[PATCH makedumpfile] handle mem_section as either a pointer or an array
Masaki Tachibana
mas-tachibana at vf.jp.nec.com
Mon Mar 5 01:15:44 PST 2018
Hi Thadeu,
Sorry for the late reply.
"handle mem_section as either a pointer or an array" patch and
"Always use bigger SECTION_MAP_MASK" patch modify the same line.
I would like to reply about both patches by the end of the next week.
Thanks
Tachibana
> -----Original Message-----
> From: kexec [mailto:kexec-bounces at lists.infradead.org] On Behalf Of Thadeu Lima de Souza Cascardo
> Sent: Friday, March 02, 2018 11:33 PM
> To: kexec at lists.infradead.org
> Subject: Re: [PATCH makedumpfile] handle mem_section as either a pointer or an array
>
> Any comments or reviews on the patch below?
>
> Thanks.
> Cascardo.
>
> On Mon, Feb 19, 2018 at 05:04:59PM -0300, Thadeu Lima de Souza Cascardo wrote:
> > Some kernel versions that have been recently shipped have mem_section point to
> > a pointer to the array, instead of pointing directly to the array. That only
> > happens on SPARSEMEM_EXTREME configurations.
> >
> > As dwarf information might not be present that would have allowed us to detect
> > which type it is, we need to try it either as an array or as the pointer to the
> > array. Then, we validate all section_mem_map: they must either be present or
> > null. If any problems are found when traversing it, consider it invalid. Only
> > one way may be valid. Otherwise, fail.
> >
> > This has been tested with both types of kernels and succeeded in producing a
> > compressed dump that could be analyzed with crash 7.2.1.
> >
> > Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
> > ---
> > makedumpfile.c | 153 +++++++++++++++++++++++++++++++++++++++++++--------------
> > makedumpfile.h | 1 +
> > 2 files changed, 118 insertions(+), 36 deletions(-)
> >
> > diff --git a/makedumpfile.c b/makedumpfile.c
> > index ed138d3..cd3fa4d 100644
> > --- a/makedumpfile.c
> > +++ b/makedumpfile.c
> > @@ -3297,7 +3297,7 @@ get_mm_discontigmem(void)
> > return TRUE;
> > }
> >
> > -unsigned long
> > +static unsigned long
> > nr_to_section(unsigned long nr, unsigned long *mem_sec)
> > {
> > unsigned long addr;
> > @@ -3311,17 +3311,17 @@ nr_to_section(unsigned long nr, unsigned long *mem_sec)
> > addr = SYMBOL(mem_section) + (nr * SIZE(mem_section));
> > }
> >
> > - if (!is_kvaddr(addr))
> > - return NOT_KV_ADDR;
> > -
> > return addr;
> > }
> >
> > -unsigned long
> > -section_mem_map_addr(unsigned long addr)
> > +static unsigned long
> > +section_mem_map_addr(unsigned long addr, unsigned long *map_mask)
> > {
> > char *mem_section;
> > unsigned long map;
> > + unsigned long mask;
> > +
> > + *map_mask = 0;
> >
> > if (!is_kvaddr(addr))
> > return NOT_KV_ADDR;
> > @@ -3338,15 +3338,19 @@ section_mem_map_addr(unsigned long addr)
> > }
> > map = ULONG(mem_section + OFFSET(mem_section.section_mem_map));
> > if (info->kernel_version < KERNEL_VERSION(4, 13, 0))
> > - map &= SECTION_MAP_MASK_4_12;
> > + mask = SECTION_MAP_MASK_4_12;
> > else
> > - map &= SECTION_MAP_MASK;
> > + mask = SECTION_MAP_MASK;
> > + *map_mask = map & ~mask;
> > + if (map == 0x0)
> > + *map_mask |= SECTION_MARKED_PRESENT;
> > + map &= mask;
> > free(mem_section);
> >
> > return map;
> > }
> >
> > -unsigned long
> > +static unsigned long
> > sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long section_nr)
> > {
> > unsigned long mem_map;
> > @@ -3354,17 +3358,110 @@ sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long section_nr)
> > mem_map = coded_mem_map +
> > (SECTION_NR_TO_PFN(section_nr) * SIZE(page));
> >
> > - if (!is_kvaddr(mem_map))
> > - return NOT_KV_ADDR;
> > return mem_map;
> > }
> > +
> > +/*
> > + * On some kernels, mem_section may be a pointer or an array, when
> > + * SPARSEMEM_EXTREME is on.
