feat: detect proc_ops support via header parsing instead of version check. (#411)

Some kernels (e.g. 5.4 with backports) include proc_ops despite being
older than 5.6.0. Replace hardcoded version check with runtime header
detection to handle these cases.

- Check for "struct proc_ops" in include/linux/proc_fs.h
- Use KSU_COMPAT_HAS_PROC_OPS macro for conditional compilation
- Fixes build failures on kernels with backported proc_ops

Signed-off-by: JackAltman

kernel/Makefile

@@ -126,6 +126,11 @@ $(info -- KernelSU/compat: new vfs_getattr() found)
 ccflags-y += -DKSU_HAS_NEW_VFS_GETATTR
 endif
 
+# Function proc_ops check
+ifeq ($(shell grep -q "struct proc_ops " $(srctree)/include/linux/proc_fs.h; echo $$?),0)
+ccflags-y += -DKSU_COMPAT_HAS_PROC_OPS
+endif
+
 # Custom Signs
 ifdef KSU_EXPECTED_SIZE
 ccflags-y += -DEXPECTED_SIZE=$(KSU_EXPECTED_SIZE)

kernel/throne_comm.c

@@ -78,7 +78,7 @@ static ssize_t uid_scanner_write(struct file *file, const char __user *buffer,
 	return count;
 }
 
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,6,0)
+#ifdef KSU_COMPAT_HAS_PROC_OPS
 static const struct proc_ops uid_scanner_proc_ops = {
 	.proc_open = uid_scanner_open,
 	.proc_read = seq_read,
@@ -133,4 +133,4 @@ void ksu_throne_comm_exit(void)
 	}
 	
 	pr_info("throne communication cleaned up\n");
-}
+}