[glibc/rearnsha/mte-v3.0] aarch64: Add sysv specific enabling code for memory tagging
Richard Earnshaw
rearnsha@sourceware.org
Mon Nov 23 15:18:01 GMT 2020
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=05ab98edbda5a751ca3831058d196309b48e8d2b
commit 05ab98edbda5a751ca3831058d196309b48e8d2b
Author: Richard Earnshaw <rearnsha@arm.com>
Date: Fri Nov 20 17:20:10 2020 +0000
aarch64: Add sysv specific enabling code for memory tagging
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.
Diff:
---
sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h | 1 +
sysdeps/unix/sysv/linux/aarch64/bits/mman.h | 7 +++++++
sysdeps/unix/sysv/linux/aarch64/cpu-features.c | 28 ++++++++++++++++++++++++++
sysdeps/unix/sysv/linux/aarch64/cpu-features.h | 1 +
4 files changed, 37 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..3658b958b5 100644
--- a/sysdeps/unix/sysv/linux/aarch64/bits/mman.h
+++ b/sysdeps/unix/sysv/linux/aarch64/bits/mman.h
@@ -1,4 +1,5 @@
/* Definitions for POSIX memory map interface. Linux/AArch64 version.
+
Copyright (C) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
@@ -25,6 +26,12 @@
#define PROT_BTI 0x10
+/* The following definitions basically come from the kernel headers.
+ But the kernel header is not namespace clean. */
+
+/* Other flags. */
+#define PROT_MTE 0x20 /* Normal Tagged mapping. */
+
#include <bits/mman-map-flags-generic.h>
/* Include generic Linux declarations. */
diff --git a/sysdeps/unix/sysv/linux/aarch64/cpu-features.c b/sysdeps/unix/sysv/linux/aarch64/cpu-features.c
index b9ab827aca..aa4a82c6e8 100644
--- a/sysdeps/unix/sysv/linux/aarch64/cpu-features.c
+++ b/sysdeps/unix/sysv/linux/aarch64/cpu-features.c
@@ -19,6 +19,7 @@
#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)
@@ -86,4 +87,31 @@ 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 _LIBC_MTAG
+# if HAVE_TUNABLES
+ int mte_state = TUNABLE_GET (glibc, memtag, enable, 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, memtag, enable, unsigned, cpu_features->mte_state);
+# endif
+
+ /* For now, disallow tag 0, so that we can clearly see when tagged
+ addresses are being allocated. */
+ if (cpu_features->mte_state & 2)
+ __prctl (PR_SET_TAGGED_ADDR_CTRL,
+ (PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_SYNC
+ | (0xfffe << PR_MTE_TAG_SHIFT)),
+ 0, 0, 0);
+ else if (cpu_features->mte_state)
+ __prctl (PR_SET_TAGGED_ADDR_CTRL,
+ (PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_ASYNC
+ | (0xfffe << PR_MTE_TAG_SHIFT)),
+ 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..838d5c9aba 100644
--- a/sysdeps/unix/sysv/linux/aarch64/cpu-features.h
+++ b/sysdeps/unix/sysv/linux/aarch64/cpu-features.h
@@ -70,6 +70,7 @@ struct cpu_features
uint64_t midr_el1;
unsigned zva_size;
bool bti;
+ unsigned mte_state;
};
#endif /* _CPU_FEATURES_AARCH64_H */
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