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s390/kernel: expand exception table logic to allow new handling options

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This is a s390 port of commit 548acf1923 ("x86/mm: Expand the
exception table logic to allow new handling options"), which is needed
for implementing BPF_PROBE_MEM on s390.

The new handler field is made 64-bit in order to allow pointing from
dynamically allocated entries to handlers in kernel text. Unlike on x86,
NULL is used instead of ex_handler_default. This is because exception
tables are used by boot/text_dma.S, and it would be a pain to preserve
ex_handler_default.

The new infrastructure is ignored in early_pgm_check_handler, since
there is no pt_regs.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Ilya Leoshkevich 2020-06-30 20:52:03 +02:00 committed by Heiko Carstens
parent 88aa8939c9
commit 05a68e892e
6 changed files with 94 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
arch/s390/include/asm/extable.h
View File

@ -1,12 +1,20 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __S390_EXTABLE_H
#define __S390_EXTABLE_H
#include <asm/ptrace.h>
#include <linux/compiler.h>
/*
* The exception table consists of pairs of addresses: the first is the
* address of an instruction that is allowed to fault, and the second is
* the address at which the program should continue. No registers are
* modified, so it is entirely up to the continuation code to figure out
* what to do.
* The exception table consists of three addresses:
*
* - Address of an instruction that is allowed to fault.
* - Address at which the program should continue.
* - Optional address of handler that takes pt_regs * argument and runs in
* interrupt context.
*
* No registers are modified, so it is entirely up to the continuation code
* to figure out what to do.
*
* All the routines below use bits of fixup code that are out of line
* with the main instruction path. This means when everything is well,
@ -17,6 +25,7 @@
struct exception_table_entry
{
int insn, fixup;
long handler;
};
extern struct exception_table_entry *__start_dma_ex_table;
@ -29,6 +38,39 @@ static inline unsigned long extable_fixup(const struct exception_table_entry *x)
return (unsigned long)&x->fixup + x->fixup;
}
typedef bool (*ex_handler_t)(const struct exception_table_entry *,
struct pt_regs *);
static inline ex_handler_t
ex_fixup_handler(const struct exception_table_entry *x)
{
if (likely(!x->handler))
return NULL;
return (ex_handler_t)((unsigned long)&x->handler + x->handler);
}
static inline bool ex_handle(const struct exception_table_entry *x,
struct pt_regs *regs)
{
ex_handler_t handler = ex_fixup_handler(x);
if (unlikely(handler))
return handler(x, regs);
regs->psw.addr = extable_fixup(x);
return true;
}
#define ARCH_HAS_RELATIVE_EXTABLE
static inline void swap_ex_entry_fixup(struct exception_table_entry *a,
struct exception_table_entry *b,
struct exception_table_entry tmp,
int delta)
{
a->fixup = b->fixup + delta;
b->fixup = tmp.fixup - delta;
a->handler = b->handler + delta;
b->handler = tmp.handler - delta;
}
#endif

3
arch/s390/include/asm/linkage.h
View File

@ -14,9 +14,10 @@
#define __EX_TABLE(_section, _fault, _target) \
stringify_in_c(.section _section,"a";) \
stringify_in_c(.align 4;) \
stringify_in_c(.align 8;) \
stringify_in_c(.long (_fault) - .;) \
stringify_in_c(.long (_target) - .;) \
stringify_in_c(.quad 0;) \
stringify_in_c(.previous)
#define EX_TABLE(_fault, _target) \

4
arch/s390/kernel/kprobes.c
View File

@ -523,10 +523,8 @@ static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
* zero, try to fix up.
*/
entry = s390_search_extables(regs->psw.addr);
if (entry) {
regs->psw.addr = extable_fixup(entry);
if (entry && ex_handle(entry, regs))
return 1;
}
/*
* fixup_exception() could not handle it,

7
arch/s390/kernel/traps.c
View File

@ -50,11 +50,8 @@ void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)
} else {
const struct exception_table_entry *fixup;
fixup = s390_search_extables(regs->psw.addr);
if (fixup)
regs->psw.addr = extable_fixup(fixup);
else {
if (!fixup || !ex_handle(fixup, regs))
die(regs, str);
}
}
}
@ -251,7 +248,7 @@ void monitor_event_exception(struct pt_regs *regs)
case BUG_TRAP_TYPE_NONE:
fixup = s390_search_extables(regs->psw.addr);
if (fixup)
regs->psw.addr = extable_fixup(fixup);
ex_handle(fixup, regs);
break;
case BUG_TRAP_TYPE_WARN:
break;

4
arch/s390/mm/fault.c
View File

@ -255,10 +255,8 @@ static noinline void do_no_context(struct pt_regs *regs)
/* Are we prepared to handle this kernel fault? */
fixup = s390_search_extables(regs->psw.addr);
if (fixup) {
regs->psw.addr = extable_fixup(fixup);
if (fixup && ex_handle(fixup, regs))
return;
}
/*
* Oops. The kernel tried to access some bad page. We'll have to

41
scripts/sorttable.c
View File

@ -255,6 +255,45 @@ static void x86_sort_relative_table(char *extab_image, int image_size)
}
}
static void s390_sort_relative_table(char *extab_image, int image_size)
{
int i;
for (i = 0; i < image_size; i += 16) {
char *loc = extab_image + i;
uint64_t handler;
w(r((uint32_t *)loc) + i, (uint32_t *)loc);
w(r((uint32_t *)(loc + 4)) + (i + 4), (uint32_t *)(loc + 4));
/*
* 0 is a special self-relative handler value, which means that
* handler should be ignored. It is safe, because it means that
* handler field points to itself, which should never happen.
* When creating extable-relative values, keep it as 0, since
* this should never occur either: it would mean that handler
* field points to the first extable entry.
*/
handler = r8((uint64_t *)(loc + 8));
if (handler)
handler += i + 8;
w8(handler, (uint64_t *)(loc + 8));
}
qsort(extab_image, image_size / 16, 16, compare_relative_table);
for (i = 0; i < image_size; i += 16) {
char *loc = extab_image + i;
uint64_t handler;
w(r((uint32_t *)loc) - i, (uint32_t *)loc);
w(r((uint32_t *)(loc + 4)) - (i + 4), (uint32_t *)(loc + 4));
handler = r8((uint64_t *)(loc + 8));
if (handler)
handler -= i + 8;
w8(handler, (uint64_t *)(loc + 8));
}
}
static int do_file(char const *const fname, void *addr)
{
int rc = -1;
@ -297,6 +336,8 @@ static int do_file(char const *const fname, void *addr)
custom_sort = x86_sort_relative_table;
break;
case EM_S390:
custom_sort = s390_sort_relative_table;
break;
case EM_AARCH64:
case EM_PARISC:
case EM_PPC: