summaryrefslogtreecommitdiffstats
path: root/scripts/recordmcount.c
diff options
context:
space:
mode:
Diffstat (limited to 'scripts/recordmcount.c')
-rw-r--r--scripts/recordmcount.c363
1 files changed, 363 insertions, 0 deletions
diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
new file mode 100644
index 000000000000..26e1271259ba
--- /dev/null
+++ b/scripts/recordmcount.c
@@ -0,0 +1,363 @@
+/*
+ * 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 <elf.h>
+#include <fcntl.h>
+#include <setjmp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+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 */
+
+/* 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(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_t
+ulseek(int const fd, off_t const offset, int const whence)
+{
+ off_t const w = lseek(fd, offset, whence);
+ if ((off_t)-1 == w) {
+ perror("lseek");
+ fail_file();
+ }
+ return w;
+}
+
+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;
+}
+
+static size_t
+uwrite(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 (0 == addr) {
+ fprintf(stderr, "malloc failed: %zu bytes\n", size);
+ fail_file();
+ }
+ return addr;
+}
+
+/*
+ * 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 (0 > fd_map || 0 > fstat(fd_map, &sb)) {
+ 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 (MAP_FAILED == addr) {
+ 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 int
+is_mcounted_section_name(char const *const txtname)
+{
+ return 0 == strcmp(".text", txtname) ||
+ 0 == strcmp(".sched.text", txtname) ||
+ 0 == strcmp(".spinlock.text", txtname) ||
+ 0 == strcmp(".irqentry.text", txtname) ||
+ 0 == strcmp(".text.unlikely", txtname);
+}
+
+/* 32 bit and 64 bit are very similar */
+#include "recordmcount.h"
+#define RECORD_MCOUNT_64
+#include "recordmcount.h"
+
+static void
+do_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 (1 != *(unsigned char const *)&endian) {
+ /* main() is big endian, file.o is little endian. */
+ w = w4rev;
+ w2 = w2rev;
+ w8 = w8rev;
+ }
+ } break;
+ case ELFDATA2MSB: {
+ if (0 != *(unsigned char const *)&endian) {
+ /* main() is little endian, file.o is big endian. */
+ w = w4rev;
+ w2 = w2rev;
+ w8 = w8rev;
+ }
+ } break;
+ } /* end switch */
+ if (0 != memcmp(ELFMAG, ehdr->e_ident, SELFMAG)
+ || ET_REL != w2(ehdr->e_type)
+ || EV_CURRENT != ehdr->e_ident[EI_VERSION]) {
+ 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; break;
+ case EM_ARM: reltype = R_ARM_ABS32; break;
+ case EM_IA_64: reltype = R_IA64_IMM64; 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: reltype = R_X86_64_64; 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 (sizeof(Elf32_Ehdr) != w2(ehdr->e_ehsize)
+ || sizeof(Elf32_Shdr) != w2(ehdr->e_shentsize)) {
+ fprintf(stderr,
+ "unrecognized ET_REL file: %s\n", fname);
+ fail_file();
+ }
+ if (EM_S390 == w2(ehdr->e_machine))
+ reltype = R_390_32;
+ do32(ehdr, fname, reltype);
+ } break;
+ case ELFCLASS64: {
+ Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
+ if (sizeof(Elf64_Ehdr) != w2(ghdr->e_ehsize)
+ || sizeof(Elf64_Shdr) != w2(ghdr->e_shentsize)) {
+ fprintf(stderr,
+ "unrecognized ET_REL file: %s\n", fname);
+ fail_file();
+ }
+ if (EM_S390 == w2(ghdr->e_machine))
+ reltype = R_390_64;
+ do64(ghdr, fname, reltype);
+ } break;
+ } /* end switch */
+
+ cleanup();
+}
+
+int
+main(int argc, char const *argv[])
+{
+ const char ftrace[] = "kernel/trace/ftrace.o";
+ int ftrace_size = sizeof(ftrace) - 1;
+ int n_error = 0; /* gcc-4.3.0 false positive complaint */
+
+ if (argc <= 1) {
+ fprintf(stderr, "usage: recordmcount file.o...\n");
+ return 0;
+ }
+
+ /* Process each file in turn, allowing deep failure. */
+ for (--argc, ++argv; 0 < argc; --argc, ++argv) {
+ 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(argv[0]);
+ if (len >= ftrace_size &&
+ strcmp(argv[0] + (len - ftrace_size), ftrace) == 0)
+ continue;
+
+ switch (sjval) {
+ default: {
+ fprintf(stderr, "internal error: %s\n", argv[0]);
+ exit(1);
+ } break;
+ case SJ_SETJMP: { /* normal sequence */
+ /* Avoid problems if early cleanup() */
+ fd_map = -1;
+ ehdr_curr = NULL;
+ mmap_failed = 1;
+ do_file(argv[0]);
+ } 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;
+}
+
+
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-09 16:32:00 +0000