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 <[email protected]> Cc: [email protected] --- arch/x86/entry/syscall_32.c | 19 +++++-------------- arch/x86/entry/syscall_64.c | 3 +-- arch/x86/include/asm/entry-common.h | 1 - 3 files changed, 6 insertions(+), 17 deletions(-) --- a/arch/x86/entry/syscall_32.c +++ b/arch/x86/entry/syscall_32.c @@ -142,10 +142,9 @@ static __always_inline bool int80_is_ext * 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 @@ DEFINE_FREDENTRY_RAW(int80_emulation) * 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 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)) { --- a/arch/x86/entry/syscall_64.c +++ b/arch/x86/entry/syscall_64.c @@ -86,10 +86,9 @@ static __always_inline bool do_syscall_x /* 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. */ --- a/arch/x86/include/asm/entry-common.h +++ b/arch/x86/include/asm/entry-common.h @@ -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>
