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x86/entry: Use generic syscall entry function

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Replace the syscall entry work handling with the generic version. Provide
the necessary helper inlines to handle the real architecture specific
parts, e.g. ptrace.

Use a temporary define for idtentry_enter_user which will be cleaned up
seperately.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20200722220520.376213694@linutronix.de
This commit is contained in:
Thomas Gleixner
2020-07-23 00:00:04 +02:00
parent 0bf019ea59
commit 27d6b4d14f
5 changed files with 45 additions and 179 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/Kconfig
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@ -115,6 +115,7 @@ config X86
select GENERIC_CPU_AUTOPROBE
select GENERIC_CPU_VULNERABILITIES
select GENERIC_EARLY_IOREMAP
select GENERIC_ENTRY
select GENERIC_FIND_FIRST_BIT
select GENERIC_IOMAP
select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP

181
arch/x86/entry/common.c
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@ -10,13 +10,13 @@
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/entry-common.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/tracehook.h>
#include <linux/audit.h>
#include <linux/seccomp.h>
#include <linux/signal.h>
#include <linux/export.h>
#include <linux/context_tracking.h>
@ -42,70 +42,8 @@
#include <asm/syscall.h>
#include <asm/irq_stack.h>
#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>
/* Check that the stack and regs on entry from user mode are sane. */
static noinstr void check_user_regs(struct pt_regs *regs)
{
if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) {
/*
* Make sure that the entry code gave us a sensible EFLAGS
* register. Native because we want to check the actual CPU
* state, not the interrupt state as imagined by Xen.
*/
unsigned long flags = native_save_fl();
WARN_ON_ONCE(flags & (X86_EFLAGS_AC | X86_EFLAGS_DF |
X86_EFLAGS_NT));
/* We think we came from user mode. Make sure pt_regs agrees. */
WARN_ON_ONCE(!user_mode(regs));
/*
* All entries from user mode (except #DF) should be on the
* normal thread stack and should have user pt_regs in the
* correct location.
*/
WARN_ON_ONCE(!on_thread_stack());
WARN_ON_ONCE(regs != task_pt_regs(current));
}
}
#ifdef CONFIG_CONTEXT_TRACKING
/**
* enter_from_user_mode - Establish state when coming from user mode
*
* Syscall entry disables interrupts, but user mode is traced as interrupts
* enabled. Also with NO_HZ_FULL RCU might be idle.
*
* 1) Tell lockdep that interrupts are disabled
* 2) Invoke context tracking if enabled to reactivate RCU
* 3) Trace interrupts off state
*/
static noinstr void enter_from_user_mode(struct pt_regs *regs)
{
enum ctx_state state = ct_state();
check_user_regs(regs);
lockdep_hardirqs_off(CALLER_ADDR0);
user_exit_irqoff();
instrumentation_begin();
CT_WARN_ON(state != CONTEXT_USER);
trace_hardirqs_off_finish();
instrumentation_end();
}
#else
static __always_inline void enter_from_user_mode(struct pt_regs *regs)
{
check_user_regs(regs);
lockdep_hardirqs_off(CALLER_ADDR0);
instrumentation_begin();
trace_hardirqs_off_finish();
instrumentation_end();
}
#endif
/**
* exit_to_user_mode - Fixup state when exiting to user mode
*
@ -129,83 +67,6 @@ static __always_inline void exit_to_user_mode(void)
lockdep_hardirqs_on(CALLER_ADDR0);
}
static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
{
#ifdef CONFIG_X86_64
if (arch == AUDIT_ARCH_X86_64) {
audit_syscall_entry(regs->orig_ax, regs->di,
regs->si, regs->dx, regs->r10);
} else
#endif
{
audit_syscall_entry(regs->orig_ax, regs->bx,
regs->cx, regs->dx, regs->si);
}
}
/*
* Returns the syscall nr to run (which should match regs->orig_ax) or -1
* to skip the syscall.
*/
static long syscall_trace_enter(struct pt_regs *regs)
{
u32 arch = in_ia32_syscall() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
struct thread_info *ti = current_thread_info();
unsigned long ret = 0;
u32 work;
work = READ_ONCE(ti->flags);
if (work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
ret = tracehook_report_syscall_entry(regs);
if (ret || (work & _TIF_SYSCALL_EMU))
return -1L;
}
#ifdef CONFIG_SECCOMP
/*
* Do seccomp after ptrace, to catch any tracer changes.
*/
if (work & _TIF_SECCOMP) {
struct seccomp_data sd;
sd.arch = arch;
sd.nr = regs->orig_ax;
sd.instruction_pointer = regs->ip;
#ifdef CONFIG_X86_64
if (arch == AUDIT_ARCH_X86_64) {
sd.args[0] = regs->di;
sd.args[1] = regs->si;
sd.args[2] = regs->dx;
sd.args[3] = regs->r10;
sd.args[4] = regs->r8;
sd.args[5] = regs->r9;
} else
#endif
{
sd.args[0] = regs->bx;
sd.args[1] = regs->cx;
sd.args[2] = regs->dx;
sd.args[3] = regs->si;
sd.args[4] = regs->di;
sd.args[5] = regs->bp;
}
ret = __secure_computing(&sd);
if (ret == -1)
return ret;
}
#endif
if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
trace_sys_enter(regs, regs->orig_ax);
do_audit_syscall_entry(regs, arch);
return ret ?: regs->orig_ax;
}
#define EXIT_TO_USERMODE_LOOP_FLAGS \
(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
_TIF_NEED_RESCHED | _TIF_PATCH_PENDING)
@ -366,26 +227,10 @@ __visible noinstr void syscall_return_slowpath(struct pt_regs *regs)
exit_to_user_mode();
}
static noinstr long syscall_enter(struct pt_regs *regs, unsigned long nr)
{
struct thread_info *ti;
enter_from_user_mode(regs);
instrumentation_begin();
local_irq_enable();
ti = current_thread_info();
if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY)
nr = syscall_trace_enter(regs);
instrumentation_end();
return nr;
}
#ifdef CONFIG_X86_64
__visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs)
{
nr = syscall_enter(regs, nr);
nr = syscall_enter_from_user_mode(regs, nr);
instrumentation_begin();
if (likely(nr < NR_syscalls)) {
@ -407,6 +252,8 @@ __visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs)
#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
static __always_inline unsigned int syscall_32_enter(struct pt_regs *regs)
{
unsigned int nr = (unsigned int)regs->orig_ax;
if (IS_ENABLED(CONFIG_IA32_EMULATION))
current_thread_info()->status |= TS_COMPAT;
/*
@ -414,7 +261,7 @@ static __always_inline unsigned int syscall_32_enter(struct pt_regs *regs)
* orig_ax, the unsigned int return value truncates it. This may
* or may not be necessary, but it matches the old asm behavior.
*/
return syscall_enter(regs, (unsigned int)regs->orig_ax);
return (unsigned int)syscall_enter_from_user_mode(regs, nr);
}
/*
@ -568,7 +415,7 @@ SYSCALL_DEFINE0(ni_syscall)
* solves the problem of kernel mode pagefaults which can schedule, which
* is not possible after invoking rcu_irq_enter() without undoing it.
*
* For user mode entries enter_from_user_mode() must be invoked to
* For user mode entries irqentry_enter_from_user_mode() must be invoked to
* establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
* would not be possible.
*
@ -584,7 +431,7 @@ idtentry_state_t noinstr idtentry_enter(struct pt_regs *regs)
};
if (user_mode(regs)) {
enter_from_user_mode(regs);
irqentry_enter_from_user_mode(regs);
return ret;
}
@ -615,7 +462,7 @@ idtentry_state_t noinstr idtentry_enter(struct pt_regs *regs)
/*
* If RCU is not watching then the same careful
* sequence vs. lockdep and tracing is required
* as in enter_from_user_mode().
* as in irqentry_enter_from_user_mode().
*/
lockdep_hardirqs_off(CALLER_ADDR0);
rcu_irq_enter();
@ -708,18 +555,6 @@ void noinstr idtentry_exit(struct pt_regs *regs, idtentry_state_t state)
}
}
/**
* idtentry_enter_user - Handle state tracking on idtentry from user mode
* @regs: Pointer to pt_regs of interrupted context
*
* Invokes enter_from_user_mode() to establish the proper context for
* NOHZ_FULL. Otherwise scheduling on exit would not be possible.
*/
void noinstr idtentry_enter_user(struct pt_regs *regs)
{
enter_from_user_mode(regs);
}
/**
* idtentry_exit_user - Handle return from exception to user mode
* @regs: Pointer to pt_regs (exception entry regs)

