[hal] Use setcap instead of setuid for setting thread priorities (#3613)

We originally moved to setuid admin so user programs could do other things requiring admin if they wanted. However, these things, like setting RT priorities of other processes, can usually be done instead as admin during the GradleRIO 2022 deploy process, or adding commands to the robotCommand script. By going back to setcap, we can simplify the HAL code.
wpilibsuite · Oct 4, 2021 · cc31079 · cc31079
1 parent 4676648
commit cc31079
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Showing 2 changed files with 6 additions and 49 deletions.
diff --git a/hal/src/main/native/athena/Threads.cpp b/hal/src/main/native/athena/Threads.cpp
@@ -6,42 +6,9 @@
 
 #include <pthread.h>
 #include <sched.h>
-#include <unistd.h>
-
-#include <cerrno>
-#include <cstdlib>
-#include <system_error>
-
-#include <fmt/format.h>
 
 #include "hal/Errors.h"
 
-namespace {
-class UidSetter {
- public:
-  explicit UidSetter(uid_t uid) {
-    m_uid = geteuid();
-    if (uid == 0 && setuid(uid) == -1) {
-      throw std::system_error(errno, std::generic_category(),
-                              fmt::format("setuid({}) failed", uid));
-    } else if (uid != 0 && seteuid(uid) == -1) {
-      throw std::system_error(errno, std::generic_category(),
-                              fmt::format("seteuid({}) failed", uid));
-    }
-  }
-
-  ~UidSetter() noexcept(false) {
-    if (geteuid() != m_uid && seteuid(m_uid) == -1) {
-      throw std::system_error(errno, std::generic_category(),
-                              fmt::format("seteuid({}) failed", m_uid));
-    }
-  }
-
- private:
-  uid_t m_uid;
-};
-}  // namespace
-
 namespace hal::init {
 void InitializeThreads() {}
 }  // namespace hal::init
@@ -104,20 +71,13 @@ HAL_Bool HAL_SetThreadPriority(NativeThreadHandle handle, HAL_Bool realTime,
     sch.sched_priority = 0;
   }
 
-  try {
-    UidSetter uidSetter{0};
-
-    if (pthread_setschedparam(*reinterpret_cast<const pthread_t*>(handle),
-                              scheduler, &sch)) {
-      *status = HAL_THREAD_PRIORITY_ERROR;
-      return false;
-    } else {
-      *status = 0;
-      return true;
-    }
-  } catch (const std::system_error& e) {
-    *status = HAL_SETUID_ERROR;
+  if (pthread_setschedparam(*reinterpret_cast<const pthread_t*>(handle),
+                            scheduler, &sch)) {
+    *status = HAL_THREAD_PRIORITY_ERROR;
     return false;
+  } else {
+    *status = 0;
+    return true;
   }
 }
 

diff --git a/hal/src/main/native/include/hal/Errors.h b/hal/src/main/native/include/hal/Errors.h
@@ -135,9 +135,6 @@
 #define HAL_USE_LAST_ERROR_MESSAGE \
   "HAL: Use HAL_GetLastError(status) to get last error"
 
-#define HAL_SETUID_ERROR -1157
-#define HAL_SETUID_ERROR_MESSAGE "HAL: Setting the effective user ID has failed"
-
 #define HAL_CAN_BUFFER_OVERRUN -35007
 #define HAL_CAN_BUFFER_OVERRUN_MESSAGE \
   "HAL: CAN Output Buffer Full. Ensure a device is attached"