[PATCH 3.2 062/104] x86/retpoline/hyperv: Convert assembler indirect jumps

From: Ben Hutchings
Date: Sun Mar 11 2018 - 23:21:24 EST


3.2.101-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 3.2:
- 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
@@ -27,6 +27,7 @@
#include <linux/vmalloc.h>
#include <linux/hyperv.h>
#include <asm/hyperv.h>
+#include <asm/nospec-branch.h>
#include "hyperv_vmbus.h"

/* The one and only */
@@ -113,10 +114,13 @@ 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;

@@ -134,11 +138,14 @@ 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 */