32
arch/x86/include/asm/entry-common.h Normal file
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@ -0,0 +1,32 @@
/* SPDX-License-Identifier: GPL-2.0-only */
#ifndef _ASM_X86_ENTRY_COMMON_H
#define _ASM_X86_ENTRY_COMMON_H
/* Check that the stack and regs on entry from user mode are sane. */
static __always_inline void arch_check_user_regs(struct pt_regs *regs)
{
if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) {
/*
* Make sure that the entry code gave us a sensible EFLAGS
* register. Native because we want to check the actual CPU
* state, not the interrupt state as imagined by Xen.
*/
unsigned long flags = native_save_fl();
WARN_ON_ONCE(flags & (X86_EFLAGS_AC | X86_EFLAGS_DF |
X86_EFLAGS_NT));
/* We think we came from user mode. Make sure pt_regs agrees. */
WARN_ON_ONCE(!user_mode(regs));
/*
* All entries from user mode (except #DF) should be on the
* normal thread stack and should have user pt_regs in the
* correct location.
*/
WARN_ON_ONCE(!on_thread_stack());
WARN_ON_ONCE(regs != task_pt_regs(current));
}
}
#define arch_check_user_regs arch_check_user_regs
#endif

5
arch/x86/include/asm/idtentry.h
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@ -6,11 +6,14 @@
#include <asm/trapnr.h>
#ifndef __ASSEMBLY__
#include <linux/entry-common.h>
#include <linux/hardirq.h>
#include <asm/irq_stack.h>
void idtentry_enter_user(struct pt_regs *regs);
/* Temporary define */
#define idtentry_enter_user irqentry_enter_from_user_mode
void idtentry_exit_user(struct pt_regs *regs);
typedef struct idtentry_state {

5
arch/x86/include/asm/thread_info.h
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@ -133,11 +133,6 @@ struct thread_info {
#define _TIF_X32 (1 << TIF_X32)
#define _TIF_FSCHECK (1 << TIF_FSCHECK)
/* Work to do before invoking the actual syscall. */
#define _TIF_WORK_SYSCALL_ENTRY \
(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_AUDIT | \
_TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT)
/* flags to check in __switch_to() */
#define _TIF_WORK_CTXSW_BASE \
(_TIF_NOCPUID | _TIF_NOTSC | _TIF_BLOCKSTEP | \