Merge tag 'trace-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:

 - Addition of multiprobes to kprobe and uprobe events (allows for more
   than one probe attached to the same location)

 - Addition of adding immediates to probe parameters

 - Clean up of the recordmcount.c code. This brings us closer to merging
   recordmcount into objtool, and reuse code.

 - Other small clean ups

* tag 'trace-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (33 commits)
  selftests/ftrace: Update kprobe event error testcase
  tracing/probe: Reject exactly same probe event
  tracing/probe: Fix to allow user to enable events on unloaded modules
  selftests/ftrace: Select an existing function in kprobe_eventname test
  tracing/kprobe: Fix NULL pointer access in trace_porbe_unlink()
  tracing: Make sure variable reference alias has correct var_ref_idx
  tracing: Be more clever when dumping hex in __print_hex()
  ftrace: Simplify ftrace hash lookup code in clear_func_from_hash()
  tracing: Add "gfp_t" support in synthetic_events
  tracing: Rename tracing_reset() to tracing_reset_cpu()
  tracing: Document the stack trace algorithm in the comments
  tracing/arm64: Have max stack tracer handle the case of return address after data
  recordmcount: Clarify what cleanup() does
  recordmcount: Remove redundant cleanup() calls
  recordmcount: Kernel style formatting
  recordmcount: Kernel style function signature formatting
  recordmcount: Rewrite error/success handling
  selftests/ftrace: Add syntax error test for multiprobe
  selftests/ftrace: Add syntax error test for immediates
  selftests/ftrace: Add a testcase for kprobe multiprobe event
  ...

2 files changed, 259 insertions, 212 deletions

diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
index 8387a9bc064a..612268eabef4 100644
--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -27,7 +27,6 @@
 #include <getopt.h>
 #include <elf.h>
 #include <fcntl.h>
-#include <setjmp.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -43,56 +42,37 @@ 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)
+static void file_append_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;
 }
 
-static void __attribute__((noreturn))
-fail_file(void)
+static void mmap_cleanup(void)
 {
-	cleanup();
-	longjmp(jmpenv, SJ_FAIL);
-}
-
-static void __attribute__((noreturn))
-succeed_file(void)
-{
-	cleanup();
-	longjmp(jmpenv, SJ_SUCCEED);
+	if (!mmap_failed)
+		munmap(file_map, sb.st_size);
+	else
+		free(file_map);
+	file_map = NULL;
 }
 
-/* ulseek, uread, ...:  Check return value for errors. */
+/* ulseek, uwrite, ...:  Check return value for errors. */
 
-static off_t
-ulseek(int const fd, off_t const offset, int const whence)
+static off_t ulseek(off_t const offset, int const whence)
 {
 	switch (whence) {
 	case SEEK_SET:
@@ -107,24 +87,12 @@ ulseek(int const fd, off_t const offset, int const whence)
 	}
 	if (file_ptr < file_map) {
 		fprintf(stderr, "lseek: seek before file\n");
-		fail_file();
+		return -1;
 	}
 	return file_ptr - file_map;
 }
 
-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)
+static ssize_t uwrite(void const *const buf, size_t const count)
 {
 	size_t cnt = count;
 	off_t idx = 0;
@@ -140,7 +108,9 @@ uwrite(int const fd, void const *const buf, size_t const count)
 		}
 		if (!file_append) {
 			perror("write");
-			fail_file();
+			file_append_cleanup();
+			mmap_cleanup();
+			return -1;
 		}
 		if (file_ptr < file_end) {
 			cnt = file_end - file_ptr;
@@ -160,17 +130,81 @@ uwrite(int const fd, void const *const buf, size_t const count)
 	return count;
 }
 
