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@xxxxxxxxxxxxx>
> ---
> 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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