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Date: Thu, 3 Mar 2016 10:08:19 +1100
From: Julian Calaby <julian.calaby@...il.com>
To: Khalid Aziz <khalid.aziz@...cle.com>
Cc: "David S. Miller" <davem@...emloft.net>, corbet@....net,
Andrew Morton <akpm@...ux-foundation.org>,
dingel@...ux.vnet.ibm.com, zhenzhang.zhang@...wei.com,
bob.picco@...cle.com, kirill.shutemov@...ux.intel.com,
aneesh.kumar@...ux.vnet.ibm.com, aarcange@...hat.com,
Arnd Bergmann <arnd@...db.de>,
sparclinux <sparclinux@...r.kernel.org>, rob.gardner@...cle.com,
mhocko@...e.cz, chris.hyser@...cle.com, richard@....at,
vbabka@...e.cz, koct9i@...il.com, oleg@...hat.com,
gthelen@...gle.com, jack@...e.cz, xiexiuqi@...wei.com,
Vineet.Gupta1@...opsys.com, Andy Lutomirski <luto@...nel.org>,
ebiederm@...ssion.com, bsegall@...gle.com,
Geert Uytterhoeven <geert@...ux-m68k.org>, dave@...olabs.net,
Alexey Dobriyan <adobriyan@...il.com>,
linux-doc@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
linux-mm@...ck.org, linux-arch@...r.kernel.org,
linux-api@...r.kernel.org
Subject: Re: [PATCH v2] sparc64: Add support for Application Data Integrity (ADI)
Hi Khalid,
On Thu, Mar 3, 2016 at 7:39 AM, Khalid Aziz <khalid.aziz@...cle.com> 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.
I can't comment on the actual functionality here, but I do see a few
minor style issues in your patch.
My big concern is that you're defining a lot of new code that is ADI
specific but isn't inside a CONFIG_SPARC_ADI ifdef. (That said,
handling ADI specific traps if ADI isn't enabled looks like a good
idea to me, however most of the other stuff is just dead code if
CONFIG_SPARC_ADI isn't enabled.)
> Signed-off-by: Khalid Aziz <khalid.aziz@...cle.com>
> ---
> 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.
>
> v2:
> - Fixed a build error
>
> 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 | 222 ++++++++++++++++++++++++++++++++++
> 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, 826 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
I must admit that I'm slightly impressed that the documentation is
over a quarter of the lines added. =)
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index 56442d2..0aac0ae 100644
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -80,6 +80,7 @@ config SPARC64
> select NO_BOOTMEM
> select HAVE_ARCH_AUDITSYSCALL
> select ARCH_SUPPORTS_ATOMIC_RMW
> + select SPARC_ADI
This doesn't look right.
> config ARCH_DEFCONFIG
> string
> @@ -314,6 +315,17 @@ if SPARC64
> source "kernel/power/Kconfig"
> endif
>
> +config SPARC_ADI
> + bool "Application Data Integrity support"
> + def_bool y if SPARC64
def_bool is for config options without names (i.e. "this is a boolean
value and it's default is...")
So if you want people to be able to disable this option, then you
should remove the select above and just have:
bool "Application Data Integrity support"
default y if SPARC64
If you don't want people disabling it, then there's no point in having
a separate Kconfig symbol.
> + help
> + Support for Application Data Integrity (ADI). ADI feature allows
> + a process to tag memory blocks with version tags. Once ADI is
> + enabled and version tag is set on a memory block, any access to
> + it is allowed only if the correct version tag is presented by
> + a process. This feature is meant to help catch rogue accesses
> + to memory.
> +
You should probably mention that it's only available on newer
processors and recommend that it's enabled on them.
This code won't break anything on older processors, right? I haven't
looked very closely, but I don't see anything that specifically
disables the code if it's run on, say, a UltraSparc I.
