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From: Peter Collingbourne <pcc@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Will Deacon <will@kernel.org>,
	 Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Szabolcs Nagy <szabolcs.nagy@arm.com>,
	 Richard Earnshaw <Richard.Earnshaw@arm.com>,
	Kevin Brodsky <kevin.brodsky@arm.com>,
	 Andrey Konovalov <andreyknvl@google.com>,
	linux-mm@kvack.org, linux-arch@vger.kernel.org,
	 Alan Hayward <Alan.Hayward@arm.com>,
	Luis Machado <luis.machado@linaro.org>,
	 Omair Javaid <omair.javaid@linaro.org>
Subject: Re: [PATCH v3 19/23] arm64: mte: Add PTRACE_{PEEK,POKE}MTETAGS support
Date: Fri, 24 Apr 2020 16:28:27 -0700	[thread overview]
Message-ID: <CAMn1gO5+tuR1=o7L3WE9bg0XMBeMGdybZMQCO0U0NOcRvFhqyQ@mail.gmail.com> (raw)
In-Reply-To: <20200421142603.3894-20-catalin.marinas@arm.com>

On Tue, Apr 21, 2020 at 7:26 AM Catalin Marinas <catalin.marinas@arm.com> wrote:
>
> 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>
> ---
>
> Notes:
>     New in v3.
>
>  arch/arm64/include/asm/mte.h         |  17 ++++
>  arch/arm64/include/uapi/asm/ptrace.h |   3 +
>  arch/arm64/kernel/mte.c              | 127 +++++++++++++++++++++++++++
>  arch/arm64/kernel/ptrace.c           |  15 +++-
>  arch/arm64/lib/mte.S                 |  50 +++++++++++
>  5 files changed, 211 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
> index 22eb3e06f311..0ca2aaff07a1 100644
> --- a/arch/arm64/include/asm/mte.h
> +++ b/arch/arm64/include/asm/mte.h
> @@ -2,12 +2,21 @@
>  #ifndef __ASM_MTE_H
>  #define __ASM_MTE_H
>
> +#define MTE_ALLOC_SIZE UL(16)
> +#define MTE_ALLOC_MASK (~(MTE_ALLOC_SIZE - 1))
> +#define MTE_TAG_SHIFT  (56)
> +#define MTE_TAG_SIZE   (4)
> +
>  #ifndef __ASSEMBLY__
>
>  #include <linux/sched.h>
>
>  /* Memory Tagging API */
>  int mte_memcmp_pages(const void *page1_addr, const void *page2_addr);
> +unsigned long mte_copy_tags_from_user(void *to, const void __user *from,
> +                                     unsigned long n);
> +unsigned long mte_copy_tags_to_user(void __user *to, void *from,
> +                                   unsigned long n);
>
>  #ifdef CONFIG_ARM64_MTE
>  void flush_mte_state(void);
> @@ -15,6 +24,8 @@ void mte_thread_switch(struct task_struct *next);
>  void mte_suspend_exit(void);
>  long set_mte_ctrl(unsigned long arg);
>  long get_mte_ctrl(void);
> +int mte_ptrace_copy_tags(struct task_struct *child, long request,
> +                        unsigned long addr, unsigned long data);
>  #else
>  static inline void flush_mte_state(void)
>  {
> @@ -33,6 +44,12 @@ static inline long get_mte_ctrl(void)
>  {
>         return 0;
>  }
> +static inline int mte_ptrace_copy_tags(struct task_struct *child,
> +                                      long request, unsigned long addr,
> +                                      unsigned long data)
> +{
> +       return -EIO;
> +}
>  #endif
>
>  #endif /* __ASSEMBLY__ */
> diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
> index 1daf6dda8af0..cd2a4a164de3 100644
> --- a/arch/arm64/include/uapi/asm/ptrace.h
> +++ b/arch/arm64/include/uapi/asm/ptrace.h
> @@ -67,6 +67,9 @@
>  /* syscall emulation path in ptrace */
>  #define PTRACE_SYSEMU            31
>  #define PTRACE_SYSEMU_SINGLESTEP  32
> +/* MTE allocation tag access */
> +#define PTRACE_PEEKMTETAGS       33
> +#define PTRACE_POKEMTETAGS       34
>
>  #ifndef __ASSEMBLY__
>
> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> index fa4a4196b248..0cb496ed9bf9 100644
> --- a/arch/arm64/kernel/mte.c
> +++ b/arch/arm64/kernel/mte.c
> @@ -3,12 +3,17 @@
>   * Copyright (C) 2020 ARM Ltd.
>   */
>
> +#include <linux/kernel.h>
> +#include <linux/mm.h>
>  #include <linux/prctl.h>
>  #include <linux/sched.h>
> +#include <linux/sched/mm.h>
>  #include <linux/thread_info.h>
> +#include <linux/uio.h>
>
>  #include <asm/cpufeature.h>
>  #include <asm/mte.h>
> +#include <asm/ptrace.h>
>  #include <asm/sysreg.h>
>
>  static void update_sctlr_el1_tcf0(u64 tcf0)
> @@ -133,3 +138,125 @@ long get_mte_ctrl(void)
>
>         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 task_struct *tsk, 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 (down_read_killable(&mm->mmap_sem))