> > + *
> > + * We assume that section_mem_map is either 0 or has the present bit set.
> > + *
> > + */
> > +
> > +static int
> > +validate_mem_section(unsigned long *mem_sec,
> > + unsigned long mem_section_ptr, unsigned int mem_section_size,
> > + unsigned long *mem_maps, unsigned int num_section)
> > +{
> > + unsigned int section_nr;
> > + unsigned long map_mask;
> > + unsigned long section, mem_map;
> > + if (!readmem(VADDR, mem_section_ptr, mem_sec, mem_section_size)) {
> > + ERRMSG("Can't read mem_section array.\n");
> > + return FALSE;
> > + }
> > + for (section_nr = 0; section_nr < num_section; section_nr++) {
> > + section = nr_to_section(section_nr, mem_sec);
> > + if (section == NOT_KV_ADDR) {
> > + mem_map = NOT_MEMMAP_ADDR;
> > + } else {
> > + mem_map = section_mem_map_addr(section, &map_mask);
> > + if (!(map_mask & SECTION_MARKED_PRESENT)) {
> > + return FALSE;
> > + }
> > + if (mem_map == 0) {
> > + mem_map = NOT_MEMMAP_ADDR;
> > + } else {
> > + mem_map = sparse_decode_mem_map(mem_map,
> > + section_nr);
> > + if (!is_kvaddr(mem_map)) {
> > + return FALSE;
> > + }
> > + }
> > + }
> > + mem_maps[section_nr] = mem_map;
> > + }
> > + return TRUE;
> > +}
> > +
> > +static int
> > +get_mem_section(unsigned int mem_section_size, unsigned long *mem_maps,
> > + unsigned int num_section)
> > +{
> > + unsigned long mem_section_ptr;
> > + int ret = FALSE;
> > + unsigned long *mem_sec = NULL;
> > +
> > + if ((mem_sec = malloc(mem_section_size)) == NULL) {
> > + ERRMSG("Can't allocate memory for the mem_section. %s\n",
> > + strerror(errno));
> > + return FALSE;
> > + }
> > + ret = validate_mem_section(mem_sec, SYMBOL(mem_section),
> > + mem_section_size, mem_maps, num_section);
> > +
> > + if (is_sparsemem_extreme()) {
> > + int symbol_valid = ret;
> > + int pointer_valid;
> > + int mem_maps_size = sizeof(*mem_maps) * num_section;
> > + unsigned long *mem_maps_ex = NULL;
> > + if (!readmem(VADDR, SYMBOL(mem_section), &mem_section_ptr,
> > + sizeof(mem_section_ptr)))
> > + goto out;
> > +
> > + if ((mem_maps_ex = malloc(mem_maps_size)) == NULL) {
> > + ERRMSG("Can't allocate memory for the mem_maps. %s\n",
> > + strerror(errno));
> > + goto out;
> > + }
> > +
> > + pointer_valid = validate_mem_section(mem_sec,
> > + mem_section_ptr,
> > + mem_section_size,
> > + mem_maps_ex,
> > + num_section);
> > + if (pointer_valid)
> > + memcpy(mem_maps, mem_maps_ex, mem_maps_size);
> > + if (mem_maps_ex)
> > + free(mem_maps_ex);
> > + ret = symbol_valid ^ pointer_valid;
> > + if (!ret) {
> > + ERRMSG("Could not validate mem_section.\n");
> > + }
> > + }
> > +out:
> > + if (mem_sec != NULL)
> > + free(mem_sec);
> > + return ret;
> > +}
> > +
> > int
> > get_mm_sparsemem(void)
> > {
