tools/perf/arch/powerpc/util/skip-callchain-idx.c - third_party/linux - Git at Google

 /*
  * Use DWARF Debug information to skip unnecessary callchain entries.
  *
  * Copyright (C) 2014 Sukadev Bhattiprolu, IBM Corporation.
  * Copyright (C) 2014 Ulrich Weigand, IBM Corporation.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version
  * 2 of the License, or (at your option) any later version.
  */
 #include <inttypes.h>
 #include <dwarf.h>
 #include <elfutils/libdwfl.h>

 #include "util/thread.h"
 #include "util/callchain.h"
 #include "util/debug.h"

 /*
  * When saving the callchain on Power, the kernel conservatively saves
  * excess entries in the callchain. A few of these entries are needed
  * in some cases but not others. If the unnecessary entries are not
  * ignored, we end up with duplicate arcs in the call-graphs. Use
  * DWARF debug information to skip over any unnecessary callchain
  * entries.
  *
  * See function header for arch_adjust_callchain() below for more details.
  *
  * The libdwfl code in this file is based on code from elfutils
  * (libdwfl/argp-std.c, libdwfl/tests/addrcfi.c, etc).
  */
 static char *debuginfo_path;

 static const Dwfl_Callbacks offline_callbacks = {
 	.debuginfo_path = &debuginfo_path,
 	.find_debuginfo = dwfl_standard_find_debuginfo,
 	.section_address = dwfl_offline_section_address,
 };


 /*
  * Use the DWARF expression for the Call-frame-address and determine
  * if return address is in LR and if a new frame was allocated.
  */
 static int check_return_reg(int ra_regno, Dwarf_Frame *frame)
 {
 	Dwarf_Op ops_mem[2];
 	Dwarf_Op dummy;
 	Dwarf_Op *ops = &dummy;
 	size_t nops;
 	int result;

 	result = dwarf_frame_register(frame, ra_regno, ops_mem, &ops, &nops);
 	if (result < 0) {
 		pr_debug("dwarf_frame_register() %s\n", dwarf_errmsg(-1));
 		return -1;
 	}

 	/*
 	 * Check if return address is on the stack.
 	 */
 	if (nops != 0 || ops != NULL)
 		return 0;

 	/*
 	 * Return address is in LR. Check if a frame was allocated
 	 * but not-yet used.
 	 */
 	result = dwarf_frame_cfa(frame, &ops, &nops);
 	if (result < 0) {
 		pr_debug("dwarf_frame_cfa() returns %d, %s\n", result,
 					dwarf_errmsg(-1));
 		return -1;
 	}

 	/*
 	 * If call frame address is in r1, no new frame was allocated.
 	 */
 	if (nops == 1 && ops[0].atom == DW_OP_bregx && ops[0].number == 1 &&
 				ops[0].number2 == 0)
 		return 1;

 	/*
 	 * A new frame was allocated but has not yet been used.
 	 */
 	return 2;
 }

 /*
  * Get the DWARF frame from the .eh_frame section.
  */
 static Dwarf_Frame *get_eh_frame(Dwfl_Module *mod, Dwarf_Addr pc)
 {
 	int		result;
 	Dwarf_Addr	bias;
 	Dwarf_CFI	*cfi;
 	Dwarf_Frame	*frame;

 	cfi = dwfl_module_eh_cfi(mod, &bias);
 	if (!cfi) {
 		pr_debug("%s(): no CFI - %s\n", __func__, dwfl_errmsg(-1));
 		return NULL;
 	}

 	result = dwarf_cfi_addrframe(cfi, pc-bias, &frame);
 	if (result) {
 		pr_debug("%s(): %s\n", __func__, dwfl_errmsg(-1));
 		return NULL;
 	}

 	return frame;
 }

 /*
  * Get the DWARF frame from the .debug_frame section.
  */
 static Dwarf_Frame *get_dwarf_frame(Dwfl_Module *mod, Dwarf_Addr pc)
 {
 	Dwarf_CFI       *cfi;
 	Dwarf_Addr      bias;
 	Dwarf_Frame     *frame;
 	int             result;

 	cfi = dwfl_module_dwarf_cfi(mod, &bias);
 	if (!cfi) {
 		pr_debug("%s(): no CFI - %s\n", __func__, dwfl_errmsg(-1));
 		return NULL;
 	}

