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add teardown/free functions for kpatch_elf data structures

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Because create-diff-object is a one-shot program (not a long lived
process) we haven't really bothered with cleaning up and freeing any
allocated memory.  However, freeing data when it passes out of the
logical scope does have debugging benefits.

This commit adds two new functions for tearing down and freeing the
primary struct kpatch_elf data structures.  The idea is the if a stale
pointer still references the old data structure that has passed out of
the logical scope, an issue will be more immediately apparent (i.e. NULL
references).

Signed-off-by: Seth Jennings <sjenning@redhat.com>
This commit is contained in:
Seth Jennings 2014-05-20 09:54:02 -05:00
parent b6e77846e8
commit b95f0f53af
1 changed files with 60 additions and 1 deletions
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61
kpatch-build/create-diff-object.c
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@ -44,6 +44,7 @@
#include <gelf.h>
#include <argp.h>
#include <libgen.h>
#include <unistd.h>
#include "list.h"
#include "lookup.h"
@ -136,7 +137,7 @@ struct kpatch_elf {
Elf *elf;
struct list_head sections;
struct list_head symbols;
int sections_nr;
int fd, sections_nr;
};
/*******************
@ -426,6 +427,7 @@ struct kpatch_elf *kpatch_elf_open(const char *name)
/* read and store section, symbol entries from file */
kelf->elf = elf;
kelf->fd = fd;
kpatch_create_section_list(kelf);
kpatch_create_symbol_list(kelf);
@ -1732,6 +1734,48 @@ static error_t parse_opt (int key, char *arg, struct argp_state *state)
static struct argp argp = { options, parse_opt, args_doc, 0 };
/*
* While this is a one-shot program without a lot of proper cleanup in case
* of an error, this function serves a debugging purpose: to break down and
* zero data structures we shouldn't be accessing anymore. This should
* help cause an immediate and obvious issue when a logic error leads to
* accessing data that is not intended to be accessed past a particular point.
*/
void kpatch_elf_teardown(struct kpatch_elf *kelf)
{
struct section *sec, *safesec;
struct symbol *sym, *safesym;
struct rela *rela, *saferela;
list_for_each_entry_safe(sec, safesec, &kelf->sections, list) {
if (is_rela_section(sec)) {
list_for_each_entry_safe(rela, saferela, &sec->relas, list) {
memset(rela, 0, sizeof(*rela));
free(rela);
}
memset(sec, 0, sizeof(*sec));
free(sec);
}
}
list_for_each_entry_safe(sym, safesym, &kelf->symbols, list) {
memset(sym, 0, sizeof(*sym));
free(sym);
}
INIT_LIST_HEAD(&kelf->sections);
INIT_LIST_HEAD(&kelf->symbols);
kelf->sections_nr = 0;
}
void kpatch_elf_free(struct kpatch_elf *kelf)
{
elf_end(kelf->elf);
close(kelf->fd);
memset(kelf, 0, sizeof(*kelf));
free(kelf);
}
int main(int argc, char *argv[])
{
struct kpatch_elf *kelf_base, *kelf_patched, *kelf_out;
@ -1769,6 +1813,8 @@ int main(int argc, char *argv[])
* section, symbol, and rela lists of kelf_patched.
*/
kpatch_compare_correlated_elements(kelf_patched);
kpatch_elf_teardown(kelf_base);
kpatch_elf_free(kelf_base);
/*
* Mangle the relas a little. The compiler will sometimes
@ -1799,6 +1845,15 @@ int main(int argc, char *argv[])
/* this is destructive to kelf_patched */
kpatch_generate_output(kelf_patched, &kelf_out);
/*
* Teardown kelf_patched since we shouldn't access sections or symbols
* through it anymore. Don't free however, since our section and symbol
* name fields still point to strings in the Elf object owned by
* kpatch_patched.
*/
kpatch_elf_teardown(kelf_patched);
kpatch_update_rela_section_headers(kelf_out);
list_for_each_entry(sym, &kelf_out->symbols, list) {
@ -1826,5 +1881,9 @@ int main(int argc, char *argv[])
kpatch_write_output_elf(kelf_out, kelf_patched->elf, outfile);
kpatch_elf_free(kelf_patched);
kpatch_elf_teardown(kelf_out);
kpatch_elf_free(kelf_out);
return 0;
}