The following commit has been merged into the sched/core branch of tip:
Commit-ID: 317c8194e6aeb8b3b573ad139fc2a0635856498e
Gitweb: https://git.kernel.org/tip/317c8194e6aeb8b3b573ad139fc2a0635856498e
Author: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
AuthorDate: Tue, 22 Nov 2022 15:39:04 -05:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 27 Dec 2022 12:52:10 +01:00
rseq: Introduce feature size and alignment ELF auxiliary vector entries
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@xxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221122203932.231377-3-mathieu.desnoyers@xxxxxxxxxxxx
---
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 de63572..0ba86f0 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 c7e502b..6991c4b 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 77ee207..05d3c4c 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 */
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