From 16974ba9c90984e667f057e13630cea6c27d0ae9 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 7 Jun 2022 14:24:59 +0200
Subject: [PATCH 21/21] OvmfPkg/Sec: fix stack switch

The ebp/rbp register can either be used for the frame pointer or
as general purpose register.  With gcc (and clang) this depends
on the -f(no-)omit-frame-pointer switch.

This patch updates tools_def.template to explicitly set the compiler
option and also add a define to allow conditionally compile code.

The new define is used to fix stack switching in TemporaryRamMigration.
The ebp/rbp must not be touched when the compiler can use it as general
purpose register.  With version 12 gcc starts actually using the
register, so changing it leads to firmware crashes in some
configurations.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3934
Reported-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 OvmfPkg/Sec/SecMain.c             | 4 ++++
 BaseTools/Conf/tools_def.template | 6 +++---
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 1167d22a68cc..3ca0dcdfd3dd 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -1052,11 +1052,15 @@ TemporaryRamMigration (
   if (SetJump (&JumpBuffer) == 0) {
  #if defined (MDE_CPU_IA32)
     JumpBuffer.Esp = JumpBuffer.Esp + DebugAgentContext.StackMigrateOffset;
+ #ifndef OMIT_FRAME_POINTER
     JumpBuffer.Ebp = JumpBuffer.Ebp + DebugAgentContext.StackMigrateOffset;
  #endif
+ #endif
  #if defined (MDE_CPU_X64)
     JumpBuffer.Rsp = JumpBuffer.Rsp + DebugAgentContext.StackMigrateOffset;
+ #ifndef OMIT_FRAME_POINTER
     JumpBuffer.Rbp = JumpBuffer.Rbp + DebugAgentContext.StackMigrateOffset;
+ #endif
  #endif
     LongJump (&JumpBuffer, (UINTN)-1);
   }
diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template
index 5901d9eecb5d..3b5f1f915c96 100755
--- a/BaseTools/Conf/tools_def.template
+++ b/BaseTools/Conf/tools_def.template
@@ -1849,9 +1849,9 @@ NOOPT_*_*_OBJCOPY_ADDDEBUGFLAG     = --add-gnu-debuglink=$(DEBUG_DIR)/$(MODULE_N
 *_*_*_DTC_PATH                     = DEF(DTC_BIN)
 
 DEFINE GCC_ALL_CC_FLAGS            = -g -Os -fshort-wchar -fno-builtin -fno-strict-aliasing -Wall -Werror -Wno-array-bounds -include AutoGen.h -fno-common
-DEFINE GCC_IA32_CC_FLAGS           = DEF(GCC_ALL_CC_FLAGS) -m32 -malign-double -freorder-blocks -freorder-blocks-and-partition -O2 -mno-stack-arg-probe
-DEFINE GCC_X64_CC_FLAGS            = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-address -mno-stack-arg-probe
-DEFINE GCC_ARM_CC_FLAGS            = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -Wno-address -mthumb -mfloat-abi=soft -fno-pic -fno-pie
+DEFINE GCC_IA32_CC_FLAGS           = DEF(GCC_ALL_CC_FLAGS) -m32 -malign-double -freorder-blocks -freorder-blocks-and-partition -O2 -mno-stack-arg-probe -fno-omit-frame-pointer
+DEFINE GCC_X64_CC_FLAGS            = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-address -mno-stack-arg-probe -fomit-frame-pointer -DOMIT_FRAME_POINTER=1
+DEFINE GCC_ARM_CC_FLAGS            = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -DOMIT_FRAME_POINTER=1 -Wno-address -mthumb -mfloat-abi=soft -fno-pic -fno-pie
 DEFINE GCC_ARM_CC_XIPFLAGS         = -mno-unaligned-access
 DEFINE GCC_AARCH64_CC_FLAGS        = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char  -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-unwind-tables -fno-pic -fno-pie -ffixed-x18
 DEFINE GCC_AARCH64_CC_XIPFLAGS     = -mstrict-align -mgeneral-regs-only
-- 
2.36.1