4.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Andy Lutomirski <l...@kernel.org> commit d375cf1530595e33961a8844192cddab913650e3 upstream. On x86_64, we can easily calculate sp0 when needed instead of storing it in thread_struct. On x86_32, a similar cleanup would be possible, but it would require cleaning up the vm86 code first, and that can wait for a later cleanup series. Signed-off-by: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <bpet...@suse.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Dave Hansen <dave.han...@intel.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/719cd9c66c548c4350d98a90f050aee8b17f8919.1509609304.git.l...@kernel.org Signed-off-by: Ingo Molnar <mi...@kernel.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- arch/x86/include/asm/compat.h | 1 + arch/x86/include/asm/processor.h | 28 +++++++++------------------- arch/x86/include/asm/switch_to.h | 6 ++++++ arch/x86/kernel/process_64.c | 1 - 4 files changed, 16 insertions(+), 20 deletions(-) --- a/arch/x86/include/asm/compat.h +++ b/arch/x86/include/asm/compat.h @@ -7,6 +7,7 @@ */ #include <linux/types.h> #include <linux/sched.h> +#include <linux/sched/task_stack.h> #include <asm/processor.h> #include <asm/user32.h> #include <asm/unistd.h> --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -431,7 +431,9 @@ typedef struct { struct thread_struct { /* Cached TLS descriptors: */ struct desc_struct tls_array[GDT_ENTRY_TLS_ENTRIES]; +#ifdef CONFIG_X86_32 unsigned long sp0; +#endif unsigned long sp; #ifdef CONFIG_X86_32 unsigned long sysenter_cs; @@ -798,6 +800,13 @@ static inline void spin_lock_prefetch(co #define task_top_of_stack(task) ((unsigned long)(task_pt_regs(task) + 1)) +#define task_pt_regs(task) \ +({ \ + unsigned long __ptr = (unsigned long)task_stack_page(task); \ + __ptr += THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING; \ + ((struct pt_regs *)__ptr) - 1; \ +}) + #ifdef CONFIG_X86_32 /* * User space process size: 3GB (default). @@ -817,23 +826,6 @@ static inline void spin_lock_prefetch(co .addr_limit = KERNEL_DS, \ } -/* - * TOP_OF_KERNEL_STACK_PADDING reserves 8 bytes on top of the ring0 stack. - * This is necessary to guarantee that the entire "struct pt_regs" - * is accessible even if the CPU haven't stored the SS/ESP registers - * on the stack (interrupt gate does not save these registers - * when switching to the same priv ring). - * Therefore beware: accessing the ss/esp fields of the - * "struct pt_regs" is possible, but they may contain the - * completely wrong values. - */ -#define task_pt_regs(task) \ -({ \ - unsigned long __ptr = (unsigned long)task_stack_page(task); \ - __ptr += THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING; \ - ((struct pt_regs *)__ptr) - 1; \ -}) - #define KSTK_ESP(task) (task_pt_regs(task)->sp) #else @@ -867,11 +859,9 @@ static inline void spin_lock_prefetch(co #define STACK_TOP_MAX TASK_SIZE_MAX #define INIT_THREAD { \ - .sp0 = TOP_OF_INIT_STACK, \ .addr_limit = KERNEL_DS, \ } -#define task_pt_regs(tsk) ((struct pt_regs *)(tsk)->thread.sp0 - 1) extern unsigned long KSTK_ESP(struct task_struct *task); #endif /* CONFIG_X86_64 */ --- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -2,6 +2,8 @@ #ifndef _ASM_X86_SWITCH_TO_H #define _ASM_X86_SWITCH_TO_H +#include <linux/sched/task_stack.h> + struct task_struct; /* one of the stranger aspects of C forward declarations */ struct task_struct *__switch_to_asm(struct task_struct *prev, @@ -88,7 +90,11 @@ static inline void refresh_sysenter_cs(s /* This is used when switching tasks or entering/exiting vm86 mode. */ static inline void update_sp0(struct task_struct *task) { +#ifdef CONFIG_X86_32 load_sp0(task->thread.sp0); +#else + load_sp0(task_top_of_stack(task)); +#endif } #endif /* _ASM_X86_SWITCH_TO_H */ --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -274,7 +274,6 @@ int copy_thread_tls(unsigned long clone_ struct inactive_task_frame *frame; struct task_struct *me = current; - p->thread.sp0 = (unsigned long)task_stack_page(p) + THREAD_SIZE; childregs = task_pt_regs(p); fork_frame = container_of(childregs, struct fork_frame, regs); frame = &fork_frame->frame;
