From b4e53e389d2a04678fb28bc445cd5b554bb175e0 Mon Sep 17 00:00:00 2001
From: Olivier Martin <olivier.martin@arm.com>
Date: Mon, 4 Aug 2014 14:18:13 +0000
Subject: ArmPkg/ArmSmcLib: Fixed SMC helper functions

The SMC helper functions were buggy as they were assuming that
the values in x1-x7 registers were preserved across an SMC call,
which is not the case.  This patch fixes this issue.

It also simplifies the code by providing only 1 version of the SMC
helper function.  We used to have 4 versions depending on the number
of arguments.  The problem with this approach was that the number of
arguments also dictated the number of return values, which is
completely unrelated.  E.g. you can have an SMC call that takes
1 argument but returns 4 values.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>



git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15748 6f19259b-4bc3-4df7-8a09-765794883524
---
 ArmPkg/Library/ArmSmcLib/Arm/ArmSmc.asm | 79 ++++++++++++---------------------
 1 file changed, 28 insertions(+), 51 deletions(-)

(limited to 'ArmPkg/Library/ArmSmcLib/Arm/ArmSmc.asm')

diff --git a/ArmPkg/Library/ArmSmcLib/Arm/ArmSmc.asm b/ArmPkg/Library/ArmSmcLib/Arm/ArmSmc.asm
index f46bd7ecd4..ad55ae7752 100644
--- a/ArmPkg/Library/ArmSmcLib/Arm/ArmSmc.asm
+++ b/ArmPkg/Library/ArmSmcLib/Arm/ArmSmc.asm
@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2012, ARM Limited. All rights reserved.
+//  Copyright (c) 2012-2014, ARM Limited. All rights reserved.
 //
 //  This program and the accompanying materials
 //  are licensed and made available under the terms and conditions of the BSD License
@@ -12,64 +12,41 @@
 //
 
     EXPORT ArmCallSmc
-    EXPORT ArmCallSmcArg1
-    EXPORT ArmCallSmcArg2
-    EXPORT ArmCallSmcArg3
 
     AREA   ArmSmc, CODE, READONLY
 
 ArmCallSmc
-    push    {r1}
-    mov     r1, r0
-    ldr     r0,[r1]
-    smc     #0
-    str     r0,[r1]
-    pop     {r1}
-    bx      lr
+    push    {r4-r8}
+    // r0 will be popped just after the SMC call
+    pop     {r0}
 
-ArmCallSmcArg1
-    push    {r2-r3}
-    mov     r2, r0
-    mov     r3, r1
-    ldr     r0,[r2]
-    ldr     r1,[r3]
-    smc     #0
-    str     r0,[r2]
-    str     r1,[r3]
-    pop     {r2-r3}
-    bx      lr
+    // Load the SMC arguments values into the appropriate registers
+    ldr     r7, [r0, #28]
+    ldr     r6, [r0, #24]
+    ldr     r5, [r0, #20]
+    ldr     r4, [r0, #16]
+    ldr     r3, [r0, #12]
+    ldr     r2, [r0, #8]
+    ldr     r1, [r0, #4]
+    ldr     r0, [r0, #0]
 
-ArmCallSmcArg2
-    push    {r3-r5}
-    mov     r3, r0
-    mov     r4, r1
-    mov     r5, r2
-    ldr     r0,[r3]
-    ldr     r1,[r4]
-    ldr     r2,[r5]
     smc     #0
-    str     r0,[r3]
-    str     r1,[r4]
-    str     r2,[r5]
-    pop     {r3-r5}
-    bx      lr
 
-ArmCallSmcArg3
-    push    {r4-r7}
-    mov     r4, r0
-    mov     r5, r1
-    mov     r6, r2
-    mov     r7, r3
-    ldr     r0,[r4]
-    ldr     r1,[r5]
-    ldr     r2,[r6]
-    ldr     r3,[r7]
-    smc     #0
-    str     r0,[r4]
-    str     r1,[r5]
-    str     r2,[r6]
-    str     r3,[r7]
-    pop     {r4-r7}
+    // Pop the ARM_SMC_ARGS structure address from the stack into r8
+    pop     {r8}
+
+    // Load the SMC returned values into the appropriate registers
+    // A SMC call can return up to 4 values - we do not need to store back r4-r7.
+    str     r3, [r8, #12]
+    str     r2, [r8, #8]
+    str     r1, [r8, #4]
+    str     r0, [r8, #0]
+
+    mov     r0, r8
+
+    // Restore the registers r4-r8
+    pop     {r4-r8}
+
     bx      lr
 
     END
-- 
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