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From:   Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
To:     linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Sai Praneeth <sai.praneeth.prakhya@intel.com>,
        "Lee, Chun-Yi" <jlee@suse.com>, Borislav Petkov <bp@alien8.de>,
        Tony Luck <tony.luck@intel.com>,
        Will Deacon <will.deacon@arm.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Bhupesh Sharma <bhsharma@redhat.com>,
        Ricardo Neri <ricardo.neri@intel.com>,
        Ravi Shankar <ravi.v.shankar@intel.com>,
        Matt Fleming <matt@codeblueprint.co.uk>,
        Peter Zijlstra <peter.zijlstra@intel.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Dan Williams <dan.j.williams@intel.com>
Subject: [PATCH V1 2/3] efi: Introduce efi_rts_workqueue and necessary infrastructure to invoke all efi_runtime_services()
Date:   Sat, 24 Feb 2018 14:10:48 -0800
Message-Id: <1519510249-31447-3-git-send-email-sai.praneeth.prakhya@intel.com>
In-Reply-To: <1519510249-31447-1-git-send-email-sai.praneeth.prakhya@intel.com>
References: <1519510249-31447-1-git-send-email-sai.praneeth.prakhya@intel.com>
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From: Sai Praneeth <sai.praneeth.prakhya@intel.com>

When a process requests the kernel to execute any efi_runtime_service(),
the requested efi_runtime_service (represented as an identifier) and its
arguments are packed into a struct named efi_runtime_work and queued
onto work queue named efi_rts_wq. The caller then waits until the work
is completed.

Introduce necessary infrastructure:
1. Creating workqueue named efi_rts_wq
2. A macro (efi_queue_work()) that
	a. populates efi_runtime_work
	b. queues work onto efi_rts_wq and
	c. waits until worker thread returns
3. A handler function that
	a. understands efi_runtime_work and
	b. invokes the appropriate efi_runtime_service() with the
	appropriate arguments

The caller thread has to wait until the worker thread returns, because
it's dependent on the return status of efi_runtime_service() and, in
specific cases, the arguments populated by efi_runtime_service(). Some
efi_runtime_services() takes a pointer to buffer as an argument and
fills up the buffer with requested data. For instance,
efi_get_variable() and efi_get_next_variable(). Hence, caller process
cannot just post the work and get going.

Some facts about efi_runtime_services():
1. A quick look at all the efi_runtime_services() shows that any
efi_runtime_service() has five or less arguments.
2. An argument of efi_runtime_service() can be a value (of any type)
or a pointer (of any type).
Hence, efi_runtime_work has five void pointers to store these arguments.

Semantics followed by efi_call_rts() to understand efi_runtime_work:
1. If argument was a pointer, recast it from void pointer to original
pointer type.
2. If argument was a value, recast it from void pointer to original
pointer type and dereference it.

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Suggested-by: Andy Lutomirski <luto@kernel.org>
Cc: Lee, Chun-Yi <jlee@suse.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peter.zijlstra@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Dan Williams <dan.j.williams@intel.com>
---
 drivers/firmware/efi/efi.c              |  11 +++
 drivers/firmware/efi/runtime-wrappers.c | 143 ++++++++++++++++++++++++++++++++
 include/linux/efi.h                     |  23 +++++
 3 files changed, 177 insertions(+)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index ac5db5f8dbbf..4714b305ca90 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -76,6 +76,8 @@ static unsigned long *efi_tables[] = {
 	&efi.mem_attr_table,
 };
 
+struct workqueue_struct *efi_rts_wq;
+
 static bool disable_runtime;
 static int __init setup_noefi(char *arg)
 {
@@ -329,6 +331,15 @@ static int __init efisubsys_init(void)
 	if (!efi_enabled(EFI_BOOT))
 		return 0;
 