> > unsigned int section_nr, mem_section_size, num_section;
> > mdf_pfn_t pfn_start, pfn_end;
> > - unsigned long section, mem_map;
> > - unsigned long *mem_sec = NULL;
> > + unsigned long *mem_maps = NULL;
> >
> > int ret = FALSE;
> >
> > @@ -3379,13 +3476,12 @@ get_mm_sparsemem(void)
> > info->sections_per_root = _SECTIONS_PER_ROOT();
> > mem_section_size = SIZE(mem_section) * NR_SECTION_ROOTS();
> > }
> > - if ((mem_sec = malloc(mem_section_size)) == NULL) {
> > - ERRMSG("Can't allocate memory for the mem_section. %s\n",
> > - strerror(errno));
> > + if ((mem_maps = malloc(sizeof(*mem_maps) * num_section)) == NULL) {
> > + ERRMSG("Can't allocate memory for the mem_maps. %s\n",
> > + strerror(errno));
> > return FALSE;
> > }
> > - if (!readmem(VADDR, SYMBOL(mem_section), mem_sec,
> > - mem_section_size)) {
> > + if (!get_mem_section(mem_section_size, mem_maps, num_section)) {
> > ERRMSG("Can't get the address of mem_section.\n");
> > goto out;
> > }
> > @@ -3397,31 +3493,16 @@ get_mm_sparsemem(void)
> > goto out;
> > }
> > for (section_nr = 0; section_nr < num_section; section_nr++) {
> > - section = nr_to_section(section_nr, mem_sec);
> > - if (section == NOT_KV_ADDR) {
> > - mem_map = NOT_MEMMAP_ADDR;
> > - } else {
> > - mem_map = section_mem_map_addr(section);
> > - if (mem_map == 0) {
> > - mem_map = NOT_MEMMAP_ADDR;
> > - } else {
> > - mem_map = sparse_decode_mem_map(mem_map,
> > - section_nr);
> > - if (!is_kvaddr(mem_map))
> > - mem_map = NOT_MEMMAP_ADDR;
> > - }
> > - }
> > pfn_start = section_nr * PAGES_PER_SECTION();
> > pfn_end = pfn_start + PAGES_PER_SECTION();
> > if (info->max_mapnr < pfn_end)
> > pfn_end = info->max_mapnr;
> > - dump_mem_map(pfn_start, pfn_end, mem_map, section_nr);
> > + dump_mem_map(pfn_start, pfn_end, mem_maps[section_nr], section_nr);
> > }
> > ret = TRUE;
> > out:
> > - if (mem_sec != NULL)
> > - free(mem_sec);
> > -
> > + if (mem_maps != NULL)
> > + free(mem_maps);
> > return ret;
> > }
> >
> > diff --git a/makedumpfile.h b/makedumpfile.h
> > index 01eece2..58e1aaa 100644
> > --- a/makedumpfile.h
> > +++ b/makedumpfile.h
> > @@ -184,6 +184,7 @@ isAnon(unsigned long mapping)
> > #define SECTIONS_PER_ROOT() (info->sections_per_root)
> > #define SECTION_ROOT_MASK() (SECTIONS_PER_ROOT() - 1)
> > #define SECTION_NR_TO_ROOT(sec) ((sec) / SECTIONS_PER_ROOT())
> > +#define SECTION_MARKED_PRESENT (1UL<<0)
> > #define SECTION_IS_ONLINE (1UL<<2)
> > #define SECTION_MAP_LAST_BIT (1UL<<3)
> > #define SECTION_MAP_MASK_4_12 (~(SECTION_IS_ONLINE-1))
> > --
> > 2.14.1
> >
> >
> > _______________________________________________
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> > kexec at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
>
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