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3e9e67e129
On arm64, this prctl controls access to CNTVCT_EL0, CNTVCTSS_EL0 and
CNTFRQ_EL0 via CNTKCTL_EL1.EL0VCTEN. Since this bit is also used to
implement various erratum workarounds, check whether the CPU needs
a workaround whenever we potentially need to change it.
This is needed for a correct implementation of non-instrumenting
record-replay debugging on arm64 (i.e. rr; https://rr-project.org/).
rr must trap and record any sources of non-determinism from the
userspace program's perspective so it can be replayed later. This
includes the results of syscalls as well as the results of access
to architected timers exposed directly to the program. This prctl
was originally added for x86 by commit 8fb402bccf ("generic, x86:
add prctl commands PR_GET_TSC and PR_SET_TSC"), and rr uses it to
trap RDTSC on x86 for the same reason.
We also considered exposing this as a PTRACE_EVENT. However, prctl
seems like a better choice for these reasons:
1) In general an in-process control seems more useful than an
out-of-process control, since anything that you would be able to
do with ptrace could also be done with prctl (tracer can inject a
call to the prctl and handle signal-delivery-stops), and it avoids
needing an additional process (which will complicate debugging
of the ptraced process since it cannot have more than one tracer,
and will be incompatible with ptrace_scope=3) in cases where that
is not otherwise necessary.
2) Consistency with x86_64. Note that on x86_64, RDTSC has been there
since the start, so it's the same situation as on arm64.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/I233a1867d1ccebe2933a347552e7eae862344421
Link: https://lore.kernel.org/r/20240824015415.488474-1-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>
128 lines
4.0 KiB
C
128 lines
4.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Based on arch/arm/include/asm/thread_info.h
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*
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* Copyright (C) 2002 Russell King.
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* Copyright (C) 2012 ARM Ltd.
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*/
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#ifndef __ASM_THREAD_INFO_H
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#define __ASM_THREAD_INFO_H
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#include <linux/compiler.h>
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#ifndef __ASSEMBLY__
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struct task_struct;
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#include <asm/memory.h>
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#include <asm/stack_pointer.h>
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#include <asm/types.h>
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/*
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* low level task data that entry.S needs immediate access to.
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*/
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struct thread_info {
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unsigned long flags; /* low level flags */
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#ifdef CONFIG_ARM64_SW_TTBR0_PAN
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u64 ttbr0; /* saved TTBR0_EL1 */
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#endif
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union {
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u64 preempt_count; /* 0 => preemptible, <0 => bug */
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struct {
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#ifdef CONFIG_CPU_BIG_ENDIAN
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u32 need_resched;
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u32 count;
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#else
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u32 count;
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u32 need_resched;
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#endif
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} preempt;
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};
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#ifdef CONFIG_SHADOW_CALL_STACK
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void *scs_base;
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void *scs_sp;
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#endif
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u32 cpu;
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};
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#define thread_saved_pc(tsk) \
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((unsigned long)(tsk->thread.cpu_context.pc))
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#define thread_saved_sp(tsk) \
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((unsigned long)(tsk->thread.cpu_context.sp))
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#define thread_saved_fp(tsk) \
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((unsigned long)(tsk->thread.cpu_context.fp))
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void arch_setup_new_exec(void);
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#define arch_setup_new_exec arch_setup_new_exec
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#endif
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#define TIF_SIGPENDING 0 /* signal pending */
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#define TIF_NEED_RESCHED 1 /* rescheduling necessary */
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#define TIF_NOTIFY_RESUME 2 /* callback before returning to user */
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#define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */
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#define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */
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#define TIF_MTE_ASYNC_FAULT 5 /* MTE Asynchronous Tag Check Fault */
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#define TIF_NOTIFY_SIGNAL 6 /* signal notifications exist */
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#define TIF_SYSCALL_TRACE 8 /* syscall trace active */
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#define TIF_SYSCALL_AUDIT 9 /* syscall auditing */
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#define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for ftrace */
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#define TIF_SECCOMP 11 /* syscall secure computing */
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#define TIF_SYSCALL_EMU 12 /* syscall emulation active */
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#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
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#define TIF_FREEZE 19
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#define TIF_RESTORE_SIGMASK 20
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#define TIF_SINGLESTEP 21
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#define TIF_32BIT 22 /* 32bit process */
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#define TIF_SVE 23 /* Scalable Vector Extension in use */
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#define TIF_SVE_VL_INHERIT 24 /* Inherit SVE vl_onexec across exec */
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#define TIF_SSBD 25 /* Wants SSB mitigation */
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#define TIF_TAGGED_ADDR 26 /* Allow tagged user addresses */
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#define TIF_SME 27 /* SME in use */
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#define TIF_SME_VL_INHERIT 28 /* Inherit SME vl_onexec across exec */
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#define TIF_KERNEL_FPSTATE 29 /* Task is in a kernel mode FPSIMD section */
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#define TIF_TSC_SIGSEGV 30 /* SIGSEGV on counter-timer access */
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#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
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#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
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#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
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#define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE)
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#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
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#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
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#define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
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#define _TIF_SECCOMP (1 << TIF_SECCOMP)
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#define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU)
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#define _TIF_UPROBE (1 << TIF_UPROBE)
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#define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP)
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#define _TIF_32BIT (1 << TIF_32BIT)
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#define _TIF_SVE (1 << TIF_SVE)
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#define _TIF_MTE_ASYNC_FAULT (1 << TIF_MTE_ASYNC_FAULT)
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#define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL)
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#define _TIF_TSC_SIGSEGV (1 << TIF_TSC_SIGSEGV)
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#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
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_TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
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_TIF_UPROBE | _TIF_MTE_ASYNC_FAULT | \
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_TIF_NOTIFY_SIGNAL)
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#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
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_TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
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_TIF_SYSCALL_EMU)
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#ifdef CONFIG_SHADOW_CALL_STACK
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#define INIT_SCS \
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.scs_base = init_shadow_call_stack, \
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.scs_sp = init_shadow_call_stack,
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#else
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#define INIT_SCS
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#endif
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#define INIT_THREAD_INFO(tsk) \
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{ \
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.flags = _TIF_FOREIGN_FPSTATE, \
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.preempt_count = INIT_PREEMPT_COUNT, \
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INIT_SCS \
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}
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#endif /* __ASM_THREAD_INFO_H */
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