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/* * recordmcount.c: construct a table of the locations of calls to 'mcount' * so that ftrace can find them quickly. * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>.  All rights reserved. * Licensed under the GNU General Public License, version 2 (GPLv2). * * Restructured to fit Linux format, as well as other updates: *  Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc. */ /* * Strategy: alter the .o file in-place. * * Append a new STRTAB that has the new section names, followed by a new array * ElfXX_Shdr[] that has the new section headers, followed by the section * contents for __mcount_loc and its relocations.  The old shstrtab strings, * and the old ElfXX_Shdr[] array, remain as "garbage" (commonly, a couple * kilobytes.)  Subsequent processing by /bin/ld (or the kernel module loader) * will ignore the garbage regions, because they are not designated by the * new .e_shoff nor the new ElfXX_Shdr[].  [In order to remove the garbage, * then use "ld -r" to create a new file that omits the garbage.] */ #include <sys/types.h>#include <sys/mman.h>#include <sys/stat.h>#include <getopt.h>#include <elf.h>#include <fcntl.h>#include <setjmp.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h> /* * glibc synced up and added the metag number but didn't add the relocations. * Work around this in a crude manner for now. */#ifndef EM_METAG#define EM_METAG      174#endif#ifndef R_METAG_ADDR32#define R_METAG_ADDR32                   2#endif#ifndef R_METAG_NONE#define R_METAG_NONE                     3#endif #ifndef EM_AARCH64#define EM_AARCH64	183#define R_AARCH64_NONE		0#define R_AARCH64_ABS64	257#endif static int fd_map;	/* File descriptor for file being modified. */static int mmap_failed; /* Boolean flag. */static char gpfx;	/* prefix for global symbol name (sometimes '_') */static struct stat sb;	/* Remember .st_size, etc. */static jmp_buf jmpenv;	/* setjmp/longjmp per-file error escape */static const char *altmcount;	/* alternate mcount symbol name */static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */static void *file_map;	/* pointer of the mapped file */static void *file_end;	/* pointer to the end of the mapped file */static int file_updated; /* flag to state file was changed */static void *file_ptr;	/* current file pointer location */static void *file_append; /* added to the end of the file */static size_t file_append_size; /* how much is added to end of file */ /* setjmp() return values */enum {	SJ_SETJMP = 0,  /* hardwired first return */	SJ_FAIL,	SJ_SUCCEED}; /* Per-file resource cleanup when multiple files. */static voidcleanup(void){	if (!mmap_failed)		munmap(file_map, sb.st_size);	else		free(file_map);	file_map = NULL;	free(file_append);	file_append = NULL;	file_append_size = 0;	file_updated = 0;} static void __attribute__((noreturn))fail_file(void){	cleanup();	longjmp(jmpenv, SJ_FAIL);} static void __attribute__((noreturn))succeed_file(void){	cleanup();	longjmp(jmpenv, SJ_SUCCEED);} /* ulseek, uread, ...:  Check return value for errors. */ static off_tulseek(int const fd, off_t const offset, int const whence){	switch (whence) {	case SEEK_SET:		file_ptr = file_map + offset;		break;	case SEEK_CUR:		file_ptr += offset;		break;	case SEEK_END:		file_ptr = file_map + (sb.st_size - offset);		break;	}	if (file_ptr < file_map) {		fprintf(stderr, "lseek: seek before file\n");		fail_file();	}	return file_ptr - file_map;} static size_turead(int const fd, void *const buf, size_t const count){	size_t const n = read(fd, buf, count);	if (n != count) {		perror("read");		fail_file();	}	return n;} static size_tuwrite(int const fd, void const *const buf, size_t const count){	size_t cnt = count;	off_t idx = 0; 	file_updated = 1; 	if (file_ptr + count >= file_end) {		off_t aoffset = (file_ptr + count) - file_end; 		if (aoffset > file_append_size) {			file_append = realloc(file_append, aoffset);			file_append_size = aoffset;		}		if (!file_append) {			perror("write");			fail_file();		}		if (file_ptr < file_end) {			cnt = file_end - file_ptr;		} else {			cnt = 0;			idx = aoffset - count;		}	} 	if (cnt)		memcpy(file_ptr, buf, cnt); 	if (cnt < count)		memcpy(file_append + idx, buf + cnt, count - cnt); 	file_ptr += count;	return count;} static void *umalloc(size_t size){	void *const addr = malloc(size);	if (addr == 0) {		fprintf(stderr, "malloc failed: %zu bytes\n", size);		fail_file();	}	return addr;} static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };static unsigned char *ideal_nop; static char rel_type_nop; static int (*make_nop)(void *map, size_t const offset); static int make_nop_x86(void *map, size_t const offset){	uint32_t *ptr;	unsigned char *op; 	/* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */	ptr = map + offset;	if (*ptr != 0)		return -1; 	op = map + offset - 1;	if (*op != 0xe8)		return -1; 	/* convert to nop */	ulseek(fd_map, offset - 1, SEEK_SET);	uwrite(fd_map, ideal_nop, 5);	return 0;} static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};static int make_nop_arm64(void *map, size_t const offset){	uint32_t *ptr; 	ptr = map + offset;	/* bl <_mcount> is 0x94000000 before relocation */	if (*ptr != 0x94000000)		return -1; 	/* Convert to nop */	ulseek(fd_map, offset, SEEK_SET);	uwrite(fd_map, ideal_nop, 4);	return 0;} /* * Get the whole file as a programming convenience in order to avoid * malloc+lseek+read+free of many pieces.  If successful, then mmap * avoids copying unused pieces; else just read the whole file. * Open for both read and write; new info will be appended to the file. * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr * do not propagate to the file until an explicit overwrite at the last. * This preserves most aspects of consistency (all except .st_size) * for simultaneous readers of the file while we are appending to it. * However, multiple writers still are bad.  We choose not to use * locking because it is expensive and the use case of kernel build * makes multiple writers unlikely. */static void *mmap_file(char const *fname){	fd_map = open(fname, O_RDONLY);	if (fd_map < 0 || fstat(fd_map, &sb) < 0) {		perror(fname);		fail_file();	}	if (!S_ISREG(sb.st_mode)) {		fprintf(stderr, "not a regular file: %s\n", fname);		fail_file();	}	file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,			fd_map, 0);	mmap_failed = 0;	if (file_map == MAP_FAILED) {		mmap_failed = 1;		file_map = umalloc(sb.st_size);		uread(fd_map, file_map, sb.st_size);	}	close(fd_map); 	file_end = file_map + sb.st_size; 	return file_map;} static void write_file(const char *fname){	char tmp_file[strlen(fname) + 4];	size_t n; 	if (!file_updated)		return; 	sprintf(tmp_file, "%s.rc", fname); 	/*	 * After reading the entire file into memory, delete it	 * and write it back, to prevent weird side effects of modifying	 * an object file in place.	 */	fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode);	if (fd_map < 0) {		perror(fname);		fail_file();	}	n = write(fd_map, file_map, sb.st_size);	if (n != sb.st_size) {		perror("write");		fail_file();	}	if (file_append_size) {		n = write(fd_map, file_append, file_append_size);		if (n != file_append_size) {			perror("write");			fail_file();		}	}	close(fd_map);	if (rename(tmp_file, fname) < 0) {		perror(fname);		fail_file();	}} /* w8rev, w8nat, ...: Handle endianness. */ static uint64_t w8rev(uint64_t const x){	return   ((0xff & (x >> (0 * 8))) << (7 * 8))	       | ((0xff & (x >> (1 * 8))) << (6 * 8))	       | ((0xff & (x >> (2 * 8))) << (5 * 8))	       | ((0xff & (x >> (3 * 8))) << (4 * 8))	       | ((0xff & (x >> (4 * 8))) << (3 * 8))	       | ((0xff & (x >> (5 * 8))) << (2 * 8))	       | ((0xff & (x >> (6 * 8))) << (1 * 8))	       | ((0xff & (x >> (7 * 8))) << (0 * 8));} static uint32_t w4rev(uint32_t const x){	return   ((0xff & (x >> (0 * 8))) << (3 * 8))	       | ((0xff & (x >> (1 * 8))) << (2 * 8))	       | ((0xff & (x >> (2 * 8))) << (1 * 8))	       | ((0xff & (x >> (3 * 8))) << (0 * 8));} static uint32_t w2rev(uint16_t const x){	return   ((0xff & (x >> (0 * 8))) << (1 * 8))	       | ((0xff & (x >> (1 * 8))) << (0 * 8));} static uint64_t w8nat(uint64_t const x){	return x;} static uint32_t w4nat(uint32_t const x){	return x;} static uint32_t