ce2e751555
I don't actually think this is worthwhile, but I figured
I would check it in before reverting it, so that it can
be in the revision history.
Pros:
* curproc doesn't need to turn on/off interrupts
* scheduler doesn't have to edit curproc anymore
Cons:
* it's ugly
* all the stack computation is more complicated.
* it doesn't actually simplify anything but curproc,
and even curproc is harder to follow.
76 lines
2.4 KiB
C
76 lines
2.4 KiB
C
// Segments in proc->gdt
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#define SEG_KCODE 1 // kernel code
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#define SEG_KDATA 2 // kernel data+stack
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#define SEG_UCODE 3
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#define SEG_UDATA 4
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#define SEG_TSS 5 // this process's task state
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#define SEG_CPUSTACK 6
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#define SEG_PROCSTACK 7
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#define NSEGS 8
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// Saved registers for kernel context switches.
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// Don't need to save all the %fs etc. segment registers,
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// because they are constant across kernel contexts.
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// Save all the regular registers so we don't need to care
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// which are caller save, but not the return register %eax.
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// (Not saving %eax just simplifies the switching code.)
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// The layout of context must match code in swtch.S.
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struct context {
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int eip;
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int esp;
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int ebx;
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int ecx;
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int edx;
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int esi;
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int edi;
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int ebp;
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int ss;
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};
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enum proc_state { UNUSED, EMBRYO, SLEEPING, RUNNABLE, RUNNING, ZOMBIE };
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// Per-process state
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struct proc {
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char *mem; // Start of process memory (kernel address)
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uint sz; // Size of process memory (bytes)
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char *kstack; // Bottom of kernel stack for this process
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enum proc_state state; // Process state
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int pid; // Process ID
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struct proc *parent; // Parent process
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void *chan; // If non-zero, sleeping on chan
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int killed; // If non-zero, have been killed
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struct file *ofile[NOFILE]; // Open files
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struct inode *cwd; // Current directory
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struct context context; // Switch here to run process
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struct trapframe *tf; // Trap frame for current interrupt
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char name[16]; // Process name (debugging)
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};
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// The word at kstack + KSTACKTOP is a pointer to the struct proc.
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#define KSTACKTOP (KSTACKSIZE-4)
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// Process memory is laid out contiguously, low addresses first:
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// text
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// original data and bss
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// fixed-size stack
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// expandable heap
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// Per-CPU state
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struct cpu {
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uchar apicid; // Local APIC ID
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struct context context; // Switch here to enter scheduler
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struct taskstate ts; // Used by x86 to find stack for interrupt
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struct segdesc gdt[NSEGS]; // x86 global descriptor table
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char *stack;
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volatile int booted; // Has the CPU started?
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int ncli; // Depth of pushcli nesting.
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};
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extern struct cpu cpus[NCPU];
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extern int ncpu;
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// "cp" is a short alias for curproc().
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// It gets used enough to make this worthwhile.
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#define cp curproc()
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