arm64: mte: ptrace: Add PTRACE_{PEEK,POKE}MTETAGS support
Add support for bulk setting/getting of the MTE tags in a tracee's address space at 'addr' in the ptrace() syscall prototype. 'data' points to a struct iovec in the tracer's address space with iov_base representing the address of a tracer's buffer of length iov_len. The tags to be copied to/from the tracer's buffer are stored as one tag per byte. On successfully copying at least one tag, ptrace() returns 0 and updates the tracer's iov_len with the number of tags copied. In case of error, either -EIO or -EFAULT is returned, trying to follow the ptrace() man page. Note that the tag copying functions are not performance critical, therefore they lack optimisations found in typical memory copy routines. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Alan Hayward <Alan.Hayward@arm.com> Cc: Luis Machado <luis.machado@linaro.org> Cc: Omair Javaid <omair.javaid@linaro.org>
This commit is contained in:
Catalin Marinas
parent
93f067f6ca
commit
18ddbaa02b
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@ -5,6 +5,11 @@
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#ifndef __ASM_MTE_H
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#define __ASM_MTE_H
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#define MTE_GRANULE_SIZE UL(16)
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#define MTE_GRANULE_MASK (~(MTE_GRANULE_SIZE - 1))
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#define MTE_TAG_SHIFT 56
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#define MTE_TAG_SIZE 4
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#ifndef __ASSEMBLY__
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#include <linux/page-flags.h>
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@ -12,6 +17,10 @@
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#include <asm/pgtable-types.h>
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void mte_clear_page_tags(void *addr);
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unsigned long mte_copy_tags_from_user(void *to, const void __user *from,
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unsigned long n);
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unsigned long mte_copy_tags_to_user(void __user *to, void *from,
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unsigned long n);
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#ifdef CONFIG_ARM64_MTE
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@ -25,6 +34,8 @@ void mte_thread_switch(struct task_struct *next);
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void mte_suspend_exit(void);
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long set_mte_ctrl(struct task_struct *task, unsigned long arg);
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long get_mte_ctrl(struct task_struct *task);
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int mte_ptrace_copy_tags(struct task_struct *child, long request,
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unsigned long addr, unsigned long data);
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#else
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@ -54,6 +65,12 @@ static inline long get_mte_ctrl(struct task_struct *task)
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{
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return 0;
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}
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static inline int mte_ptrace_copy_tags(struct task_struct *child,
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long request, unsigned long addr,
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unsigned long data)
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{
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return -EIO;
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}
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#endif
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@ -76,6 +76,9 @@
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/* syscall emulation path in ptrace */
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#define PTRACE_SYSEMU 31
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#define PTRACE_SYSEMU_SINGLESTEP 32
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/* MTE allocation tag access */
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#define PTRACE_PEEKMTETAGS 33
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#define PTRACE_POKEMTETAGS 34
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#ifndef __ASSEMBLY__
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@ -4,14 +4,18 @@
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*/
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#include <linux/bitops.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/prctl.h>
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#include <linux/sched.h>
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#include <linux/sched/mm.h>
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#include <linux/string.h>
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#include <linux/thread_info.h>
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#include <linux/uio.h>
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#include <asm/cpufeature.h>
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#include <asm/mte.h>
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#include <asm/ptrace.h>
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#include <asm/sysreg.h>
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void mte_sync_tags(pte_t *ptep, pte_t pte)
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@ -179,3 +183,137 @@ long get_mte_ctrl(struct task_struct *task)
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return ret;
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}
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/*
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* Access MTE tags in another process' address space as given in mm. Update
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* the number of tags copied. Return 0 if any tags copied, error otherwise.
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* Inspired by __access_remote_vm().
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*/
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static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
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struct iovec *kiov, unsigned int gup_flags)
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{
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struct vm_area_struct *vma;
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void __user *buf = kiov->iov_base;
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size_t len = kiov->iov_len;
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int ret;
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int write = gup_flags & FOLL_WRITE;
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if (!access_ok(buf, len))
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return -EFAULT;
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if (mmap_read_lock_killable(mm))
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return -EIO;
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while (len) {
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unsigned long tags, offset;
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void *maddr;
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struct page *page = NULL;
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ret = get_user_pages_remote(mm, addr, 1, gup_flags, &page,
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&vma, NULL);
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if (ret <= 0)
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break;
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/*
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* Only copy tags if the page has been mapped as PROT_MTE
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* (PG_mte_tagged set). Otherwise the tags are not valid and
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* not accessible to user. Moreover, an mprotect(PROT_MTE)
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* would cause the existing tags to be cleared if the page
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* was never mapped with PROT_MTE.
