diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 05496622b4ef..464f60c50c36 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2548,6 +2548,9 @@ noalign [KNL,ARM] + noaltinstr [S390] Disables alternative instructions patching + (CPU alternatives feature). + noapic [SMP,APIC] Tells the kernel to not make use of any IOAPICs that may be present in the system. diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 5fd4a67c93b3..080a3fcc3cb8 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -537,6 +537,22 @@ config ARCH_RANDOM If unsure, say Y. +config ALTERNATIVES + def_bool y + prompt "Patch optimized instructions for running CPU type" + help + When enabled the kernel code is compiled with additional + alternative instructions blocks optimized for newer CPU types. + These alternative instructions blocks are patched at kernel boot + time when running CPU supports them. This mechanism is used to + optimize some critical code paths (i.e. spinlocks) for newer CPUs + even if kernel is build to support older machine generations. + + This mechanism could be disabled by appending "noaltinstr" + option to the kernel command line. + + If unsure, say Y. + endmenu menu "Memory setup" @@ -811,6 +827,7 @@ config PFAULT config SHARED_KERNEL bool "VM shared kernel support" depends on !JUMP_LABEL + depends on !ALTERNATIVES help Select this option, if you want to share the text segment of the Linux kernel between different VM guests. This reduces memory diff --git a/arch/s390/include/asm/alternative.h b/arch/s390/include/asm/alternative.h new file mode 100644 index 000000000000..6c268f6a51d3 --- /dev/null +++ b/arch/s390/include/asm/alternative.h @@ -0,0 +1,163 @@ +#ifndef _ASM_S390_ALTERNATIVE_H +#define _ASM_S390_ALTERNATIVE_H + +#ifndef __ASSEMBLY__ + +#include +#include +#include + +struct alt_instr { + s32 instr_offset; /* original instruction */ + s32 repl_offset; /* offset to replacement instruction */ + u16 facility; /* facility bit set for replacement */ + u8 instrlen; /* length of original instruction */ + u8 replacementlen; /* length of new instruction */ +} __packed; + +#ifdef CONFIG_ALTERNATIVES +extern void apply_alternative_instructions(void); +extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); +#else +static inline void apply_alternative_instructions(void) {}; +static inline void apply_alternatives(struct alt_instr *start, + struct alt_instr *end) {}; +#endif +/* + * |661: |662: |6620 |663: + * +-----------+---------------------+ + * | oldinstr | oldinstr_padding | + * | +----------+----------+ + * | | | | + * | | >6 bytes |6/4/2 nops| + * | |6 bytes jg-----------> + * +-----------+---------------------+ + * ^^ static padding ^^ + * + * .altinstr_replacement section + * +---------------------+-----------+ + * |6641: |6651: + * | alternative instr 1 | + * +-----------+---------+- - - - - -+ + * |6642: |6652: | + * | alternative instr 2 | padding + * +---------------------+- - - - - -+ + * ^ runtime ^ + * + * .altinstructions section + * +---------------------------------+ + * | alt_instr entries for each | + * | alternative instr | + * +---------------------------------+ + */ + +#define b_altinstr(num) "664"#num +#define e_altinstr(num) "665"#num + +#define e_oldinstr_pad_end "663" +#define oldinstr_len "662b-661b" +#define oldinstr_total_len e_oldinstr_pad_end"b-661b" +#define altinstr_len(num) e_altinstr(num)"b-"b_altinstr(num)"b" +#define oldinstr_pad_len(num) \ + "-(((" altinstr_len(num) ")-(" oldinstr_len ")) > 0) * " \ + "((" altinstr_len(num) ")-(" oldinstr_len "))" + +#define INSTR_LEN_SANITY_CHECK(len) \ + ".if " len " > 254\n" \ + "\t.error \"cpu alternatives