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x86/syscall: Use [syscall_]enter_from_user_mode_randomize_stack()

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These functions integrate the stack randomization.

syscall_enter_from_user_mode_randomize_stack() has the advantage that the
randomization happens early right after enter_from_user_mode().

In both cases also the overhead of get/put_cpu_var() in
add_random_kstack_offset() is avoided.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
Reviewed-by: Radu Rendec <radu@rendec.net>
Reviewed-by: Jinjie Ruan <ruanjinjie@huawei.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>
Reviewed-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
Link: https://patch.msgid.link/20260707190254.079478122@kernel.org
This commit is contained in:
Thomas Gleixner
2026-07-12 12:38:01 +02:00
parent 05a194d8bd
commit 9d311796e2
3 changed files with 6 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files
arch/x86/entry/syscall_32.c
+5 -14
View File
@@ -142,10 +142,9 @@ __visible noinstr void do_int80_emulation(struct pt_regs *regs)
* int80_is_external() below which calls into the APIC driver.
* Identical for soft and external interrupts.
*/
enter_from_user_mode(regs);
enter_from_user_mode_randomize_stack(regs);
instrumentation_begin();
add_random_kstack_offset();
/* Validate that this is a soft interrupt to the extent possible */
if (unlikely(int80_is_external()))
@@ -210,11 +209,9 @@ DEFINE_FREDENTRY_RAW(int80_emulation)
{
int nr;
enter_from_user_mode(regs);
enter_from_user_mode_randomize_stack(regs);
instrumentation_begin();
add_random_kstack_offset();
/*
* FRED pushed 0 into regs::orig_ax and regs::ax contains the
* syscall number.
@@ -252,10 +249,10 @@ __visible noinstr void do_int80_syscall_32(struct pt_regs *regs)
* orig_ax, the int return value truncates it. This matches
* the semantics of syscall_get_nr().
*/
nr = syscall_enter_from_user_mode(regs, nr);
nr = syscall_enter_from_user_mode_randomize_stack(regs, nr);
instrumentation_begin();
add_random_kstack_offset();
do_syscall_32_irqs_on(regs, nr);
instrumentation_end();
@@ -268,15 +265,9 @@ static noinstr bool __do_fast_syscall_32(struct pt_regs *regs)
int nr = syscall_32_enter(regs);
int res;
/*
* This cannot use syscall_enter_from_user_mode() as it has to
* fetch EBP before invoking any of the syscall entry work
* functions.
*/
enter_from_user_mode(regs);
enter_from_user_mode_randomize_stack(regs);
instrumentation_begin();
add_random_kstack_offset();
local_irq_enable();
/* Fetch EBP from where the vDSO stashed it. */
if (IS_ENABLED(CONFIG_X86_64)) {
arch/x86/entry/syscall_64.c
+1 -2
View File
@@ -86,10 +86,9 @@ static __always_inline bool do_syscall_x32(struct pt_regs *regs, int nr)
/* Returns true to return using SYSRET, or false to use IRET */
__visible noinstr bool do_syscall_64(struct pt_regs *regs, int nr)
{
nr = syscall_enter_from_user_mode(regs, nr);
nr = syscall_enter_from_user_mode_randomize_stack(regs, nr);
instrumentation_begin();
add_random_kstack_offset();
if (!do_syscall_x64(regs, nr) && !do_syscall_x32(regs, nr) && nr != -1) {
/* Invalid system call, but still a system call. */
arch/x86/include/asm/entry-common.h
-1
View File
@@ -2,7 +2,6 @@
#ifndef _ASM_X86_ENTRY_COMMON_H
#define _ASM_X86_ENTRY_COMMON_H
#include <linux/randomize_kstack.h>
#include <linux/user-return-notifier.h>
#include <asm/nospec-branch.h>