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Message-Id: <1518168340-9392-5-git-send-email-joro@8bytes.org>
Date: Fri, 9 Feb 2018 10:25:13 +0100
From: Joerg Roedel <joro@...tes.org>
To: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
"H . Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...el.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Juergen Gross <jgross@...e.com>,
Peter Zijlstra <peterz@...radead.org>,
Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Brian Gerst <brgerst@...il.com>,
David Laight <David.Laight@...lab.com>,
Denys Vlasenko <dvlasenk@...hat.com>,
Eduardo Valentin <eduval@...zon.com>,
Greg KH <gregkh@...uxfoundation.org>,
Will Deacon <will.deacon@....com>, aliguori@...zon.com,
daniel.gruss@...k.tugraz.at, hughd@...gle.com, keescook@...gle.com,
Andrea Arcangeli <aarcange@...hat.com>,
Waiman Long <llong@...hat.com>, Pavel Machek <pavel@....cz>,
jroedel@...e.de, joro@...tes.org
Subject: [PATCH 04/31] x86/entry/32: Put ESPFIX code into a macro
From: Joerg Roedel <jroedel@...e.de>
This makes it easier to split up the shared iret code path.
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
arch/x86/entry/entry_32.S | 97 ++++++++++++++++++++++++-----------------------
1 file changed, 49 insertions(+), 48 deletions(-)
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index e659776..0289bde 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -221,6 +221,54 @@
POP_GS_EX
.endm
+.macro CHECK_AND_APPLY_ESPFIX
+#ifdef CONFIG_X86_ESPFIX32
+#define GDT_ESPFIX_SS PER_CPU_VAR(gdt_page) + (GDT_ENTRY_ESPFIX_SS * 8)
+
+ ALTERNATIVE "jmp .Lend_\@", "", X86_BUG_ESPFIX
+
+ movl PT_EFLAGS(%esp), %eax # mix EFLAGS, SS and CS
+ /*
+ * Warning: PT_OLDSS(%esp) contains the wrong/random values if we
+ * are returning to the kernel.
+ * See comments in process.c:copy_thread() for details.
+ */
+ movb PT_OLDSS(%esp), %ah
+ movb PT_CS(%esp), %al
+ andl $(X86_EFLAGS_VM | (SEGMENT_TI_MASK << 8) | SEGMENT_RPL_MASK), %eax
+ cmpl $((SEGMENT_LDT << 8) | USER_RPL), %eax
+ jne .Lend_\@ # returning to user-space with LDT SS
+
+ /*
+ * Setup and switch to ESPFIX stack
+ *
+ * We're returning to userspace with a 16 bit stack. The CPU will not
+ * restore the high word of ESP for us on executing iret... This is an
+ * "official" bug of all the x86-compatible CPUs, which we can work
+ * around to make dosemu and wine happy. We do this by preloading the
+ * high word of ESP with the high word of the userspace ESP while
+ * compensating for the offset by changing to the ESPFIX segment with
+ * a base address that matches for the difference.
+ */
+ mov %esp, %edx /* load kernel esp */
+ mov PT_OLDESP(%esp), %eax /* load userspace esp */
+ mov %dx, %ax /* eax: new kernel esp */
+ sub %eax, %edx /* offset (low word is 0) */
+ shr $16, %edx
+ mov %dl, GDT_ESPFIX_SS + 4 /* bits 16..23 */
+ mov %dh, GDT_ESPFIX_SS + 7 /* bits 24..31 */
+ pushl $__ESPFIX_SS
+ pushl %eax /* new kernel esp */
+ /*
+ * Disable interrupts, but do not irqtrace this section: we
+ * will soon execute iret and the tracer was already set to
+ * the irqstate after the IRET:
+ */
+ DISABLE_INTERRUPTS(CLBR_ANY)
+ lss (%esp), %esp /* switch to espfix segment */
+.Lend_\@:
+#endif /* CONFIG_X86_ESPFIX32 */
+.endm
/*
* %eax: prev task
* %edx: next task
@@ -548,21 +596,7 @@ ENTRY(entry_INT80_32)
restore_all:
TRACE_IRQS_IRET
.Lrestore_all_notrace:
-#ifdef CONFIG_X86_ESPFIX32
- ALTERNATIVE "jmp .Lrestore_nocheck", "", X86_BUG_ESPFIX
-
- movl PT_EFLAGS(%esp), %eax # mix EFLAGS, SS and CS
- /*
- * Warning: PT_OLDSS(%esp) contains the wrong/random values if we
- * are returning to the kernel.
- * See comments in process.c:copy_thread() for details.
- */
- movb PT_OLDSS(%esp), %ah
- movb PT_CS(%esp), %al
- andl $(X86_EFLAGS_VM | (SEGMENT_TI_MASK << 8) | SEGMENT_RPL_MASK), %eax
- cmpl $((SEGMENT_LDT << 8) | USER_RPL), %eax
- je .Lldt_ss # returning to user-space with LDT SS
-#endif
+ CHECK_AND_APPLY_ESPFIX
.Lrestore_nocheck:
RESTORE_REGS 4 # skip orig_eax/error_code
.Lirq_return:
@@ -575,39 +609,6 @@ ENTRY(iret_exc )
jmp common_exception
.previous
_ASM_EXTABLE(.Lirq_return, iret_exc)
-
-#ifdef CONFIG_X86_ESPFIX32
-.Lldt_ss:
-/*
- * Setup and switch to ESPFIX stack
- *
- * We're returning to userspace with a 16 bit stack. The CPU will not
- * restore the high word of ESP for us on executing iret... This is an
- * "official" bug of all the x86-compatible CPUs, which we can work
- * around to make dosemu and wine happy. We do this by preloading the
- * high word of ESP with the high word of the userspace ESP while
- * compensating for the offset by changing to the ESPFIX segment with
- * a base address that matches for the difference.
- */
-#define GDT_ESPFIX_SS PER_CPU_VAR(gdt_page) + (GDT_ENTRY_ESPFIX_SS * 8)
- mov %esp, %edx /* load kernel esp */
- mov PT_OLDESP(%esp), %eax /* load userspace esp */
- mov %dx, %ax /* eax: new kernel esp */
- sub %eax, %edx /* offset (low word is 0) */
- shr $16, %edx
- mov %dl, GDT_ESPFIX_SS + 4 /* bits 16..23 */
- mov %dh, GDT_ESPFIX_SS + 7 /* bits 24..31 */
- pushl $__ESPFIX_SS
- pushl %eax /* new kernel esp */
- /*
- * Disable interrupts, but do not irqtrace this section: we
- * will soon execute iret and the tracer was already set to
- * the irqstate after the IRET:
- */
- DISABLE_INTERRUPTS(CLBR_ANY)
- lss (%esp), %esp /* switch to espfix segment */
- jmp .Lrestore_nocheck
-#endif
ENDPROC(entry_INT80_32)
.macro FIXUP_ESPFIX_STACK
--
2.7.4
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