From 99645488f068496073cf9216caf091665675f60f Mon Sep 17 00:00:00 2001
From: AuxXxilium <info@auxxxilium.tech>
Date: Fri, 1 Mar 2024 15:43:47 +0100
Subject: [PATCH] lkm5: add ioscheduler fixer

Signed-off-by: AuxXxilium <info@auxxxilium.tech>
---
 Makefile                     |  2 +-
 internal/ioscheduler_fixer.c | 26 ++++++++++++++++++++++++++
 internal/ioscheduler_fixer.h |  6 ++++++
 redpill_main.c               |  1 +
 4 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 internal/ioscheduler_fixer.c
 create mode 100644 internal/ioscheduler_fixer.h

diff --git a/Makefile b/Makefile
index 41a0a45..4810b08 100644
--- a/Makefile
+++ b/Makefile
@@ -13,7 +13,7 @@ SRCS-y  += compat/string_compat.c \
 		   internal/override/override_symbol.c internal/override/override_syscall.c internal/intercept_execve.c \
 		   internal/call_protected.c internal/intercept_driver_register.c internal/stealth/sanitize_cmdline.c \
 		   internal/stealth.c internal/virtual_pci.c internal/uart/uart_swapper.c internal/uart/vuart_virtual_irq.c \
-		   internal/uart/virtual_uart.c \
+		   internal/uart/virtual_uart.c internal/ioscheduler_fixer.c \
 		   \
 		   config/cmdline_delegate.c config/runtime_config.c \
 		   \
diff --git a/internal/ioscheduler_fixer.c b/internal/ioscheduler_fixer.c
new file mode 100644
index 0000000..6c1405e
--- /dev/null
+++ b/internal/ioscheduler_fixer.c
@@ -0,0 +1,26 @@
+/**
+ * This very simple submodule which prevents kernel log from being flooded with "I/O scheduler elevator not found"
+ *
+ * When this shim is loaded as a I/O scheduler (to load very early) it is being set as a I/O scheduler. As we later
+ * remove the module file the system will constantly try to load now non-existing module "elevator-iosched". By
+ * resetting the "chosen_elevator" using the same function called by "elevator=" handler we can pretend no custom
+ * I/O scheduler was ever set (so that the system uses default one and stops complaining)
+ */
+#include "ioscheduler_fixer.h"
+#include "../common.h"
+#include "call_protected.h" //is_system_booting(), elevator_setup()
+#include <linux/kernel.h> //system_state
+
+#define SHIM_NAME "I/O scheduler fixer"
+
+int reset_elevator(void)
+{
+    if (!is_system_booting()) {
+        pr_loc_wrn("Cannot reset I/O scheduler / elevator= set - system is past booting stage (state=%d)",
+                   system_state);
+        return 0; //This is not an error technically speaking
+    }
+
+    pr_loc_dbg("Resetting I/O scheduler to default");
+    return _elevator_setup("") == 1 ? 0 : -EINVAL;
+}
\ No newline at end of file
diff --git a/internal/ioscheduler_fixer.h b/internal/ioscheduler_fixer.h
new file mode 100644
index 0000000..728f789
--- /dev/null
+++ b/internal/ioscheduler_fixer.h
@@ -0,0 +1,6 @@
+#ifndef REDPILL_IOSCHEDULER_FIXER_H
+#define REDPILL_IOSCHEDULER_FIXER_H
+
+int reset_elevator(void);
+
+#endif //REDPILL_IOSCHEDULER_FIXER_H
diff --git a/redpill_main.c b/redpill_main.c
index a3d1cc7..874f042 100644
--- a/redpill_main.c
+++ b/redpill_main.c
@@ -63,6 +63,7 @@ static int __init init_(void)
          || (out = register_disk_smart_shim()) != 0 //provide fake SMART to userspace
          || (out = register_pmu_shim(current_config.hw_config)) != 0 //this is used as early as mfgBIOS loads (=late)
          || (out = initialize_stealth(&current_config)) != 0 //Should be after any shims to let shims have real stuff
+         || (out = reset_elevator()) != 0 //Cosmetic, can be the last one
        )
         goto error_out;