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recordmcount: Clarify what cleanup() does

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cleanup() mostly frees/unmaps the malloc'd/privately-mapped
copy of the ELF file recordmcount is working on, which is
set up in mmap_file(). It also deals with positioning within
the pseduo prive-mapping of the file and appending to the ELF
file.

Split into two steps:
	mmap_cleanup() for the mapping itself
	file_append_cleanup() for allocations storing the
		appended ELF data.

Also, move the global variable initializations out of the main,
per-object-file loop and nearer to the alloc/init (mmap_file())
and two cleanup functions so we can more clearly see how they're
related.

Link: http://lkml.kernel.org/r/2a387ac86d133d22c68f57b9933c32bab1d09a2d.1564596289.git.mhelsley@vmware.com

Signed-off-by: Matt Helsley <mhelsley@vmware.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Matt Helsley 2019-07-31 11:24:16 -07:00 committed by Steven Rostedt (VMware)
parent c97fea2625
commit 4fbcf07416
1 changed files with 81 additions and 70 deletions
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151
scripts/recordmcount.c
View File

@ -48,21 +48,26 @@ 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 */
/* Per-file resource cleanup when multiple files. */
static void cleanup(void)
static void file_append_cleanup(void)
{
free(file_append);
file_append = NULL;
file_append_size = 0;
file_updated = 0;
}
static void mmap_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;
}
/* ulseek, uwrite, ...: Check return value for errors. */
@ -103,7 +108,8 @@ static ssize_t uwrite(void const *const buf, size_t const count)
}
if (!file_append) {
perror("write");
cleanup();
file_append_cleanup();
mmap_cleanup();
return -1;
}
if (file_ptr < file_end) {
@ -129,12 +135,76 @@ static void * umalloc(size_t size)
void *const addr = malloc(size);
if (addr == 0) {
fprintf(stderr, "malloc failed: %zu bytes\n", size);
cleanup();
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;
@ -238,61 +308,6 @@ static int make_nop_arm64(void *map, size_t const offset)
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)
{
file_map = NULL;
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);
mmap_failed = 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;
}
}
out:
close(fd_map);
file_end = file_map + sb.st_size;
return file_map;
}
static int write_file(const char *fname)
{
char tmp_file[strlen(fname) + 4];
@ -438,10 +453,11 @@ static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
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;
@ -577,7 +593,8 @@ static int do_file(char const *const fname)
rc = write_file(fname);
out:
cleanup();
file_append_cleanup();
mmap_cleanup();
return rc;
}
@ -620,12 +637,6 @@ int main(int argc, char *argv[])
strcmp(file + (len - ftrace_size), ftrace) == 0)
continue;
/* Avoid problems if early cleanup() */
fd_map = -1;
mmap_failed = 1;
file_map = NULL;
file_ptr = NULL;
file_updated = 0;
if (do_file(file)) {
fprintf(stderr, "%s: failed\n", file);
++n_error;