[tip: x86/fred] x86/fred: Reserve space for the FRED stack frame

[tip-bot2 for H. Peter Anvin (Intel)]

The following commit has been merged into the x86/fred branch of tip:

Commit-ID:     fcd06abf6de2b81724a1e39c121d288f66b1d392
Gitweb:        https://git.kernel.org/tip/fcd06abf6de2b81724a1e39c121d288f66b1d392
Author:        H. Peter Anvin (Intel) <hpa@xxxxxxxxx>
AuthorDate:    Tue, 05 Dec 2023 02:50:05 -08:00
Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Tue, 30 Jan 2024 18:20:35 +01:00

x86/fred: Reserve space for the FRED stack frame

When using FRED, reserve space at the top of the stack frame, just
like i386 does.

Signed-off-by: H. Peter Anvin (Intel) <hpa@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
Link: https://lore.kernel.org/r/20231205105030.8698-17-xin3.li@xxxxxxxxx

---
 arch/x86/include/asm/thread_info.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index d63b029..12da7df 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -31,7 +31,9 @@
  * In vm86 mode, the hardware frame is much longer still, so add 16
  * bytes to make room for the real-mode segments.
  *
- * x86_64 has a fixed-length stack frame.
+ * x86-64 has a fixed-length stack frame, but it depends on whether
+ * or not FRED is enabled. Future versions of FRED might make this
+ * dynamic, but for now it is always 2 words longer.
  */
 #ifdef CONFIG_X86_32
 # ifdef CONFIG_VM86
@@ -39,8 +41,12 @@
 # else
 #  define TOP_OF_KERNEL_STACK_PADDING 8
 # endif
-#else
-# define TOP_OF_KERNEL_STACK_PADDING 0
+#else /* x86-64 */
+# ifdef CONFIG_X86_FRED
+#  define TOP_OF_KERNEL_STACK_PADDING (2 * 8)
+# else
+#  define TOP_OF_KERNEL_STACK_PADDING 0
+# endif
 #endif
 
 /*