Re: [Bug 1895080] [NEW] pgb_reserved_va: Assertion `addr == test' failed

[Hansni Bu]

> > No, it's not set by CentOS-7.5.
> > Does it mean that we just cannot run the ELF in such a case? I've tried
> > many times, the assert always fails. Maybe, we can blame CentOS-7.5.
>
> The trouble is without MAP_FIXED_NOREPLACE we are at the mercy of the
> host kernel to allow the address request to be honoured. A plain
> MAP_FIXED won't do as it can clober existing mappings. In theory a
> suitable hole has been identified but sometimes the kernel makes a
> decision to offset the suggested mapping for it's own reasons.
>

MAP_FIXED_NOREPLACE is quite a new feature.


> > BTW: with the option "-p 65536", the case runs successfully.
>
> Hmm interesting. I wonder if we are seeing a fail due to mmap_min_addr?
> What does:
>
>   /proc/sys/vm/mmap_min_addr
>
> give you on the system?
>

It gives me 4096. And guest_base has this value. Maybe that's the strange
point. mmap_min_addr give us 0x1000. While we are requesting this address,
the kernel gives us 0x10000.


>
> You can manually set the reserved_va and the base address using -R and
> -B although that is more of a developer work around. I think moving the
> assert to the condition above would be an improvement just because it
> tells us what the requested base address was and what the kernel decided
> to give us.
>

Setting guest_base with -B to 0x10000 works. Tried some -R values, no luck.
Agree to print a more hintful message.


