arch/s390/kernel/ftrace.c - linux - Git at Google

 // 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/hardirq.h>
 #include <linux/uaccess.h>
 #include <linux/ftrace.h>
 #include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/kmsan-checks.h>
 #include <linux/kprobes.h>
 #include <linux/execmem.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;

 #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 = execmem_alloc(EXECMEM_FTRACE, 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_rox((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;

 	if (unlikely(kprobe_ftrace_disabled))
 		return;

 	bit = ftrace_test_recursion_trylock(ip, parent_ip);
 	if (bit < 0)
 		return;

 	kmsan_unpoison_memory(fregs, sizeof(*fregs));
 	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
	// 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/hardirq.h>
	#include <linux/uaccess.h>
	#include <linux/ftrace.h>
	#include <linux/kernel.h>
	#include <linux/types.h>
	#include <linux/kmsan-checks.h>
	#include <linux/kprobes.h>
	#include <linux/execmem.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;

	#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 = execmem_alloc(EXECMEM_FTRACE, 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_rox((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;

	if (unlikely(kprobe_ftrace_disabled))
	return;

	bit = ftrace_test_recursion_trylock(ip, parent_ip);
	if (bit < 0)
	return;

	kmsan_unpoison_memory(fregs, sizeof(*fregs));
	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