[PATCH 3.16 28/76] x86/retpoline/hyperv: Convert assembler indirect jumps

[Ben Hutchings]

3.16.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: David Woodhouse <dwmw@xxxxxxxxxxxx>

commit e70e5892b28c18f517f29ab6e83bd57705104b31 upstream.

Convert all indirect jumps in hyperv inline asm code to use non-speculative
sequences when CONFIG_RETPOLINE is enabled.

Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: gnomes@xxxxxxxxxxxxxxxxxxx
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: thomas.lendacky@xxxxxxx
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Jiri Kosina <jikos@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/1515707194-20531-9-git-send-email-dwmw@xxxxxxxxxxxx
[bwh: Backported to 3.16:
 - Drop changes to hv_do_fast_hypercall8()
 - Include earlier updates to the asm constraints
 - Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/hv/hv.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -29,6 +29,7 @@
 #include <linux/version.h>
 #include <linux/interrupt.h>
 #include <asm/hyperv.h>
+#include <asm/nospec-branch.h>
 #include "hyperv_vmbus.h"
 
 /* The one and only */
@@ -93,10 +94,13 @@ static u64 do_hypercall(u64 control, voi
 	u64 output_address = (output) ? virt_to_phys(output) : 0;
 	void *hypercall_page = hv_context.hypercall_page;
 
-	__asm__ __volatile__("mov %0, %%r8" : : "r" (output_address) : "r8");
-	__asm__ __volatile__("call *%3" : "=a" (hv_status) :
-			     "c" (control), "d" (input_address),
-			     "m" (hypercall_page));
+	__asm__ __volatile__("mov %4, %%r8\n"
+			     CALL_NOSPEC
+			     : "=a" (hv_status), ASM_CALL_CONSTRAINT,
+			       "+c" (control), "+d" (input_address)
+			     :  "r" (output_address),
+				THUNK_TARGET(hypercall_page)
+			     : "cc", "memory", "r8", "r9", "r10", "r11");
 
 	return hv_status;
 
@@ -114,11 +118,14 @@ static u64 do_hypercall(u64 control, voi
 	u32 output_address_lo = output_address & 0xFFFFFFFF;
 	void *hypercall_page = hv_context.hypercall_page;
 
-	__asm__ __volatile__ ("call *%8" : "=d"(hv_status_hi),
-			      "=a"(hv_status_lo) : "d" (control_hi),
-			      "a" (control_lo), "b" (input_address_hi),
-			      "c" (input_address_lo), "D"(output_address_hi),
-			      "S"(output_address_lo), "m" (hypercall_page));
+	__asm__ __volatile__(CALL_NOSPEC
+			     : "=d" (hv_status_hi), "=a" (hv_status_lo),
+			       "+c" (input_address_lo), ASM_CALL_CONSTRAINT
+			     : "d" (control_hi), "a" (control_lo),
+			       "b" (input_address_hi),
+			       "D"(output_address_hi), "S"(output_address_lo),
+			       THUNK_TARGET(hypercall_page)
+			     : "cc", "memory");
 
 	return hv_status_lo | ((u64)hv_status_hi << 32);
 #endif /* !x86_64 */