does not support instructions " \ + "blocks > 254 bytes\"\n" \ + ".endif\n" \ + ".if (" len ") %% 2\n" \ + "\t.error \"cpu alternatives instructions length is odd\"\n" \ + ".endif\n" + +#define OLDINSTR_PADDING(oldinstr, num) \ + ".if " oldinstr_pad_len(num) " > 6\n" \ + "\tjg " e_oldinstr_pad_end "f\n" \ + "6620:\n" \ + "\t.fill (" oldinstr_pad_len(num) " - (6620b-662b)) / 2, 2, 0x0700\n" \ + ".else\n" \ + "\t.fill " oldinstr_pad_len(num) " / 6, 6, 0xc0040000\n" \ + "\t.fill " oldinstr_pad_len(num) " %% 6 / 4, 4, 0x47000000\n" \ + "\t.fill " oldinstr_pad_len(num) " %% 6 %% 4 / 2, 2, 0x0700\n" \ + ".endif\n" + +#define OLDINSTR(oldinstr, num) \ + "661:\n\t" oldinstr "\n662:\n" \ + OLDINSTR_PADDING(oldinstr, num) \ + e_oldinstr_pad_end ":\n" \ + INSTR_LEN_SANITY_CHECK(oldinstr_len) + +#define OLDINSTR_2(oldinstr, num1, num2) \ + "661:\n\t" oldinstr "\n662:\n" \ + ".if " altinstr_len(num1) " < " altinstr_len(num2) "\n" \ + OLDINSTR_PADDING(oldinstr, num2) \ + ".else\n" \ + OLDINSTR_PADDING(oldinstr, num1) \ + ".endif\n" \ + e_oldinstr_pad_end ":\n" \ + INSTR_LEN_SANITY_CHECK(oldinstr_len) + +#define ALTINSTR_ENTRY(facility, num) \ + "\t.long 661b - .\n" /* old instruction */ \ + "\t.long " b_altinstr(num)"b - .\n" /* alt instruction */ \ + "\t.word " __stringify(facility) "\n" /* facility bit */ \ + "\t.byte " oldinstr_total_len "\n" /* source len */ \ + "\t.byte " altinstr_len(num) "\n" /* alt instruction len */ + +#define ALTINSTR_REPLACEMENT(altinstr, num) /* replacement */ \ + b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n" \ + INSTR_LEN_SANITY_CHECK(altinstr_len(num)) + +#ifdef CONFIG_ALTERNATIVES +/* alternative assembly primitive: */ +#define ALTERNATIVE(oldinstr, altinstr, facility) \ + ".pushsection .altinstr_replacement, \"ax\"\n" \ + ALTINSTR_REPLACEMENT(altinstr, 1) \ + ".popsection\n" \ + OLDINSTR(oldinstr, 1) \ + ".pushsection .altinstructions,\"a\"\n" \ + ALTINSTR_ENTRY(facility, 1) \ + ".popsection\n" + +#define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\ + ".pushsection .altinstr_replacement, \"ax\"\n" \ + ALTINSTR_REPLACEMENT(altinstr1, 1) \ + ALTINSTR_REPLACEMENT(altinstr2, 2) \ + ".popsection\n" \ + OLDINSTR_2(oldinstr, 1, 2) \ + ".pushsection .altinstructions,\"a\"\n" \ + ALTINSTR_ENTRY(facility1, 1) \ + ALTINSTR_ENTRY(facility2, 2) \ + ".popsection\n" +#else +/* Alternative instructions are disabled, let's put just oldinstr in */ +#define ALTERNATIVE(oldinstr, altinstr, facility) \ + oldinstr "\n" + +#define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \ + oldinstr "\n" +#endif + +/* + * Alternative instructions for different CPU types or capabilities. + * + * This allows to use optimized instructions even on generic binary + * kernels. + * + * oldinstr is padded with jump and nops at compile time if altinstr is + * longer. altinstr is padded with jump and nops at run-time during patching. + * + * For non barrier like inlines please define new variants + * without volatile and memory clobber. + */ +#define alternative(oldinstr, altinstr, facility) \ + asm volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory") + +#define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \ + asm volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1, \ + altinstr2, facility2) ::: "memory") + +#endif /* __ASSEMBLY__ */ + +#endif /* _ASM_S390_ALTERNATIVE_H */ 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 +#include +#include + +#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 #include #include +#include #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 #include #include +#include #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)