Commit 317c8194 authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Peter Zijlstra
Browse files

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: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221122203932.231377-3-mathieu.desnoyers@efficios.com
parent 4842dadf

fs/binfmt_elf.c

+5 −0
Original line number Diff line number Diff line
@@ -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 +

include/uapi/linux/auxvec.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */

include/uapi/linux/rseq.h

+5 −0
Original line number Diff line number Diff line
@@ -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 */