linux/arch/s390/kernel/kprobes_insn_page.S
Heiko Carstens b61e1f3281 s390/kprobes: move insn_page to text segment
Move the in-kernel kprobes insn page to text segment. Rationale:
having that page in rw data segment is suboptimal, since as soon as a
kprobe is set, this will split the 1:1 kernel mapping for a single
page which get new permissions.

Note: there is always at least one kprobe present for the kretprobe
trampoline; so the mapping will always be split into smaller 4k
mappings because of this.

Moving the kprobes insn page into text segment makes sure that the
page is mapped RO/X in any case, and avoids that the 1:1 mapping is
split.

The kprobe insn_page is defined as a dummy function which is filled
with "br %r14" instructions.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
2020-10-09 23:45:30 +02:00

23 lines
746 B
ArmAsm

/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/linkage.h>
/*
* insn_page is a special 4k aligned dummy function for kprobes.
* It will contain all kprobed instructions that are out-of-line executed.
* The page must be within the kernel image to guarantee that the
* out-of-line instructions are within 2GB distance of their original
* location. Using a dummy function ensures that the insn_page is within
* the text section of the kernel and mapped read-only/executable from
* the beginning on, thus avoiding to split large mappings if the page
* would be in the data section instead.
*/
.section .kprobes.text, "ax"
.align 4096
ENTRY(kprobes_insn_page)
.rept 2048
.word 0x07fe
.endr
ENDPROC(kprobes_insn_page)
.previous