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// Segments in proc->gdt.
// Also known to bootasm.S and trapasm.S
#define SEG_KCODE 1 // kernel code
#define SEG_KDATA 2 // kernel data+stack
#define SEG_KCPU 3 // kernel per-cpu data
#define SEG_UCODE 4
#define SEG_UDATA 5
#define SEG_TSS 6 // this process's task state
#define NSEGS 7
// Saved registers for kernel context switches.
// Don't need to save all the segment registers (%cs, etc),
// because they are constant across kernel contexts.
// Don't need to save %eax, %ecx, %edx, because the
// x86 convention is that the caller has saved them.
// Contexts are stored at the bottom of the stack they
// describe; the stack pointer is the address of the context.
// The layout of the context must match the code in swtch.S.
struct context {
uint edi;
uint esi;
uint ebx;
uint ebp;
uint eip;
};
enum procstate { UNUSED, EMBRYO, SLEEPING, RUNNABLE, RUNNING, ZOMBIE };
// Per-process state
struct proc {
char *mem; // Start of process memory (kernel address)
uint sz; // Size of process memory (bytes)
char *kstack; // Bottom of kernel stack for this process
enum procstate state; // Process state
volatile int pid; // Process ID
struct proc *parent; // Parent process
struct trapframe *tf; // Trap frame for current syscall
struct context *context; // Switch here to run process
void *chan; // If non-zero, sleeping on chan
int killed; // If non-zero, have been killed
struct file *ofile[NOFILE]; // Open files
struct inode *cwd; // Current directory
char name[16]; // Process name (debugging)
};
// Process memory is laid out contiguously, low addresses first:
// text
// original data and bss
// fixed-size stack
// expandable heap
// Per-CPU state
struct cpu {
uchar id; // Local APIC ID; index into cpus[] below
struct context *scheduler; // Switch here to enter scheduler
struct taskstate ts; // Used by x86 to find stack for interrupt
struct segdesc gdt[NSEGS]; // x86 global descriptor table
volatile uint booted; // Has the CPU started?
int ncli; // Depth of pushcli nesting.
int intena; // Were interrupts enabled before pushcli?
void *tls[2];
};
extern struct cpu cpus[NCPU];
extern int ncpu;
// Per-CPU variables, holding pointers to the
// current cpu and to the current process.
// The __thread prefix tells gcc to refer to them in the segment
// pointed at by gs; the name __thread derives from the use
// of the same mechanism to provide per-thread storage in
// multithreaded user programs.
extern __thread struct cpu *cpu; // This cpu.
extern __thread struct proc *proc; // Current process on this cpu.
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