In the course of making ASan work on OpenBSD I ran into an accounting
limitation. struct vmspace declares vm_dsize as segsz_t (aka int32_t).
This effectively limits it to 2^31 pages (2^43 bytes on amd64). This
would be enough if didn't also count sparse allocation.
ASan allocates 1/8th of the process address space as shadow memory. It
is very sparsely populated, still given VM_MAXUSER_ADDRESS value of
0x00007f7fffffc000, it goes up to 2^47 bytes which then requires 2^44
bytes of shadow. So, it won't fit.
Hence the following unfinished patch which allows simple ASan'd programs
to detect memory errors. If people don't see an alternative solution,
I'll fix up the users of kinfo_proc.p_vm_dsize and we can decide
when/how this should land.
>From 42c776531620e9baa6735da71349c3c045fb64d8 Mon Sep 17 00:00:00 2001
From: Greg Steuck <g...@nest.cx>
Date: Sun, 5 Sep 2021 13:28:43 -0700
Subject: [PATCH] Change struct vmspace to use vsize_t vm_dused
This was overflowing given high MAXDSIZ. This is very appropriate given
that the field is usually incremented by a value returned by
uvmspace_dused which returns vsize_t.
The change is not finished, only kernel is fixed so far. Userspace
tools consuming p_vm_dsize from kinfo_proc are likely not correct.
---
sys/sys/sysctl.h | 2 +-
sys/uvm/uvm_extern.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/sys/sys/sysctl.h b/sys/sys/sysctl.h
index afdc0689dee..868ef82c696 100644
--- a/sys/sys/sysctl.h
+++ b/sys/sys/sysctl.h
@@ -443,7 +443,7 @@ struct kinfo_proc {
int32_t p_vm_rssize; /* SEGSZ_T: current resident set size
in pages */
int32_t p_vm_tsize; /* SEGSZ_T: text size (pages) */
- int32_t p_vm_dsize; /* SEGSZ_T: data size (pages) */
+ u_int64_t p_vm_dsize; /* VSIZE_T: data size (pages) */
int32_t p_vm_ssize; /* SEGSZ_T: stack size (pages) */
int64_t p_uvalid; /* CHAR: following p_u* members from
struct user are valid */
diff --git a/sys/uvm/uvm_extern.h b/sys/uvm/uvm_extern.h
index faa4a2e5449..ebc74d97917 100644
--- a/sys/uvm/uvm_extern.h
+++ b/sys/uvm/uvm_extern.h
@@ -207,7 +207,7 @@ struct vmspace {
segsz_t vm_swrss; /* resident set size before last swap */
segsz_t vm_tsize; /* text size (pages) XXX */
segsz_t vm_dsize; /* data size (pages) XXX */
- segsz_t vm_dused; /* data segment length (pages) XXX */
+ vsize_t vm_dused; /* data segment length (pages) XXX */
segsz_t vm_ssize; /* [v] stack size (pages) */
caddr_t vm_taddr; /* [I] user virtual address of text */
caddr_t vm_daddr; /* [I] user virtual address of data */
--
2.33.0
