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Message-Id: <dccf8c7b3750199b4b30383c812d4e2931811509.1509609304.git.luto@kernel.org>
Date: Thu, 2 Nov 2017 00:58:59 -0700
From: Andy Lutomirski <luto@...nel.org>
To: X86 ML <x86@...nel.org>
Cc: Borislav Petkov <bpetkov@...e.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Brian Gerst <brgerst@...il.com>,
Dave Hansen <dave.hansen@...el.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v2 02/20] x86/asm/64: Split the iret-to-user and iret-to-kernel paths
These code paths will diverge soon.
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
arch/x86/entry/entry_64.S | 34 +++++++++++++++++++++++++---------
arch/x86/entry/entry_64_compat.S | 2 +-
arch/x86/kernel/head_64.S | 2 +-
3 files changed, 27 insertions(+), 11 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index afe1f403fa0e..07fe816f0d28 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -321,7 +321,7 @@ syscall_return_via_sysret:
opportunistic_sysret_failed:
SWAPGS
- jmp restore_regs_and_iret
+ jmp restore_regs_and_return_to_usermode
END(entry_SYSCALL_64)
ENTRY(stub_ptregs_64)
@@ -423,7 +423,7 @@ ENTRY(ret_from_fork)
call syscall_return_slowpath /* returns with IRQs disabled */
TRACE_IRQS_ON /* user mode is traced as IRQS on */
SWAPGS
- jmp restore_regs_and_iret
+ jmp restore_regs_and_return_to_usermode
1:
/* kernel thread */
@@ -612,7 +612,20 @@ GLOBAL(retint_user)
call prepare_exit_to_usermode
TRACE_IRQS_IRETQ
SWAPGS
- jmp restore_regs_and_iret
+
+GLOBAL(restore_regs_and_return_to_usermode)
+#ifdef CONFIG_DEBUG_ENTRY
+ /* Assert that pt_regs indicates user mode. */
+ testl $3, CS(%rsp)
+ jnz 1f
+ ud2
+1:
+#endif
+ RESTORE_EXTRA_REGS
+ RESTORE_C_REGS
+ REMOVE_PT_GPREGS_FROM_STACK 8
+ INTERRUPT_RETURN
+
/* Returning to kernel space */
retint_kernel:
@@ -632,11 +645,14 @@ retint_kernel:
*/
TRACE_IRQS_IRETQ
-/*
- * At this label, code paths which return to kernel and to user,
- * which come from interrupts/exception and from syscalls, merge.
- */
-GLOBAL(restore_regs_and_iret)
+GLOBAL(restore_regs_and_return_to_kernel)
+#ifdef CONFIG_DEBUG_ENTRY
+ /* Assert that pt_regs indicates kernel mode. */
+ testl $3, CS(%rsp)
+ jz 1f
+ ud2
+1:
+#endif
RESTORE_EXTRA_REGS
RESTORE_C_REGS
REMOVE_PT_GPREGS_FROM_STACK 8
@@ -1327,7 +1343,7 @@ ENTRY(nmi)
* work, because we don't want to enable interrupts.
*/
SWAPGS
- jmp restore_regs_and_iret
+ jmp restore_regs_and_return_to_usermode
.Lnmi_from_kernel:
/*
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index e26c25ca7756..9ca014a99968 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -337,7 +337,7 @@ ENTRY(entry_INT80_compat)
/* Go back to user mode. */
TRACE_IRQS_ON
SWAPGS
- jmp restore_regs_and_iret
+ jmp restore_regs_and_return_to_usermode
END(entry_INT80_compat)
ENTRY(stub32_clone)
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 513cbb012ecc..0b01a105251b 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -326,7 +326,7 @@ early_idt_handler_common:
20:
decl early_recursion_flag(%rip)
- jmp restore_regs_and_iret
+ jmp restore_regs_and_return_to_kernel
ENDPROC(early_idt_handler_common)
__INITDATA
--
2.13.6
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