Re: [PATCH] sparc64: Add support for Application Data Integrity (ADI)

From: Julian Calaby
Date: Wed Mar 02 2016 - 20:33:57 EST

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Hi Khalid,

A couple of other comments:

On Thu, Mar 3, 2016 at 5:54 AM, Khalid Aziz <khalid.aziz@xxxxxxxxxx> wrote:
>
> Enable Application Data Integrity (ADI) support in the sparc
> kernel for applications to use ADI in userspace. ADI is a new
> feature supported on sparc M7 and newer processors. ADI is supported
> for data fetches only and not instruction fetches. This patch adds
> prctl commands to enable and disable ADI (TSTATE.mcde), return ADI
> parameters to userspace, enable/disable MCD (Memory Corruption
> Detection) on selected memory ranges and enable TTE.mcd in PTEs. It
> also adds handlers for all traps related to MCD. ADI is not enabled
> by default for any task and a task must explicitly enable ADI
> (TSTATE.mcde), turn MCD on on a memory range and set version tag
> for ADI to be effective for the task. This patch adds support for
> ADI for hugepages only. Addresses passed into system calls must be
> non-ADI tagged addresses.
>
> Signed-off-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
> ---
> NOTES: ADI is a new feature added to M7 processor to allow hardware
> to catch rogue accesses to memory. An app can enable ADI on
> its data pages, set version tags on them and use versioned
> addresses (bits 63-60 of the address contain a version tag)
> to access the data pages. If a rogue app attempts to access
> ADI enabled data pages, its access is blocked and processor
> generates an exception. Enabling this functionality for all
> data pages of an app requires adding infrastructure to save
> version tags for any data pages that get swapped out and
> restoring those tags when pages are swapped back in. In this
> first implementation I am enabling ADI for hugepages only
> since these pages are locked in memory and hence avoid the
> issue of saving and restoring tags. Once this core functionality
> is stable, ADI for other memory pages can be enabled more
> easily.
>
> Documentation/prctl/sparc_adi.txt | 62 ++++++++++
> Documentation/sparc/adi.txt | 206 +++++++++++++++++++++++++++++++
> arch/sparc/Kconfig | 12 ++
> arch/sparc/include/asm/hugetlb.h | 14 +++
> arch/sparc/include/asm/hypervisor.h | 2 +
> arch/sparc/include/asm/mmu_64.h | 1 +
> arch/sparc/include/asm/pgtable_64.h | 15 +++
> arch/sparc/include/asm/processor_64.h | 19 +++
> arch/sparc/include/asm/ttable.h | 10 ++
> arch/sparc/include/uapi/asm/asi.h | 3 +
> arch/sparc/include/uapi/asm/pstate.h | 10 ++
> arch/sparc/kernel/entry.h | 3 +
> arch/sparc/kernel/head_64.S | 1 +
> arch/sparc/kernel/mdesc.c | 81 +++++++++++++
> arch/sparc/kernel/process_64.c | 221 ++++++++++++++++++++++++++++++++++
> arch/sparc/kernel/sun4v_mcd.S | 16 +++
> arch/sparc/kernel/traps_64.c | 96 ++++++++++++++-
> arch/sparc/kernel/ttable_64.S | 6 +-
> include/linux/mm.h | 2 +
> include/uapi/asm-generic/siginfo.h | 5 +-
> include/uapi/linux/prctl.h | 16 +++
> kernel/sys.c | 30 +++++
> 22 files changed, 825 insertions(+), 6 deletions(-)
> create mode 100644 Documentation/prctl/sparc_adi.txt
> create mode 100644 Documentation/sparc/adi.txt
> create mode 100644 arch/sparc/kernel/sun4v_mcd.S
>
> diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
> index 131d36f..cddea30 100644
> --- a/arch/sparc/include/asm/pgtable_64.h
> +++ b/arch/sparc/include/asm/pgtable_64.h
> @@ -162,6 +162,9 @@ bool kern_addr_valid(unsigned long addr);
> #define _PAGE_E_4V _AC(0x0000000000000800,UL) /* side-Effect */
> #define _PAGE_CP_4V _AC(0x0000000000000400,UL) /* Cacheable in P-Cache */
> #define _PAGE_CV_4V _AC(0x0000000000000200,UL) /* Cacheable in V-Cache */
> +/* Bit 9 is used to enable MCD corruption detection instead on M7
> + */
> +#define _PAGE_MCD_4V _AC(0x0000000000000200,UL) /* Memory Corruption */

I'm not sure that everywhere _PAGE_CV_4V is used is guarded against
setting it on M7, could someone who knows the code better than I do
please check that? It looks like the tests around it's use are
essentially "is it sun4v".

I'm probably being paranoid, but reused values like this make me worry.

