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Subject[PATCH 03/11] x86/retpoline/entry: Convert entry assembler indirect jumps
Date
From: Andi Kleen <ak@linux.intel.com>

Convert all indirect jumps in core 32/64bit entry assembler code to use
non speculative sequences.

Based on code from David Woodhouse and Tim Chen

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
arch/x86/entry/entry_32.S | 5 +++--
arch/x86/entry/entry_64.S | 12 +++++++-----
2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index ace8f321a5a1..a4b88260d6f7 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -44,6 +44,7 @@
#include <asm/asm.h>
#include <asm/smap.h>
#include <asm/frame.h>
+#include <asm/jump-asm.h>

.section .entry.text, "ax"

@@ -290,7 +291,7 @@ ENTRY(ret_from_fork)

/* kernel thread */
1: movl %edi, %eax
- call *%ebx
+ NOSPEC_CALL %ebx
/*
* A kernel thread is allowed to return here after successfully
* calling do_execve(). Exit to userspace to complete the execve()
@@ -919,7 +920,7 @@ common_exception:
movl %ecx, %es
TRACE_IRQS_OFF
movl %esp, %eax # pt_regs pointer
- call *%edi
+ NOSPEC_CALL %edi
jmp ret_from_exception
END(common_exception)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index f048e384ff54..486990fb3e4d 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -37,6 +37,7 @@
#include <asm/pgtable_types.h>
#include <asm/export.h>
#include <asm/frame.h>
+#include <asm/jump-asm.h>
#include <linux/err.h>

#include "calling.h"
@@ -191,7 +192,7 @@ ENTRY(entry_SYSCALL_64_trampoline)
*/
pushq %rdi
movq $entry_SYSCALL_64_stage2, %rdi
- jmp *%rdi
+ NOSPEC_JMP %rdi
END(entry_SYSCALL_64_trampoline)

.popsection
@@ -269,8 +270,9 @@ entry_SYSCALL_64_fastpath:
* This call instruction is handled specially in stub_ptregs_64.
* It might end up jumping to the slow path. If it jumps, RAX
* and all argument registers are clobbered.
- */
- call *sys_call_table(, %rax, 8)
+ */
+ movq sys_call_table(, %rax, 8), %rax
+ NOSPEC_CALL %rax
.Lentry_SYSCALL_64_after_fastpath_call:

movq %rax, RAX(%rsp)
@@ -442,7 +444,7 @@ ENTRY(stub_ptregs_64)
jmp entry_SYSCALL64_slow_path

1:
- jmp *%rax /* Called from C */
+ NOSPEC_JMP %rax /* Called from C */
END(stub_ptregs_64)

.macro ptregs_stub func
@@ -521,7 +523,7 @@ ENTRY(ret_from_fork)
1:
/* kernel thread */
movq %r12, %rdi
- call *%rbx
+ NOSPEC_CALL %rbx
/*
* A kernel thread is allowed to return here after successfully
* calling do_execve(). Exit to userspace to complete the execve()
--
2.14.3
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