/amd64/platform.mk
+++ b/etc/make/amd64/platform.mk
@@ -25,7 +25,8 @@ OBJS+=$(O)/sys/amd64/hw/rs232.o \
 	  $(O)/sys/amd64/mm/phys.o \
 	  $(O)/sys/amd64/mm/vmalloc.o \
 	  $(O)/sys/amd64/mm/pool.o \
-	  $(O)/sys/amd64/syscall_s.o
+	  $(O)/sys/amd64/syscall_s.o \
+	  $(O)/sys/amd64/syscall.o
 
 kernel_OBJS=$(O)/sys/amd64/entry.o \
 			$(OBJS)
diff --git a/sys/amd64/sys/sched.c b/sys/amd64/sys/sched.c
index 1cb46f7..5ff37e6 100644
--- a/sys/amd64/sys/sched.c
+++ b/sys/amd64/sys/sched.c
@@ -19,10 +19,23 @@ static char t_stack3[IDLE_STACK * AMD64_MAX_SMP] = {0};
 static struct thread t_idle[AMD64_MAX_SMP] = {0};
 
 void func0(uintptr_t id, int state) {
+    uintptr_t a0 = 0, a1 = 0;
     uint16_t attr = (id + 0x2) << 8;
     uint16_t letter = '0' + id;
     *((uint16_t *) MM_VIRTUALIZE(0xB8000) + 80 * 0 + id) = state * attr | letter;
+    {
+        register uintptr_t rsp asm ("rsp");
+        a0 = rsp;
+    }
     asm volatile ("syscall");
+    {
+        register uintptr_t rsp asm ("rsp");
+        a1 = rsp;
+    }
+
+    if (a0 != a1) {
+        while (1);
+    }
 }
 
 void idle_func(uintptr_t id) {
@@ -31,7 +44,6 @@ void idle_func(uintptr_t id) {
     uintptr_t a0 = 0, a1 = 0;
 
     *((uint16_t *) MM_VIRTUALIZE(0xB8000) + 80 * 1 + id) = (id + 'A') | ((id + 0x9) << 8);
-
     {
         register uintptr_t rsp asm ("rsp");
         a0 = rsp;
@@ -48,7 +60,19 @@ void idle_func(uintptr_t id) {
 
     while (1) {
         func0(id, state);
-        asm volatile ("syscall");
+    {
+        register uintptr_t rsp asm ("rsp");
+        a0 = rsp;
+    }
+    asm volatile ("syscall");
+    {
+        register uintptr_t rsp asm ("rsp");
+        a1 = rsp;
+    }
+
+    if (a0 != a1) {
+        while (1);
+    }
         state = !state;
         for (size_t i = 0; i < 10000000; ++i);
     }
diff --git a/sys/amd64/syscall.c b/sys/amd64/syscall.c
new file mode 100644
index 0000000..1f922ac
--- /dev/null
+++ b/sys/amd64/syscall.c
@@ -0,0 +1,6 @@
+#include "sys/types.h"
+#include "sys/debug.h"
+
+int amd64_syscall(uintptr_t rdi, uintptr_t rsi, uintptr_t rdx, uintptr_t rcx, uintptr_t r10, uintptr_t rax) {
+    return 0;
+}
diff --git a/sys/amd64/syscall_s.S b/sys/amd64/syscall_s.S
index 30c9b9a..342b4c8 100644
--- a/sys/amd64/syscall_s.S
+++ b/sys/amd64/syscall_s.S
@@ -55,21 +55,54 @@ amd64_syscall_entry:
     movq get_cpu(0x08), %rsp
     movq (%rsp), %rsp
 
-    pushq %rax
-    movq get_cpu(0x20), %rax
-    pushq %rax
+    pushq %rcx
+    movq get_cpu(0x20), %rcx
+    pushq %rcx
+    pushq %r11
 
-    movq $100000000, %rax
+    // Safe for interrupts now
     sti
 
-1:
-    decq %rax
-    jnz 1b
+    // Userspace:
+    //  %rdi %rsi %rdx %rcx %8 %r9
+    // Syscall:
+    //  %rdi %rsi %rdx %r10 %r8 %r9
+    //  %rax
+    // Now it's done like
+    //  %rdi -> %rdi
+    //  %rsi -> %rsi
+    //  %rdx -> %rdx
+    //  %r10 -> %rcx
+    //  %r8  -> %r8
+    //  %rax -> %r9
+    // FIXME: use %rax properly and
+    //        have a table of system calls
+
+    movq %r10, %rcx
+    movq %rax, %r9
+    call amd64_syscall
+
+    // Disable interrupts
     cli
 
+    popq %r11
     popq %rdi
-    popq %rax
+    popq %rcx
+
+    // We could've been interrupted by irq0, which could've
+    // scheduled a new task, which could've rewritten the TSS/RSP0
+    // with weird values, so just fix that up
+    movq %rsp, %rdx
+    movq get_cpu(0x08), %rsi
+    movq %rdx, (%rsi)
+    movq get_cpu(0x18), %rsi
+    addq $(25 * 8), %rdx
+    movq %rdx, 4(%rsi)
+
     movq %rdi, %rsp
 
     swapgs
     sysretq
+
+_fmt0:
+    .string "rsp = %p\n"