From 05a68e892e89c97df6650cd8cc55058002657cbc Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Tue, 30 Jun 2020 20:52:03 +0200 Subject: [PATCH] s390/kernel: expand exception table logic to allow new handling options This is a s390 port of commit 548acf19234d ("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 Reviewed-by: Heiko Carstens Signed-off-by: Heiko Carstens --- arch/s390/include/asm/extable.h | 52 +++++++++++++++++++++++++++++++++++++---- arch/s390/include/asm/linkage.h | 3 ++- arch/s390/kernel/kprobes.c | 4 +--- arch/s390/kernel/traps.c | 7 ++---- arch/s390/mm/fault.c | 4 +--- scripts/sorttable.c | 41 ++++++++++++++++++++++++++++++++ 6 files changed, 94 insertions(+), 17 deletions(-) diff --git a/arch/s390/include/asm/extable.h b/arch/s390/include/asm/extable.h index ae27f75..3beb294 100644 --- a/arch/s390/include/asm/extable.h +++ b/arch/s390/include/asm/extable.h @@ -1,12 +1,20 @@ /* SPDX-License-Identifier: GPL-2.0 */ #ifndef __S390_EXTABLE_H #define __S390_EXTABLE_H + +#include +#include + /* - * 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 diff --git a/arch/s390/include/asm/linkage.h b/arch/s390/include/asm/linkage.h index 1b52c07..a0a7a2c 100644 --- a/arch/s390/include/asm/linkage.h +++ b/arch/s390/include/asm/linkage.h @@ -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) \ diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c index 548d0ea..d2a71d8 100644 --- a/arch/s390/kernel/kprobes.c +++ b/arch/s390/kernel/kprobes.c @@ -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, diff --git a/arch/s390/kernel/traps.c b/arch/s390/kernel/traps.c index ff9cc4c..8d1e8a1a 100644 --- a/arch/s390/kernel/traps.c +++ b/arch/s390/kernel/traps.c @@ -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; diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c index 5988285..aebf918 100644 --- a/arch/s390/mm/fault.c +++ b/arch/s390/mm/fault.c @@ -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 diff --git a/scripts/sorttable.c b/scripts/sorttable.c index ec6b5e8..0ef3abf 100644 --- a/scripts/sorttable.c +++ b/scripts/sorttable.c @@ -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: -- 2.7.4