> +               return -EIO;
> +
> +       if (!access_ok(buf, len))
> +               return -EFAULT;
> +
> +       while (len) {
> +               unsigned long tags, offset;
> +               void *maddr;
> +               struct page *page = NULL;
> +
> +               ret = get_user_pages_remote(tsk, mm, addr, 1, gup_flags,
> +                                           &page, &vma, NULL);
> +               if (ret <= 0)
> +                       break;
> +
> +               /* limit access to the end of the page */
> +               offset = offset_in_page(addr);
> +               tags = min(len, (PAGE_SIZE - offset) / MTE_ALLOC_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_ALLOC_SIZE;
> +       }
> +       up_read(&mm->mmap_sem);
> +
> +       /* 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(tsk, 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_ALLOC_MASK;
> +
> +       ret = access_remote_tags(child, addr, &kiov, gup_flags);
> +       if (!ret)
> +               ret = __put_user(kiov.iov_len, &uiov->iov_len);
> +
> +       return ret;
> +}
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 077e352495eb..1fdb841ad536 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -34,6 +34,7 @@
>  #include <asm/cpufeature.h>
>  #include <asm/debug-monitors.h>
>  #include <asm/fpsimd.h>
> +#include <asm/mte.h>
>  #include <asm/pgtable.h>
>  #include <asm/pointer_auth.h>
>  #include <asm/stacktrace.h>
> @@ -1797,7 +1798,19 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task)
>  long arch_ptrace(struct task_struct *child, long request,
>                  unsigned long addr, unsigned long data)
>  {
> -       return ptrace_request(child, request, addr, data);
> +       int ret;
> +
> +       switch (request) {
> +       case PTRACE_PEEKMTETAGS:
> +       case PTRACE_POKEMTETAGS:
> +               ret = mte_ptrace_copy_tags(child, request, addr, data);
> +               break;
> +       default:
> +               ret = ptrace_request(child, request, addr, data);
> +               break;
> +       }
> +
> +       return ret;
>  }
>
>  enum ptrace_syscall_dir {
> diff --git a/arch/arm64/lib/mte.S b/arch/arm64/lib/mte.S
> index bd51ea7e2fcb..45be04a8c73c 100644
> --- a/arch/arm64/lib/mte.S
> +++ b/arch/arm64/lib/mte.S
> @@ -5,6 +5,7 @@
>  #include <linux/linkage.h>
>
>  #include <asm/assembler.h>
> +#include <asm/mte.h>
>
>  /*
>   * Compare tags of two pages
> @@ -44,3 +45,52 @@ SYM_FUNC_START(mte_memcmp_pages)
>
>         ret
>  SYM_FUNC_END(mte_memcmp_pages)
> +
> +/*
> + * Read tags from a user buffer (one tag per byte) and set the corresponding
> + * tags at the given kernel address. Used by PTRACE_POKEMTETAGS.
> + *   x0 - kernel address (to)
> + *   x1 - user buffer (from)
> + *   x2 - number of tags/bytes (n)
> + * Returns:
> + *   x0 - number of tags read/set
> + */
> +SYM_FUNC_START(mte_copy_tags_from_user)
> +       mov     x3, x1
> +1:
> +USER(2f, ldtrb w4, [x1])
> +       lsl     x4, x4, #MTE_TAG_SHIFT
> +       stg     x4, [x0], #MTE_ALLOC_SIZE
> +       add     x1, x1, #1
> +       subs    x2, x2, #1
> +       b.ne    1b
> +
> +       // exception handling and function return
> +2:     sub     x0, x1, x3              // update the number of tags set
> +       ret
> +SYM_FUNC_END(mte_copy_tags_from_user)
> +
> +/*
> + * Get the tags from a kernel address range and write the tag values to the
> + * given user buffer (one tag per byte). Used by PTRACE_PEEKMTETAGS.
> + *   x0 - user buffer (to)
> + *   x1 - kernel address (from)
> + *   x2 - number of tags/bytes (n)
> + * Returns:
> + *   x0 - number of tags read/set
> + */
> +SYM_FUNC_START(mte_copy_tags_to_user)
> +       mov     x3, x0
> +1:
> +       ldg     x4, [x1]
> +       ubfx    x4, x4, #MTE_TAG_SHIFT, #MTE_TAG_SIZE
> +USER(2f, sttrb w4, [x0])
> +       add     x0, x0, #1
> +       add     x1, x1, #MTE_ALLOC_SIZE
> +       subs    x2, x2, #1
> +       b.ne    1b
> +
> +       // exception handling and function return
> +2:     sub     x0, x0, x3              // update the number of tags copied
> +       ret
> +SYM_FUNC_END(mte_copy_tags_from_user)

Nit: should be SYM_FUNC_END(mte_copy_tags_to_user).

