From 317c8194e6aeb8b3b573ad139fc2a0635856498e Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Tue, 22 Nov 2022 15:39:04 -0500 Subject: [PATCH] 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 Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20221122203932.231377-3-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 de63572a9404..0ba86f0b1477 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -46,6 +46,7 @@ #include #include #include +#include #include #include @@ -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 */