1 files changed, 363 insertions, 0 deletions

diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
new file mode 100644
index 00000000000..26e1271259b
--- /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;
+}
+
+