Imbus/xv6-riscv-kernel
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Make sysexit and trapret paths the same, so that forkret can return through

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either path.  This helped tracking down a bug: use 144 instead of 32 to find cs
in trapframe so that gs is correctly saved and restored.

For good measure update linker script, because newer versions of GCC sometimes
places symbols passed end.
This commit is contained in:
Frans Kaashoek 2018-09-29 08:30:50 -04:00
parent 322990649b
commit 3bfcaeaf01
3 changed files with 22 additions and 12 deletions
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16
proc.c
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@ -6,7 +6,6 @@
#include "x86.h"
#include "proc.h"
#include "spinlock.h"
#include "msr.h"
struct {
struct spinlock lock;
@ -17,7 +16,11 @@ static struct proc *initproc;
int nextpid = 1;
extern void forkret(void);
// we can return two ways out of the kernel and
// for new processes we can choose either way
extern void sysexit(void);
extern void trapret(void);
static void wakeup1(void *chan);
@ -101,6 +104,10 @@ found:
// Leave room for trap frame.
sp -= sizeof *p->tf;
if ((uint64) sp % 16)
panic("misaligned sp");
p->tf = (struct trapframe*)sp;
// Set up new context to start executing at forkret,
@ -132,6 +139,8 @@ userinit(void)
inituvm(p->pgdir, _binary_initcode_start, (uint64)_binary_initcode_size);
p->sz = PGSIZE;
memset(p->tf, 0, sizeof(*p->tf));
p->tf->cs = UCSEG | 0x3;
p->tf->ss = UDSEG | 0x3;
p->tf->r11 = FL_IF;
p->tf->rsp = PGSIZE;
p->tf->rcx = 0; // beginning of initcode.S
@ -321,12 +330,12 @@ scheduler(void)
{
struct proc *p;
struct cpu *c = mycpu();
c->proc = 0;
for(;;){
// Enable interrupts on this processor.
sti();
// Loop over process table looking for process to run.
acquire(&ptable.lock);
for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
@ -336,7 +345,6 @@ scheduler(void)
// Switch to chosen process. It is the process's job
// to release ptable.lock and then reacquire it
// before jumping back to us.
c->proc = p;
switchuvm(p);
p->state = RUNNING;