Kernel/LibC: Implement sched_* functionality to set/get process priority

Right now, we allow anything inside a user to raise or lower any other process's priority. This feels simple enough to me. Linux disallows raising, but that's annoying in practice.
luteresa · May 30, 2019 · 9cd0f6f · 9cd0f6f
1 parent b160677
commit 9cd0f6f
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Showing 8 changed files with 103 additions and 1 deletion.
diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
@@ -2282,6 +2282,49 @@ int Process::sys$getpeername(int sockfd, sockaddr* addr, socklen_t* addrlen)
  return 0;
 }
 
+int Process::sys$sched_setparam(pid_t pid, const struct sched_param* param)
+{
+ if (!validate_read_typed(param))
+ return -EFAULT;
+
+ InterruptDisabler disabler;
+ auto* peer = this;
+ if (pid != 0)
+ peer = Process::from_pid(pid);
+
+ if (!peer)
+ return -ESRCH;
+
+ if (!is_superuser() && m_euid != peer->m_uid && m_uid != peer->m_uid)
+ return -EPERM;
+
+ if (param->sched_priority < Process::FirstPriority || param->sched_priority > Process::LastPriority)
+ return -EINVAL;
+
+ peer->set_priority(Priority(param->sched_priority));
+ return 0;
+}
+
+int Process::sys$sched_getparam(pid_t pid, struct sched_param* param)
+{
+ if (!validate_read_typed(param))
+ return -EFAULT;
+
+ InterruptDisabler disabler;
+ auto* peer = this;
+ if (pid != 0)
+ peer = Process::from_pid(pid);
+
+ if (!peer)
+ return -ESRCH;
+
+ if (!is_superuser() && m_euid != peer->m_uid && m_uid != peer->m_uid)
+ return -EPERM;
+
+ param->sched_priority = peer->priority();
+ return 0;
+}
+
 int Process::sys$getsockopt(const Syscall::SC_getsockopt_params* params)
 {
  if (!validate_read_typed(params))

diff --git a/Kernel/Process.h b/Kernel/Process.h
@@ -40,9 +40,11 @@ class Process : public InlineLinkedListNode<Process>
  enum Priority
  {
  IdlePriority,
+ FirstPriority = IdlePriority,
  LowPriority,
  NormalPriority,
  HighPriority,
+ LastPriority = HighPriority,
  };
 
  enum RingLevel
@@ -186,6 +188,8 @@ class Process : public InlineLinkedListNode<Process>
  int sys$setsockopt(const Syscall::SC_setsockopt_params*);
  int sys$getsockname(int sockfd, sockaddr* addr, socklen_t* addrlen);
  int sys$getpeername(int sockfd, sockaddr* addr, socklen_t* addrlen);
+ int sys$sched_setparam(pid_t pid, const struct sched_param* param);
+ int sys$sched_getparam(pid_t pid, struct sched_param* param);
  int sys$restore_signal_mask(dword mask);
  int sys$create_thread(int (*)(void*), void*);
  void sys$exit_thread(int code);

diff --git a/Kernel/Syscall.cpp b/Kernel/Syscall.cpp
@@ -276,6 +276,10 @@ static dword handle(RegisterDump& regs, dword function, dword arg1, dword arg2,
  return current->process().sys$getsockname((int)arg1, (sockaddr*)arg2, (socklen_t*)arg3);
  case Syscall::SC_getpeername:
  return current->process().sys$getpeername((int)arg1, (sockaddr*)arg2, (socklen_t*)arg3);
+ case Syscall::SC_sched_setparam:
+ return current->process().sys$sched_setparam((pid_t)arg1, (struct sched_param*)arg2);
+ case Syscall::SC_sched_getparam:
+ return current->process().sys$sched_setparam((pid_t)arg1, (struct sched_param*)arg2);
  default:
  kprintf("<%u> int0x82: Unknown function %u requested {%x, %x, %x}\n", current->process().pid(), function, arg1, arg2, arg3);
  return -ENOSYS;

diff --git a/Kernel/Syscall.h b/Kernel/Syscall.h
@@ -105,7 +105,9 @@
  __ENUMERATE_SYSCALL(writev) \
  __ENUMERATE_SYSCALL(beep) \
  __ENUMERATE_SYSCALL(getsockname) \
- __ENUMERATE_SYSCALL(getpeername)
+ __ENUMERATE_SYSCALL(getpeername) \
+ __ENUMERATE_SYSCALL(sched_setparam) \
+ __ENUMERATE_SYSCALL(sched_getparam)
 
 namespace Syscall {
 

diff --git a/Kernel/UnixTypes.h b/Kernel/UnixTypes.h
@@ -400,3 +400,7 @@ struct iovec {
  void* iov_base;
  size_t iov_len;
 };
+
+struct sched_param {
+ int sched_priority;
+};
diff --git a/LibC/sched.cpp b/LibC/sched.cpp
@@ -10,5 +10,29 @@ int sched_yield()
  __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
+int sched_get_priority_min(int policy)
+{
+ (void)policy;
+ return 0; // Idle
+}
+
+int sched_get_priority_max(int policy)
+{
+ (void)policy;
+ return 3; // High
+}
+
+int sched_setparam(pid_t pid, const struct sched_param *param)
+{
+ int rc = syscall(SC_sched_setparam, pid, param);
+ __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
+int sched_getparam(pid_t pid, struct sched_param *param)
+{
+ int rc = syscall(SC_sched_getparam, pid, param);
+ __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
 }
 
diff --git a/LibC/sched.h b/LibC/sched.h
@@ -1,9 +1,24 @@
 #pragma once
 
+#include <sys/types.h>
 #include <sys/cdefs.h>
 
 __BEGIN_DECLS
 
 int sched_yield();
 
+struct sched_param {
+ int sched_priority;
+};
+
+#define SCHED_FIFO 0
+#define SCHED_RR 1
+#define SCHED_OTHER 2
+#define SCHED_BATCH 3
+
+int sched_get_priority_min(int policy);
+int sched_get_priority_max(int policy);
+int sched_setparam(pid_t pid, const struct sched_param *param);
+int sched_getparam(pid_t pid, struct sched_param *param);
+
 __END_DECLS
diff --git a/LibC/unistd.h b/LibC/unistd.h
@@ -107,4 +107,10 @@ enum
 #define X_OK 1
 #define F_OK 0
 
+/*
+ * We aren't fully compliant (don't support policies, and don't have a wide
+ * range of values), but we do have process priorities.
+ */
+#define _POSIX_PRIORITY_SCHEDULING
+
 __END_DECLS