 	result = dwarf_cfi_addrframe(cfi, pc-bias, &frame);
 	if (result) {
 		pr_debug("%s(): %s\n", __func__, dwfl_errmsg(-1));
 		return NULL;
 	}

 	return frame;
 }

 /*
  * Return:
  *	0 if return address for the program counter @pc is on stack
  *	1 if return address is in LR and no new stack frame was allocated
  *	2 if return address is in LR and a new frame was allocated (but not
  *		yet used)
  *	-1 in case of errors
  */
 static int check_return_addr(struct dso *dso, u64 map_start, Dwarf_Addr pc)
 {
 	int		rc = -1;
 	Dwfl		*dwfl;
 	Dwfl_Module	*mod;
 	Dwarf_Frame	*frame;
 	int		ra_regno;
 	Dwarf_Addr	start = pc;
 	Dwarf_Addr	end = pc;
 	bool		signalp;
 	const char	*exec_file = dso->long_name;

 	dwfl = dso->dwfl;

 	if (!dwfl) {
 		dwfl = dwfl_begin(&offline_callbacks);
 		if (!dwfl) {
 			pr_debug("dwfl_begin() failed: %s\n", dwarf_errmsg(-1));
 			return -1;
 		}

 		mod = dwfl_report_elf(dwfl, exec_file, exec_file, -1,
 						map_start, false);
 		if (!mod) {
 			pr_debug("dwfl_report_elf() failed %s\n",
 						dwarf_errmsg(-1));
 			/*
 			 * We normally cache the DWARF debug info and never
 			 * call dwfl_end(). But to prevent fd leak, free in
 			 * case of error.
 			 */
 			dwfl_end(dwfl);
 			goto out;
 		}
 		dso->dwfl = dwfl;
 	}

 	mod = dwfl_addrmodule(dwfl, pc);
 	if (!mod) {
 		pr_debug("dwfl_addrmodule() failed, %s\n", dwarf_errmsg(-1));
 		goto out;
 	}

 	/*
 	 * To work with split debug info files (eg: glibc), check both
 	 * .eh_frame and .debug_frame sections of the ELF header.
 	 */
 	frame = get_eh_frame(mod, pc);
 	if (!frame) {
 		frame = get_dwarf_frame(mod, pc);
 		if (!frame)
 			goto out;
 	}

 	ra_regno = dwarf_frame_info(frame, &start, &end, &signalp);
 	if (ra_regno < 0) {
 		pr_debug("Return address register unavailable: %s\n",
 				dwarf_errmsg(-1));
 		goto out;
 	}

 	rc = check_return_reg(ra_regno, frame);

 out:
 	return rc;
 }

 /*
  * The callchain saved by the kernel always includes the link register (LR).
  *
  *	0:	PERF_CONTEXT_USER
  *	1:	Program counter (Next instruction pointer)
  *	2:	LR value
  *	3:	Caller's caller
  *	4:	...
  *
  * The value in LR is only needed when it holds a return address. If the
  * return address is on the stack, we should ignore the LR value.
  *
  * Further, when the return address is in the LR, if a new frame was just
  * allocated but the LR was not saved into it, then the LR contains the
  * caller, slot 4: contains the caller's caller and the contents of slot 3:
  * (chain->ips[3]) is undefined and must be ignored.
  *
  * Use DWARF debug information to determine if any entries need to be skipped.
  *
  * Return:
  *	index:	of callchain entry that needs to be ignored (if any)
  *	-1	if no entry needs to be ignored or in case of errors
  */
 int arch_skip_callchain_idx(struct thread *thread, struct ip_callchain *chain)
 {
 	struct addr_location al;
 	struct dso *dso = NULL;
 	int rc;
 	u64 ip;
 	u64 skip_slot = -1;

 	if (!chain || chain->nr < 3)
 		return skip_slot;

 	ip = chain->ips[2];

 	thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);

 	if (al.map)
 		dso = al.map->dso;

 	if (!dso) {
 		pr_debug("%" PRIx64 " dso is NULL\n", ip);
 		return skip_slot;
 	}

 	rc = check_return_addr(dso, al.map->start, ip);

 	pr_debug("[DSO %s, sym %s, ip 0x%" PRIx64 "] rc %d\n",
 				dso->long_name, al.sym->name, ip, rc);