-static void *
-umalloc(size_t size)
+static void * umalloc(size_t size)
 {
 	void *const addr = malloc(size);
 	if (addr == 0) {
 		fprintf(stderr, "malloc failed: %zu bytes\n", size);
-		fail_file();
+		file_append_cleanup();
+		mmap_cleanup();
+		return NULL;
 	}
 	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)
+{
+	/* Avoid problems if early cleanup() */
+	fd_map = -1;
+	mmap_failed = 1;
+	file_map = NULL;
+	file_ptr = NULL;
+	file_updated = 0;
+	sb.st_size = 0;
+
+	fd_map = open(fname, O_RDONLY);
+	if (fd_map < 0) {
+		perror(fname);
+		return NULL;
+	}
+	if (fstat(fd_map, &sb) < 0) {
+		perror(fname);
+		goto out;
+	}
+	if (!S_ISREG(sb.st_mode)) {
+		fprintf(stderr, "not a regular file: %s\n", fname);
+		goto out;
+	}
+	file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
+			fd_map, 0);
+	if (file_map == MAP_FAILED) {
+		mmap_failed = 1;
+		file_map = umalloc(sb.st_size);
+		if (!file_map) {
+			perror(fname);
+			goto out;
+		}
+		if (read(fd_map, file_map, sb.st_size) != sb.st_size) {
+			perror(fname);
+			free(file_map);
+			file_map = NULL;
+			goto out;
+		}
+	} else
+		mmap_failed = 0;
+out:
+	close(fd_map);
+	fd_map = -1;
+
+	file_end = file_map + sb.st_size;
+
+	return file_map;
+}
+
+
 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;
@@ -194,8 +228,10 @@ static int make_nop_x86(void *map, size_t const offset)
 		return -1;
 
 	/* convert to nop */
-	ulseek(fd_map, offset - 1, SEEK_SET);
-	uwrite(fd_map, ideal_nop, 5);
+	if (ulseek(offset - 1, SEEK_SET) < 0)
+		return -1;
+	if (uwrite(ideal_nop, 5) < 0)
+		return -1;
 	return 0;
 }
 
@@ -243,10 +279,12 @@ static int make_nop_arm(void *map, size_t const offset)
 		return -1;
 
 	/* Convert to nop */
-	ulseek(fd_map, off, SEEK_SET);
+	if (ulseek(off, SEEK_SET) < 0)
+		return -1;
 
 	do {
-		uwrite(fd_map, ideal_nop, nop_size);
+		if (uwrite(ideal_nop, nop_size) < 0)
+			return -1;
 	} while (--cnt > 0);
 
 	return 0;
@@ -263,57 +301,20 @@ static int make_nop_arm64(void *map, size_t const offset)
 		return -1;
 
 	/* Convert to nop */
-	ulseek(fd_map, offset, SEEK_SET);
-	uwrite(fd_map, ideal_nop, 4);
+	if (ulseek(offset, SEEK_SET) < 0)
+		return -1;
+	if (uwrite(ideal_nop, 4) < 0)
+		return -1;
 	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)
+static int write_file(const char *fname)
 {
 	char tmp_file[strlen(fname) + 4];
 	size_t n;
 
 	if (!file_updated)
-		return;
+		return 0;
 
 	sprintf(tmp_file, "%s.rc", fname);
 
@@ -325,25 +326,28 @@ static void write_file(const char *fname)
 	fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode);
 	if (fd_map < 0) {
 		perror(fname);
-		fail_file();
+		return -1;
 	}
 	n = write(fd_map, file_map, sb.st_size);
 	if (n != sb.st_size) {
 		perror("write");
-		fail_file();
+		close(fd_map);
+		return -1;
 	}
 	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);
+			return -1;
 		}
 	}
 	close(fd_map);
 	if (rename(tmp_file, fname) < 0) {
 		perror(fname);
-		fail_file();
+		return -1;
 	}
+	return 0;
 }
 
 /* w8rev, w8nat, ...: Handle endianness. */
@@ -394,8 +398,7 @@ 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)
+static int is_mcounted_section_name(char const *const txtname)
 {
 	return strncmp(".text",          txtname, 5) == 0 ||
 		strcmp(".init.text",     txtname) == 0 ||
@@ -405,10 +408,11 @@ is_mcounted_section_name(char const *const txtname)
 		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;
+		strcmp(".cpuidle.text", txtname) == 0;
 }
 