Peter


  reply	other threads:[~2020-04-24 23:28 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-21 14:25 [PATCH v3 00/23] arm64: Memory Tagging Extension user-space support Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 01/23] arm64: alternative: Allow alternative_insn to always issue the first instruction Catalin Marinas
2020-04-27 16:57   ` Dave Martin
2020-04-28 11:43     ` Catalin Marinas
2020-04-29 10:26       ` Dave Martin
2020-04-29 14:04         ` Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 02/23] arm64: mte: system register definitions Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 03/23] arm64: mte: CPU feature detection and initial sysreg configuration Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 04/23] arm64: mte: Use Normal Tagged attributes for the linear map Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 05/23] arm64: mte: Assembler macros and default architecture for .S files Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 06/23] arm64: mte: Tags-aware clear_page() implementation Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 07/23] arm64: mte: Tags-aware copy_page() implementation Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 08/23] arm64: Tags-aware memcmp_pages() implementation Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 09/23] arm64: mte: Add specific SIGSEGV codes Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 10/23] arm64: mte: Handle synchronous and asynchronous tag check faults Catalin Marinas
2020-04-23 10:38   ` Catalin Marinas
2020-04-27 16:58   ` Dave Martin
2020-04-28 13:43     ` Catalin Marinas
2020-04-29 10:26       ` Dave Martin
2020-04-21 14:25 ` [PATCH v3 11/23] mm: Introduce arch_calc_vm_flag_bits() Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 12/23] arm64: mte: Add PROT_MTE support to mmap() and mprotect() Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 13/23] mm: Introduce arch_validate_flags() Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 14/23] arm64: mte: Validate the PROT_MTE request via arch_validate_flags() Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 15/23] mm: Allow arm64 mmap(PROT_MTE) on RAM-based files Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 16/23] arm64: mte: Allow user control of the tag check mode via prctl() Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 17/23] arm64: mte: Allow user control of the generated random tags " Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 18/23] arm64: mte: Restore the GCR_EL1 register after a suspend Catalin Marinas
2020-04-23 15:23   ` Lorenzo Pieralisi
2020-04-21 14:25 ` [PATCH v3 19/23] arm64: mte: Add PTRACE_{PEEK,POKE}MTETAGS support Catalin Marinas
2020-04-24 23:28   ` Peter Collingbourne [this message]
2020-04-29 10:27   ` Kevin Brodsky
2020-04-29 15:24     ` Catalin Marinas
2020-04-29 16:46   ` Dave Martin
2020-04-30 10:21     ` Catalin Marinas
2020-05-04 16:40       ` Dave Martin
2020-05-05 18:03   ` Luis Machado
2020-05-12 19:05   ` Luis Machado
2020-05-13 10:48     ` Catalin Marinas
2020-05-13 12:52       ` Luis Machado
2020-05-13 14:11         ` Catalin Marinas
2020-05-13 15:09           ` Luis Machado
2020-05-13 16:45             ` Luis Machado
2020-05-13 17:11               ` Catalin Marinas
2020-05-18 16:47               ` Dave Martin
2020-05-18 17:12                 ` Luis Machado
2020-05-19 16:10                   ` Catalin Marinas
2020-04-21 14:26 ` [PATCH v3 20/23] fs: Allow copy_mount_options() to access user-space in a single pass Catalin Marinas
2020-04-21 15:29   ` Al Viro
2020-04-21 16:45     ` Catalin Marinas
2020-04-27 16:56   ` Dave Martin
2020-04-28 14:06     ` Catalin Marinas
2020-04-29 10:28       ` Dave Martin
2020-04-28 18:16   ` Kevin Brodsky
2020-04-28 19:40     ` Catalin Marinas
2020-04-29 11:58     ` Catalin Marinas
2020-04-28 19:36   ` Catalin Marinas
2020-04-29 10:26   ` Dave Martin
2020-04-29 13:52     ` Catalin Marinas
2020-05-04 16:40       ` Dave Martin
2020-04-21 14:26 ` [PATCH v3 21/23] arm64: mte: Check the DT memory nodes for MTE support Catalin Marinas
2020-04-24 13:57   ` Catalin Marinas
2020-04-24 16:17     ` Catalin Marinas
2020-04-27 11:14       ` Suzuki K Poulose
2020-04-21 14:26 ` [PATCH v3 22/23] arm64: mte: Kconfig entry Catalin Marinas
2020-04-21 14:26 ` [PATCH v3 23/23] arm64: mte: Add Memory Tagging Extension documentation Catalin Marinas
2020-04-29 16:47   ` Dave Martin
2020-04-30 16:23     ` Catalin Marinas
2020-05-04 16:46       ` Dave Martin
2020-05-11 16:40         ` Catalin Marinas
2020-05-13 15:48           ` Dave Martin
2020-05-14 11:37             ` Catalin Marinas
2020-05-15 10:38               ` Catalin Marinas
2020-05-15 11:14                 ` Szabolcs Nagy
2020-05-15 11:27                   ` Catalin Marinas
2020-05-15 12:04                     ` Szabolcs Nagy
2020-05-15 12:13                       ` Catalin Marinas
2020-05-15 12:53                         ` Szabolcs Nagy
2020-05-18 16:52                           ` Dave Martin
2020-05-18 17:13               ` Catalin Marinas
2020-05-05 10:32   ` Szabolcs Nagy
2020-05-05 17:30     ` Catalin Marinas

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