[PATCH 09/33] Adding notes infrastructure

Janani Venkataraman
2014-03-20T09:40:40Z

Creating Elf_note structure and adding the required functions to add the notes.

Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
Signed-off-by: Janani Venkataraman <jananive@linux.vnet.ibm.com>
---
src/coredump.c | 15 ++++++++++++
src/coredump.h | 13 ++++++++++
src/elf.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
src/elf32.c | 1 +
src/elf64.c | 1 +
5 files changed, 103 insertions(+)

diff --git a/src/coredump.c b/src/coredump.c
index de0a7ce..0fd6343e 100644
--- a/src/coredump.c
+++ b/src/coredump.c
@@ -166,6 +166,18 @@ int release_threads(void)
return ret;
}

+/* Free Notes */
+void free_notes(struct mem_note *head)
+{
+ struct mem_note *tmp;
+
+ while (head) {
+ tmp = head->next;
+ free(head);
+ head = tmp;
+ }
+}
+
/* Performs the core dump */
int do_coredump(int pid, char *core_file)
{
@@ -216,6 +228,9 @@ cleanup:
if (cp.elf_hdr)
free(cp.elf_hdr);

+ if (cp.notes)
+ free_notes(cp.notes);
+
errno = status;

return ret;
diff --git a/src/coredump.h b/src/coredump.h
index 4e508c1..9b19f19 100644
--- a/src/coredump.h
+++ b/src/coredump.h
@@ -25,6 +25,18 @@ struct maps {
char fname[0];
};

+/*
+ * Structure for Notes
+ * We follow this linked list data-type as we dont know the number of notes
+ * as that depends on the architecture. Also the notebuf contains the final
+ * in-file format for the note data.
+ */
+struct mem_note {
+ unsigned char *notebuf; /* Notes - type, name_sz, datasz, name and data */
+ unsigned int size; /* Size of Note */
+ struct mem_note *next;
+};
+
/* Structure for the Core of the Process */
struct core_proc {
int thread_count; /* Number of threads */
@@ -33,4 +45,5 @@ struct core_proc {
int phdrs_count; /* Number of Program headers */
int elf_class; /* Elf class of the process */
void *elf_hdr; /* Stores the ELF_header */
+ struct mem_note *notes; /* Head of Notes */
};
diff --git a/src/elf.c b/src/elf.c
index 9f65c77..dfcb1d7 100644
--- a/src/elf.c
+++ b/src/elf.c
@@ -30,6 +30,79 @@
#include <linux/elf.h>
#include "coredump.h"

+#define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y))
+
+/* Appending the note to the list */
+static void append_note(struct mem_note *new_note, struct core_proc *cp)
+{
+ struct mem_note *tmp;
+
+ if (cp->notes == NULL)
+ cp->notes = new_note;
+ else {
+ tmp = cp->notes;
+ while (tmp->next != NULL)
+ tmp = tmp->next;
+ tmp->next = new_note;
+ }
+}
+
+/* Adding a new note */
+static int add_note(const char *name, int type, unsigned int data_sz, void *data,
+ struct core_proc *cp)
+{
+ unsigned char *ptr, *notebuf;
+ unsigned int namelen, size, data_offset;
+ Elf_Nhdr *note;
+ struct mem_note *tmp = malloc(sizeof(struct mem_note));
+ if (!tmp) {
+ status = errno;
+ gencore_log("Failure in adding note.\n");
+ return -1;
+ }
+
+ /* Calculate the size of the Notes */
+ namelen = strlen(name) + 1;
+ size = sizeof(Elf_Nhdr);
+ size += namelen;
+
+ /* Note down the offset where data is to be stored */
+ data_offset = size = roundup(size, 4);
+ size += data_sz;
+ size = roundup(size, 4);
+
+ /* Allocate the required size, initialized to 0 */
+ notebuf = calloc(1, size);
+ if (!notebuf) {
+ status = errno;
+ gencore_log("Could not allocate memory for Notes buffer.\n");
+ return -1;
+ }
+
+ note = (Elf_Nhdr *)notebuf;
+
+ /* Where name should be stored */
+ ptr = (unsigned char *) (note + 1);
+
+ note->n_type = type;
+ note->n_namesz = strlen(name) + 1;
+ note->n_descsz = data_sz;
+
+ /* Store name */
+ memcpy(ptr, name, namelen);
+
+ /* Store data */
+ memcpy(notebuf + data_offset, data, data_sz);
+
+ tmp->notebuf = notebuf;
+ tmp->size = size;
+ tmp->next = NULL;
+
+ append_note(tmp, cp);
+
+ return 0;
+}
+
/* Fetchs ELF header of the executable */
static int get_elf_hdr_exe_file(int pid, Elf_Ehdr *elf)
{
diff --git a/src/elf32.c b/src/elf32.c
index 1a95ff2..01b3923 100644
--- a/src/elf32.c
+++ b/src/elf32.c
@@ -33,5 +33,6 @@
#define Elf_Ehdr Elf32_Ehdr
#define Elf_Phdr Elf32_Phdr
#define Elf_Shdr Elf32_Shdr
+#define Elf_Nhdr Elf32_Nhdr

#include "elf.c"
diff --git a/src/elf64.c b/src/elf64.c
index 953b826..a99a73b 100644
--- a/src/elf64.c
+++ b/src/elf64.c
@@ -33,5 +33,6 @@
#define Elf_Ehdr Elf64_Ehdr
#define Elf_Phdr Elf64_Phdr
#define Elf_Shdr Elf64_Shdr
+#define Elf_Nhdr Elf64_Nhdr

#include "elf.c"