+static char const *already_has_rel_mcount = "success"; /* our work here is done! */
+
 /* 32 bit and 64 bit are very similar */
 #include "recordmcount.h"
 #define RECORD_MCOUNT_64
@@ -447,11 +451,15 @@ static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
 	}).r_info;
 }
 
-static void
-do_file(char const *const fname)
+static int do_file(char const *const fname)
 {
-	Elf32_Ehdr *const ehdr = mmap_file(fname);
 	unsigned int reltype = 0;
+	Elf32_Ehdr *ehdr;
+	int rc = -1;
+
+	ehdr = mmap_file(fname);
+	if (!ehdr)
+		goto out;
 
 	w = w4nat;
 	w2 = w2nat;
@@ -461,8 +469,7 @@ do_file(char const *const fname)
 	default:
 		fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
 			ehdr->e_ident[EI_DATA], fname);
-		fail_file();
-		break;
+		goto out;
 	case ELFDATA2LSB:
 		if (*(unsigned char const *)&endian != 1) {
 			/* main() is big endian, file.o is little endian. */
@@ -490,52 +497,54 @@ do_file(char const *const fname)
 		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) {
+	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();
+		goto out;
 	}
 
-	gpfx = 0;
+	gpfx = '_';
 	switch (w2(ehdr->e_machine)) {
 	default:
 		fprintf(stderr, "unrecognized e_machine %u %s\n",
 			w2(ehdr->e_machine), fname);
-		fail_file();
-		break;
+		goto out;
 	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;
+		gpfx = 0;
+		break;
+	case EM_ARM:
+		reltype = R_ARM_ABS32;
+		altmcount = "__gnu_mcount_nc";
+		make_nop = make_nop_arm;
+		rel_type_nop = R_ARM_NONE;
+		gpfx = 0;
 		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_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;
+		reltype = R_AARCH64_ABS64;
+		make_nop = make_nop_arm64;
+		rel_type_nop = R_AARCH64_NONE;
+		ideal_nop = ideal_nop4_arm64;
+		break;
+	case EM_IA_64:	reltype = R_IA64_IMM64; break;
+	case EM_MIPS:	/* reltype: e_class    */ break;
+	case EM_PPC:	reltype = R_PPC_ADDR32; break;
+	case EM_PPC64:	reltype = R_PPC64_ADDR64; break;
+	case EM_S390:	/* reltype: e_class    */ break;
+	case EM_SH:	reltype = R_SH_DIR32; gpfx = 0; break;
+	case EM_SPARCV9: reltype = R_SPARC_64; 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;
+		gpfx = 0;
 		break;
 	}  /* end switch */
 
@@ -543,20 +552,20 @@ do_file(char const *const fname)
 	default:
 		fprintf(stderr, "unrecognized ELF class %d %s\n",
 			ehdr->e_ident[EI_CLASS], fname);
-		fail_file();
-		break;
+		goto out;
 	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();
+			goto out;
 		}
 		if (w2(ehdr->e_machine) == EM_MIPS) {
 			reltype = R_MIPS_32;
 			is_fake_mcount32 = MIPS32_is_fake_mcount;
 		}
-		do32(ehdr, fname, reltype);
+		if (do32(ehdr, fname, reltype) < 0)
+			goto out;
 		break;
 	case ELFCLASS64: {
 		Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
@@ -564,7 +573,7 @@ do_file(char const *const fname)
 		||  w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
 			fprintf(stderr,
 				"unrecognized ET_REL file: %s\n", fname);
-			fail_file();
+			goto out;
 		}
 		if (w2(ghdr->e_machine) == EM_S390) {
 			reltype = R_390_64;
@@ -576,17 +585,20 @@ do_file(char const *const fname)
 			Elf64_r_info = MIPS64_r_info;
 			is_fake_mcount64 = MIPS64_is_fake_mcount;
 		}
-		do64(ghdr, fname, reltype);
+		if (do64(ghdr, fname, reltype) < 0)
+			goto out;
 		break;
 	}
 	}  /* end switch */
 
-	write_file(fname);
-	cleanup();
+	rc = write_file(fname);
+out:
+	file_append_cleanup();
+	mmap_cleanup();
+	return rc;
 }
 