+	/* Create a work queue to run EFI Runtime Services */
+	efi_rts_wq = create_workqueue("efi_rts_workqueue");
+	if (!efi_rts_wq) {
+		pr_err("Failed to create efi_rts_workqueue, EFI runtime services "
+		       "disabled.\n");
+		clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
+		return 0;
+	}
+
 	/*
 	 * Clean DUMMY object calls EFI Runtime Service, set_variable(), so
 	 * it should be invoked only after efi_rts_workqueue is ready.
diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
index ae54870b2788..5cdb787da5d3 100644
--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -1,6 +1,14 @@
 /*
  * runtime-wrappers.c - Runtime Services function call wrappers
  *
+ * Implementation summary:
+ * -----------------------
+ * 1. When user/kernel thread requests to execute efi_runtime_service(),
+ * enqueue work to efi_rts_workqueue.
+ * 2. Caller thread waits until the work is finished because it's
+ * dependent on the return status and execution of efi_runtime_service().
+ * For instance, get_variable() and get_next_variable().
+ *
  * Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>
  *
  * Split off from arch/x86/platform/efi/efi.c
@@ -22,6 +30,8 @@
 #include <linux/mutex.h>
 #include <linux/semaphore.h>
 #include <linux/stringify.h>
+#include <linux/workqueue.h>
+
 #include <asm/efi.h>
 
 /*
@@ -33,6 +43,50 @@
 #define __efi_call_virt(f, args...) \
 	__efi_call_virt_pointer(efi.systab->runtime, f, args)
 
