Changeset 3fcea34 in mainline for kernel/generic/src/proc/thread.c

Timestamp:

2024-09-20T12:16:28Z (5 months ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

master

Children:

d3109ff

Parents:

2cf8f994

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2024-09-20 11:42:13)

git-committer:

Jiří Zárevúcky <zarevucky.jiri@…> (2024-09-20 12:16:28)

Message:

Simplify the SYS_THREAD_CREATE syscall interface

Removed the beefy uarg structure. Instead, the syscall gets two
parameters: %pc (program counter) and %sp (stack pointer). It starts
a thread with those values in corresponding registers, with no other
fuss whatsoever.

libc initializes threads by storing any other needed arguments on
the stack and retrieving them in thread_entry. Importantly, this
includes the address of the thread_main function which is now
called indirectly to fix dynamic linking issues on some archs.

There's a bit of weirdness on SPARC and IA-64, because of their
stacked register handling. The current solution is that we require
some space *above* the stack pointer to be available for those
architectures. I think for SPARC, it can be made more normal.

For the remaining ones, we can (probably) just set the initial
%sp to the top edge of the stack. There's some lingering offsets
on some archs just because I didn't want to accidentally break
anything. The initial thread bringup should be functionally
unchanged from the previous state, and no binaries are currently
multithreaded except thread1 test, so there should be minimal
risk of breakage. Naturally, I tested all available emulator
builds, save for msim.

File:

• kernel/generic/src/proc/thread.c (modified) (2 diffs)

kernel/generic/src/proc/thread.c

@@ -944 +944 @@
 
 /** Process syscall to create new thread.
- *
- */
-sys_errno_t sys_thread_create(uspace_ptr_uspace_arg_t uspace_uarg, uspace_ptr_char uspace_name,
-    size_t name_len, uspace_ptr_thread_id_t uspace_thread_id)
+ * The started thread will have initial pc and sp set to the exact values passed
+ * to the syscall. The kernel will not touch any stack data below the stack
+ * pointer, but some architectures may require some space to be available
+ * for use above it. See userspace() in kernel, and <libarch/thread.h> in libc.
+ *
+ */
+sys_errno_t sys_thread_create(sysarg_t pc, sysarg_t sp,
+    uspace_ptr_char uspace_name, size_t name_len)
 {
         if (name_len > THREAD_NAME_BUFLEN - 1)
@@ -963 +967 @@
          * In case of success, kernel_uarg will be freed in uinit().
          */
-        uspace_arg_t *kernel_uarg =
-            (uspace_arg_t *) malloc(sizeof(uspace_arg_t));
+        uinit_arg_t *kernel_uarg = malloc(sizeof(uinit_arg_t));
         if (!kernel_uarg)
                 return (sys_errno_t) ENOMEM;
 
-        rc = copy_from_uspace(kernel_uarg, uspace_uarg, sizeof(uspace_arg_t));
-        if (rc != EOK) {
-                free(kernel_uarg);
-                return (sys_errno_t) rc;
-        }
+        kernel_uarg->pc = pc;
+        kernel_uarg->sp = sp;
+
+        // TODO: fix some unnecessary inconsistencies between architectures
 
         thread_t *thread = thread_create(uinit, kernel_uarg, TASK,
             THREAD_FLAG_USPACE | THREAD_FLAG_NOATTACH, namebuf);
-        if (thread) {
-                if (uspace_thread_id) {
-                        rc = copy_to_uspace(uspace_thread_id, &thread->tid,
-                            sizeof(thread->tid));
-                        if (rc != EOK) {
-                                /*
-                                 * We have encountered a failure, but the thread
-                                 * has already been created. We need to undo its
-                                 * creation now.
-                                 */
-
-                                /*
-                                 * The new thread structure is initialized, but
-                                 * is still not visible to the system.
-                                 * We can safely deallocate it.
-                                 */
-                                slab_free(thread_cache, thread);
-                                free(kernel_uarg);
-
-                                return (sys_errno_t) rc;
-                        }
-                }
+        if (!thread) {
+                free(kernel_uarg);
+                return (sys_errno_t) ENOMEM;
+        }
 
 #ifdef CONFIG_UDEBUG
-                /*
-                 * Generate udebug THREAD_B event and attach the thread.
-                 * This must be done atomically (with the debug locks held),
-                 * otherwise we would either miss some thread or receive
-                 * THREAD_B events for threads that already existed
-                 * and could be detected with THREAD_READ before.
-                 */
-                udebug_thread_b_event_attach(thread, TASK);
+        /*
+         * Generate udebug THREAD_B event and attach the thread.
+         * This must be done atomically (with the debug locks held),
+         * otherwise we would either miss some thread or receive
+         * THREAD_B events for threads that already existed
+         * and could be detected with THREAD_READ before.
+         */
+        udebug_thread_b_event_attach(thread, TASK);
 #else
-                thread_attach(thread, TASK);
+        thread_attach(thread, TASK);
 #endif
-                thread_start(thread);
-                thread_put(thread);
-
-                return 0;
-        } else
-                free(kernel_uarg);
-
-        return (sys_errno_t) ENOMEM;
+        thread_start(thread);
+        thread_put(thread);
+
+        return (sys_errno_t) EOK;
 }