-int
-main(int argc, char *argv[])
+int main(int argc, char *argv[])
 {
 	const char ftrace[] = "/ftrace.o";
 	int ftrace_size = sizeof(ftrace) - 1;
@@ -613,7 +625,6 @@ main(int argc, char *argv[])
 	/* 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;
 
 		/*
@@ -626,28 +637,10 @@ main(int argc, char *argv[])
 		    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;
-			mmap_failed = 1;
-			file_map = NULL;
-			file_ptr = NULL;
-			file_updated = 0;
-			do_file(file);
-			break;
-		case SJ_FAIL:    /* error in do_file or below */
+		if (do_file(file)) {
 			fprintf(stderr, "%s: failed\n", file);
 			++n_error;
-			break;
-		case SJ_SUCCEED:    /* premature success */
-			/* do nothing */
-			break;
-		}  /* end switch */
+		}
 	}
 	return !!n_error;
 }
diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
index 47fca2c69a73..8f0a278ce0af 100644
--- a/scripts/recordmcount.h
+++ b/scripts/recordmcount.h
@@ -174,7 +174,7 @@ static int MIPS_is_fake_mcount(Elf_Rel const *rp)
 }
 
 /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
-static void append_func(Elf_Ehdr *const ehdr,
+static int append_func(Elf_Ehdr *const ehdr,
 			Elf_Shdr *const shstr,
 			uint_t const *const mloc0,
 			uint_t const *const mlocp,
@@ -202,15 +202,20 @@ static void append_func(Elf_Ehdr *const ehdr,
 	new_e_shoff = t;
 
 	/* body for new shstrtab */
-	ulseek(fd_map, sb.st_size, SEEK_SET);
-	uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size);
-	uwrite(fd_map, mc_name, 1 + strlen(mc_name));
+	if (ulseek(sb.st_size, SEEK_SET) < 0)
+		return -1;
+	if (uwrite(old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size) < 0)
+		return -1;
+	if (uwrite(mc_name, 1 + strlen(mc_name)) < 0)
+		return -1;
 
 	/* old(modified) Elf_Shdr table, word-byte aligned */
-	ulseek(fd_map, t, SEEK_SET);
+	if (ulseek(t, SEEK_SET) < 0)
+		return -1;
 	t += sizeof(Elf_Shdr) * old_shnum;
-	uwrite(fd_map, old_shoff + (void *)ehdr,
-	       sizeof(Elf_Shdr) * old_shnum);
+	if (uwrite(old_shoff + (void *)ehdr,
+	       sizeof(Elf_Shdr) * old_shnum) < 0)
+		return -1;
 
 	/* new sections __mcount_loc and .rel__mcount_loc */
 	t += 2*sizeof(mcsec);
@@ -225,7 +230,8 @@ static void append_func(Elf_Ehdr *const ehdr,
 	mcsec.sh_info = 0;
 	mcsec.sh_addralign = _w(_size);
 	mcsec.sh_entsize = _w(_size);
-	uwrite(fd_map, &mcsec, sizeof(mcsec));
+	if (uwrite(&mcsec, sizeof(mcsec)) < 0)
+		return -1;
 
 	mcsec.sh_name = w(old_shstr_sh_size);
 	mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
@@ -239,15 +245,22 @@ static void append_func(Elf_Ehdr *const ehdr,
 	mcsec.sh_info = w(old_shnum);
 	mcsec.sh_addralign = _w(_size);
 	mcsec.sh_entsize = _w(rel_entsize);
-	uwrite(fd_map, &mcsec, sizeof(mcsec));
 
