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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xenproject.org>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Wei Liu" <wl@xen.org>, "Jan Beulich" <JBeulich@suse.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: [PATCH v2 09/14] x86/spec-ctrl: Adjust DO_OVERWRITE_RSB to be shadow stack compatible
Date: Wed, 27 May 2020 20:18:42 +0100	[thread overview]
Message-ID: <20200527191847.17207-10-andrew.cooper3@citrix.com> (raw)
In-Reply-To: <20200527191847.17207-1-andrew.cooper3@citrix.com>

The 32 calls need dropping from the shadow stack as well as the regular stack.
To shorten the code, we can use the 32bit forms of RDSSP/INCSSP, but need to
double up the input to INCSSP to counter the operand size based multiplier.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wl@xen.org>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/include/asm-x86/spec_ctrl_asm.h | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/xen/include/asm-x86/spec_ctrl_asm.h b/xen/include/asm-x86/spec_ctrl_asm.h
index c60093b090..cb34299a86 100644
--- a/xen/include/asm-x86/spec_ctrl_asm.h
+++ b/xen/include/asm-x86/spec_ctrl_asm.h
@@ -83,9 +83,9 @@
  * Requires nothing
  * Clobbers \tmp (%rax by default), %rcx
  *
- * Requires 256 bytes of stack space, but %rsp has no net change. Based on
- * Google's performance numbers, the loop is unrolled to 16 iterations and two
- * calls per iteration.
+ * Requires 256 bytes of {,shadow}stack space, but %rsp/SSP has no net
+ * change. Based on Google's performance numbers, the loop is unrolled to 16
+ * iterations and two calls per iteration.
  *
  * The call filling the RSB needs a nonzero displacement.  A nop would do, but
  * we use "1: pause; lfence; jmp 1b" to safely contains any ret-based
@@ -114,6 +114,16 @@
     sub $1, %ecx
     jnz .L\@_fill_rsb_loop
     mov %\tmp, %rsp                 /* Restore old %rsp */
+
+#ifdef CONFIG_XEN_SHSTK
+    mov $1, %ecx
+    rdsspd %ecx
+    cmp $1, %ecx
+    je .L\@_shstk_done
+    mov $64, %ecx                   /* 64 * 4 bytes, given incsspd */
+    incsspd %ecx                    /* Restore old SSP */
+.L\@_shstk_done:
+#endif
 .endm
 
 .macro DO_SPEC_CTRL_ENTRY_FROM_HVM
-- 
2.11.0



  parent reply	other threads:[~2020-05-27 19:19 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-27 19:18 [PATCH v2 00/14] x86: Support for CET Supervisor Shadow Stacks Andrew Cooper
2020-05-27 19:18 ` [PATCH v2 01/14] x86/traps: Clean up printing in {do_reserved, fatal}_trap() Andrew Cooper
2020-05-28  9:45   ` [PATCH v2 01/14] x86/traps: Clean up printing in {do_reserved,fatal}_trap() Jan Beulich
2020-05-27 19:18 ` [PATCH v2 02/14] x86/traps: Factor out extable_fixup() and make printing consistent Andrew Cooper
2020-05-28  9:50   ` Jan Beulich
2020-05-28 17:26     ` Andrew Cooper
2020-05-27 19:18 ` [PATCH v2 03/14] x86/shstk: Introduce Supervisor Shadow Stack support Andrew Cooper
2020-05-28 10:25   ` Jan Beulich
2020-05-28 18:10     ` Andrew Cooper
2020-05-29 11:59       ` Jan Beulich
2020-05-29 15:51         ` Anthony PERARD
2020-05-29 18:39           ` Andrew Cooper
2020-06-02 12:09             ` Jan Beulich
2020-05-29 18:36         ` Andrew Cooper
2020-06-02 12:06           ` Jan Beulich
2020-06-02 12:26             ` Anthony PERARD
2020-06-02 12:41               ` Jan Beulich
2020-06-02 13:50                 ` Anthony PERARD
2020-06-02 14:13                   ` Jan Beulich
2020-05-27 19:18 ` [PATCH v2 04/14] x86/traps: Implement #CP handler and extend #PF for shadow stacks Andrew Cooper
2020-05-28 12:03   ` Jan Beulich
2020-05-28 13:22     ` Andrew Cooper
2020-05-28 13:31       ` Jan Beulich
2020-05-29 18:50         ` Andrew Cooper
2020-05-27 19:18 ` [PATCH v2 05/14] x86/shstk: Re-layout the stack block " Andrew Cooper
2020-05-28 12:33   ` Jan Beulich
2020-05-29 19:21     ` Andrew Cooper
2020-05-27 19:18 ` [PATCH v2 06/14] x86/shstk: Create " Andrew Cooper
2020-05-28 12:50   ` Jan Beulich
2020-05-29 19:35     ` Andrew Cooper
2020-05-29 21:45       ` Andrew Cooper
2020-06-02 12:32         ` Jan Beulich
2020-06-02 12:35       ` Jan Beulich
2020-05-27 19:18 ` [PATCH v2 07/14] x86/cpu: Adjust enable_nmis() to be shadow stack compatible Andrew Cooper
2020-05-27 19:18 ` [PATCH v2 08/14] x86/cpu: Adjust reset_stack_and_jump() " Andrew Cooper
2020-05-28 14:41   ` Jan Beulich
2020-05-27 19:18 ` Andrew Cooper [this message]
2020-05-27 19:18 ` [PATCH v2 10/14] x86/extable: Adjust extable handling " Andrew Cooper
2020-05-28 16:15   ` Jan Beulich
2020-05-29 19:43     ` Andrew Cooper
2020-05-29 21:17       ` Andrew Cooper
2020-06-02 13:11         ` Jan Beulich
2020-06-02 12:57       ` Jan Beulich
2020-05-27 19:18 ` [PATCH v2 11/14] x86/alt: Adjust _alternative_instructions() to not create shadow stacks Andrew Cooper
2020-05-29 12:23   ` Jan Beulich
2020-05-29 19:46     ` Andrew Cooper
2020-05-27 19:18 ` [PATCH v2 12/14] x86/entry: Adjust guest paths to be shadow stack compatible Andrew Cooper
2020-05-29 12:40   ` Jan Beulich
2020-05-29 19:58     ` Andrew Cooper
2020-05-27 19:18 ` [PATCH v2 13/14] x86/S3: Save and restore Shadow Stack configuration Andrew Cooper
2020-05-29 12:52   ` Jan Beulich
2020-05-29 20:00     ` Andrew Cooper
2020-05-27 19:18 ` [PATCH v2 14/14] x86/shstk: Activate Supervisor Shadow Stacks Andrew Cooper
2020-05-29 13:09   ` Jan Beulich
2020-05-29 20:28     ` Andrew Cooper
2020-05-29 22:28 ` [PATCH v2 00/14] x86: Support for CET " Andrew Cooper

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