> config SCHED_SMT
> bool "SMT (Hyperthreading) scheduler support"
> depends on SPARC64 && SMP
> diff --git a/arch/sparc/include/asm/processor_64.h b/arch/sparc/include/asm/processor_64.h
> index 6924bde..9a71701 100644
> --- a/arch/sparc/include/asm/processor_64.h
> +++ b/arch/sparc/include/asm/processor_64.h
> @@ -97,6 +97,25 @@ struct thread_struct {
> struct task_struct;
> unsigned long thread_saved_pc(struct task_struct *);
>
> +#ifdef CONFIG_SPARC_ADI
> +extern struct adi_caps *get_adi_caps(void);
> +extern long get_sparc_adicaps(unsigned long);
> +extern long set_sparc_pstate_mcde(unsigned long);
> +extern long enable_sparc_adi(unsigned long, unsigned long);
> +extern long disable_sparc_adi(unsigned long, unsigned long);
> +extern long get_sparc_adi_status(unsigned long);
> +extern bool adi_capable(void);
> +
> +#define GET_SPARC_ADICAPS(a) get_sparc_adicaps(a)
> +#define SET_SPARC_MCDE(a) set_sparc_pstate_mcde(a)
> +#define ENABLE_SPARC_ADI(a, b) enable_sparc_adi(a, b)
> +#define DISABLE_SPARC_ADI(a, b) disable_sparc_adi(a, b)
> +#define GET_SPARC_ADI_STATUS(a) get_sparc_adi_status(a)
> +#define ADI_CAPABLE() adi_capable()
Get rid of the ADI_CAPABLE macro, the usual pattern here is to define
a static inline function for the entire API when the symbol is
disabled, i.e.
#ifdef CONFIG_SPARC_ADI
...
extern bool adi_capable(void);
#else
...
static inline bool adi_capable(void) {
return false;
}
#endif
That way you get type checking on the arguments even if the option is
disabled and modern compilers are smart enough to optimise all the
no-op code away. (Not that the type checking is needed here.)
Also, in all but one place you use the ADI_CAPABLE() macro when the
adi_capable() function is defined and available.
> +#else
> +#define ADI_CAPABLE() 0
> +#endif
> +
> /* On Uniprocessor, even in RMO processes see TSO semantics */
> #ifdef CONFIG_SMP
> #define TSTATE_INITIAL_MM TSTATE_TSO
> diff --git a/arch/sparc/kernel/mdesc.c b/arch/sparc/kernel/mdesc.c
> index 6f80936..79f981c 100644
> --- a/arch/sparc/kernel/mdesc.c
> +++ b/arch/sparc/kernel/mdesc.c
> @@ -1007,6 +1013,80 @@ static int mdesc_open(struct inode *inode, struct file *file)
> return 0;
> }
>
> +bool adi_capable(void)
> +{
> + return adi_state.enabled;
> +}
> +
> +struct adi_caps *get_adi_caps(void)
> +{
> + return &adi_state.caps;
> +}
> +
> +void __init
> +init_adi(void)
> +{
> + struct mdesc_handle *hp = mdesc_grab();
> + const char *prop;
> + u64 pn, *val;
> + int len;
> +
> + adi_state.enabled = false;
> +
> + if (!hp)
> + return;
> +
> + pn = mdesc_node_by_name(hp, MDESC_NODE_NULL, "cpu");
> + if (pn == MDESC_NODE_NULL)
> + goto out;
> +
> + prop = mdesc_get_property(hp, pn, "hwcap-list", &len);
> + if (!prop)
> + goto out;
> +
> + /*
> + * Look for "adp" keyword in hwcap-list which would indicate
> + * ADI support
> + */
> + while (len) {
> + int plen;
> +
> + if (!strcmp(prop, "adp")) {
> + adi_state.enabled = true;
> + break;
> + }
> +
> + plen = strlen(prop) + 1;
> + prop += plen;
> + len -= plen;
> + }
> +
> + if (!adi_state.enabled)
> + goto out;
> +
> + pn = mdesc_node_by_name(hp, MDESC_NODE_NULL, "platform");
> + if (pn == MDESC_NODE_NULL)
> + goto out;
> +
> + val = (u64 *) mdesc_get_property(hp, pn, "adp-blksz", &len);
> + if (!val)
> + goto out;
> + adi_state.caps.blksz = *val;
> +
> + val = (u64 *) mdesc_get_property(hp, pn, "adp-nbits", &len);
> + if (!val)
> + goto out;
> + adi_state.caps.nbits = *val;
> +
> + val = (u64 *) mdesc_get_property(hp, pn, "ue-on-adp", &len);
> + if (!val)
> + goto out;
> + adi_state.caps.ue_on_adi = *val;
> +
> +out:
> + mdesc_release(hp);
> +}
> +
Should all the ADI related functions above be within a #ifdef CONFIG_SPARC_ADI?
