From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Richard Earnshaw <rearnsha@arm.com>
Cc: libc-alpha@sourceware.org, dj@redhat.com
Subject: Re: [PATCH v4 5/6] aarch64: Add sysv specific enabling code for memory tagging
Date: Mon, 21 Dec 2020 12:27:10 +0000 [thread overview]
Message-ID: <20201221122710.GA720@arm.com> (raw)
In-Reply-To: <20201218192957.11035-6-rearnsha@arm.com>
The 12/18/2020 19:29, Richard Earnshaw wrote:
> Add various defines and stubs for enabling MTE on AArch64 sysv-like
> systems such as Linux. The HWCAP feature bit is copied over in the
> same way as other feature bits. Similarly we add a new wrapper header
> for mman.h to define the PROT_MTE flag that can be used with mmap and
> related functions.
>
> We add a new field to struct cpu_features that can be used, for
> example, to check whether or not certain ifunc'd routines should be
> bound to MTE-safe versions.
>
> Finally, if we detect that MTE should be enabled (ie via the glibc
> tunable); we enable MTE during startup as required.
i'd mention in the commit message that the linux api is
committed in linux version 5.10.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
> ---
> sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h | 1 +
> sysdeps/unix/sysv/linux/aarch64/bits/mman.h | 1 +
> .../unix/sysv/linux/aarch64/cpu-features.c | 30 +++++++++++++++++++
> .../unix/sysv/linux/aarch64/cpu-features.h | 2 ++
> 4 files changed, 34 insertions(+)
>
> diff --git a/sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h b/sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h
> index af90d8a626..389852f1d9 100644
> --- a/sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h
> +++ b/sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h
> @@ -73,3 +73,4 @@
> #define HWCAP2_DGH (1 << 15)
> #define HWCAP2_RNG (1 << 16)
> #define HWCAP2_BTI (1 << 17)
> +#define HWCAP2_MTE (1 << 18)
> diff --git a/sysdeps/unix/sysv/linux/aarch64/bits/mman.h b/sysdeps/unix/sysv/linux/aarch64/bits/mman.h
> index ecae046344..c5ec0aa7d0 100644
> --- a/sysdeps/unix/sysv/linux/aarch64/bits/mman.h
> +++ b/sysdeps/unix/sysv/linux/aarch64/bits/mman.h
> @@ -24,6 +24,7 @@
> arch/arm64/include/uapi/asm/mman.h. */
>
> #define PROT_BTI 0x10
> +#define PROT_MTE 0x20
>
> #include <bits/mman-map-flags-generic.h>
>
> diff --git a/sysdeps/unix/sysv/linux/aarch64/cpu-features.c b/sysdeps/unix/sysv/linux/aarch64/cpu-features.c
> index b9ab827aca..bd899c4b09 100644
> --- a/sysdeps/unix/sysv/linux/aarch64/cpu-features.c
> +++ b/sysdeps/unix/sysv/linux/aarch64/cpu-features.c
> @@ -19,10 +19,17 @@
> #include <cpu-features.h>
> #include <sys/auxv.h>
> #include <elf/dl-hwcaps.h>
> +#include <sys/prctl.h>
>
> #define DCZID_DZP_MASK (1 << 4)
> #define DCZID_BS_MASK (0xf)
>
> +/* The maximal set of permitted tags that the MTE random tag generation
> + instruction may use. We exclude tag 0 because a) we want to reserve
> + that for the libc heap structures and b) because it makes it easier
> + to see when pointer have been correctly tagged. */
> +#define MTE_ALLOWED_TAGS (0xfffe << PR_MTE_TAG_SHIFT)
> +
> #if HAVE_TUNABLES
> struct cpu_list
> {