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*/
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if (!test_bit(PG_mte_tagged, &page->flags)) {
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ret = -EOPNOTSUPP;
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put_page(page);
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break;
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}
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/* limit access to the end of the page */
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offset = offset_in_page(addr);
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tags = min(len, (PAGE_SIZE - offset) / MTE_GRANULE_SIZE);
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maddr = page_address(page);
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if (write) {
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tags = mte_copy_tags_from_user(maddr + offset, buf, tags);
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set_page_dirty_lock(page);
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} else {
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tags = mte_copy_tags_to_user(buf, maddr + offset, tags);
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}
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put_page(page);
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/* error accessing the tracer's buffer */
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if (!tags)
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break;
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len -= tags;
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buf += tags;
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addr += tags * MTE_GRANULE_SIZE;
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}
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mmap_read_unlock(mm);
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/* return an error if no tags copied */
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kiov->iov_len = buf - kiov->iov_base;
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if (!kiov->iov_len) {
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/* check for error accessing the tracee's address space */
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if (ret <= 0)
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return -EIO;
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else
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return -EFAULT;
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}
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return 0;
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}
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/*
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* Copy MTE tags in another process' address space at 'addr' to/from tracer's
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* iovec buffer. Return 0 on success. Inspired by ptrace_access_vm().
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*/
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static int access_remote_tags(struct task_struct *tsk, unsigned long addr,
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struct iovec *kiov, unsigned int gup_flags)
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{
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struct mm_struct *mm;
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int ret;
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mm = get_task_mm(tsk);
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if (!mm)
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return -EPERM;
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if (!tsk->ptrace || (current != tsk->parent) ||
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((get_dumpable(mm) != SUID_DUMP_USER) &&
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!ptracer_capable(tsk, mm->user_ns))) {
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mmput(mm);
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return -EPERM;
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}
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ret = __access_remote_tags(mm, addr, kiov, gup_flags);
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mmput(mm);
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return ret;
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}
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int mte_ptrace_copy_tags(struct task_struct *child, long request,
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unsigned long addr, unsigned long data)
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{
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int ret;
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struct iovec kiov;
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struct iovec __user *uiov = (void __user *)data;
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unsigned int gup_flags = FOLL_FORCE;
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if (!system_supports_mte())
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return -EIO;
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if (get_user(kiov.iov_base, &uiov->iov_base) ||
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get_user(kiov.iov_len, &uiov->iov_len))
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return -EFAULT;
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if (request == PTRACE_POKEMTETAGS)
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gup_flags |= FOLL_WRITE;
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/* align addr to the MTE tag granule */
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addr &= MTE_GRANULE_MASK;
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ret = access_remote_tags(child, addr, &kiov, gup_flags);
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if (!ret)
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ret = put_user(kiov.iov_len, &uiov->iov_len);
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return ret;
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}
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@ -34,6 +34,7 @@
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#include <asm/cpufeature.h>
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#include <asm/debug-monitors.h>
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#include <asm/fpsimd.h>
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#include <asm/mte.h>
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#include <asm/pointer_auth.h>
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#include <asm/stacktrace.h>
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#include <asm/syscall.h>
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@ -1691,6 +1692,12 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task)
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long arch_ptrace(struct task_struct *child, long request,
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unsigned long addr, unsigned long data)
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{
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switch (request) {
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case PTRACE_PEEKMTETAGS:
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case PTRACE_POKEMTETAGS:
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return mte_ptrace_copy_tags(child, request, addr, data);
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}
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return ptrace_request(child, request, addr, data);
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}
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@ -4,7 +4,9 @@
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*/
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#include <linux/linkage.h>
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#include <asm/alternative.h>
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#include <asm/assembler.h>
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#include <asm/mte.h>
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#include <asm/page.h>
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#include <asm/sysreg.h>
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@ -51,3 +53,54 @@ SYM_FUNC_START(mte_copy_page_tags)
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b.ne 1b
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ret
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SYM_FUNC_END(mte_copy_page_tags)
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/*
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* Read tags from a user buffer (one tag per byte) and set the corresponding
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* tags at the given kernel address. Used by PTRACE_POKEMTETAGS.
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* x0 - kernel address (to)
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* x1 - user buffer (from)
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* x2 - number of tags/bytes (n)
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* Returns:
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* x0 - number of tags read/set
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*/
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SYM_FUNC_START(mte_copy_tags_from_user)
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mov x3, x1
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cbz x2, 2f
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1:
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uao_user_alternative 2f, ldrb, ldtrb, w4, x1, 0
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lsl x4, x4, #MTE_TAG_SHIFT
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stg x4, [x0], #MTE_GRANULE_SIZE
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add x1, x1, #1
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subs x2, x2, #1
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b.ne 1b
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// exception handling and function return
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2: sub x0, x1, x3 // update the number of tags set
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ret
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SYM_FUNC_END(mte_copy_tags_from_user)
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/*
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* Get the tags from a kernel address range and write the tag values to the
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* given user buffer (one tag per byte). Used by PTRACE_PEEKMTETAGS.
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* x0 - user buffer (to)
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* x1 - kernel address (from)
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* x2 - number of tags/bytes (n)
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* Returns:
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* x0 - number of tags read/set
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*/
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SYM_FUNC_START(mte_copy_tags_to_user)
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mov x3, x0
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cbz x2, 2f
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1:
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ldg x4, [x1]
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ubfx x4, x4, #MTE_TAG_SHIFT, #MTE_TAG_SIZE
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uao_user_alternative 2f, strb, sttrb, w4, x0, 0
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add x0, x0, #1
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add x1, x1, #MTE_GRANULE_SIZE
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subs x2, x2, #1
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b.ne 1b
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// exception handling and function return
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2: sub x0, x0, x3 // update the number of tags copied
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ret
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SYM_FUNC_END(mte_copy_tags_to_user)
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