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): Heiko Carstens <heiko.carstens@de.ibm.com>,
  *		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/cacheflush.h>
 #include <asm/set_memory.h>
 #include "entry.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:
  * >	brasl	%r0,ftrace_caller	# offset 0
  *	larl	%r1,<&counter>		# offset 6
  *	brasl	%r14,_mcount		# offset 12
  *	lg	%r14,8(%r15)		# offset 18
  * 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;

 static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn)
 {
 #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
 }

 static inline int is_kprobe_on_ftrace(struct ftrace_insn *insn)
 {
 #ifdef CONFIG_KPROBES
 	if (insn->opc == BREAKPOINT_INSTRUCTION)
 		return 1;
 #endif
 	return 0;
 }

 static inline void ftrace_generate_kprobe_nop_insn(struct ftrace_insn *insn)
 {
 #ifdef CONFIG_KPROBES
 	insn->opc = BREAKPOINT_INSTRUCTION;
 	insn->disp = KPROBE_ON_FTRACE_NOP;
 #endif
 }

 static inline void ftrace_generate_kprobe_call_insn(struct ftrace_insn *insn)
 {
 #ifdef CONFIG_KPROBES
 	insn->opc = BREAKPOINT_INSTRUCTION;
 	insn->disp = KPROBE_ON_FTRACE_CALL;
 #endif
 }

 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 		       unsigned long addr)
 {
 	return 0;
 }

 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 		    unsigned long addr)
 {
 	struct ftrace_insn orig, new, old;

 	if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
 		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)))
 		return -EINVAL;
 	s390_kernel_write((void *) rec->ip, &new, sizeof(new));
 	return 0;
 }

 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	struct ftrace_insn orig, new, old;

 	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;
 }

 int ftrace_update_ftrace_func(ftrace_func_t func)
 {
 	return 0;
 }

 int __init ftrace_dyn_arch_init(void)
 {
 	return 0;
 }

 #ifdef CONFIG_MODULES

 static int __init ftrace_plt_init(void)
 {
 	unsigned int *ip;

 	ftrace_plt = (unsigned long) 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);
 	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)
 {
 	u8 op = 0x04; /* set mask field to zero */

 	s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
 	return 0;
 }

 int ftrace_disable_ftrace_graph_caller(void)
 {
 	u8 op = 0xf4; /* set mask field to all ones */

 	s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
 	return 0;
 }

 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Dynamic function tracer architecture backend.
	*
	* Copyright IBM Corp. 2009,2014
	*
	* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
	* 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/cacheflush.h>
	#include <asm/set_memory.h>
	#include "entry.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:
	* > brasl %r0,ftrace_caller # offset 0
	* larl %r1,<&counter> # offset 6
	* brasl %r14,_mcount # offset 12
	* lg %r14,8(%r15) # offset 18
	* 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;

	static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn)
	{
	#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
	}

	static inline int is_kprobe_on_ftrace(struct ftrace_insn *insn)
	{
	#ifdef CONFIG_KPROBES
	if (insn->opc == BREAKPOINT_INSTRUCTION)
	return 1;
	#endif
	return 0;
	}

	static inline void ftrace_generate_kprobe_nop_insn(struct ftrace_insn *insn)
	{
	#ifdef CONFIG_KPROBES
	insn->opc = BREAKPOINT_INSTRUCTION;
	insn->disp = KPROBE_ON_FTRACE_NOP;
	#endif
	}

	static inline void ftrace_generate_kprobe_call_insn(struct ftrace_insn *insn)
	{
	#ifdef CONFIG_KPROBES
	insn->opc = BREAKPOINT_INSTRUCTION;
	insn->disp = KPROBE_ON_FTRACE_CALL;
	#endif
	}

	int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
	unsigned long addr)
	{
	return 0;
	}

	int ftrace_make_nop(struct module mod, struct dyn_ftrace rec,
	unsigned long addr)
	{
	struct ftrace_insn orig, new, old;

	if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
	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)))
	return -EINVAL;
	s390_kernel_write((void *) rec->ip, &new, sizeof(new));
	return 0;
	}

	int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	{
	struct ftrace_insn orig, new, old;

	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;
	}

	int ftrace_update_ftrace_func(ftrace_func_t func)
	{
	return 0;
	}

	int __init ftrace_dyn_arch_init(void)
	{
	return 0;
	}

	#ifdef CONFIG_MODULES

	static int __init ftrace_plt_init(void)
	{
	unsigned int *ip;

	ftrace_plt = (unsigned long) 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);
	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)
	{
	u8 op = 0x04; /* set mask field to zero */

	s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
	return 0;
	}

	int ftrace_disable_ftrace_graph_caller(void)
	{
	u8 op = 0xf4; /* set mask field to all ones */

	s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
	return 0;
	}

	#endif /* CONFIG_FUNCTION_GRAPH_TRACER */