mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-28 11:18:45 +07:00
6690e86be8
Effectively reverts commit:2c7577a758("sched/x86_64: Don't save flags on context switch") Specifically because SMAP uses FLAGS.AC which invalidates the claim that the kernel has clean flags. In particular; while preemption from interrupt return is fine (the IRET frame on the exception stack contains FLAGS) it breaks any code that does synchonous scheduling, including preempt_enable(). This has become a significant issue ever since commit:5b24a7a2aa("Add 'unsafe' user access functions for batched accesses") provided for means of having 'normal' C code between STAC / CLAC, exposing the FLAGS.AC state. So far this hasn't led to trouble, however fix it before it comes apart. Reported-by: Julien Thierry <julien.thierry@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: stable@kernel.org Fixes:5b24a7a2aa("Add 'unsafe' user access functions for batched accesses") Signed-off-by: Ingo Molnar <mingo@kernel.org>
110 lines
3.0 KiB
C
110 lines
3.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#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,
|
|
struct task_struct *next);
|
|
|
|
__visible struct task_struct *__switch_to(struct task_struct *prev,
|
|
struct task_struct *next);
|
|
|
|
/* This runs runs on the previous thread's stack. */
|
|
static inline void prepare_switch_to(struct task_struct *next)
|
|
{
|
|
#ifdef CONFIG_VMAP_STACK
|
|
/*
|
|
* If we switch to a stack that has a top-level paging entry
|
|
* that is not present in the current mm, the resulting #PF will
|
|
* will be promoted to a double-fault and we'll panic. Probe
|
|
* the new stack now so that vmalloc_fault can fix up the page
|
|
* tables if needed. This can only happen if we use a stack
|
|
* in vmap space.
|
|
*
|
|
* We assume that the stack is aligned so that it never spans
|
|
* more than one top-level paging entry.
|
|
*
|
|
* To minimize cache pollution, just follow the stack pointer.
|
|
*/
|
|
READ_ONCE(*(unsigned char *)next->thread.sp);
|
|
#endif
|
|
}
|
|
|
|
asmlinkage void ret_from_fork(void);
|
|
|
|
/*
|
|
* This is the structure pointed to by thread.sp for an inactive task. The
|
|
* order of the fields must match the code in __switch_to_asm().
|
|
*/
|
|
struct inactive_task_frame {
|
|
unsigned long flags;
|
|
#ifdef CONFIG_X86_64
|
|
unsigned long r15;
|
|
unsigned long r14;
|
|
unsigned long r13;
|
|
unsigned long r12;
|
|
#else
|
|
unsigned long si;
|
|
unsigned long di;
|
|
#endif
|
|
unsigned long bx;
|
|
|
|
/*
|
|
* These two fields must be together. They form a stack frame header,
|
|
* needed by get_frame_pointer().
|
|
*/
|
|
unsigned long bp;
|
|
unsigned long ret_addr;
|
|
};
|
|
|
|
struct fork_frame {
|
|
struct inactive_task_frame frame;
|
|
struct pt_regs regs;
|
|
};
|
|
|
|
#define switch_to(prev, next, last) \
|
|
do { \
|
|
prepare_switch_to(next); \
|
|
\
|
|
((last) = __switch_to_asm((prev), (next))); \
|
|
} while (0)
|
|
|
|
#ifdef CONFIG_X86_32
|
|
static inline void refresh_sysenter_cs(struct thread_struct *thread)
|
|
{
|
|
/* Only happens when SEP is enabled, no need to test "SEP"arately: */
|
|
if (unlikely(this_cpu_read(cpu_tss_rw.x86_tss.ss1) == thread->sysenter_cs))
|
|
return;
|
|
|
|
this_cpu_write(cpu_tss_rw.x86_tss.ss1, thread->sysenter_cs);
|
|
wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
|
|
}
|
|
#endif
|
|
|
|
/* This is used when switching tasks or entering/exiting vm86 mode. */
|
|
static inline void update_task_stack(struct task_struct *task)
|
|
{
|
|
/* sp0 always points to the entry trampoline stack, which is constant: */
|
|
#ifdef CONFIG_X86_32
|
|
if (static_cpu_has(X86_FEATURE_XENPV))
|
|
load_sp0(task->thread.sp0);
|
|
else
|
|
this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0);
|
|
#else
|
|
/*
|
|
* x86-64 updates x86_tss.sp1 via cpu_current_top_of_stack. That
|
|
* doesn't work on x86-32 because sp1 and
|
|
* cpu_current_top_of_stack have different values (because of
|
|
* the non-zero stack-padding on 32bit).
|
|
*/
|
|
if (static_cpu_has(X86_FEATURE_XENPV))
|
|
load_sp0(task_top_of_stack(task));
|
|
#endif
|
|
|
|
}
|
|
|
|
#endif /* _ASM_X86_SWITCH_TO_H */
|