> #define _PAGE_P_4V _AC(0x0000000000000100,UL) /* Privileged Page */
> #define _PAGE_EXEC_4V _AC(0x0000000000000080,UL) /* Executable Page */
> #define _PAGE_W_4V _AC(0x0000000000000040,UL) /* Writable */
> diff --git a/arch/sparc/include/uapi/asm/pstate.h b/arch/sparc/include/uapi/asm/pstate.h
> index cf832e1..d0521db 100644
> --- a/arch/sparc/include/uapi/asm/pstate.h
> +++ b/arch/sparc/include/uapi/asm/pstate.h
> @@ -10,7 +10,12 @@
> * -----------------------------------------------------------------------
> * 63 12 11 10 9 8 7 6 5 4 3 2 1 0
> */
> +/* IG on V9 conflicts with MCDE on M7. PSTATE_MCDE will only be used on
> + * processors that support ADI which do not use IG, hence there is no
> + * functional conflict
> + */
> #define PSTATE_IG _AC(0x0000000000000800,UL) /* Interrupt Globals. */
> +#define PSTATE_MCDE _AC(0x0000000000000800,UL) /* MCD Enable */

Again, I can't tell if the code that uses PSTATE_IG is guarded against
use on M7. Could someone else please check? It's used in cherrs.S
which appears to be Cheetah specific, so that's not a problem, however
it's also used in ultra.S in xcall_sync_tick which might get patched
out however I don't know the code well enough to be certain. I'm also
guessing that as this file is in include/uapi, userspace could use it
for something.

> #define PSTATE_MG _AC(0x0000000000000400,UL) /* MMU Globals. */
> #define PSTATE_CLE _AC(0x0000000000000200,UL) /* Current Little Endian.*/
> #define PSTATE_TLE _AC(0x0000000000000100,UL) /* Trap Little Endian. */
> @@ -47,7 +52,12 @@
> #define TSTATE_ASI _AC(0x00000000ff000000,UL) /* AddrSpace ID. */
> #define TSTATE_PIL _AC(0x0000000000f00000,UL) /* %pil (Linux traps)*/
> #define TSTATE_PSTATE _AC(0x00000000000fff00,UL) /* PSTATE. */
> +/* IG on V9 conflicts with MCDE on M7. TSTATE_MCDE will only be used on
> + * processors that support ADI which do not support IG, hence there is
> + * no functional conflict
> + */
> #define TSTATE_IG _AC(0x0000000000080000,UL) /* Interrupt Globals.*/
> +#define TSTATE_MCDE _AC(0x0000000000080000,UL) /* MCD enable. */

TSTATE_IG only seems to be referenced in cherrs.S which appears to be
Cheetah specific, so I'm guessing this is safe unless userspace does
something with it.

> #define TSTATE_MG _AC(0x0000000000040000,UL) /* MMU Globals. */
> #define TSTATE_CLE _AC(0x0000000000020000,UL) /* CurrLittleEndian. */
> #define TSTATE_TLE _AC(0x0000000000010000,UL) /* TrapLittleEndian. */
> diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
> index 46a5964..33fcc85 100644
> --- a/arch/sparc/kernel/process_64.c
> +++ b/arch/sparc/kernel/process_64.c
> @@ -777,3 +779,222 @@ unsigned long get_wchan(struct task_struct *task)
> out:
> return ret;
> }
> +
> +#ifdef CONFIG_SPARC_ADI
> +long get_sparc_adicaps(unsigned long val)
> +{
> + struct adi_caps *caps;
> +
> + if (!ADI_CAPABLE())
> + return -EINVAL;
> +
> + caps = get_adi_caps();
> + if (val)

Should we return 0 before calling get_adi_caps() if val is null?

> + if (copy_to_user((void *)val, caps, sizeof(struct adi_caps)))
> + return -EFAULT;
> + return 0;
> +}
> +
> +long set_sparc_pstate_mcde(unsigned long val)
> +{
> + unsigned long error;
> + struct pt_regs *regs;
> +
> + if (!ADI_CAPABLE())
> + return -EINVAL;
> +
> + /* We do not allow anonymous tasks to enable ADI because they
> + * run in borrowed aadress space.
> + */
> + if (current->mm == NULL)
> + return -EINVAL;
> +
> + regs = task_pt_regs(current);
> + if (regs->tstate & TSTATE_MCDE)
> + error = 1;
> + else
> + error = 0;
> + switch (val) {
> + case 1:
> + regs->tstate |= TSTATE_MCDE;
> + current->mm->context.adi = 1;
> + break;
> + case 0:
> + regs->tstate &= ~TSTATE_MCDE;
> + current->mm->context.adi = 0;
> + break;
> + default:
> + break;
> + }
> +
> + return error;
> +}
> +
> +long enable_sparc_adi(unsigned long addr, unsigned long len)
> +{
> + unsigned long end, pagemask;
> + int error;
> + struct vm_area_struct *vma, *vma2;
> + struct mm_struct *mm;
> +
> + if (!ADI_CAPABLE())
> + return -EINVAL;
> +
> + vma = find_vma(current->mm, addr);
> + if (unlikely(!vma) || (vma->vm_start > addr))
> + return -EFAULT;
> +
> + /* ADI is supported for hugepages only
> + */
> + if (!is_vm_hugetlb_page(vma))
> + return -EFAULT;
> +
> + /* Is the start address page aligned and is the length multiple
> + * of page size?
> + */
> + pagemask = ~(vma_kernel_pagesize(vma) - 1);
> + if (addr & ~pagemask)
> + return -EINVAL;
> + if (len & ~pagemask)
> + return -EINVAL;
> +
> + end = addr + len;
> + if (end == addr)
> + return 0;

Should we check if len == 0 before calculating the pagemask?

