82 lines
3.1 KiB
C
82 lines
3.1 KiB
C
// Segments in proc->gdt.
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// Also known to bootasm.S and trapasm.S
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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_KCPU 3 // kernel per-cpu data
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#define SEG_UCODE 4 // user code
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#define SEG_UDATA 5 // user data+stack
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#define SEG_TSS 6 // this process's task state
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#define NSEGS 7
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// Saved registers for kernel context switches.
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// Don't need to save all the segment registers (%cs, etc),
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// because they are constant across kernel contexts.
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// Don't need to save %eax, %ecx, %edx, because the
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// x86 convention is that the caller has saved them.
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// Contexts are stored at the bottom of the stack they
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// describe; the stack pointer is the address of the context.
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// The layout of the context matches the layout of the stack in swtch.S
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// at "Switch stacks" comment. Switch itself doesn't save eip explicitly,
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// but it is on the stack and allocproc() manipulates it.
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struct context {
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uint edi;
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uint esi;
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uint ebx;
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uint ebp;
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uint eip;
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};
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enum procstate { UNUSED, EMBRYO, SLEEPING, RUNNABLE, RUNNING, ZOMBIE };
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// Per-process state
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struct proc {
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uint sz; // Size of process memory (bytes)
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pde_t* pgdir; // linear address of proc's pgdir
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char *kstack; // Bottom of kernel stack for this process
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enum procstate state; // Process state
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volatile int pid; // Process ID
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struct proc *parent; // Parent process
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struct trapframe *tf; // Trap frame for current syscall
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struct context *context; // Switch here to run 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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char name[16]; // Process name (debugging)
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};
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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 id; // Local APIC ID; index into cpus[] below
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struct context *scheduler; // 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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volatile uint booted; // Has the CPU started?
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int ncli; // Depth of pushcli nesting.
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int intena; // Were interrupts enabled before pushcli?
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// Cpu-local storage variables; see below
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struct cpu *cpu;
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struct proc *proc;
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};
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extern struct cpu cpus[NCPU];
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extern int ncpu;
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// Per-CPU variables, holding pointers to the
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// current cpu and to the current process.
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// The asm suffix tells gcc to use "%gs:0" to refer to cpu
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// and "%gs:4" to refer to proc. ksegment sets up the
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// %gs segment register so that %gs refers to the memory
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// holding those two variables in the local cpu's struct cpu.
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// This is similar to how thread-local variables are implemented
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// in thread libraries such as Linux pthreads.
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extern struct cpu *cpu asm("%gs:0"); // This cpu.
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extern struct proc *proc asm("%gs:4"); // Current proc on this cpu.
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