----- Original Message -----
> The kernel might have added a new elf-note of type NT_NOCOREDUMP for various
> reasons. This patch teaches crash tool to look for the same inside a vmcore
> before further analysis. If present, display the error description and exit
> early.
>
> Signed-off-by: K.Prasad <[email protected]>
At this point, I'll admit I'm not sure I totally understand
this patch or what the dumpfile header layout would look like.
Your new "myload64" pointer is not pointing to a PT_LOAD, but
rather the first PT_NOTE, so its name doesn't even make sense
in that respect. And for that matter, I don't see why you
didn't just use the currently existing nd->notes64 pointer,
which points to the same place? Also, the re-definition of the
currently-existing "size" value scares the hell out of me
w/respect to backwards-compatibility. And lastly, if I'm not
mistaken, when you do the realloc() of tmp_elf_header, it may
return a different address -- so wouldn't nd->elf_header be
left pointing to the old buffer? And by extension, stale pointer
values could be left in nd->elf64, nd->num_pt_load_segments,
nd->notes64, nd->load64, etc?
I would rather that you is_netdump() is left intact -- except for
a call to a new "check_nocoredump()" function, one which does not
tinker with the is_netdump() pointers, sizes, buffers, etc...
Let that function do its own thing, and if it finds that there's
no coredump, then it's not going to return and we're done. But
in 99.99% of the time, there will be a coredump, and your function
will not have screwed around with any of is_netdump()'s bookkeeping.
Anyway, when the feature is accepted upstream in the kernel,
and then by makedumpfile, we'll revisit this.
Thanks,
Dave
> ---
> netdump.c | 136
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
> 1 files changed, 131 insertions(+), 5 deletions(-)
>
> diff --git a/netdump.c b/netdump.c
> index 1e9960c..3b4edec 100644
> --- a/netdump.c
> +++ b/netdump.c
> @@ -95,6 +95,74 @@ map_cpus_to_prstatus(void)
> }
>
> /*
> + * Temporary definition of new elf-note type for compilation
> purposes.
> + * Not required when run on a new kernel containing this definition.
> + */
> +#define NT_NOCOREDUMP 21
> +
> +/*
> + * Function to verify if the vmcore contains and elf-note of type
> NT_NOCOREDUMP.
> + * The kernel adds such an elf-note when it is known that the crash
> is
> + * triggered due to a reason that does not need analysis of the
> entire kernel
> + * memory dump (e.g. crash triggered due to a faulty memory DIMM).
> + */
> +static void
> +has_nt_nocoredump(void *note_ptr, unsigned long size_note)
> +{
> + Elf32_Nhdr *note32 = NULL;
> + Elf64_Nhdr *note64 = NULL;
> + size_t tot, len = 0;
> + int num = 0;
> +
> + for (tot = 0; tot < size_note; tot += len) {
> + if (machine_type("X86_64")) {
> + note64 = note_ptr + tot;
> + /*
> + * If vmcore is generated due to fatal hardware
> + * errors (such as Machine Check Exception, we only have
> + * a 'slim' crashdump. Don't analyse further, inform the
> + * user about it and exit.
> + */
> + if (note64->n_type == NT_NOCOREDUMP) {
> + fprintf(fp, "\"System crashed due to a hardware"
> + " memory error. No coredump"
> + " available.\"\n");
> +
> + /* Do we have an accompanying error message? */
> + if (note64->n_descsz == 0)
> + goto exit;
> + fprintf(fp,"Nocoredump Reason: %s",
> + (char *)note64 + sizeof(Elf64_Nhdr));
> + }
> +
> + len = sizeof(Elf64_Nhdr);
> + len = roundup(len + note64->n_namesz, 4);
> + len = roundup(len + note64->n_descsz, 4);
> + } else if (machine_type("X86")) {
> + note32 = note_ptr + tot;
> + if (note32->n_type == NT_NOCOREDUMP) {
> + fprintf(fp, "\"System crashed due to a hardware"
> + " memory error. No coredump"
> + " available.\"\n");
> +
> + /* Do we have an accompanying error message? */
> + if (note32->n_descsz == 0)
> + goto exit;
> +
> + fprintf(fp,"Nocoredump Reason: %s",
> + (char *)note32 + sizeof(Elf32_Nhdr));
> +exit:
> + clean_exit(0);
> + }
> +
> + len = sizeof(Elf32_Nhdr);
> + len = roundup(len + note32->n_namesz, 4);
> + len = roundup(len + note32->n_descsz, 4);
> + }
> + }
> +}
> +
> +/*
> * Determine whether a file is a netdump/diskdump/kdump creation,
> * and if TRUE, initialize the vmcore_data structure.
