From 563b3023bbb8cfac20d46129e7f63457d91e96e4 Mon Sep 17 00:00:00 2001
From: Mark <alnyan@airmail.cc>
Date: Sun, 29 Dec 2019 01:54:46 +0200
Subject: [PATCH] Can handle process page faults by killing them

---
 etc/make/amd64/conf.mk  |  4 ++++
 sys/amd64/hw/pfault.c   |  4 +++-
 sys/amd64/hw/pfault_s.S |  9 +++++++++
 usr/init.c              | 19 +++++++++++++++++++
 4 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/etc/make/amd64/conf.mk b/etc/make/amd64/conf.mk
index 1cf964f..c75d4d3 100644
--- a/etc/make/amd64/conf.mk
+++ b/etc/make/amd64/conf.mk
@@ -112,6 +112,10 @@ QEMU_OPTS?=-m $(QEMU_MEM) \
 		   $(QEMU_DEVS) \
 		   -smp $(QEMU_SMP)
 
+ifdef QEMU_DEBUG
+QEMU_OPTS+=-s -S
+endif
+
 $(O)/sys/amd64/image.iso: $(O)/sys/amd64/kernel.elf \
 						  $(O)/sys/amd64/loader.elf \
 						  $(O)/sys/amd64/initrd.img \
diff --git a/sys/amd64/hw/pfault.c b/sys/amd64/hw/pfault.c
index fb4609a..33cb953 100644
--- a/sys/amd64/hw/pfault.c
+++ b/sys/amd64/hw/pfault.c
@@ -3,6 +3,8 @@
 #include "sys/thread.h"
 #include "sys/debug.h"
 
+extern void amd64_syscall_yield_stopped();
+
 int amd64_pfault(uintptr_t cr2) {
     struct cpu *cpu = get_cpu();
     _assert(cpu);
@@ -13,8 +15,8 @@ int amd64_pfault(uintptr_t cr2) {
         thr->pid);
 
     kdebug("CR2 = %p\n", cr2);
-    //0xffffff000220f668
 
+    amd64_syscall_yield_stopped();
     return -1;
 }
 
diff --git a/sys/amd64/hw/pfault_s.S b/sys/amd64/hw/pfault_s.S
index ae05d80..0242149 100644
--- a/sys/amd64/hw/pfault_s.S
+++ b/sys/amd64/hw/pfault_s.S
@@ -39,6 +39,15 @@ amd64_exc_isr_14:
     movq %cr2, %rdi
     call amd64_pfault
 
+    // If fault handler returned zero, it means next task is selected
+    // and should be run
+    test %rax, %rax
+    jnz 1f
+
+    // Ok, continue
+
+
+    // Fail
 1:
     cli
     hlt
diff --git a/usr/init.c b/usr/init.c
index bfa25cc..416e9f9 100644
--- a/usr/init.c
+++ b/usr/init.c
@@ -21,6 +21,25 @@ static int cmd_exec(const char *cmd) {
         }
     }
 
+    if (!strcmp(cmd, "crash")) {
+        uint32_t *value_ptr = (uint32_t *) 0;
+        *value_ptr = 123;
+        return 0;
+    }
+
+    if (!strcmp(cmd, "fork-crash")) {
+        int pid = fork();
+
+        if (pid == 0) {
+            printf("Crashing child\n");
+            uint32_t *value_ptr = (uint32_t *) 0;
+            *value_ptr = 123;
+            printf("Shouldn't run\n");
+            exit(-1);
+        }
+        return 0;
+    }
+
     if (!strcmp(cmd, "hello")) {
         int res;