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s390/kprobes: Remove custom insn slot allocator

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Since commit c98d2ecae0 ("s390/mm: Uncouple physical vs virtual address
spaces") the kernel image and module area are within the same 4GB area.

This eliminates the need of a custom insn slot allocator for kprobes within
the kernel image, since standard module_alloc() allocated pages are
sufficient for PC relative instructions with a signed 32 bit offset.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2024-05-15 14:52:21 +02:00
parent e7dec0b792
commit d890e6af50
4 changed files with 10 additions and 89 deletions
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1
arch/s390/kernel/Makefile
View file

@ -59,7 +59,6 @@ obj-$(CONFIG_COMPAT) += compat_linux.o compat_signal.o
obj-$(CONFIG_COMPAT) += $(compat-obj-y)
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_KPROBES) += kprobes_insn_page.o
obj-$(CONFIG_KPROBES) += mcount.o
obj-$(CONFIG_RETHOOK) += rethook.o
obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o

67
arch/s390/kernel/kprobes.c
View file

@ -24,7 +24,6 @@
#include <asm/set_memory.h>
#include <asm/sections.h>
#include <asm/dis.h>
#include "kprobes.h"
#include "entry.h"
DEFINE_PER_CPU(struct kprobe *, current_kprobe);
@ -32,8 +31,6 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
struct kretprobe_blackpoint kretprobe_blacklist[] = { };
static int insn_page_in_use;
void *alloc_insn_page(void)
{
void *page;
@ -45,26 +42,6 @@ void *alloc_insn_page(void)
return page;
}
static void *alloc_s390_insn_page(void)
{
if (xchg(&insn_page_in_use, 1) == 1)
return NULL;
return &kprobes_insn_page;
}
static void free_s390_insn_page(void *page)
{
xchg(&insn_page_in_use, 0);
}
struct kprobe_insn_cache kprobe_s390_insn_slots = {
.mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
.alloc = alloc_s390_insn_page,
.free = free_s390_insn_page,
.pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
.insn_size = MAX_INSN_SIZE,
};
static void copy_instruction(struct kprobe *p)
{
kprobe_opcode_t insn[MAX_INSN_SIZE];
@ -78,10 +55,10 @@ static void copy_instruction(struct kprobe *p)
if (probe_is_insn_relative_long(&insn[0])) {
/*
* For pc-relative instructions in RIL-b or RIL-c format patch
* the RI2 displacement field. We have already made sure that
* the insn slot for the patched instruction is within the same
* 2GB area as the original instruction (either kernel image or
* module area). Therefore the new displacement will always fit.
* the RI2 displacement field. The insn slot for the to be
* patched instruction is within the same 4GB area like the
* original instruction. Therefore the new displacement will
* always fit.
*/
disp = *(s32 *)&insn[1];
addr = (u64)(unsigned long)p->addr;
@ -93,34 +70,6 @@ static void copy_instruction(struct kprobe *p)
}
NOKPROBE_SYMBOL(copy_instruction);
static int s390_get_insn_slot(struct kprobe *p)
{
/*
* Get an insn slot that is within the same 2GB area like the original
* instruction. That way instructions with a 32bit signed displacement
* field can be patched and executed within the insn slot.
*/
p->ainsn.insn = NULL;
if (is_kernel((unsigned long)p->addr))
p->ainsn.insn = get_s390_insn_slot();
else if (is_module_addr(p->addr))
p->ainsn.insn = get_insn_slot();
return p->ainsn.insn ? 0 : -ENOMEM;
}
NOKPROBE_SYMBOL(s390_get_insn_slot);
static void s390_free_insn_slot(struct kprobe *p)
{
if (!p->ainsn.insn)
return;
if (is_kernel((unsigned long)p->addr))
free_s390_insn_slot(p->ainsn.insn, 0);
else
free_insn_slot(p->ainsn.insn, 0);
p->ainsn.insn = NULL;
}
NOKPROBE_SYMBOL(s390_free_insn_slot);
/* Check if paddr is at an instruction boundary */
static bool can_probe(unsigned long paddr)
{
@ -174,7 +123,8 @@ int arch_prepare_kprobe(struct kprobe *p)
/* Make sure the probe isn't going on a difficult instruction */
if (probe_is_prohibited_opcode(p->addr))
return -EINVAL;
if (s390_get_insn_slot(p))
p->ainsn.insn = get_insn_slot();
if (!p->ainsn.insn)
return -ENOMEM;
copy_instruction(p);
return 0;
@ -216,7 +166,10 @@ NOKPROBE_SYMBOL(arch_disarm_kprobe);
void arch_remove_kprobe(struct kprobe *p)
{
s390_free_insn_slot(p);
if (!p->ainsn.insn)
return;
free_insn_slot(p->ainsn.insn, 0);
p->ainsn.insn = NULL;
}
NOKPROBE_SYMBOL(arch_remove_kprobe);

9
arch/s390/kernel/kprobes.h
View file

@ -1,9 +0,0 @@
/* SPDX-License-Identifier: GPL-2.0+ */
#ifndef _ARCH_S390_KPROBES_H
#define _ARCH_S390_KPROBES_H
#include <linux/kprobes.h>
DEFINE_INSN_CACHE_OPS(s390_insn);
#endif

22
arch/s390/kernel/kprobes_insn_page.S
View file

@ -1,22 +0,0 @@
/* 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"
.balign 4096
SYM_CODE_START(kprobes_insn_page)
.rept 2048
.word 0x07fe
.endr
SYM_CODE_END(kprobes_insn_page)
.previous