-	uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0);
-	uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0);
+	if (uwrite(&mcsec, sizeof(mcsec)) < 0)
+		return -1;
+
+	if (uwrite(mloc0, (void *)mlocp - (void *)mloc0) < 0)
+		return -1;
+	if (uwrite(mrel0, (void *)mrelp - (void *)mrel0) < 0)
+		return -1;
 
 	ehdr->e_shoff = _w(new_e_shoff);
 	ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum));  /* {.rel,}__mcount_loc */
-	ulseek(fd_map, 0, SEEK_SET);
-	uwrite(fd_map, ehdr, sizeof(*ehdr));
+	if (ulseek(0, SEEK_SET) < 0)
+		return -1;
+	if (uwrite(ehdr, sizeof(*ehdr)) < 0)
+		return -1;
+	return 0;
 }
 
 static unsigned get_mcountsym(Elf_Sym const *const sym0,
@@ -351,9 +364,9 @@ static uint_t *sift_rel_mcount(uint_t *mlocp,
  * that are not going to be traced. The mcount calls here will be converted
  * into nops.
  */
-static void nop_mcount(Elf_Shdr const *const relhdr,
-		       Elf_Ehdr const *const ehdr,
-		       const char *const txtname)
+static int nop_mcount(Elf_Shdr const *const relhdr,
+		      Elf_Ehdr const *const ehdr,
+		      const char *const txtname)
 {
 	Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
 		+ (void *)ehdr);
@@ -376,15 +389,18 @@ static void nop_mcount(Elf_Shdr const *const relhdr,
 			mcountsym = get_mcountsym(sym0, relp, str0);
 
 		if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
-			if (make_nop)
+			if (make_nop) {
 				ret = make_nop((void *)ehdr, _w(shdr->sh_offset) + _w(relp->r_offset));
+				if (ret < 0)
+					return -1;
+			}
 			if (warn_on_notrace_sect && !once) {
 				printf("Section %s has mcount callers being ignored\n",
 				       txtname);
 				once = 1;
 				/* just warn? */
 				if (!make_nop)
-					return;
+					return 0;
 			}
 		}
 
@@ -396,14 +412,16 @@ static void nop_mcount(Elf_Shdr const *const relhdr,
 			Elf_Rel rel;
 			rel = *(Elf_Rel *)relp;
 			Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop);
-			ulseek(fd_map, (void *)relp - (void *)ehdr, SEEK_SET);
-			uwrite(fd_map, &rel, sizeof(rel));
+			if (ulseek((void *)relp - (void *)ehdr, SEEK_SET) < 0)
+				return -1;
+			if (uwrite(&rel, sizeof(rel)) < 0)
+				return -1;
 		}
 		relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
 	}
+	return 0;
 }
 
-
 /*
  * Find a symbol in the given section, to be used as the base for relocating
  * the table of offsets of calls to mcount.  A local or global symbol suffices,
@@ -414,9 +432,10 @@ static void nop_mcount(Elf_Shdr const *const relhdr,
  *    Num:    Value  Size Type    Bind   Vis      Ndx Name
  *      2: 00000000     0 SECTION LOCAL  DEFAULT    1
  */
-static unsigned find_secsym_ndx(unsigned const txtndx,
+static int find_secsym_ndx(unsigned const txtndx,
 				char const *const txtname,
 				uint_t *const recvalp,
+				unsigned int *sym_index,
 				Elf_Shdr const *const symhdr,
 				Elf_Ehdr const *const ehdr)
 {
@@ -438,21 +457,20 @@ static unsigned find_secsym_ndx(unsigned const txtndx,
 				continue;
 
 			*recvalp = _w(symp->st_value);
-			return symp - sym0;
+			*sym_index = symp - sym0;
+			return 0;
 		}
 	}
 	fprintf(stderr, "Cannot find symbol for section %u: %s.\n",
 		txtndx, txtname);
-	fail_file();
+	return -1;
 }
 
-
 /* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
-static char const *
-__has_rel_mcount(Elf_Shdr const *const relhdr,  /* is SHT_REL or SHT_RELA */
-		 Elf_Shdr const *const shdr0,
-		 char const *const shstrtab,
-		 char const *const fname)
+static char const * __has_rel_mcount(Elf_Shdr const *const relhdr, /* reltype */
+				     Elf_Shdr const *const shdr0,
+				     char const *const shstrtab,
+				     char const *const fname)
 {
 	/* .sh_info depends on .sh_type == SHT_REL[,A] */
 	Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)];
@@ -461,7 +479,7 @@ __has_rel_mcount(Elf_Shdr const *const relhdr,  /* is SHT_REL or SHT_RELA */
 	if (strcmp("__mcount_loc", txtname) == 0) {
 		fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
 			fname);
-		succeed_file();
+		return already_has_rel_mcount;
 	}
 	if (w(txthdr->sh_type) != SHT_PROGBITS ||
 	    !(_w(txthdr->sh_flags) & SHF_EXECINSTR))
@@ -491,6 +509,10 @@ static unsigned tot_relsize(Elf_Shdr const *const shdr0,
 
