Orange Pi5 kernel

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2020 ARM Ltd.
 */
 
#include <linux/bitops.h>
#include <linux/cpu.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/prctl.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/string.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/thread_info.h>
#include <linux/types.h>
#include <linux/uio.h>
 
#include <asm/barrier.h>
#include <asm/cpufeature.h>
#include <asm/mte.h>
#include <asm/ptrace.h>
#include <asm/sysreg.h>
 
static bool report_fault_once = true;
 
static DEFINE_PER_CPU_READ_MOSTLY(u64, mte_tcf_preferred);
 
#ifdef CONFIG_KASAN_HW_TAGS
/* Whether the MTE asynchronous mode is enabled. */
DEFINE_STATIC_KEY_FALSE(mte_async_mode);
EXPORT_SYMBOL_GPL(mte_async_mode);
#endif
 
static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
{
<------>pte_t old_pte = READ_ONCE(*ptep);
 
<------>if (check_swap && is_swap_pte(old_pte)) {
<------><------>swp_entry_t entry = pte_to_swp_entry(old_pte);
 
<------><------>if (!non_swap_entry(entry) && mte_restore_tags(entry, page))
<------><------><------>return;
<------>}
 
<------>page_kasan_tag_reset(page);
<------>/*
<------> * We need smp_wmb() in between setting the flags and clearing the
<------> * tags because if another thread reads page->flags and builds a
<------> * tagged address out of it, there is an actual dependency to the
<------> * memory access, but on the current thread we do not guarantee that
<------> * the new page->flags are visible before the tags were updated.
<------> */
<------>smp_wmb();
<------>mte_clear_page_tags(page_address(page));
}
 
void mte_sync_tags(pte_t *ptep, pte_t pte)
{
<------>struct page *page = pte_page(pte);
<------>long i, nr_pages = compound_nr(page);
<------>bool check_swap = nr_pages == 1;
 
<------>/* if PG_mte_tagged is set, tags have already been initialised */
<------>for (i = 0; i < nr_pages; i++, page++) {
<------><------>if (!test_and_set_bit(PG_mte_tagged, &page->flags))
<------><------><------>mte_sync_page_tags(page, ptep, check_swap);
<------>}
}
 
int memcmp_pages(struct page *page1, struct page *page2)
{
<------>char *addr1, *addr2;
<------>int ret;
 
<------>addr1 = page_address(page1);
<------>addr2 = page_address(page2);
<------>ret = memcmp(addr1, addr2, PAGE_SIZE);
 
<------>if (!system_supports_mte() || ret)
<------><------>return ret;
 
<------>/*
<------> * If the page content is identical but at least one of the pages is
<------> * tagged, return non-zero to avoid KSM merging. If only one of the
<------> * pages is tagged, set_pte_at() may zero or change the tags of the
<------> * other page via mte_sync_tags().
<------> */
<------>if (test_bit(PG_mte_tagged, &page1->flags) ||
<------>    test_bit(PG_mte_tagged, &page2->flags))
<------><------>return addr1 != addr2;
 
<------>return ret;
}
 
static inline void __mte_enable_kernel(const char *mode, unsigned long tcf)
{
<------>/* Enable MTE Sync Mode for EL1. */
<------>sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, tcf);
<------>isb();
 
<------>pr_info_once("MTE: enabled in %s mode at EL1\n", mode);
}
 
#ifdef CONFIG_KASAN_HW_TAGS
void mte_enable_kernel_sync(void)
{
<------>/*
<------> * Make sure we enter this function when no PE has set
<------> * async mode previously.
<------> */
<------>WARN_ONCE(system_uses_mte_async_mode(),
<------><------><------>"MTE async mode enabled system wide!");
 
<------>__mte_enable_kernel("synchronous", SCTLR_ELx_TCF_SYNC);
}
 
void mte_enable_kernel_async(void)
{
<------>__mte_enable_kernel("asynchronous", SCTLR_ELx_TCF_ASYNC);
 
<------>/*
<------> * MTE async mode is set system wide by the first PE that
<------> * executes this function.
<------> *
<------> * Note: If in future KASAN acquires a runtime switching
<------> * mode in between sync and async, this strategy needs
<------> * to be reviewed.
<------> */
<------>if (!system_uses_mte_async_mode())
<------><------>static_branch_enable(&mte_async_mode);
}
#endif
 
void mte_set_report_once(bool state)
{
<------>WRITE_ONCE(report_fault_once, state);
}
 
bool mte_report_once(void)
{
<------>return READ_ONCE(report_fault_once);
}
 
#ifdef CONFIG_KASAN_HW_TAGS
void mte_check_tfsr_el1(void)
{
<------>u64 tfsr_el1 = read_sysreg_s(SYS_TFSR_EL1);
 
