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

tip-bot2 for H. Peter Anvin (Intel)
2024-01-25T18:21:32Z

Commit-ID: c83ce06e137034b155ce56f2830637e7dc9c56ce
Gitweb: https://git.kernel.org/tip/c83ce06e137034b155ce56f2830637e7dc9c56ce
Author: H. Peter Anvin (Intel) <hpa@zytor.com>
AuthorDate: Tue, 05 Dec 2023 02:50:05 -08:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 25 Jan 2024 19:10:31 +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@zytor.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Shan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-17-xin3.li@intel.com

---
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

/*