 	if (rc == 0) {
 		/*
 		 * Return address on stack. Ignore LR value in callchain
 		 */
 		skip_slot = 2;
 	} else if (rc == 2) {
 		/*
 		 * New frame allocated but return address still in LR.
 		 * Ignore the caller's caller entry in callchain.
 		 */
 		skip_slot = 3;
 	}
 	return skip_slot;
 }
	/*
	* Use DWARF Debug information to skip unnecessary callchain entries.
	*
	* Copyright (C) 2014 Sukadev Bhattiprolu, IBM Corporation.
	* Copyright (C) 2014 Ulrich Weigand, IBM Corporation.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*/
	#include <inttypes.h>
	#include <dwarf.h>
	#include <elfutils/libdwfl.h>

	#include "util/thread.h"
	#include "util/callchain.h"
	#include "util/debug.h"

	/*
	* When saving the callchain on Power, the kernel conservatively saves
	* excess entries in the callchain. A few of these entries are needed
	* in some cases but not others. If the unnecessary entries are not
	* ignored, we end up with duplicate arcs in the call-graphs. Use
	* DWARF debug information to skip over any unnecessary callchain
	* entries.
	*
	* See function header for arch_adjust_callchain() below for more details.
	*
	* The libdwfl code in this file is based on code from elfutils
	* (libdwfl/argp-std.c, libdwfl/tests/addrcfi.c, etc).
	*/
	static char *debuginfo_path;

	static const Dwfl_Callbacks offline_callbacks = {
	.debuginfo_path = &debuginfo_path,
	.find_debuginfo = dwfl_standard_find_debuginfo,
	.section_address = dwfl_offline_section_address,
	};


	/*
	* Use the DWARF expression for the Call-frame-address and determine
	* if return address is in LR and if a new frame was allocated.
	*/
	static int check_return_reg(int ra_regno, Dwarf_Frame *frame)
	{
	Dwarf_Op ops_mem[2];
	Dwarf_Op dummy;
	Dwarf_Op *ops = &dummy;
	size_t nops;
	int result;

	result = dwarf_frame_register(frame, ra_regno, ops_mem, &ops, &nops);
	if (result < 0) {
	pr_debug("dwarf_frame_register() %s\n", dwarf_errmsg(-1));
	return -1;
	}

	/*
	* Check if return address is on the stack.
	*/
	if (nops != 0 \|\| ops != NULL)
	return 0;

	/*
	* Return address is in LR. Check if a frame was allocated
	* but not-yet used.
	*/
	result = dwarf_frame_cfa(frame, &ops, &nops);
	if (result < 0) {
	pr_debug("dwarf_frame_cfa() returns %d, %s\n", result,
	dwarf_errmsg(-1));
	return -1;
	}

	/*
	* If call frame address is in r1, no new frame was allocated.
	*/
	if (nops == 1 && ops[0].atom == DW_OP_bregx && ops[0].number == 1 &&
	ops[0].number2 == 0)
	return 1;

	/*
	* A new frame was allocated but has not yet been used.
	*/
	return 2;
	}

	/*
	* Get the DWARF frame from the .eh_frame section.
	*/
	static Dwarf_Frame get_eh_frame(Dwfl_Module mod, Dwarf_Addr pc)
	{
	int result;
	Dwarf_Addr bias;
	Dwarf_CFI *cfi;
	Dwarf_Frame *frame;

	cfi = dwfl_module_eh_cfi(mod, &bias);
	if (!cfi) {
	pr_debug("%s(): no CFI - %s\n", __func__, dwfl_errmsg(-1));
	return NULL;
	}

	result = dwarf_cfi_addrframe(cfi, pc-bias, &frame);
	if (result) {
	pr_debug("%s(): %s\n", __func__, dwfl_errmsg(-1));
	return NULL;
	}

	return frame;
	}

	/*
	* Get the DWARF frame from the .debug_frame section.
	*/
	static Dwarf_Frame get_dwarf_frame(Dwfl_Module mod, Dwarf_Addr pc)
	{
	Dwarf_CFI *cfi;
	Dwarf_Addr bias;
	Dwarf_Frame *frame;
	int result;

	cfi = dwfl_module_dwarf_cfi(mod, &bias);
	if (!cfi) {
	pr_debug("%s(): no CFI - %s\n", __func__, dwfl_errmsg(-1));
	return NULL;
	}

