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1e3ad78334
Make <asm/syscall.h> build a switch statement instead, and the compiler can either decide to generate an indirect jump, or - more likely these days due to mitigations - just a series of conditional branches. Yes, the conditional branches also have branch prediction, but the branch prediction is much more controlled, in that it just causes speculatively running the wrong system call (harmless), rather than speculatively running possibly wrong random less controlled code gadgets. This doesn't mitigate other indirect calls, but the system call indirection is the first and most easily triggered case. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
136 lines
3.4 KiB
C
136 lines
3.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Access to user system call parameters and results
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*
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* Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved.
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*
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* See asm-generic/syscall.h for descriptions of what we must do here.
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*/
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#ifndef _ASM_X86_SYSCALL_H
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#define _ASM_X86_SYSCALL_H
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#include <uapi/linux/audit.h>
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#include <linux/sched.h>
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#include <linux/err.h>
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#include <asm/thread_info.h> /* for TS_COMPAT */
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#include <asm/unistd.h>
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/* This is used purely for kernel/trace/trace_syscalls.c */
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typedef long (*sys_call_ptr_t)(const struct pt_regs *);
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extern const sys_call_ptr_t sys_call_table[];
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/*
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* These may not exist, but still put the prototypes in so we
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* can use IS_ENABLED().
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*/
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extern long ia32_sys_call(const struct pt_regs *, unsigned int nr);
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extern long x32_sys_call(const struct pt_regs *, unsigned int nr);
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extern long x64_sys_call(const struct pt_regs *, unsigned int nr);
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/*
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* Only the low 32 bits of orig_ax are meaningful, so we return int.
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* This importantly ignores the high bits on 64-bit, so comparisons
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* sign-extend the low 32 bits.
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*/
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static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
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{
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return regs->orig_ax;
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}
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static inline void syscall_rollback(struct task_struct *task,
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struct pt_regs *regs)
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{
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regs->ax = regs->orig_ax;
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}
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static inline long syscall_get_error(struct task_struct *task,
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struct pt_regs *regs)
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{
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unsigned long error = regs->ax;
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#ifdef CONFIG_IA32_EMULATION
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/*
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* TS_COMPAT is set for 32-bit syscall entries and then
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* remains set until we return to user mode.
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*/
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if (task->thread_info.status & (TS_COMPAT|TS_I386_REGS_POKED))
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/*
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* Sign-extend the value so (int)-EFOO becomes (long)-EFOO
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* and will match correctly in comparisons.
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*/
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error = (long) (int) error;
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#endif
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return IS_ERR_VALUE(error) ? error : 0;
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}
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static inline long syscall_get_return_value(struct task_struct *task,
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struct pt_regs *regs)
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{
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return regs->ax;
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}
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static inline void syscall_set_return_value(struct task_struct *task,
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struct pt_regs *regs,
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int error, long val)
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{
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regs->ax = (long) error ?: val;
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}
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#ifdef CONFIG_X86_32
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static inline void syscall_get_arguments(struct task_struct *task,
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struct pt_regs *regs,
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unsigned long *args)
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{
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memcpy(args, ®s->bx, 6 * sizeof(args[0]));
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}
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static inline int syscall_get_arch(struct task_struct *task)
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{
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return AUDIT_ARCH_I386;
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}
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#else /* CONFIG_X86_64 */
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static inline void syscall_get_arguments(struct task_struct *task,
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struct pt_regs *regs,
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unsigned long *args)
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{
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# ifdef CONFIG_IA32_EMULATION
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if (task->thread_info.status & TS_COMPAT) {
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*args++ = regs->bx;
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*args++ = regs->cx;
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*args++ = regs->dx;
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*args++ = regs->si;
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*args++ = regs->di;
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*args = regs->bp;
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} else
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# endif
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{
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*args++ = regs->di;
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*args++ = regs->si;
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*args++ = regs->dx;
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*args++ = regs->r10;
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*args++ = regs->r8;
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*args = regs->r9;
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}
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}
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static inline int syscall_get_arch(struct task_struct *task)
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{
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/* x32 tasks should be considered AUDIT_ARCH_X86_64. */
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return (IS_ENABLED(CONFIG_IA32_EMULATION) &&
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task->thread_info.status & TS_COMPAT)
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? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
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}
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bool do_syscall_64(struct pt_regs *regs, int nr);
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#endif /* CONFIG_X86_32 */
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void do_int80_syscall_32(struct pt_regs *regs);
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bool do_fast_syscall_32(struct pt_regs *regs);
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bool do_SYSENTER_32(struct pt_regs *regs);
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#endif /* _ASM_X86_SYSCALL_H */
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