diff options
Diffstat (limited to 'arch/s390/kernel/ftrace.c')
| -rw-r--r-- | arch/s390/kernel/ftrace.c | 335 |
1 files changed, 216 insertions, 119 deletions
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index 1bb85f60c0dd..c46381ea04ec 100644 --- a/arch/s390/kernel/ftrace.c +++ b/arch/s390/kernel/ftrace.c @@ -4,8 +4,7 @@ * * Copyright IBM Corp. 2009,2014 * - * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>, - * Martin Schwidefsky <schwidefsky@de.ibm.com> + * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com> */ #include <linux/moduleloader.h> @@ -17,179 +16,217 @@ #include <linux/kprobes.h> #include <trace/syscall.h> #include <asm/asm-offsets.h> +#include <asm/text-patching.h> #include <asm/cacheflush.h> +#include <asm/ftrace.lds.h> +#include <asm/nospec-branch.h> #include <asm/set_memory.h> #include "entry.h" +#include "ftrace.h" /* - * The mcount code looks like this: - * stg %r14,8(%r15) # offset 0 - * larl %r1,<&counter> # offset 6 - * brasl %r14,_mcount # offset 12 - * lg %r14,8(%r15) # offset 18 - * Total length is 24 bytes. Only the first instruction will be patched - * by ftrace_make_call / ftrace_make_nop. - * The enabled ftrace code block looks like this: + * To generate function prologue either gcc's hotpatch feature (since gcc 4.8) + * or a combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags + * (since gcc 9 / clang 10) is used. + * In both cases the original and also the disabled function prologue contains + * only a single six byte instruction and looks like this: + * > brcl 0,0 # offset 0 + * To enable ftrace the code gets patched like above and afterwards looks + * like this: * > brasl %r0,ftrace_caller # offset 0 - * larl %r1,<&counter> # offset 6 - * brasl %r14,_mcount # offset 12 - * lg %r14,8(%r15) # offset 18 + * + * The instruction will be patched by ftrace_make_call / ftrace_make_nop. * The ftrace function gets called with a non-standard C function call ABI * where r0 contains the return address. It is also expected that the called * function only clobbers r0 and r1, but restores r2-r15. * For module code we can't directly jump to ftrace caller, but need a * trampoline (ftrace_plt), which clobbers also r1. - * The return point of the ftrace function has offset 24, so execution - * continues behind the mcount block. - * The disabled ftrace code block looks like this: - * > jg .+24 # offset 0 - * larl %r1,<&counter> # offset 6 - * brasl %r14,_mcount # offset 12 - * lg %r14,8(%r15) # offset 18 - * The jg instruction branches to offset 24 to skip as many instructions - * as possible. - * In case we use gcc's hotpatch feature the original and also the disabled - * function prologue contains only a single six byte instruction and looks - * like this: - * > brcl 0,0 # offset 0 - * To enable ftrace the code gets patched like above and afterwards looks - * like this: - * > brasl %r0,ftrace_caller # offset 0 */ -unsigned long ftrace_plt; +void *ftrace_func __read_mostly = ftrace_stub; +struct ftrace_insn { + u16 opc; + s32 disp; +} __packed; -static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn) +#ifdef CONFIG_MODULES +static char *ftrace_plt; +#endif /* CONFIG_MODULES */ + +static const char *ftrace_shared_hotpatch_trampoline(const char **end) { -#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT) - /* brcl 0,0 */ - insn->opc = 0xc004; - insn->disp = 0; -#else - /* stg r14,8(r15) */ - insn->opc = 0xe3e0; - insn->disp = 0xf0080024; -#endif + const char *tstart, *tend; + + tstart = ftrace_shared_hotpatch_trampoline_br; + tend = ftrace_shared_hotpatch_trampoline_br_end; +#ifdef CONFIG_EXPOLINE + if (!nospec_disable) { + tstart = ftrace_shared_hotpatch_trampoline_exrl; + tend = ftrace_shared_hotpatch_trampoline_exrl_end; + } +#endif /* CONFIG_EXPOLINE */ + if (end) + *end = tend; + return tstart; } -static inline int is_kprobe_on_ftrace(struct ftrace_insn *insn) +bool ftrace_need_init_nop(void) { -#ifdef CONFIG_KPROBES - if (insn->opc == BREAKPOINT_INSTRUCTION) - return 1; -#endif - return 0; + return true; } -static inline void ftrace_generate_kprobe_nop_insn(struct ftrace_insn *insn) +int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) { -#ifdef CONFIG_KPROBES - insn->opc = BREAKPOINT_INSTRUCTION; - insn->disp = KPROBE_ON_FTRACE_NOP; + static