diff options
Diffstat (limited to 'arch/s390/kernel')
-rw-r--r-- | arch/s390/kernel/Makefile | 1 | ||||
-rw-r--r-- | arch/s390/kernel/alternative.c | 110 | ||||
-rw-r--r-- | arch/s390/kernel/module.c | 17 | ||||
-rw-r--r-- | arch/s390/kernel/setup.c | 3 | ||||
-rw-r--r-- | arch/s390/kernel/vmlinux.lds.S | 23 |
5 files changed, 154 insertions, 0 deletions
diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile index 7b742ffac7d3..addf61024153 100644 --- a/arch/s390/kernel/Makefile +++ b/arch/s390/kernel/Makefile @@ -76,6 +76,7 @@ obj-$(CONFIG_KPROBES) += kprobes.o obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace.o obj-$(CONFIG_CRASH_DUMP) += crash_dump.o obj-$(CONFIG_UPROBES) += uprobes.o +obj-$(CONFIG_ALTERNATIVES) += alternative.o obj-$(CONFIG_PERF_EVENTS) += perf_event.o perf_cpum_cf.o perf_cpum_sf.o obj-$(CONFIG_PERF_EVENTS) += perf_cpum_cf_events.o diff --git a/arch/s390/kernel/alternative.c b/arch/s390/kernel/alternative.c new file mode 100644 index 000000000000..315986a06cf5 --- /dev/null +++ b/arch/s390/kernel/alternative.c @@ -0,0 +1,110 @@ +#include <linux/module.h> +#include <asm/alternative.h> +#include <asm/facility.h> + +#define MAX_PATCH_LEN (255 - 1) + +static int __initdata_or_module alt_instr_disabled; + +static int __init disable_alternative_instructions(char *str) +{ + alt_instr_disabled = 1; + return 0; +} + +early_param("noaltinstr", disable_alternative_instructions); + +struct brcl_insn { + u16 opc; + s32 disp; +} __packed; + +static u16 __initdata_or_module nop16 = 0x0700; +static u32 __initdata_or_module nop32 = 0x47000000; +static struct brcl_insn __initdata_or_module nop48 = { + 0xc004, 0 +}; + +static const void *nops[] __initdata_or_module = { + &nop16, + &nop32, + &nop48 +}; + +static void __init_or_module add_jump_padding(void *insns, unsigned int len) +{ + struct brcl_insn brcl = { + 0xc0f4, + len / 2 + }; + + memcpy(insns, &brcl, sizeof(brcl)); + insns += sizeof(brcl); + len -= sizeof(brcl); + + while (len > 0) { + memcpy(insns, &nop16, 2); + insns += 2; + len -= 2; + } +} + +static void __init_or_module add_padding(void *insns, unsigned int len) +{ + if (len > 6) + add_jump_padding(insns, len); + else if (len >= 2) + memcpy(insns, nops[len / 2 - 1], len); +} + +static void __init_or_module __apply_alternatives(struct alt_instr *start, + struct alt_instr *end) +{ + struct alt_instr *a; + u8 *instr, *replacement; + u8 insnbuf[MAX_PATCH_LEN]; + + /* + * The scan order should be from start to end. A later scanned + * alternative code can overwrite previously scanned alternative code. + */ + for (a = start; a < end; a++) { + int insnbuf_sz = 0; + + instr = (u8 *)&a->instr_offset + a->instr_offset; + replacement = (u8 *)&a->repl_offset + a->repl_offset; + + if (!test_facility(a->facility)) + continue; + + if (unlikely(a->instrlen % 2 || a->replacementlen % 2)) { + WARN_ONCE(1, "cpu alternatives instructions length is " + "odd, skipping patching\n"); + continue; + } + + memcpy(insnbuf, replacement, a->replacementlen); + insnbuf_sz = a->replacementlen; + + if (a->instrlen > a->replacementlen) { + add_padding(insnbuf + a->replacementlen, + a->instrlen - a->replacementlen); + insnbuf_sz += a->instrlen - a->replacementlen; + } + + s390_kernel_write(instr, insnbuf, insnbuf_sz); + } +} + +void __init_or_module apply_alternatives(struct alt_instr *start, + struct alt_instr *end) +{ + if (!alt_instr_disabled) + __apply_alternatives(start, end); +} + +extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; +void __init apply_alternative_instructions(void) +{ + apply_alternatives(__alt_instructions, __alt_instructions_end); +} diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c index 1a27f307a920..6d9f73bb4142 100644 --- a/arch/s390/kernel/module.c +++ b/arch/s390/kernel/module.c @@ -31,6 +31,7 @@ #include <linux/kernel.h> #include <linux/moduleloader.h> #include <linux/bug.h> +#include <asm/alternative.h> #if 0 #define DEBUGP printk @@ -429,6 +430,22 @@ int module_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, struct module *me) { + const Elf_Shdr *s; + char *secstrings; + + if (IS_ENABLED(CONFIG_ALTERNATIVES)) { + secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; + for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) { + if (!strcmp(".altinstructions", + secstrings + s->sh_name)) { + /* patch .altinstructions */ + void *aseg = (void *)s->sh_addr; + + apply_alternatives(aseg, aseg + s->sh_size); + } + } + } + jump_label_apply_nops(me); return 0; } diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c index b2c9af9b88d5..c07e6d6a91cc 100644 --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -66,6 +66,7 @@ #include <asm/sclp.h> #include <asm/sysinfo.h> #include <asm/numa.h> +#include <asm/alternative.h> #include "entry.h" /* @@ -957,6 +958,8 @@ void __init setup_arch(char **cmdline_p) conmode_default(); set_preferred_console(); + apply_alternative_instructions(); + /* Setup zfcpdump support */ setup_zfcpdump(); diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S index 6e2c42bd1c3b..7c9fcf7cb43d 100644 --- a/arch/s390/kernel/vmlinux.lds.S +++ b/arch/s390/kernel/vmlinux.lds.S @@ -104,6 +104,29 @@ SECTIONS EXIT_DATA } + /* + * struct alt_inst entries. From the header (alternative.h): + * "Alternative instructions for different CPU types or capabilities" + * Think locking instructions on spinlocks. + * Note, that it is a part of __init region. + */ + . = ALIGN(8); + .altinstructions : { + __alt_instructions = .; + *(.altinstructions) + __alt_instructions_end = .; + } + + /* + * And here are the replacement instructions. The linker sticks + * them as binary blobs. The .altinstructions has enough data to + * get the address and the length of them to patch the kernel safely. + * Note, that it is a part of __init region. + */ + .altinstr_replacement : { + *(.altinstr_replacement) + } + /* early.c uses stsi, which requires page aligned data. */ . = ALIGN(PAGE_SIZE); INIT_DATA_SECTION(0x100) |