linux-kernel - [PATCH 3.12 040/100] x86, asmlinkage, lguest: Pass in globals into assembler statement

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Date:   Fri, 19 Aug 2016 09:10:39 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        x86@...nel.org, rusty@...tcorp.com.au, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 040/100] x86, asmlinkage, lguest: Pass in globals into assembler statement

From: Andi Kleen <ak@...ux.intel.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit cdd77e87eae52b7251acc5990207a1c4500a84ce upstream.

Tell the compiler that the inline assembler statement
references lguest_entry.

This fixes compile problems with LTO where the variable
and the assembler code may end up in different files.

Cc: x86@...nel.org
Cc: rusty@...tcorp.com.au
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/lguest/x86/core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index 516923926335..922a1acbf652 100644
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -157,7 +157,7 @@ static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages)
 	 * stack, then the address of this call.  This stack layout happens to
 	 * exactly match the stack layout created by an interrupt...
 	 */
-	asm volatile("pushf; lcall *lguest_entry"
+	asm volatile("pushf; lcall *%4"
 		     /*
 		      * This is how we tell GCC that %eax ("a") and %ebx ("b")
 		      * are changed by this routine.  The "=" means output.
@@ -169,7 +169,9 @@ static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages)
 		      * physical address of the Guest's top-level page
 		      * directory.
 		      */
-		     : "0"(pages), "1"(__pa(cpu->lg->pgdirs[cpu->cpu_pgd].pgdir))
+		     : "0"(pages), 
+		       "1"(__pa(cpu->lg->pgdirs[cpu->cpu_pgd].pgdir)),
+		       "m"(lguest_entry)
 		     /*
 		      * We tell gcc that all these registers could change,
 		      * which means we don't have to save and restore them in
-- 
2.9.3