Created student weenix repository

1 files changed, 150 insertions, 0 deletions

diff --git a/kernel/proc/context.c b/kernel/proc/context.c
new file mode 100644
index 0000000..b1902d8
--- /dev/null
+++ b/kernel/proc/context.c
@@ -0,0 +1,150 @@
+
+#include "proc/context.h"
+#include "proc/kthread.h"
+#include <main/cpuid.h>
+
+#include "main/apic.h"
+#include "main/gdt.h"
+
+typedef struct context_initial_func_args
+{
+    context_func_t func;
+    long arg1;
+    void *arg2;
+} packed context_initial_func_args_t;
+
+static void __context_thread_initial_func(context_initial_func_args_t args)
+{
+    preemption_reset();
+    apic_setipl(IPL_LOW);
+    intr_enable();
+
+    void *result = (args.func)(args.arg1, args.arg2);
+    kthread_exit(result);
+
+    panic("\nReturned from kthread_exit.\n");
+}
+
+void context_setup_raw(context_t *c, void (*func)(), void *kstack,
+                       size_t kstacksz, pml4_t *pml4)
+{
+    KASSERT(NULL != pml4);
+    KASSERT(PAGE_ALIGNED(kstack));
+    c->c_kstack = (uintptr_t)kstack;
+    c->c_kstacksz = kstacksz;
+    c->c_pml4 = pml4;
+    c->c_rsp = (uintptr_t)kstack + kstacksz;
+    c->c_rsp -= sizeof(uintptr_t);
+    *((uintptr_t *)c->c_rsp) = 0;
+    c->c_rbp = c->c_rsp;
+    c->c_rip = (uintptr_t)func;
+}
+
+/*
+ * Initializes a context_t struct with the given parameters. arg1 and arg2 will
+ * appear as arguments to the function passed in when this context is first
+ * used.
+ */
+void context_setup(context_t *c, context_func_t func, long arg1, void *arg2,
+                   void *kstack, size_t kstacksz, pml4_t *pml4)
+{
+    KASSERT(NULL != pml4);
+    KASSERT(PAGE_ALIGNED(kstack));
+
+    c->c_kstack = (uintptr_t)kstack;
+    c->c_kstacksz = kstacksz;
+    c->c_pml4 = pml4;
+
+    /* put the arguments for __context_thread_initial_func onto the
+     * stack */
+    c->c_rsp = (uintptr_t)kstack + kstacksz;
+    c->c_rsp -= sizeof(arg2);
+    *(void **)c->c_rsp = arg2;
+    c->c_rsp -= sizeof(arg1);
+    *(long *)c->c_rsp = arg1;
+    c->c_rsp -= sizeof(context_func_t);
+    *(context_func_t *)c->c_rsp = func;
+    // Take space for the function return address (unused)
+    c->c_rsp -= sizeof(uintptr_t);
+
+    c->c_rbp = c->c_rsp;
+    c->c_rip = (uintptr_t)__context_thread_initial_func;
+}
+
+/*
+ * WARNING!! POTENTIAL EDITOR BEWARE!!
+ * IF YOU REMOVE THE PT_SET CALLS BELOW,
+ * YOU ***MUST*** DEAL WITH SMP TLB SHOOTDOWN
+ *
+ * IN OTHER WORDS, THINK *VERY* CAREFULLY BEFORE
+ * REMOVING THE CALLS TO PT_SET BELOW
+ */
+
+void context_make_active(context_t *c)
+{
+    // gdt_set_kernel_stack((void *)((uintptr_t)c->c_kstack + c->c_kstacksz));
+    pt_set(c->c_pml4);
+
+    /* Switch stacks and run the thread */
+    __asm__ volatile(
+        "movq %0,%%rbp\n\t" /* update rbp */
+        "movq %1,%%rsp\n\t" /* update rsp */
+        "push %2\n\t"       /* save rip   */
+        "ret"               /* jump to new rip */
+        ::"m"(c->c_rbp),
+        "m"(c->c_rsp), "m"(c->c_rip));
+}
+
+void context_switch(context_t *oldc, context_t *newc)
+{
+    gdt_set_kernel_stack(
+        (void *)((uintptr_t)newc->c_kstack + newc->c_kstacksz));
+
+    // sanity check that core-specific data is being managed (paged in)
+    // correctly
+    KASSERT(oldc->c_pml4 == pt_get());
+    uintptr_t curthr_paddr =
+        pt_virt_to_phys_helper(oldc->c_pml4, (uintptr_t)&curthr);
+    uintptr_t new_curthr_paddr =
+        pt_virt_to_phys_helper(newc->c_pml4, (uintptr_t)&curthr);
+
+    kthread_t *prev_curthr = curthr;
+    pt_set(newc->c_pml4);
+    KASSERT(pt_get() == newc->c_pml4);
+
+    KASSERT(curthr_paddr == new_curthr_paddr);
+    KASSERT(prev_curthr == curthr);
+
+    /*
+     * Save the current value of the stack pointer and the frame pointer into
+     * the old context. Set the instruction pointer to the return address
+     * (whoever called us).
+     */
+    __asm__ volatile(
+        "pushfq;"             /* save RFLAGS on the stack */
+        "pushq  %%rbp     \n" /* save base pointer */
+        "pushq  %%rbx     \n" /* save other callee-saved registers */
+        "pushq  %%r12     \n"
+        "pushq  %%r13     \n"
+        "pushq  %%r14     \n"
+        "pushq  %%r15     \n"
+        "movq   %%rsp, %0 \n" /* save RSP into oldc */
+        "movq   %2, %%rsp \n" /* restore RSP from newc */
+        "pushq %%rax\n\t"
+        "movabs  $1f, %%rax   \n\t" /* save RIP into oldc (saves the label '1'
+                                       below) */
+        "mov %%rax, %1\n\t"
+        "popq %%rax\n\t"
+        "pushq  %3        \n\t" /* restore RIP */
+        "ret              \n\t"
+        "1:\t"                  /* this is where oldc starts executing later */
+        "popq   %%r15     \n\t" /* restore callee-saved registers */
+        "popq   %%r14     \n\t"
+        "popq   %%r13     \n\t"
+        "popq   %%r12     \n\t"
+        "popq   %%rbx     \n\t"
+        "popq   %%rbp     \n\t" /* restore base pointer */
+        "popfq"                 /* restore RFLAGS */
+        : "=m"(oldc->c_rsp), "=m"(oldc->c_rip)
+        : "m"(newc->c_rsp), "m"(newc->c_rip));
+}