struct ftrace_hotpatch_trampoline *next_vmlinux_trampoline = + __ftrace_hotpatch_trampolines_start; + static const char orig[6] = { 0xc0, 0x04, 0x00, 0x00, 0x00, 0x00 }; + static struct ftrace_hotpatch_trampoline *trampoline; + struct ftrace_hotpatch_trampoline **next_trampoline; + struct ftrace_hotpatch_trampoline *trampolines_end; + struct ftrace_hotpatch_trampoline tmp; + struct ftrace_insn *insn; + const char *shared; + s32 disp; + + BUILD_BUG_ON(sizeof(struct ftrace_hotpatch_trampoline) != + SIZEOF_FTRACE_HOTPATCH_TRAMPOLINE); + + next_trampoline = &next_vmlinux_trampoline; + trampolines_end = __ftrace_hotpatch_trampolines_end; + shared = ftrace_shared_hotpatch_trampoline(NULL); +#ifdef CONFIG_MODULES + if (mod) { + next_trampoline = &mod->arch.next_trampoline; + trampolines_end = mod->arch.trampolines_end; + shared = ftrace_plt; + } #endif + + if (WARN_ON_ONCE(*next_trampoline >= trampolines_end)) + return -ENOMEM; + trampoline = (*next_trampoline)++; + + /* Check for the compiler-generated fentry nop (brcl 0, .). */ + if (WARN_ON_ONCE(memcmp((const void *)rec->ip, &orig, sizeof(orig)))) + return -EINVAL; + + /* Generate the trampoline. */ + tmp.brasl_opc = 0xc015; /* brasl %r1, shared */ + tmp.brasl_disp = (shared - (const char *)&trampoline->brasl_opc) / 2; + tmp.interceptor = FTRACE_ADDR; + tmp.rest_of_intercepted_function = rec->ip + sizeof(struct ftrace_insn); + s390_kernel_write(trampoline, &tmp, sizeof(tmp)); + + /* Generate a jump to the trampoline. */ + disp = ((char *)trampoline - (char *)rec->ip) / 2; + insn = (struct ftrace_insn *)rec->ip; + s390_kernel_write(&insn->disp, &disp, sizeof(disp)); + + return 0; } -static inline void ftrace_generate_kprobe_call_insn(struct ftrace_insn *insn) +static struct ftrace_hotpatch_trampoline *ftrace_get_trampoline(struct dyn_ftrace *rec) { -#ifdef CONFIG_KPROBES - insn->opc = BREAKPOINT_INSTRUCTION; - insn->disp = KPROBE_ON_FTRACE_CALL; -#endif + struct ftrace_hotpatch_trampoline *trampoline; + struct ftrace_insn insn; + s64 disp; + u16 opc; + + if (copy_from_kernel_nofault(&insn, (void *)rec->ip, sizeof(insn))) + return ERR_PTR(-EFAULT); + disp = (s64)insn.disp * 2; + trampoline = (void *)(rec->ip + disp); + if (get_kernel_nofault(opc, &trampoline->brasl_opc)) + return ERR_PTR(-EFAULT); + if (opc != 0xc015) + return ERR_PTR(-EINVAL); + return trampoline; } int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr) { + struct ftrace_hotpatch_trampoline *trampoline; + u64 old; + + trampoline = ftrace_get_trampoline(rec); + if (IS_ERR(trampoline)) + return PTR_ERR(trampoline); + if (get_kernel_nofault(old, &trampoline->interceptor)) + return -EFAULT; + if (old != old_addr) + return -EINVAL; + s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr)); return 0; } -int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, - unsigned long addr) +static int ftrace_patch_branch_mask(void *addr, u16 expected, bool enable) { - struct ftrace_insn orig, new, old; + u16 old; + u8 op; - if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old))) + if (get_kernel_nofault(old, addr)) return -EFAULT; - if (addr == MCOUNT_ADDR) { - /* Initial code replacement */ - ftrace_generate_orig_insn(&orig); - ftrace_generate_nop_insn(&new); - } else if (is_kprobe_on_ftrace(&old)) { - /* - * If we find a breakpoint instruction, a kprobe has been - * placed at the beginning of the function. We write the - * constant KPROBE_ON_FTRACE_NOP into the remaining four - * bytes of the original instruction so that the kprobes - * handler can execute a nop, if it reaches this breakpoint. - */ - ftrace_generate_kprobe_call_insn(&orig); - ftrace_generate_kprobe_nop_insn(&new); - } else { - /* Replace ftrace call with a nop. */ - ftrace_generate_call_insn(&orig, rec->ip); - ftrace_generate_nop_insn(&new); - } - /* Verify that the to be replaced code matches what we expect. */ - if (memcmp(&orig, &old, sizeof(old))) + if (old != expected) return -EINVAL; - s390_kernel_write((void *) rec->ip, &new, sizeof(new)); + /* set mask field to all ones or zeroes */ + op = enable ? 