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Improve syscalls for new task switching

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There are a lot of under the hood changes here:
- Move syscalls to be a dispatch table, defined by syscalls.inc
- Don't need a full process state (push_all) in syscalls now
- In push_all, define REGS instead of using offsets
- Save TWO stack pointers as well as current saved stack pointer in TCB:
  - rsp0 is the base of the kernel stack for interrupts
  - rsp3 is the saved user stack from cpu_data
- Update syscall numbers in nulldrv
- Some asm-debugging enhancements to the gdb script
- fork() still not working
This commit is contained in:
Justin C. Miller
2019-04-02 00:25:36 -07:00
parent ca2362f858
commit 11a53e792f
17 changed files with 284 additions and 215 deletions
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178
src/kernel/syscall.cpp
View File

@@ -1,6 +1,7 @@
#include "console.h"
#include "cpu.h"
#include "debug.h"
#include "log.h"
#include "msr.h"
#include "process.h"
#include "scheduler.h"
@@ -11,29 +12,90 @@ extern "C" {
void syscall_handler_prelude();
}
namespace syscalls {
void
syscall_enable()
noop()
{
// IA32_EFER - set bit 0, syscall enable
uint64_t efer = rdmsr(msr::ia32_efer);
wrmsr(msr::ia32_efer, efer|1);
// IA32_STAR - high 32 bits contain k+u CS
// Kernel CS: GDT[1] ring 0 bits[47:32]
// User CS: GDT[3] ring 3 bits[63:48]
uint64_t star =
(((1ull << 3) | 0) << 32) |
(((3ull << 3) | 3) << 48);
wrmsr(msr::ia32_star, star);
// IA32_LSTAR - RIP for syscall
wrmsr(msr::ia32_lstar,
reinterpret_cast<uintptr_t>(&syscall_handler_prelude));
// IA32_FMASK - FLAGS mask inside syscall
wrmsr(msr::ia32_fmask, 0x200);
auto &s = scheduler::get();
auto *p = s.current();
log::debug(logs::syscall, "Process %d called noop syscall.", p->pid);
}
void
exit(int64_t status)
{
auto &s = scheduler::get();
auto *p = s.current();
log::debug(logs::syscall, "Process %d exiting with code %d", p->pid, status);
p->exit(status);
s.schedule();
}
pid_t
getpid()
{
auto &s = scheduler::get();
auto *p = s.current();
return p->pid;
}
pid_t fork() { return 0; }
void
message(const char *message)
{
auto &s = scheduler::get();
auto *p = s.current();
log::info(logs::syscall, "Message[%d]: %s", p->pid, message);
}
void
pause()
{
auto &s = scheduler::get();
auto *p = s.current();
p->wait_on_signal(-1ull);
s.schedule();
}
void
sleep(uint64_t til)
{
auto &s = scheduler::get();
auto *p = s.current();
log::debug(logs::syscall, "Process %d sleeping until %d", p->pid, til);
p->wait_on_time(til);
s.schedule();
}
void send() {}
void receive() {}
} // namespace syscalls
struct syscall_handler_info
{
unsigned nargs;
const char *name;
};
uintptr_t syscall_registry[static_cast<unsigned>(syscall::COUNT)];
syscall_handler_info syscall_info_registry[static_cast<unsigned>(syscall::COUNT)];
void
syscall_invalid(uint64_t call)
{
console *cons = console::get();
cons->set_color(9);
cons->printf("\nReceived unknown syscall: %d\n", call);
cons->set_color();
_halt();
}
/*
void
syscall_dispatch(cpu_state *regs)
{
@@ -56,44 +118,6 @@ syscall_dispatch(cpu_state *regs)
cons->printf(" Syscall sysret: %8d\n", __counter_syscall_sysret);
break;
case syscall::message:
cons->set_color(11);
cons->printf("\nProcess %d: Received MESSAGE syscall\n", p->pid);
cons->set_color();
break;
case syscall::pause:
{
cons->set_color(11);
auto &s = scheduler::get();
auto *p = s.current();
p->wait_on_signal(-1ull);
cons->printf("\nProcess %d: Received PAUSE syscall\n", p->pid);
cons->set_color();
s.schedule();
}
break;
case syscall::sleep:
{
cons->set_color(11);
cons->printf("\nProcess %d: Received SLEEP syscall\n", p->pid);
cons->printf("Sleeping until %lu\n", regs->rdi);
cons->set_color();
p->wait_on_time(regs->rdi);
s.schedule();
}
break;
case syscall::getpid:
cons->set_color(11);
cons->printf("\nProcess %d: Received GETPID syscall\n", p->pid);
cons->set_color();
regs->rax = p->pid;
break;
case syscall::send:
{
pid_t target = regs->rdi;
@@ -134,14 +158,6 @@ syscall_dispatch(cpu_state *regs)
}
break;
case syscall::exit:
cons->set_color(11);
cons->printf("\nProcess %d: Received EXIT syscall\n", p->pid);
cons->set_color();
p->exit(regs->rdi);
s.schedule();
break;
default:
cons->set_color(9);
cons->printf("\nReceived unknown syscall: %02x\n", call);
@@ -150,4 +166,36 @@ syscall_dispatch(cpu_state *regs)
break;
}
}
*/
void
syscall_enable()
{
// IA32_EFER - set bit 0, syscall enable
uint64_t efer = rdmsr(msr::ia32_efer);
wrmsr(msr::ia32_efer, efer|1);
// IA32_STAR - high 32 bits contain k+u CS
// Kernel CS: GDT[1] ring 0 bits[47:32]
// User CS: GDT[3] ring 3 bits[63:48]
uint64_t star =
(((1ull << 3) | 0) << 32) |
(((3ull << 3) | 3) << 48);
wrmsr(msr::ia32_star, star);
// IA32_LSTAR - RIP for syscall
wrmsr(msr::ia32_lstar,
reinterpret_cast<uintptr_t>(&syscall_handler_prelude));
// IA32_FMASK - FLAGS mask inside syscall
wrmsr(msr::ia32_fmask, 0x200);
#define SYSCALL(name, nargs) \
syscall_registry[static_cast<unsigned>(syscall::name)] = \
reinterpret_cast<uintptr_t>(syscalls::name); \
syscall_info_registry[static_cast<unsigned>(syscall::name)] = { \
nargs, #name };
#include "syscalls.inc"
#undef SYSCALL
}