<------>if (unlikely(tfsr_el1 & SYS_TFSR_EL1_TF1)) {
<------><------>/*
<------><------> * Note: isb() is not required after this direct write
<------><------> * because there is no indirect read subsequent to it
<------><------> * (per ARM DDI 0487F.c table D13-1).
<------><------> */
<------><------>write_sysreg_s(0, SYS_TFSR_EL1);
 
<------><------>kasan_report_async();
<------>}
}
#endif
 
static void mte_update_sctlr_user(struct task_struct *task)
{
<------>/*
<------> * This must be called with preemption disabled and can only be called
<------> * on the current or next task since the CPU must match where the thread
<------> * is going to run. The caller is responsible for calling
<------> * update_sctlr_el1() later in the same preemption disabled block.
<------> */
<------>unsigned long sctlr = task->thread.sctlr_user;
<------>unsigned long mte_ctrl = task->thread.mte_ctrl;
<------>unsigned long pref, resolved_mte_tcf;
 
<------>pref = __this_cpu_read(mte_tcf_preferred);
<------>resolved_mte_tcf = (mte_ctrl & pref) ? pref : mte_ctrl;
<------>sctlr &= ~SCTLR_EL1_TCF0_MASK;
<------>if (resolved_mte_tcf & MTE_CTRL_TCF_ASYNC)
<------><------>sctlr |= SCTLR_EL1_TCF0_ASYNC;
<------>else if (resolved_mte_tcf & MTE_CTRL_TCF_SYNC)
<------><------>sctlr |= SCTLR_EL1_TCF0_SYNC;
<------>task->thread.sctlr_user = sctlr;
}
 
static void mte_update_gcr_excl(struct task_struct *task)
{
<------>/*
<------> * SYS_GCR_EL1 will be set to current->thread.mte_ctrl value by
<------> * mte_set_user_gcr() in kernel_exit, but only if KASAN is enabled.
<------> */
<------>if (kasan_hw_tags_enabled())
<------><------>return;
 
<------>write_sysreg_s(
<------><------>((task->thread.mte_ctrl >> MTE_CTRL_GCR_USER_EXCL_SHIFT) &
<------><------> SYS_GCR_EL1_EXCL_MASK) | SYS_GCR_EL1_RRND,
<------><------>SYS_GCR_EL1);
}
 
void __init kasan_hw_tags_enable(struct alt_instr *alt, __le32 *origptr,
<------><------><------><------> __le32 *updptr, int nr_inst)
{
<------>BUG_ON(nr_inst != 1); /* Branch -> NOP */
 
<------>if (kasan_hw_tags_enabled())
<------><------>*updptr = cpu_to_le32(aarch64_insn_gen_nop());
}
 
void mte_thread_init_user(void)
{
<------>if (!system_supports_mte())
<------><------>return;
 
<------>/* clear any pending asynchronous tag fault */
<------>dsb(ish);
<------>write_sysreg_s(0, SYS_TFSRE0_EL1);
<------>clear_thread_flag(TIF_MTE_ASYNC_FAULT);
<------>/* disable tag checking and reset tag generation mask */
<------>set_mte_ctrl(current, 0);
}
 
void mte_thread_switch(struct task_struct *next)
{
<------>if (!system_supports_mte())
<------><------>return;
 
<------>mte_update_sctlr_user(next);
<------>mte_update_gcr_excl(next);
 
<------>/*
<------> * Check if an async tag exception occurred at EL1.
<------> *
<------> * Note: On the context switch path we rely on the dsb() present
<------> * in __switch_to() to guarantee that the indirect writes to TFSR_EL1
<------> * are synchronized before this point.
<------> */
<------>isb();
<------>mte_check_tfsr_el1();
}
 
void mte_suspend_enter(void)
{
<------>if (!system_supports_mte())
<------><------>return;
 
<------>/*
<------> * The barriers are required to guarantee that the indirect writes
<------> * to TFSR_EL1 are synchronized before we report the state.
<------> */
<------>dsb(nsh);
<------>isb();
 
