[RFC PATCH v3 24/32] x86/fred: let ret_from_fork() jmp to fred_exit_user when FRED is enabled

Xin Li
2023-02-24T07:29:23Z

Let ret_from_fork() jmp to fred_exit_user when FRED is enabled,
otherwise the existing IDT code is chosen.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
---
arch/x86/entry/entry_64.S | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 7ecd2aeeeffc..7ffd20578b8c 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -299,7 +299,12 @@ SYM_CODE_START_NOALIGN(ret_from_fork)
UNWIND_HINT_REGS
movq %rsp, %rdi
call syscall_exit_to_user_mode /* returns with IRQs disabled */
+#ifdef CONFIG_X86_FRED
+ ALTERNATIVE "jmp swapgs_restore_regs_and_return_to_usermode", \
+ "jmp fred_exit_user", X86_FEATURE_FRED
+#else
jmp swapgs_restore_regs_and_return_to_usermode
+#endif

1:
/* kernel thread */
--
2.34.1