	result = dwarf_cfi_addrframe(cfi, pc-bias, &frame);
	if (result) {
	pr_debug("%s(): %s\n", __func__, dwfl_errmsg(-1));
	return NULL;
	}

	return frame;
	}

	/*
	* Return:
	* 0 if return address for the program counter @pc is on stack
	* 1 if return address is in LR and no new stack frame was allocated
	* 2 if return address is in LR and a new frame was allocated (but not
	* yet used)
	* -1 in case of errors
	*/
	static int check_return_addr(struct dso *dso, u64 map_start, Dwarf_Addr pc)
	{
	int rc = -1;
	Dwfl *dwfl;
	Dwfl_Module *mod;
	Dwarf_Frame *frame;
	int ra_regno;
	Dwarf_Addr start = pc;
	Dwarf_Addr end = pc;
	bool signalp;
	const char *exec_file = dso->long_name;

	dwfl = dso->dwfl;

	if (!dwfl) {
	dwfl = dwfl_begin(&offline_callbacks);
	if (!dwfl) {
	pr_debug("dwfl_begin() failed: %s\n", dwarf_errmsg(-1));
	return -1;
	}

	mod = dwfl_report_elf(dwfl, exec_file, exec_file, -1,
	map_start, false);
	if (!mod) {
	pr_debug("dwfl_report_elf() failed %s\n",
	dwarf_errmsg(-1));
	/*
	* We normally cache the DWARF debug info and never
	* call dwfl_end(). But to prevent fd leak, free in
	* case of error.
	*/
	dwfl_end(dwfl);
	goto out;
	}
	dso->dwfl = dwfl;
	}

	mod = dwfl_addrmodule(dwfl, pc);
	if (!mod) {
	pr_debug("dwfl_addrmodule() failed, %s\n", dwarf_errmsg(-1));
	goto out;
	}

	/*
	* To work with split debug info files (eg: glibc), check both
	* .eh_frame and .debug_frame sections of the ELF header.
	*/
	frame = get_eh_frame(mod, pc);
	if (!frame) {
	frame = get_dwarf_frame(mod, pc);
	if (!frame)
	goto out;
	}

	ra_regno = dwarf_frame_info(frame, &start, &end, &signalp);
	if (ra_regno < 0) {
	pr_debug("Return address register unavailable: %s\n",
	dwarf_errmsg(-1));
	goto out;
	}

	rc = check_return_reg(ra_regno, frame);

	out:
	return rc;
	}

	/*
	* The callchain saved by the kernel always includes the link register (LR).
	*
	* 0: PERF_CONTEXT_USER
	* 1: Program counter (Next instruction pointer)
	* 2: LR value
	* 3: Caller's caller
	* 4: ...
	*
	* The value in LR is only needed when it holds a return address. If the
	* return address is on the stack, we should ignore the LR value.
	*
	* Further, when the return address is in the LR, if a new frame was just
	* allocated but the LR was not saved into it, then the LR contains the
	* caller, slot 4: contains the caller's caller and the contents of slot 3:
	* (chain->ips[3]) is undefined and must be ignored.
	*
	* Use DWARF debug information to determine if any entries need to be skipped.
	*
	* Return:
	* index: of callchain entry that needs to be ignored (if any)
	* -1 if no entry needs to be ignored or in case of errors
	*/
	int arch_skip_callchain_idx(struct thread thread, struct ip_callchain chain)
	{
	struct addr_location al;
	struct dso *dso = NULL;
	int rc;
	u64 ip;
	u64 skip_slot = -1;

	if (!chain \|\| chain->nr < 3)
	return skip_slot;

	ip = chain->ips[2];

	thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);

	if (al.map)
	dso = al.map->dso;

	if (!dso) {
	pr_debug("%" PRIx64 " dso is NULL\n", ip);
	return skip_slot;
	}

	rc = check_return_addr(dso, al.map->start, ip);

	pr_debug("[DSO %s, sym %s, ip 0x%" PRIx64 "] rc %d\n",
	dso->long_name, al.sym->name, ip, rc);

	if (rc == 0) {
	/*
	* Return address on stack. Ignore LR value in callchain
	*/
	skip_slot = 2;
	} else if (rc == 2) {
	/*
	* New frame allocated but return address still in LR.
	* Ignore the caller's caller entry in callchain.
	*/
	skip_slot = 3;
	}
	return skip_slot;
	}