<------>/* Report SYS_TFSR_EL1 before suspend entry */
<------>mte_check_tfsr_el1();
}
 
long set_mte_ctrl(struct task_struct *task, unsigned long arg)
{
<------>u64 mte_ctrl = (~((arg & PR_MTE_TAG_MASK) >> PR_MTE_TAG_SHIFT) &
<------><------><------>SYS_GCR_EL1_EXCL_MASK) << MTE_CTRL_GCR_USER_EXCL_SHIFT;
 
<------>if (!system_supports_mte())
<------><------>return 0;
 
<------>if (arg & PR_MTE_TCF_ASYNC)
<------><------>mte_ctrl |= MTE_CTRL_TCF_ASYNC;
<------>if (arg & PR_MTE_TCF_SYNC)
<------><------>mte_ctrl |= MTE_CTRL_TCF_SYNC;
 
<------>task->thread.mte_ctrl = mte_ctrl;
<------>if (task == current) {
<------><------>preempt_disable();
<------><------>mte_update_sctlr_user(task);
<------><------>mte_update_gcr_excl(task);
<------><------>update_sctlr_el1(task->thread.sctlr_user);
<------><------>preempt_enable();
<------>}
 
<------>return 0;
}
 
long get_mte_ctrl(struct task_struct *task)
{
<------>unsigned long ret;
<------>u64 mte_ctrl = task->thread.mte_ctrl;
<------>u64 incl = (~mte_ctrl >> MTE_CTRL_GCR_USER_EXCL_SHIFT) &
<------><------>   SYS_GCR_EL1_EXCL_MASK;
 
<------>if (!system_supports_mte())
<------><------>return 0;
 
<------>ret = incl << PR_MTE_TAG_SHIFT;
<------>if (mte_ctrl & MTE_CTRL_TCF_ASYNC)
<------><------>ret |= PR_MTE_TCF_ASYNC;
<------>if (mte_ctrl & MTE_CTRL_TCF_SYNC)
<------><------>ret |= PR_MTE_TCF_SYNC;
 
<------>return ret;
}
 
/*
 * Access MTE tags in another process' address space as given in mm. Update
 * the number of tags copied. Return 0 if any tags copied, error otherwise.
 * Inspired by __access_remote_vm().
 */
static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
<------><------><------><------>struct iovec *kiov, unsigned int gup_flags)
{
<------>struct vm_area_struct *vma;
<------>void __user *buf = kiov->iov_base;
<------>size_t len = kiov->iov_len;
<------>int ret;
<------>int write = gup_flags & FOLL_WRITE;
 
<------>if (!access_ok(buf, len))
<------><------>return -EFAULT;
 
<------>if (mmap_read_lock_killable(mm))
<------><------>return -EIO;
 
<------>while (len) {
<------><------>unsigned long tags, offset;
<------><------>void *maddr;
<------><------>struct page *page = NULL;
 
<------><------>ret = get_user_pages_remote(mm, addr, 1, gup_flags, &page,
<------><------><------><------><------>    &vma, NULL);
<------><------>if (ret <= 0)
<------><------><------>break;
 
<------><------>/*
<------><------> * Only copy tags if the page has been mapped as PROT_MTE
<------><------> * (PG_mte_tagged set). Otherwise the tags are not valid and
<------><------> * not accessible to user. Moreover, an mprotect(PROT_MTE)
<------><------> * would cause the existing tags to be cleared if the page
<------><------> * was never mapped with PROT_MTE.
<------><------> */
<------><------>if (!(vma->vm_flags & VM_MTE)) {
<------><------><------>ret = -EOPNOTSUPP;
<------><------><------>put_page(page);
<------><------><------>break;
<------><------>}
<------><------>WARN_ON_ONCE(!test_bit(PG_mte_tagged, &page->flags));
 
<------><------>/* limit access to the end of the page */
<------><------>offset = offset_in_page(addr);
<------><------>tags = min(len, (PAGE_SIZE - offset) / MTE_GRANULE_SIZE);
 
<------><------>maddr = page_address(page);
<------><------>if (write) {
<------><------><------>tags = mte_copy_tags_from_user(maddr + offset, buf, tags);
<------><------><------>set_page_dirty_lock(page);
<------><------>} else {
<------><------><------>tags = mte_copy_tags_to_user(buf, maddr + offset, tags);
<------><------>}
<------><------>put_page(page);
 
<------><------>/* error accessing the tracer's buffer */
<------><------>if (!tags)
<------><------><------>break;
 