+/* Each EFI Runtime Service is represented with a unique number */
+#define GET_TIME					0
+#define SET_TIME					1
+#define GET_WAKEUP_TIME					2
+#define SET_WAKEUP_TIME					3
+#define GET_VARIABLE					4
+#define GET_NEXT_VARIABLE				5
+#define SET_VARIABLE					6
+#define SET_VARIABLE_NONBLOCKING			7
+#define QUERY_VARIABLE_INFO				8
+#define QUERY_VARIABLE_INFO_NONBLOCKING			9
+#define GET_NEXT_HIGH_MONO_COUNT			10
+#define RESET_SYSTEM					11
+#define UPDATE_CAPSULE					12
+#define QUERY_CAPSULE_CAPS				13
+
+/*
+ * efi_queue_work:	Queue efi_runtime_service() and wait until it's done
+ * @rts:		efi_runtime_service() function identifier
+ * @rts_arg<1-5>:	efi_runtime_service() function arguments
+ *
+ * Accesses to efi_runtime_services() are serialized by a binary
+ * semaphore (efi_runtime_lock) and caller waits until the work is
+ * finished, hence _only_ one work is queued at a time. So, queue_work()
+ * should never fail.
+ */
+#define efi_queue_work(_rts, _arg1, _arg2, _arg3, _arg4, _arg5)		\
+({									\
+	struct efi_runtime_work efi_rts_work;				\
+	efi_rts_work.status = EFI_ABORTED;				\
+									\
+	INIT_WORK_ONSTACK(&efi_rts_work.work, efi_call_rts);		\
+	efi_rts_work.func = _rts;					\
+	efi_rts_work.arg1 = _arg1;					\
+	efi_rts_work.arg2 = _arg2;					\
+	efi_rts_work.arg3 = _arg3;					\
+	efi_rts_work.arg4 = _arg4;					\
+	efi_rts_work.arg5 = _arg5;					\
+	if (queue_work(efi_rts_wq, &efi_rts_work.work))			\
+		flush_work(&efi_rts_work.work);				\
+									\
+	efi_rts_work.status;						\
+})
+
 void efi_call_virt_check_flags(unsigned long flags, const char *call)
 {
 	unsigned long cur_flags, mismatch;
@@ -312,3 +366,92 @@ void efi_native_runtime_setup(void)
 	efi.update_capsule = virt_efi_update_capsule;
 	efi.query_capsule_caps = virt_efi_query_capsule_caps;
 }
+
+/*
+ * Calls the appropriate efi_runtime_service() with the appropriate
+ * arguments.
+ *
+ * Semantics followed by efi_call_rts() to understand efi_runtime_work:
+ * 1. If argument was a pointer, recast it from void pointer to original
+ * pointer type.
+ * 2. If argument was a value, recast it from void pointer to original
+ * pointer type and dereference it.
+ */
+void efi_call_rts(struct work_struct *work)
+{
+	struct efi_runtime_work *efi_rts_work;
+	void *arg1, *arg2, *arg3, *arg4, *arg5;
+	efi_status_t status = EFI_NOT_FOUND;
+
+	efi_rts_work = container_of(work, struct efi_runtime_work, work);
+	arg1 = efi_rts_work->arg1;
+	arg2 = efi_rts_work->arg2;
+	arg3 = efi_rts_work->arg3;
+	arg4 = efi_rts_work->arg4;
+	arg5 = efi_rts_work->arg5;
+
+	switch (efi_rts_work->func) {
+	case GET_TIME:
+		status = efi_call_virt(get_time, (efi_time_t *)arg1,
+				       (efi_time_cap_t *)arg2);
+		break;
+	case SET_TIME:
+		status = efi_call_virt(set_time, (efi_time_t *)arg1);
+		break;
+	case GET_WAKEUP_TIME:
+		status = efi_call_virt(get_wakeup_time, (efi_bool_t *)arg1,
+				       (efi_bool_t *)arg2, (efi_time_t *)arg3);
+		break;
+	case SET_WAKEUP_TIME:
+		status = efi_call_virt(set_wakeup_time, *(efi_bool_t *)arg1,
+				       (efi_time_t *)arg2);
+		break;
+	case GET_VARIABLE:
+		status = efi_call_virt(get_variable, (efi_char16_t *)arg1,
+				       (efi_guid_t *)arg2, (u32 *)arg3,
+				       (unsigned long *)arg4, (void *)arg5);
+		break;
+	case GET_NEXT_VARIABLE:
+		status = efi_call_virt(get_next_variable, (unsigned long *)arg1,
+				       (efi_char16_t *)arg2,
+				       (efi_guid_t *)arg3);
+		break;
+	case SET_VARIABLE:
+	case SET_VARIABLE_NONBLOCKING:
+		status = efi_call_virt(set_variable, (efi_char16_t *)arg1,
+				       (efi_guid_t *)arg2, *(u32 *)arg3,
+				       *(unsigned long *)arg4, (void *)arg5);
+		break;
+	case QUERY_VARIABLE_INFO:
+	case QUERY_VARIABLE_INFO_NONBLOCKING:
+		status = efi_call_virt(query_variable_info, *(u32 *)arg1,
+				       (u64 *)arg2, (u64 *)arg3, (u64 *)arg4);
+		break;
+	case GET_NEXT_HIGH_MONO_COUNT:
+		status = efi_call_virt(get_next_high_mono_count, (u32 *)arg1);
+		break;
+	case RESET_SYSTEM:
+		__efi_call_virt(reset_system, *(int *)arg1,
+				*(efi_status_t *)arg2,
+				*(unsigned long *)arg3,
+				(efi_char16_t *)arg4);
+		break;
+	case UPDATE_CAPSULE:
+		status = efi_call_virt(update_capsule,
+				       (efi_capsule_header_t **)arg1,
+				       *(unsigned long *)arg2,
+				       *(unsigned long *)arg3);
+		break;
+	case QUERY_CAPSULE_CAPS:
+		status = efi_call_virt(query_capsule_caps,
+				       (efi_capsule_header_t **)arg1,
+				       *(unsigned long *)arg2, (u64 *)arg3,
+				       (int *)arg4);
+		break;
+	default:
+		pr_err("Not a valid EFI_RT_SERVICE?");
+		status = EFI_NOT_FOUND;
+		break;
+	}
+	efi_rts_work->status = status;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index c4efb3ef0dfa..4abb401d40f5 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1652,4 +1652,27 @@ struct linux_efi_tpm_eventlog {
 
 extern int efi_tpm_eventlog_init(void);
 
+/*
+ * efi_runtime_work:	Details of EFI Runtime Service work
+ * @func:		EFI Runtime Service function identifier
+ * @arg<1-5>:		EFI Runtime Service function arguments
+ * @status:		Status of executing EFI Runtime Service
+ */
+struct efi_runtime_work {
+	u8 func;
+	void *arg1;
+	void *arg2;
+	void *arg3;
+	void *arg4;
+	void *arg5;
+	efi_status_t status;
+	struct work_struct work;
+};
+
+/* Workqueue to queue EFI Runtime Services */
+extern struct workqueue_struct *efi_rts_wq;
+
+/* Call back function that calls EFI Runtime Services */
+extern void efi_call_rts(struct work_struct *work);
+
 #endif /* _LINUX_EFI_H */
-- 
2.1.4