> static ssize_t mdesc_read(struct file *file, char __user *buf,
> size_t len, loff_t *offp)
> {
> diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c
> index d21cd62..29db583 100644
> --- a/arch/sparc/kernel/traps_64.c
> +++ b/arch/sparc/kernel/traps_64.c
> @@ -2531,6 +2589,38 @@ void sun4v_do_mna(struct pt_regs *regs, unsigned long addr, unsigned long type_c
> force_sig_info(SIGBUS, &info, current);
> }
>
> +void sun4v_mem_corrupt_detect_precise(struct pt_regs *regs, unsigned long addr,
> + unsigned long context)
> +{
> + siginfo_t info;
> +
> + if (!ADI_CAPABLE()) {
> + bad_trap(regs, 0x1a);
> + return;
> + }
> +
> + if (notify_die(DIE_TRAP, "memory corruption precise exception", regs,
> + 0, 0x8, SIGSEGV) == NOTIFY_STOP)
> + return;
> +
> + if (regs->tstate & TSTATE_PRIV) {
> + pr_emerg("sun4v_mem_corrupt_detect_precise: ADDR[%016lx] "
> + "CTX[%lx], going.\n", addr, context);
> + die_if_kernel("MCD precise", regs);
> + }
> +
> + if (test_thread_flag(TIF_32BIT)) {
> + regs->tpc &= 0xffffffff;
> + regs->tnpc &= 0xffffffff;
> + }
> + info.si_signo = SIGSEGV;
> + info.si_code = SEGV_ADIPERR;
> + info.si_errno = 0;
> + info.si_addr = (void __user *) addr;
> + info.si_trapno = 0;
> + force_sig_info(SIGSEGV, &info, current);
> +}
> +
Should this be ifdef'd too?
> void do_privop(struct pt_regs *regs)
> {
> enum ctx_state prev_state = exception_enter();
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 6af9212..fa7b5d9 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -103,6 +103,21 @@
> #ifndef SET_FP_MODE
> # define SET_FP_MODE(a,b) (-EINVAL)
> #endif
> +#ifndef GET_SPARC_ADICAPS
> +# define GET_SPARC_ADICAPS(a) (-EINVAL)
> +#endif
> +#ifndef SET_SPARC_MCDE
> +# define SET_SPARC_MCDE(a) (-EINVAL)
> +#endif
> +#ifndef ENABLE_SPARC_ADI
> +# define ENABLE_SPARC_ADI(a, b) (-EINVAL)
> +#endif
> +#ifndef DISABLE_SPARC_ADI
> +# define DISABLE_SPARC_ADI(a, b) (-EINVAL)
> +#endif
> +#ifndef GET_SPARC_ADI_STATUS
> +# define GET_SPARC_ADI_STATUS(a) (-EINVAL)
> +#endif
Ah, I was wondering why you were defining macros in processor_64.h.
> /*
> * this is where the system-wide overflow UID and GID are defined, for
I've got a couple more comments, I'll send another email with them shortly.
Thanks,
--
Julian Calaby
Email: julian.calaby@...il.com
Profile: http://www.google.com/profiles/julian.calaby/
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