/* * 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> #ifndef EM_METAG/* Remove this when these make it to the standard system elf.h. */#define EM_METAG      174#define R_METAG_ADDR32                   2#define R_METAG_NONE                     3#endif #ifndef EM_AARCH64#define EM_AARCH64	183#define R_AARCH64_ABS64	257#endif static int fd_map;	/* File descriptor for file being modified. */static int mmap_failed; /* Boolean flag. */static void *ehdr_curr; /* current ElfXX_Ehdr *  for resource cleanup */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 */ /* 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(ehdr_curr, sb.st_size);	else		free(ehdr_curr);	close(fd_map);} 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){	off_t const w = lseek(fd, offset, whence);	if (w == (off_t)-1) {		perror("lseek");		fail_file();	}	return w;} 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 const n = write(fd, buf, count);	if (n != count) {		perror("write");		fail_file();	}	return n;} 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;} /* * 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){	void *addr; 	fd_map = open(fname, O_RDWR);	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();	}	addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,		    fd_map, 0);	mmap_failed = 0;	if (addr == MAP_FAILED) {		mmap_failed = 1;		addr = umalloc(sb.st_size);		uread(fd_map, addr, sb.st_size);	}	return addr;} /* 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(".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; 	ehdr_curr = ehdr;	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;		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; 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;		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;	case ELFCLASS32:		if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)		||  w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {			fprintf(stderr,				"unrecognized ET_REL file: %s\n", fname);			fail_file();		}		if (w2(ehdr->e_machine) == EM_MIPS) {			reltype = R_MIPS_32;			is_fake_mcount32 = MIPS32_is_fake_mcount;		}		do32(ehdr, fname, reltype);		break;	case ELFCLASS64: {		Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;		if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)		||  w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {			fprintf(stderr,				"unrecognized ET_REL file: %s\n", fname);			fail_file();		}		if (w2(ghdr->e_machine) == EM_S390) {			reltype = R_390_64;			mcount_adjust_64 = -14;		}		if (w2(ghdr->e_machine) == EM_MIPS) {			reltype = R_MIPS_64;			Elf64_r_sym = MIPS64_r_sym;			Elf64_r_info = MIPS64_r_info;			is_fake_mcount64 = MIPS64_is_fake_mcount;		}		do64(ghdr, fname, reltype);		break;	}	}  /* end switch */ 	cleanup();} intmain(int argc, char *argv[]){	const char ftrace[] = "/ftrace.o";	int ftrace_size = sizeof(ftrace) - 1;	int n_error = 0;  /* gcc-4.3.0 false positive complaint */	int c;	int i; 	while ((c = getopt(argc, argv, "w")) >= 0) {		switch (c) {		case 'w':			warn_on_notrace_sect = 1;			break;		default:			fprintf(stderr, "usage: recordmcount [-w] file.o...\n");			return 0;		}	} 	if ((argc - optind) < 1) {		fprintf(stderr, "usage: recordmcount [-w] file.o...\n");		return 0;	} 	/* Process each file in turn, allowing deep failure. */	for (i = optind; i < argc; i++) {		char *file = argv[i];		int const sjval = setjmp(jmpenv);		int len; 		/*		 * The file kernel/trace/ftrace.o references the mcount		 * function but does not call it. Since ftrace.o should		 * not be traced anyway, we just skip it.		 */		len = strlen(file);		if (len >= ftrace_size &&		    strcmp(file + (len - ftrace_size), ftrace) == 0)			continue; 		switch (sjval) {		default:			fprintf(stderr, "internal error: %s\n", file);			exit(1);			break;		case SJ_SETJMP:    /* normal sequence */			/* Avoid problems if early cleanup() */			fd_map = -1;			ehdr_curr = NULL;			mmap_failed = 1;			do_file(file);			break;		case SJ_FAIL:    /* error in do_file or below */			++n_error;			break;		case SJ_SUCCEED:    /* premature success */			/* do nothing */			break;		}  /* end switch */	}	return !!n_error;}