> +
> + /* Verify end of the region is not out of bounds
> + */
> + vma2 = find_vma(current->mm, end-1);
> + if (unlikely(!vma2) || (vma2->vm_start > end))
> + return -EFAULT;
> +
> + error = 0;
> + while (1) {
> + /* If the address space ADI is to be enabled in, does not cover
> + * this vma in its entirety, we will need to split it.
> + */
> + mm = vma->vm_mm;
> + if (addr != vma->vm_start) {
> + error = split_vma(mm, vma, addr, 1);
> + if (error)
> + goto out;
> + }
> +
> + if (end < vma->vm_end) {
> + error = split_vma(mm, vma, end, 0);
> + if (error)
> + goto out;
> + }
> +
> + /* Update the ADI info in vma and PTE
> + */
> + vma->vm_flags |= VM_SPARC_ADI;
> +
> + if (end > vma->vm_end) {
> + change_protection(vma, addr, vma->vm_end,
> + vma->vm_page_prot,
> + vma_wants_writenotify(vma), 0);
> + addr = vma->vm_end;
> + } else {
> + change_protection(vma, addr, end, vma->vm_page_prot,
> + vma_wants_writenotify(vma), 0);
> + break;
> + }
> +
> + vma = find_vma(current->mm, addr);
> + if (unlikely(!vma) || (vma->vm_start > addr))
> + return -EFAULT;
> + }
> +out:
> + if (error == -ENOMEM)
> + error = -EAGAIN;
> + return error;
> +}
> +
> +long disable_sparc_adi(unsigned long addr, unsigned long len)
> +{
> + unsigned long end, pagemask;
> + struct vm_area_struct *vma, *vma2, *prev;
> + struct mm_struct *mm;
> + pgoff_t pgoff;
> +
> + if (!ADI_CAPABLE())
> + return -EINVAL;
> +
> + vma = find_vma(current->mm, addr);
> + if (unlikely(!vma) || (vma->vm_start > addr))
> + return -EFAULT;
> +
> + /* ADI is supported for hugepages only
> + */
> + if (!is_vm_hugetlb_page(vma))
> + return -EINVAL;
> +
> + /* Is the start address page aligned and is the length multiple
> + * of page size?
> + */
> + pagemask = ~(vma_kernel_pagesize(vma) - 1);
> + if (addr & ~pagemask)
> + return -EINVAL;
> + if (len & ~pagemask)
> + return -EINVAL;
> +
> + end = addr + len;
> + if (end == addr)
> + return 0;
> +
> + /* Verify end of the region is not out of bounds
> + */
> + vma2 = find_vma(current->mm, end-1);
> + if (unlikely(!vma2) || (vma2->vm_start > end))
> + return -EFAULT;
> +
> + while (1) {
> + mm = vma->vm_mm;
> +
> + /* Update the ADI info in vma and check if this vma can
> + * be merged with adjacent ones
> + */
> + pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT);
> + prev = vma_merge(mm, prev, addr, end, vma->vm_flags,
> + vma->anon_vma, vma->vm_file, pgoff,
> + vma_policy(vma), vma->vm_userfaultfd_ctx);
> + if (prev)
> + vma = prev;
> +
> + vma->vm_flags &= ~VM_SPARC_ADI;
> + if (end > vma->vm_end) {
> + change_protection(vma, addr, vma->vm_end,
> + vma->vm_page_prot,
> + vma_wants_writenotify(vma), 0);
> + addr = vma->vm_end;
> + } else {
> + change_protection(vma, addr, end, vma->vm_page_prot,
> + vma_wants_writenotify(vma), 0);
> + break;
> + }
> +
> + vma = find_vma_prev(current->mm, addr, &prev);
> + if (unlikely(!vma) || (vma->vm_start > addr))
> + return -EFAULT;
> + }
> + return 0;
> +}
> +
> +long get_sparc_adi_status(unsigned long addr)
> +{
> + struct vm_area_struct *vma;
> +
> + if (!ADI_CAPABLE())
> + return -EINVAL;
> +
> + vma = find_vma(current->mm, addr);
> + if (unlikely(!vma) || (vma->vm_start > addr))
> + return -EFAULT;
> +
> + if (vma->vm_flags & VM_SPARC_ADI)
> + return 1;
> +
> + return 0;
> +}
> +#endif

Thanks,

--
Julian Calaby

Email: julian.calaby@xxxxxxxxx
Profile: http://www.google.com/profiles/julian.calaby/

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