[tip: x86/fred] x86/fred: Let ret_from_fork_asm() jmp to asm_fred_exit_user when FRED is enabled

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

Commit-ID: 81e71a71266e2fbe42632f725147ed5b8f75b11e
Gitweb: https://git.kernel.org/tip/81e71a71266e2fbe42632f725147ed5b8f75b11e
Author: H. Peter Anvin (Intel) <hpa@zytor.com>
AuthorDate: Tue, 05 Dec 2023 02:50:17 -08:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 25 Jan 2024 19:10:33 +01:00

x86/fred: Let ret_from_fork_asm() jmp to asm_fred_exit_user when FRED is enabled

Let ret_from_fork_asm() jmp to asm_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>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Shan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-29-xin3.li@intel.com

---
arch/x86/entry/entry_64.S | 6 ++++++
arch/x86/entry/entry_64_fred.S | 1 +
2 files changed, 7 insertions(+)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 29ce68f..7c4b726 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -247,7 +247,13 @@ SYM_CODE_START(ret_from_fork_asm)
* and unwind should work normally.
*/
UNWIND_HINT_REGS
+
+#ifdef CONFIG_X86_FRED
+ ALTERNATIVE "jmp swapgs_restore_regs_and_return_to_usermode", \
+ "jmp asm_fred_exit_user", X86_FEATURE_FRED
+#else
jmp swapgs_restore_regs_and_return_to_usermode
+#endif
SYM_CODE_END(ret_from_fork_asm)
.popsection

diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S
index 37a1dd5..5781c34 100644
--- a/arch/x86/entry/entry_64_fred.S
+++ b/arch/x86/entry/entry_64_fred.S
@@ -32,6 +32,7 @@
SYM_CODE_START_NOALIGN(asm_fred_entrypoint_user)
FRED_ENTER
call fred_entry_from_user
+SYM_INNER_LABEL(asm_fred_exit_user, SYM_L_GLOBAL)
FRED_EXIT
ERETU
SYM_CODE_END(asm_fred_entrypoint_user)