From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E . McKenney" <paulmck@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
"H . Peter Anvin" <hpa@zytor.com>, Paul Turner <pjt@google.com>,
linux-api@vger.kernel.org, Christian Brauner <brauner@kernel.org>,
Florian Weimer <fw@deneb.enyo.de>,
David.Laight@ACULAB.COM, carlos@redhat.com,
Peter Oskolkov <posk@posk.io>,
Alexander Mikhalitsyn <alexander@mihalicyn.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: [RFC PATCH v4 01/25] rseq: Introduce feature size and alignment ELF auxiliary vector entries
Date: Wed, 21 Sep 2022 15:24:30 -0400 [thread overview]
Message-ID: <20220921192454.231662-2-mathieu.desnoyers@efficios.com> (raw)
In-Reply-To: <20220921192454.231662-1-mathieu.desnoyers@efficios.com>
Export the rseq feature size supported by the kernel as well as the
required allocation alignment for the rseq per-thread area to user-space
through ELF auxiliary vector entries.
This is part of the extensible rseq ABI.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
fs/binfmt_elf.c | 5 +++++
include/uapi/linux/auxvec.h | 2 ++
include/uapi/linux/rseq.h | 5 +++++
3 files changed, 12 insertions(+)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 63c7ebb0da89..04fca1e4cbd2 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -46,6 +46,7 @@
#include <linux/cred.h>
#include <linux/dax.h>
#include <linux/uaccess.h>
+#include <linux/rseq.h>
#include <asm/param.h>
#include <asm/page.h>
@@ -288,6 +289,10 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec,
if (bprm->have_execfd) {
NEW_AUX_ENT(AT_EXECFD, bprm->execfd);
}
+#ifdef CONFIG_RSEQ
+ NEW_AUX_ENT(AT_RSEQ_FEATURE_SIZE, offsetof(struct rseq, end));
+ NEW_AUX_ENT(AT_RSEQ_ALIGN, __alignof__(struct rseq));
+#endif
#undef NEW_AUX_ENT
/* AT_NULL is zero; clear the rest too */
memset(elf_info, 0, (char *)mm->saved_auxv +
diff --git a/include/uapi/linux/auxvec.h b/include/uapi/linux/auxvec.h
index c7e502bf5a6f..6991c4b8ab18 100644
--- a/include/uapi/linux/auxvec.h
+++ b/include/uapi/linux/auxvec.h
@@ -30,6 +30,8 @@
* differ from AT_PLATFORM. */
#define AT_RANDOM 25 /* address of 16 random bytes */
#define AT_HWCAP2 26 /* extension of AT_HWCAP */
+#define AT_RSEQ_FEATURE_SIZE 27 /* rseq supported feature size */
+#define AT_RSEQ_ALIGN 28 /* rseq allocation alignment */
#define AT_EXECFN 31 /* filename of program */
diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h
index 77ee207623a9..05d3c4cdeb40 100644
--- a/include/uapi/linux/rseq.h
+++ b/include/uapi/linux/rseq.h
@@ -130,6 +130,11 @@ struct rseq {
* this thread.
*/
__u32 flags;
+
+ /*
+ * Flexible array member at end of structure, after last feature field.
+ */
+ char end[];
} __attribute__((aligned(4 * sizeof(__u64))));
#endif /* _UAPI_LINUX_RSEQ_H */
--
2.25.1
next prev parent reply other threads:[~2022-09-21 19:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 19:24 [RFC PATCH v4 00/25] RSEQ node id and virtual cpu id extensions Mathieu Desnoyers
2022-09-21 19:24 ` Mathieu Desnoyers [this message]
2022-09-21 19:24 ` [RFC PATCH v4 02/25] rseq: Introduce extensible rseq ABI Mathieu Desnoyers
2022-09-21 19:24 ` [RFC PATCH v4 03/25] rseq: Extend struct rseq with numa node id Mathieu Desnoyers
2022-09-21 19:24 ` [RFC PATCH v4 04/25] selftests/rseq: Use ELF auxiliary vector for extensible rseq Mathieu Desnoyers
2022-09-21 19:24 ` [RFC PATCH v4 05/25] selftests/rseq: Implement rseq numa node id field selftest Mathieu Desnoyers
2022-09-21 19:54 ` [RFC PATCH v4 00/25] RSEQ node id and virtual cpu id extensions Mathieu Desnoyers
2022-09-22 8:10 ` Peter Zijlstra
2022-09-22 10:59 ` Mathieu Desnoyers
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