[tip: x86/entry] x86/entry/64: Provide sane error entry/exit

tip-bot2 for Thomas Gleixner
2020-05-19T20:01:25Z

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

Commit-ID: 3660da2d124813bed342e25b39df0251cbe2ac4f
Gitweb: https://git.kernel.org/tip/3660da2d124813bed342e25b39df0251cbe2ac4f
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Thu, 26 Mar 2020 16:56:20 +01:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Tue, 19 May 2020 16:03:56 +02:00

x86/entry/64: Provide sane error entry/exit

For gradual conversion provide a macro parameter and the required code
which allows to handle instrumentation and interrupt flags tracking in C.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505134904.058904490@linutronix.de

---
arch/x86/entry/entry_64.S | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 01bfe7f..96ad26f 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -499,8 +499,9 @@ SYM_CODE_END(spurious_entries_start)
* @vector: Vector number
* @cfunc: C function to be called
* @has_error_code: Hardware pushed error code on stack
+ * @sane: Sane variant which handles irq tracing, context tracking in C
*/
-.macro idtentry_body vector cfunc has_error_code:req
+.macro idtentry_body vector cfunc has_error_code:req sane=0

call error_entry
UNWIND_HINT_REGS
@@ -514,6 +515,7 @@ SYM_CODE_END(spurious_entries_start)
GET_CR2_INTO(%r12);
.endif

+ .if \sane == 0
TRACE_IRQS_OFF

#ifdef CONFIG_CONTEXT_TRACKING
@@ -522,6 +524,7 @@ SYM_CODE_END(spurious_entries_start)
CALL_enter_from_user_mode
.Lfrom_kernel_no_ctxt_tracking_\@:
#endif
+ .endif

movq %rsp, %rdi /* pt_regs pointer into 1st argument*/

@@ -538,7 +541,11 @@ SYM_CODE_END(spurious_entries_start)

call \cfunc

+ .if \sane == 0
jmp error_exit
+ .else
+ jmp error_return
+ .endif
.endm

/**
@@ -547,11 +554,12 @@ SYM_CODE_END(spurious_entries_start)
* @asmsym: ASM symbol for the entry point
* @cfunc: C function to be called
* @has_error_code: Hardware pushed error code on stack
+ * @sane: Sane variant which handles irq tracing, context tracking in C
*
* The macro emits code to set up the kernel context for straight forward
* and simple IDT entries. No IST stack, no paranoid entry checks.
*/
-.macro idtentry vector asmsym cfunc has_error_code:req
+.macro idtentry vector asmsym cfunc has_error_code:req sane=0
SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS offset=\has_error_code*8
ASM_CLAC
@@ -574,7 +582,7 @@ SYM_CODE_START(\asmsym)
.Lfrom_usermode_no_gap_\@:
.endif

- idtentry_body \vector \cfunc \has_error_code
+ idtentry_body \vector \cfunc \has_error_code \sane

_ASM_NOKPROBE(\asmsym)
SYM_CODE_END(\asmsym)
@@ -1403,6 +1411,14 @@ SYM_CODE_START_LOCAL(error_exit)
jmp .Lretint_user
SYM_CODE_END(error_exit)

+SYM_CODE_START_LOCAL(error_return)
+ UNWIND_HINT_REGS
+ DEBUG_ENTRY_ASSERT_IRQS_OFF
+ testb $3, CS(%rsp)
+ jz restore_regs_and_return_to_kernel
+ jmp swapgs_restore_regs_and_return_to_usermode
+SYM_CODE_END(error_return)
+
/*
* Runs on exception stack. Xen PV does not go through this path at all,
* so we can use real assembly here.