 	for (; nhdr; --nhdr, ++shdrp) {
 		txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname);
+		if (txtname == already_has_rel_mcount) {
+			totrelsz = 0;
+			break;
+		}
 		if (txtname && is_mcounted_section_name(txtname))
 			totrelsz += _w(shdrp->sh_size);
 	}
@@ -499,8 +521,8 @@ static unsigned tot_relsize(Elf_Shdr const *const shdr0,
 
 
 /* Overall supervision for Elf32 ET_REL file. */
-static void
-do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
+static int do_func(Elf_Ehdr *const ehdr, char const *const fname,
+		   unsigned const reltype)
 {
 	Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
 		+ (void *)ehdr);
@@ -513,26 +535,54 @@ do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
 	unsigned k;
 
 	/* Upper bound on space: assume all relevant relocs are for mcount. */
-	unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
-	Elf_Rel *const mrel0 = umalloc(totrelsz);
-	Elf_Rel *      mrelp = mrel0;
+	unsigned       totrelsz;
 
-	/* 2*sizeof(address) <= sizeof(Elf_Rel) */
-	uint_t *const mloc0 = umalloc(totrelsz>>1);
-	uint_t *      mlocp = mloc0;
+	Elf_Rel *      mrel0;
+	Elf_Rel *      mrelp;
+
+	uint_t *      mloc0;
+	uint_t *      mlocp;
 
 	unsigned rel_entsize = 0;
 	unsigned symsec_sh_link = 0;
 
+	int result = 0;
+
+	totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
+	if (totrelsz == 0)
+		return 0;
+	mrel0 = umalloc(totrelsz);
+	mrelp = mrel0;
+	if (!mrel0)
+		return -1;
+
+	/* 2*sizeof(address) <= sizeof(Elf_Rel) */
+	mloc0 = umalloc(totrelsz>>1);
+	mlocp = mloc0;
+	if (!mloc0) {
+		free(mrel0);
+		return -1;
+	}
+
 	for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
 		char const *const txtname = has_rel_mcount(relhdr, shdr0,
 			shstrtab, fname);
+		if (txtname == already_has_rel_mcount) {
+			result = 0;
+			file_updated = 0;
+			goto out; /* Nothing to be done; don't append! */
+		}
 		if (txtname && is_mcounted_section_name(txtname)) {
+			unsigned int recsym;
 			uint_t recval = 0;
-			unsigned const recsym = find_secsym_ndx(
-				w(relhdr->sh_info), txtname, &recval,
-				&shdr0[symsec_sh_link = w(relhdr->sh_link)],
-				ehdr);
+
+			symsec_sh_link = w(relhdr->sh_link);
+			result = find_secsym_ndx(w(relhdr->sh_info), txtname,
+						&recval, &recsym,
+						&shdr0[symsec_sh_link],
+						ehdr);
+			if (result)
+				goto out;
 
 			rel_entsize = _w(relhdr->sh_entsize);
 			mlocp = sift_rel_mcount(mlocp,
@@ -543,13 +593,17 @@ do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
 			 * This section is ignored by ftrace, but still
 			 * has mcount calls. Convert them to nops now.
 			 */
-			nop_mcount(relhdr, ehdr, txtname);
+			if (nop_mcount(relhdr, ehdr, txtname) < 0) {
+				result = -1;
+				goto out;
+			}
 		}
 	}
-	if (mloc0 != mlocp) {
-		append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
-			    rel_entsize, symsec_sh_link);
-	}
+	if (!result && mloc0 != mlocp)
+		result = append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
+				     rel_entsize, symsec_sh_link);
+out:
 	free(mrel0);
 	free(mloc0);
+	return result;
 }