0xf4 : 0x04; + s390_kernel_write((char *)addr + 1, &op, sizeof(op)); return 0; } +int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, + unsigned long addr) +{ + /* Expect brcl 0xf,... */ + return ftrace_patch_branch_mask((void *)rec->ip, 0xc0f4, false); +} + int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { - struct ftrace_insn orig, new, old; + struct ftrace_hotpatch_trampoline *trampoline; - if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old))) - return -EFAULT; - if (is_kprobe_on_ftrace(&old)) { - /* - * If we find a breakpoint instruction, a kprobe has been - * placed at the beginning of the function. We write the - * constant KPROBE_ON_FTRACE_CALL into the remaining four - * bytes of the original instruction so that the kprobes - * handler can execute a brasl if it reaches this breakpoint. - */ - ftrace_generate_kprobe_nop_insn(&orig); - ftrace_generate_kprobe_call_insn(&new); - } else { - /* Replace nop with an ftrace call. */ - ftrace_generate_nop_insn(&orig); - ftrace_generate_call_insn(&new, rec->ip); - } - /* Verify that the to be replaced code matches what we expect. */ - if (memcmp(&orig, &old, sizeof(old))) - return -EINVAL; - s390_kernel_write((void *) rec->ip, &new, sizeof(new)); - return 0; + trampoline = ftrace_get_trampoline(rec); + if (IS_ERR(trampoline)) + return PTR_ERR(trampoline); + s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr)); + /* Expect brcl 0x0,... */ + return ftrace_patch_branch_mask((void *)rec->ip, 0xc004, true); } int ftrace_update_ftrace_func(ftrace_func_t func) { + ftrace_func = func; return 0; } -int __init ftrace_dyn_arch_init(void) +void arch_ftrace_update_code(int command) { - return 0; + ftrace_modify_all_code(command); +} + +void ftrace_arch_code_modify_post_process(void) +{ + /* + * Flush any pre-fetched instructions on all + * CPUs to make the new code visible. + */ + text_poke_sync_lock(); } #ifdef CONFIG_MODULES static int __init ftrace_plt_init(void) { - unsigned int *ip; + const char *start, *end; - ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE); + ftrace_plt = module_alloc(PAGE_SIZE); if (!ftrace_plt) panic("cannot allocate ftrace plt\n"); - ip = (unsigned int *) ftrace_plt; - ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */ - ip[1] = 0x100a0004; - ip[2] = 0x07f10000; - ip[3] = FTRACE_ADDR >> 32; - ip[4] = FTRACE_ADDR & 0xffffffff; - set_memory_ro(ftrace_plt, 1); + + start = ftrace_shared_hotpatch_trampoline(&end); + memcpy(ftrace_plt, start, end - start); + set_memory_rox((unsigned long)ftrace_plt, 1); return 0; } device_initcall(ftrace_plt_init); @@ -226,18 +263,78 @@ NOKPROBE_SYMBOL(prepare_ftrace_return); */ int ftrace_enable_ftrace_graph_caller(void) { - u8 op = 0x04; /* set mask field to zero */ + int rc; - s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op)); + /* Expect brc 0xf,... */ + rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa7f4, false); + if (rc) + return rc; + text_poke_sync_lock(); return 0; } int ftrace_disable_ftrace_graph_caller(void) { - u8 op = 0xf4; /* set mask field to all ones */ + int rc; - s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op)); + /* Expect brc 0x0,... */ + rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa704, true); + if (rc) + return rc; + text_poke_sync_lock(); return 0; } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ + +#ifdef CONFIG_KPROBES_ON_FTRACE +void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, + struct ftrace_ops *ops, struct ftrace_regs *fregs) +{ + struct kprobe_ctlblk *kcb; + struct pt_regs *regs; + struct kprobe *p; + int bit; + + bit = ftrace_test_recursion_trylock(ip, parent_ip); + if (bit < 0) + return; + + regs = ftrace_get_regs(fregs); + p = get_kprobe((kprobe_opcode_t *)ip); + if (!regs || unlikely(!p) || kprobe_disabled(p)) + goto out; + + if (kprobe_running()) { + kprobes_inc_nmissed_count(p); + goto out; + } + + __this_cpu_write(current_kprobe, p); + + kcb = get_kprobe_ctlblk(); + kcb->kprobe_status = KPROBE_HIT_ACTIVE; + + instruction_pointer_set(regs, ip); + + if (!p->pre_handler || !p->pre_handler(p, regs)) { + + instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE); + + if (unlikely(p->post_handler)) { + kcb->kprobe_status = KPROBE_HIT_SSDONE; + p->post_handler(p, regs, 0); + } + } + __this_cpu_write(current_kprobe, NULL); +out: + ftrace_test_recursion_unlock(bit); +} +NOKPROBE_SYMBOL(kprobe_ftrace_handler); + +int arch_prepare_kprobe_ftrace(struct kprobe *p) +{ + p->ainsn.insn = NULL; + return 0; +} +#endif |