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-rw-r--r--arch/s390/kernel/ftrace.c360
1 files changed, 360 insertions, 0 deletions
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
new file mode 100644
index 000000000..416b5a943
--- /dev/null
+++ b/arch/s390/kernel/ftrace.c
@@ -0,0 +1,360 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Dynamic function tracer architecture backend.
+ *
+ * Copyright IBM Corp. 2009,2014
+ *
+ * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
+ */
+
+#include <linux/moduleloader.h>
+#include <linux/hardirq.h>
+#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#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"
+
+/*
+ * 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
+ *
+ * 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.
+ */
+
+void *ftrace_func __read_mostly = ftrace_stub;
+struct ftrace_insn {
+ u16 opc;
+ s32 disp;
+} __packed;
+
+asm(
+ " .align 16\n"
+ "ftrace_shared_hotpatch_trampoline_br:\n"
+ " lmg %r0,%r1,2(%r1)\n"
+ " br %r1\n"
+ "ftrace_shared_hotpatch_trampoline_br_end:\n"
+);
+
+#ifdef CONFIG_EXPOLINE
+asm(
+ " .align 16\n"
+ "ftrace_shared_hotpatch_trampoline_exrl:\n"
+ " lmg %r0,%r1,2(%r1)\n"
+ " exrl %r0,0f\n"
+ " j .\n"
+ "0: br %r1\n"
+ "ftrace_shared_hotpatch_trampoline_exrl_end:\n"
+);
+#endif /* CONFIG_EXPOLINE */
+
+#ifdef CONFIG_MODULES
+static char *ftrace_plt;
+#endif /* CONFIG_MODULES */
+
+static const char *ftrace_shared_hotpatch_trampoline(const char **end)
+{
+ 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;
+}
+
+bool ftrace_need_init_nop(void)
+{
+ return true;
+}
+
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
+{
+ 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 struct ftrace_hotpatch_trampoline *ftrace_get_trampoline(struct dyn_ftrace *rec)
+{
+ 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;
+}
+
+static int ftrace_patch_branch_mask(void *addr, u16 expected, bool enable)
+{
+ u16 old;
+ u8 op;
+
+ if (get_kernel_nofault(old, addr))
+ return -EFAULT;
+ if (old != expected)
+ return -EINVAL;
+ /* 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_hotpatch_trampoline *trampoline;
+
+ 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;
+}
+
+void arch_ftrace_update_code(int command)
+{
+ 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)
+{
+ const char *start, *end;
+
+ ftrace_plt = module_alloc(PAGE_SIZE);
+ if (!ftrace_plt)
+ panic("cannot allocate ftrace plt\n");
+
+ start = ftrace_shared_hotpatch_trampoline(&end);
+ memcpy(ftrace_plt, start, end - start);
+ set_memory_ro((unsigned long)ftrace_plt, 1);
+ return 0;
+}
+device_initcall(ftrace_plt_init);
+
+#endif /* CONFIG_MODULES */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/*
+ * Hook the return address and push it in the stack of return addresses
+ * in current thread info.
+ */
+unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
+ unsigned long ip)
+{
+ if (unlikely(ftrace_graph_is_dead()))
+ goto out;
+ if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ goto out;
+ ip -= MCOUNT_INSN_SIZE;
+ if (!function_graph_enter(ra, ip, 0, (void *) sp))
+ ra = (unsigned long) return_to_handler;
+out:
+ return ra;
+}
+NOKPROBE_SYMBOL(prepare_ftrace_return);
+
+/*
+ * Patch the kernel code at ftrace_graph_caller location. The instruction
+ * there is branch relative on condition. To enable the ftrace graph code
+ * block, we simply patch the mask field of the instruction to zero and
+ * turn the instruction into a nop.
+ * To disable the ftrace graph code the mask field will be patched to
+ * all ones, which turns the instruction into an unconditional branch.
+ */
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ int rc;
+
+ /* 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)
+{
+ int rc;
+
+ /* 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