> @@ -86,4 +93,27 @@ init_cpu_features (struct cpu_features *cpu_features)
>
> /* Check if BTI is supported. */
> cpu_features->bti = GLRO (dl_hwcap2) & HWCAP2_BTI;
> +
> + /* Setup memory tagging support if the HW and kernel support it, and if
> + the user has requested it. */
> + cpu_features->mte_state = 0;
> +
> +#ifdef USE_MTAG
> +# if HAVE_TUNABLES
> + int mte_state = TUNABLE_GET (glibc, mem, tagging, unsigned, 0);
> + cpu_features->mte_state = (GLRO (dl_hwcap2) & HWCAP2_MTE) ? mte_state : 0;
> + /* If we lack the MTE feature, disable the tunable, since it will
> + otherwise cause instructions that won't run on this CPU to be used. */
> + TUNABLE_SET (glibc, mem, tagging, unsigned, cpu_features->mte_state);
> +# endif
> +
> + if (cpu_features->mte_state & 2)
> + __prctl (PR_SET_TAGGED_ADDR_CTRL,
> + (PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_SYNC | MTE_ALLOWED_TAGS),
> + 0, 0, 0);
> + else if (cpu_features->mte_state)
> + __prctl (PR_SET_TAGGED_ADDR_CTRL,
> + (PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_ASYNC | MTE_ALLOWED_TAGS),
> + 0, 0, 0);
> +#endif
> }
> diff --git a/sysdeps/unix/sysv/linux/aarch64/cpu-features.h b/sysdeps/unix/sysv/linux/aarch64/cpu-features.h
> index 00a4d0c8e7..bebf321a21 100644
> --- a/sysdeps/unix/sysv/linux/aarch64/cpu-features.h
> +++ b/sysdeps/unix/sysv/linux/aarch64/cpu-features.h
> @@ -70,6 +70,8 @@ struct cpu_features
> uint64_t midr_el1;
> unsigned zva_size;
> bool bti;
> + /* Currently, the GLIBC memory tagging tunable only defines 8 bits. */
> + uint8_t mte_state;
> };
>
> #endif /* _CPU_FEATURES_AARCH64_H */
next prev parent reply other threads:[~2020-12-21 12:27 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 19:29 [PATCH v4 0/6] Memory tagging support Richard Earnshaw
2020-12-18 19:29 ` [PATCH v4 1/6] config: Allow memory tagging to be enabled when configuring glibc Richard Earnshaw
2020-12-21 12:40 ` Siddhesh Poyarekar
2020-12-18 19:29 ` [PATCH v4 2/6] elf: Add a tunable to control use of tagged memory Richard Earnshaw
2020-12-21 12:42 ` Siddhesh Poyarekar
2020-12-18 19:29 ` [PATCH v4 3/6] malloc: Basic support for memory tagging in the malloc() family Richard Earnshaw
2020-12-21 13:27 ` Siddhesh Poyarekar
2020-12-21 13:46 ` Florian Weimer
2020-12-21 14:31 ` Richard Earnshaw
2020-12-21 14:31 ` Szabolcs Nagy
2020-12-18 19:29 ` [PATCH v4 4/6] linux: Add compatibility definitions to sys/prctl.h for MTE Richard Earnshaw
2020-12-21 13:32 ` Siddhesh Poyarekar
2020-12-21 13:34 ` Richard Earnshaw
2020-12-21 13:38 ` Siddhesh Poyarekar
2020-12-21 13:39 ` Florian Weimer
2020-12-21 13:41 ` Siddhesh Poyarekar
2020-12-18 19:29 ` [PATCH v4 5/6] aarch64: Add sysv specific enabling code for memory tagging Richard Earnshaw
2020-12-21 12:27 ` Szabolcs Nagy [this message]
2020-12-21 13:36 ` Siddhesh Poyarekar
2020-12-18 19:29 ` [PATCH v4 6/6] aarch64: Add aarch64-specific files for memory tagging support Richard Earnshaw
2020-12-21 12:44 ` Szabolcs Nagy
2020-12-21 12:50 ` Richard Earnshaw
2020-12-18 20:18 ` [PATCH v4 0/6] Memory " H.J. Lu
2020-12-21 12:28 ` Siddhesh Poyarekar
2020-12-21 13:44 ` Siddhesh Poyarekar
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