cregit-Linux how code gets into the kernel

Release 4.15 scripts/recordmcount.c

Directory: scripts
/*
 * 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 void cleanup(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; }

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John Reiser2959.18%150.00%
Steven Rostedt2040.82%150.00%
Total49100.00%2100.00%

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_t ulseek(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; }

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Steven Rostedt4960.49%150.00%
John Reiser3239.51%150.00%
Total81100.00%2100.00%


static size_t uread(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; }

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John Reiser51100.00%1100.00%
Total51100.00%1100.00%


static size_t uwrite(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; }

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Steven Rostedt11974.84%150.00%
John Reiser4025.16%150.00%
Total159100.00%2100.00%


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; }

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John Reiser4195.35%150.00%
Steven Rostedt24.65%150.00%
Total43100.00%2100.00%

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; }

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Steven Rostedt84100.00%1100.00%
Total84100.00%1100.00%

static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */ static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */ static unsigned char *ideal_nop4_arm; static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */ static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */ static unsigned char *bl_mcount_arm; static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */ static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */ static unsigned char *push_arm; static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */ static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */ static unsigned char *ideal_nop2_thumb; static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */ static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */ static unsigned char *push_bl_mcount_thumb;
static int make_nop_arm(void *map, size_t const offset) { char *ptr; int cnt = 1; int nop_size; size_t off = offset; ptr = map + offset; if (memcmp(ptr, bl_mcount_arm, 4) == 0) { if (memcmp(ptr - 4, push_arm, 4) == 0) { off -= 4; cnt = 2; } ideal_nop = ideal_nop4_arm; nop_size = 4; } else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) { cnt = 3; nop_size = 2; off -= 2; ideal_nop = ideal_nop2_thumb; } else return -1; /* Convert to nop */ ulseek(fd_map, off, SEEK_SET); do { uwrite(fd_map, ideal_nop, nop_size); } while (--cnt > 0); return 0; }

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Stephen Boyd157100.00%1100.00%
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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; }

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Li Bin58100.00%1100.00%
Total58100.00%1100.00%

/* * 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; }

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John Reiser11680.56%125.00%
Steven Rostedt2315.97%250.00%
Russell King53.47%125.00%
Total144100.00%4100.00%


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(); } }

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Steven Rostedt11670.73%133.33%
Russell King4728.66%133.33%
John Reiser10.61%133.33%
Total164100.00%3100.00%

/* 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)); }

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John Reiser187100.00%1100.00%
Total187100.00%1100.00%


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)); }

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John Reiser99100.00%1100.00%
Total99100.00%1100.00%


static uint32_t w2rev(uint16_t const x) { return ((0xff & (x >> (0 * 8))) << (1 * 8)) | ((0xff & (x >> (1 * 8))) << (0 * 8)); }

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John Reiser55100.00%1100.00%
Total55100.00%1100.00%


static uint64_t w8nat(uint64_t const x) { return x; }

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John Reiser13100.00%1100.00%
Total13100.00%1100.00%


static uint32_t w4nat(uint32_t const x) { return x; }

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John Reiser13100.00%1100.00%
Total13100.00%1100.00%


static uint32_t w2nat(uint16_t const x) { return x; }

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John Reiser13100.00%1100.00%
Total13100.00%1100.00%

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 int is_mcounted_section_name(char const *const txtname) { return strcmp(".text", txtname) == 0 || strcmp(".init.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(".cpuidle.text", txtname) == 0 || strcmp(".text.unlikely", txtname) == 0; }

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John Reiser4846.60%114.29%
Steven Rostedt3735.92%457.14%
Chris Metcalf98.74%114.29%
Dmitriy Vyukov98.74%114.29%
Total103100.00%7100.00%

/* 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); }

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John Reiser34100.00%1100.00%
Total34100.00%1100.00%


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; }

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John Reiser49100.00%1100.00%
Total49100.00%1100.00%


static void do_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; } ideal_nop4_arm = ideal_nop4_arm_le; bl_mcount_arm = bl_mcount_arm_le; push_arm = push_arm_le; ideal_nop2_thumb = ideal_nop2_thumb_le; push_bl_mcount_thumb = push_bl_mcount_thumb_le; break; case ELFDATA2MSB: if (*(unsigned char const *)&endian != 0) { /* main() is little endian, file.o is big endian. */ w = w4rev; w2 = w2rev; w8 = w8rev; } ideal_nop4_arm = ideal_nop4_arm_be; bl_mcount_arm = bl_mcount_arm_be; push_arm = push_arm_be; ideal_nop2_thumb = ideal_nop2_thumb_be; push_bl_mcount_thumb = push_bl_mcount_thumb_be; 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"; make_nop = make_nop_arm; rel_type_nop = R_ARM_NONE; 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; 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: {