> */
> @@ -103,12 +171,12 @@ is_netdump(char *file, ulong source_query)
> {
> int i, fd, swap;
> Elf32_Ehdr *elf32;
> - Elf32_Phdr *load32;
> + Elf32_Phdr *load32, *myload32;
> Elf64_Ehdr *elf64;
> - Elf64_Phdr *load64;
> + Elf64_Phdr *load64, *myload64;
> char eheader[MIN_NETDUMP_ELF_HEADER_SIZE];
> char buf[BUFSIZE];
> - size_t size, len, tot;
> + size_t size, mysize, len, tot;
> Elf32_Off offset32;
> Elf64_Off offset64;
> ulong tmp_flags;
> @@ -195,7 +263,10 @@ is_netdump(char *file, ulong source_query)
>
> load32 = (Elf32_Phdr *)
> &eheader[sizeof(Elf32_Ehdr)+sizeof(Elf32_Phdr)];
> - size = (size_t)load32->p_offset;
> + myload32 = (Elf32_Phdr *)
> + &eheader[sizeof(Elf32_Ehdr)];
> +
> + size = (size_t)myload32->p_offset;
>
> if ((load32->p_offset & (MIN_PAGE_SIZE-1)) &&
> (load32->p_align == 0))
> @@ -249,7 +320,10 @@ is_netdump(char *file, ulong source_query)
>
> load64 = (Elf64_Phdr *)
> &eheader[sizeof(Elf64_Ehdr)+sizeof(Elf64_Phdr)];
> - size = (size_t)load64->p_offset;
> + myload64 = (Elf64_Phdr *)
> + &eheader[sizeof(Elf64_Ehdr)];
> +
> + size = (size_t)myload64->p_offset;
> if ((load64->p_offset & (MIN_PAGE_SIZE-1)) &&
> (load64->p_align == 0))
> tmp_flags |= KDUMP_ELF64;
> @@ -362,6 +436,58 @@ is_netdump(char *file, ulong source_query)
> &nd->elf_header[sizeof(Elf64_Ehdr)];
> nd->load64 = (Elf64_Phdr *)
> &nd->elf_header[sizeof(Elf64_Ehdr)+sizeof(Elf64_Phdr)];
> + /*
> + * Find out if there exists an elf-note of type NT_NOCOREDUMP.
> + * If so, exit early from crash analysis after displaying the
> + * description string.
> + *
> + * Allocate a temporary buffer to store the PT_NOTE section and
> + * loop through them to look for NT_NOCOREDUMP.
> + */
> + for (i = 0; i < elf64->e_phnum; i++, myload64++) {
> + mysize += myload64->p_memsz;
> + if (myload64->p_type == PT_NOTE) {
> + break;
> + }
> + }
> +
> + if (mysize == 0) {
> + fprintf(stderr, "No PT_NOTE section found\n");
> + clean_exit(1);
> + }
> +
> + /*
> + * Size of the buffer should accommodate the Elf_Ehdr, Elf_Phdr
> + * and all sections upto the first PT_NOTE.
> + */
> + mysize += size;
> + tmp_elf_header = realloc(tmp_elf_header, mysize);
> + if (tmp_elf_header == NULL) {
> + fprintf(stderr, "cannot malloc notes buffer\n");
> + clean_exit(1);
> + }
> + if (FLAT_FORMAT()) {
> + if (!read_flattened_format(fd, 0, tmp_elf_header,
> mysize)) {
> + free(tmp_elf_header);
> + goto bailout;
> + }
> + } else {
> + if (lseek(fd, 0, SEEK_SET) != 0) {
> + sprintf(buf, "%s: lseek", file);
> + perror(buf);
> + goto bailout;
> + }
> + if (read(fd, tmp_elf_header, mysize) != mysize) {
> + sprintf(buf, "%s: read", file);
> + perror(buf);
> + free(tmp_elf_header);
> + goto bailout;
> + }
> + }
> +
> + has_nt_nocoredump((char *)tmp_elf_header + myload64->p_offset,
> + myload64->p_memsz);
> +
> if (DUMPFILE_FORMAT(nd->flags) == NETDUMP_ELF64)
> nd->page_size = (uint)nd->load64->p_align;
> dump_Elf64_Ehdr(nd->elf64);
> --
> 1.7.4.1
>
>
--
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