w2nat(uint16_t const x){	return x;} static uint64_t (*w8)(uint64_t);static uint32_t (*w)(uint32_t);static uint32_t (*w2)(uint16_t); /* Names of the sections that could contain calls to mcount. */static intis_mcounted_section_name(char const *const txtname){	return strcmp(".text",           txtname) == 0 ||		strcmp(".ref.text",      txtname) == 0 ||		strcmp(".sched.text",    txtname) == 0 ||		strcmp(".spinlock.text", txtname) == 0 ||		strcmp(".irqentry.text", txtname) == 0 ||		strcmp(".softirqentry.text", txtname) == 0 ||		strcmp(".kprobes.text", txtname) == 0 ||		strcmp(".text.unlikely", txtname) == 0;} /* 32 bit and 64 bit are very similar */#include "recordmcount.h"#define RECORD_MCOUNT_64#include "recordmcount.h" /* 64-bit EM_MIPS has weird ELF64_Rela.r_info. * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40] * to imply the order of the members; the spec does not say so. *	typedef unsigned char Elf64_Byte; * fails on MIPS64 because their <elf.h> already has it! */ typedef uint8_t myElf64_Byte;		/* Type for a 8-bit quantity.  */ union mips_r_info {	Elf64_Xword r_info;	struct {		Elf64_Word r_sym;		/* Symbol index.  */		myElf64_Byte r_ssym;		/* Special symbol.  */		myElf64_Byte r_type3;		/* Third relocation.  */		myElf64_Byte r_type2;		/* Second relocation.  */		myElf64_Byte r_type;		/* First relocation.  */	} r_mips;}; static uint64_t MIPS64_r_sym(Elf64_Rel const *rp){	return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);} static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type){	rp->r_info = ((union mips_r_info){		.r_mips = { .r_sym = w(sym), .r_type = type }	}).r_info;} static voiddo_file(char const *const fname){	Elf32_Ehdr *const ehdr = mmap_file(fname);	unsigned int reltype = 0; 	w = w4nat;	w2 = w2nat;	w8 = w8nat;	switch (ehdr->e_ident[EI_DATA]) {		static unsigned int const endian = 1;	default:		fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",			ehdr->e_ident[EI_DATA], fname);		fail_file();		break;	case ELFDATA2LSB:		if (*(unsigned char const *)&endian != 1) {			/* main() is big endian, file.o is little endian. */			w = w4rev;			w2 = w2rev;			w8 = w8rev;		}		break;	case ELFDATA2MSB:		if (*(unsigned char const *)&endian != 0) {			/* main() is little endian, file.o is big endian. */			w = w4rev;			w2 = w2rev;			w8 = w8rev;		}		break;	}  /* end switch */	if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0	||  w2(ehdr->e_type) != ET_REL	||  ehdr->e_ident[EI_VERSION] != EV_CURRENT) {		fprintf(stderr, "unrecognized ET_REL file %s\n", fname);		fail_file();	} 	gpfx = 0;	switch (w2(ehdr->e_machine)) {	default:		fprintf(stderr, "unrecognized e_machine %d %s\n",			w2(ehdr->e_machine), fname);		fail_file();		break;	case EM_386:		reltype = R_386_32;		rel_type_nop = R_386_NONE;		make_nop = make_nop_x86;		ideal_nop = ideal_nop5_x86_32;		mcount_adjust_32 = -1;		break;	case EM_ARM:	 reltype = R_ARM_ABS32;			 altmcount = "__gnu_mcount_nc";			 break;	case EM_AARCH64:			reltype = R_AARCH64_ABS64;			make_nop = make_nop_arm64;			rel_type_nop = R_AARCH64_NONE;			ideal_nop = ideal_nop4_arm64;			gpfx = '_';			break;	case EM_IA_64:	 reltype = R_IA64_IMM64;   gpfx = '_'; break;	case EM_METAG:	 reltype = R_METAG_ADDR32;			 altmcount = "_mcount_wrapper";			 rel_type_nop = R_METAG_NONE;			 /* We happen to have the same requirement as MIPS */			 is_fake_mcount32 = MIPS32_is_fake_mcount;			 break;	case EM_MIPS:	 /* reltype: e_class    */ gpfx = '_'; break;	case EM_PPC:	 reltype = R_PPC_ADDR32;   gpfx = '_'; break;	case EM_PPC64:	 reltype = R_PPC64_ADDR64; gpfx = '_'; break;	case EM_S390:    /* reltype: e_class    */ gpfx = '_'; break;	case EM_SH:	 reltype = R_SH_DIR32;                 break;	case EM_SPARCV9: reltype = R_SPARC_64;     gpfx = '_'; break;	case EM_X86_64:		make_nop = make_nop_x86;		ideal_nop = ideal_nop5_x86_64;		reltype = R_X86_64_64;		rel_type_nop = R_X86_64_NONE;		mcount_adjust_64 = -1;		break;	}  /* end switch */ 	switch (ehdr->e_ident[EI_CLASS]) {	default:		fprintf(stderr, "unrecognized ELF class %d %s\n",			ehdr->e_ident[EI_CLASS], fname);		fail_file();		break;

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