On Thu, May 18, 2023 at 12:28 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx> wrote:
Kernel commit 869176a09606 ("mm/vmalloc.c: add flags to mark vm_map_ram
area"), which is contained in Linux 6.3 and later, added "flags" member
to struct vmap_area. This was the revival of the "flags" member as
kernel commit 688fcbfc06e4 had eliminated it before.
As a result, crash started to use the old procedure using the member and
displays no vmalloc'd regions, because it does not have the same flag
value as the old one.
crash> kmem -v
VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE
crash>
To fix this, also check if vmap_area.purge_list exists, which was
introduced with the flags and removed later, to determine that the flags
member is the old one.
Related vmap_area history:
v2.6.28 db64fe02258f introduced vmap_area with flags and purge_list
v5.4 688fcbfc06e4 removed flags
v5.11 96e2db456135 removed purge_list
v6.3 869176a09606 added flags again
Thank you for the fix, Kazu.
It looks good to me. So: Ack.
Thanks.
Lianbo
Signed-off-by: Kazuhito Hagio <k-hagio-ab@xxxxxxx>
---
defs.h | 1 +
memory.c | 4 +++-
symbols.c | 1 +
3 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/defs.h b/defs.h
index 21cc760444d1..bfa07c3f5150 100644
--- a/defs.h
+++ b/defs.h
@@ -2216,6 +2216,7 @@ struct offset_table { /* stash of commonly-used offsets */
long in6_addr_in6_u;
long kset_kobj;
long subsys_private_subsys;
+ long vmap_area_purge_list;
};
struct size_table { /* stash of commonly-used sizes */
diff --git a/memory.c b/memory.c
index 953fc380c03c..15fa8b2f08f1 100644
--- a/memory.c
+++ b/memory.c
@@ -429,6 +429,7 @@ vm_init(void)
MEMBER_OFFSET_INIT(vmap_area_vm, "vmap_area", "vm");
if (INVALID_MEMBER(vmap_area_vm))
MEMBER_OFFSET_INIT(vmap_area_vm, "vmap_area", "private");
+ MEMBER_OFFSET_INIT(vmap_area_purge_list, "vmap_area", "purge_list");
STRUCT_SIZE_INIT(vmap_area, "vmap_area");
if (VALID_MEMBER(vmap_area_va_start) &&
VALID_MEMBER(vmap_area_va_end) &&
@@ -9063,7 +9064,8 @@ dump_vmap_area(struct meminfo *vi)
readmem(ld->list_ptr[i], KVADDR, vmap_area_buf,
SIZE(vmap_area), "vmap_area struct", FAULT_ON_ERROR);
- if (VALID_MEMBER(vmap_area_flags)) {
+ if (VALID_MEMBER(vmap_area_flags) &&
+ VALID_MEMBER(vmap_area_purge_list)) {
flags = ULONG(vmap_area_buf + OFFSET(vmap_area_flags));
if (flags != VM_VM_AREA)
continue;
diff --git a/symbols.c b/symbols.c
index f0721023816d..7b1d59203b90 100644
--- a/symbols.c
+++ b/symbols.c
@@ -9169,6 +9169,7 @@ dump_offset_table(char *spec, ulong makestruct)
OFFSET(vmap_area_vm));
fprintf(fp, " vmap_area_flags: %ld\n",
OFFSET(vmap_area_flags));
+ fprintf(fp, " vmap_area_purge_list: %ld\n", OFFSET(vmap_area_purge_list));
fprintf(fp, " module_size_of_struct: %ld\n",
OFFSET(module_size_of_struct));
--
2.31.1
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