<------><------>len -= tags;
<------><------>buf += tags;
<------><------>addr += tags * MTE_GRANULE_SIZE;
<------>}
<------>mmap_read_unlock(mm);
 
<------>/* return an error if no tags copied */
<------>kiov->iov_len = buf - kiov->iov_base;
<------>if (!kiov->iov_len) {
<------><------>/* check for error accessing the tracee's address space */
<------><------>if (ret <= 0)
<------><------><------>return -EIO;
<------><------>else
<------><------><------>return -EFAULT;
<------>}
 
<------>return 0;
}
 
/*
 * Copy MTE tags in another process' address space at 'addr' to/from tracer's
 * iovec buffer. Return 0 on success. Inspired by ptrace_access_vm().
 */
static int access_remote_tags(struct task_struct *tsk, unsigned long addr,
<------><------><------>      struct iovec *kiov, unsigned int gup_flags)
{
<------>struct mm_struct *mm;
<------>int ret;
 
<------>mm = get_task_mm(tsk);
<------>if (!mm)
<------><------>return -EPERM;
 
<------>if (!tsk->ptrace || (current != tsk->parent) ||
<------>    ((get_dumpable(mm) != SUID_DUMP_USER) &&
<------>     !ptracer_capable(tsk, mm->user_ns))) {
<------><------>mmput(mm);
<------><------>return -EPERM;
<------>}
 
<------>ret = __access_remote_tags(mm, addr, kiov, gup_flags);
<------>mmput(mm);
 
<------>return ret;
}
 
int mte_ptrace_copy_tags(struct task_struct *child, long request,
<------><------><------> unsigned long addr, unsigned long data)
{
<------>int ret;
<------>struct iovec kiov;
<------>struct iovec __user *uiov = (void __user *)data;
<------>unsigned int gup_flags = FOLL_FORCE;
 
<------>if (!system_supports_mte())
<------><------>return -EIO;
 
<------>if (get_user(kiov.iov_base, &uiov->iov_base) ||
<------>    get_user(kiov.iov_len, &uiov->iov_len))
<------><------>return -EFAULT;
 
<------>if (request == PTRACE_POKEMTETAGS)
<------><------>gup_flags |= FOLL_WRITE;
 
<------>/* align addr to the MTE tag granule */
<------>addr &= MTE_GRANULE_MASK;
 
<------>ret = access_remote_tags(child, addr, &kiov, gup_flags);
<------>if (!ret)
<------><------>ret = put_user(kiov.iov_len, &uiov->iov_len);
 
<------>return ret;
}
 
static ssize_t mte_tcf_preferred_show(struct device *dev,
<------><------><------><------>      struct device_attribute *attr, char *buf)
{
<------>switch (per_cpu(mte_tcf_preferred, dev->id)) {
<------>case MTE_CTRL_TCF_ASYNC:
<------><------>return sysfs_emit(buf, "async\n");
<------>case MTE_CTRL_TCF_SYNC:
<------><------>return sysfs_emit(buf, "sync\n");
<------>default:
<------><------>return sysfs_emit(buf, "???\n");
<------>}
}
 
static ssize_t mte_tcf_preferred_store(struct device *dev,
<------><------><------><------>       struct device_attribute *attr,
<------><------><------><------>       const char *buf, size_t count)
{
<------>u64 tcf;
 
<------>if (sysfs_streq(buf, "async"))
<------><------>tcf = MTE_CTRL_TCF_ASYNC;
<------>else if (sysfs_streq(buf, "sync"))
<------><------>tcf = MTE_CTRL_TCF_SYNC;
<------>else
<------><------>return -EINVAL;
 
<------>device_lock(dev);
<------>per_cpu(mte_tcf_preferred, dev->id) = tcf;
<------>device_unlock(dev);
 
<------>return count;
}
static DEVICE_ATTR_RW(mte_tcf_preferred);
 
static int register_mte_tcf_preferred_sysctl(void)
{
<------>unsigned int cpu;
 
<------>if (!system_supports_mte())
<------><------>return 0;
 
<------>for_each_possible_cpu(cpu) {
<------><------>per_cpu(mte_tcf_preferred, cpu) = MTE_CTRL_TCF_ASYNC;
<------><------>device_create_file(get_cpu_device(cpu),
<------><------><------><------>   &dev_attr_mte_tcf_preferred);
<------>}
 
<------>return 0;
}
subsys_initcall(register_mte_tcf_preferred_sysctl);