>
> >
> > On Fri, Sep 11, 2020 at 5:50 PM Alex Bennée <1895080@bugs.launchpad.net>
> > wrote:
> >
> >> Alex Bennée <alex.bennee@linaro.org> writes:
> >>
> >> > Laurent Vivier <laurent@vivier.eu> writes:
> >> >
> >> <snip>
> >> >>> Then trying qemu-riscv32 with a simple ELF, I get:
> >> >>> linux-user/elfload.c:2341: pgb_reserved_va: Assertion `addr == test'
> >> failed.
> >> >>>
> >> >>> strace shows that:
> >> >>> mmap(0x1000, 4294963200, PROT_NONE,
> >> MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x10000
> >> >>> write(2, "qemu-riscv32: ../qemu.git/linux-"..., 103qemu-riscv32:
> >> ../qemu.git/linux-user/elfload.c:2341: pgb_reserved_va: Assertion `addr
> ==
> >> test' failed.
> >> >>> ) = 103
> >> >>>
> >> >>> The source code is in the function pgb_reserved_va (linux-
> >> >>> user/elfload.c). I think mmap cannot guarantee that the returned
> >> pointer
> >> >>> (test) equals to the parameter of addr. So is this a bug to assert
> >> (addr
> >> >>> == test)?
> >> >>
> >> > I'm assuming CentOS 7.5 actually has a definition for
> >> > MAP_FIXED_NOREPLACE which should ensure we get what we asked for -
> >> > otherwise we are in the position of hoping the kernel honours what we
> >> > asked for.
> >>
> >> Doh re-reading I see it's not set in the strace output. Maybe we should
> >> promote the assert case to the failure leg so we have:
> >>
> >>     if (addr == MAP_FAILED || addr != test) {
> >>         error_report(...)
> >>     }
> >>
> >> so we at least fail with a user friendly error rather than an abort?
> >>
> >> --
> >> Alex Bennée
> >>
> >> --
> >> You received this bug notification because you are subscribed to the bug
> >> report.
> >> https://bugs.launchpad.net/bugs/1895080
> >>
> >> Title:
> >>   pgb_reserved_va: Assertion `addr == test' failed
> >>
> >> Status in QEMU:
> >>   New
> >>
> >> Bug description:
> >>   This problem occurs on CentOS-7.5 (64-bit) with qemu-5.1.0, qemu head
> >>   (commit 9435a8b3dd35f1f926f1b9127e8a906217a5518a) for riscv32-linux-
> >>   user.
> >>
> >>   Firstly, compile fails:
> >>   Compiling C object
> libqemu-riscv32-linux-user.fa.p/linux-user_strace.c.o
> >>   ../qemu.git/linux-user/strace.c:1210:18: error: ‘FALLOC_FL_KEEP_SIZE’
> >> undeclared here (not in a function)
> >>        FLAG_GENERIC(FALLOC_FL_KEEP_SIZE),
> >>
> >>   I have to add below include to linux-user/strace.c
> >>   diff --git a/linux-user/strace.c b/linux-user/strace.c
> >>   index 11fea14fba..22e51d4a8a 100644
> >>   --- a/linux-user/strace.c
> >>   +++ b/linux-user/strace.c
> >>   @@ -7,6 +7,7 @@
> >>    #include <sys/mount.h>
> >>    #include <arpa/inet.h>
> >>    #include <netinet/tcp.h>
> >>   +#include <linux/falloc.h>
> >>    #include <linux/if_packet.h>
> >>    #include <linux/netlink.h>
> >>    #include <sched.h>
> >>
> >>   Then trying qemu-riscv32 with a simple ELF, I get:
> >>   linux-user/elfload.c:2341: pgb_reserved_va: Assertion `addr == test'
> >> failed.
> >>
> >>   strace shows that:
> >>   mmap(0x1000, 4294963200, PROT_NONE,
> >> MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x10000
> >>   write(2, "qemu-riscv32: ../qemu.git/linux-"..., 103qemu-riscv32:
> >> ../qemu.git/linux-user/elfload.c:2341: pgb_reserved_va: Assertion `addr
> ==
> >> test' failed.
> >>   ) = 103
> >>
> >>   The source code is in the function pgb_reserved_va (linux-
> >>   user/elfload.c). I think mmap cannot guarantee that the returned
> >>   pointer (test) equals to the parameter of addr. So is this a bug to
> >>   assert (addr == test)?
> >>
> >>   Attached configure script and test ELF file.
> >>
> >>   Thanks.
> >>
> >> To manage notifications about this bug go to:
> >> https://bugs.launchpad.net/qemu/+bug/1895080/+subscriptions
> >>
>
>
> --
> Alex Bennée
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1895080
>
> Title:
>   pgb_reserved_va: Assertion `addr == test' failed
>
> Status in QEMU:
>   New
>
> Bug description:
>   This problem occurs on CentOS-7.5 (64-bit) with qemu-5.1.0, qemu head
>   (commit 9435a8b3dd35f1f926f1b9127e8a906217a5518a) for riscv32-linux-
>   user.
>
>   Firstly, compile fails:
>   Compiling C object libqemu-riscv32-linux-user.fa.p/linux-user_strace.c.o
>   ../qemu.git/linux-user/strace.c:1210:18: error: ‘FALLOC_FL_KEEP_SIZE’
> undeclared here (not in a function)
>        FLAG_GENERIC(FALLOC_FL_KEEP_SIZE),
>
>   I have to add below include to linux-user/strace.c
>   diff --git a/linux-user/strace.c b/linux-user/strace.c
>   index 11fea14fba..22e51d4a8a 100644
>   --- a/linux-user/strace.c
>   +++ b/linux-user/strace.c
>   @@ -7,6 +7,7 @@
>    #include <sys/mount.h>
>    #include <arpa/inet.h>
>    #include <netinet/tcp.h>
>   +#include <linux/falloc.h>
>    #include <linux/if_packet.h>
>    #include <linux/netlink.h>
>    #include <sched.h>
>
>   Then trying qemu-riscv32 with a simple ELF, I get:
>   linux-user/elfload.c:2341: pgb_reserved_va: Assertion `addr == test'
> failed.
>
>   strace shows that:
>   mmap(0x1000, 4294963200, PROT_NONE,
> MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x10000
>   write(2, "qemu-riscv32: ../qemu.git/linux-"..., 103qemu-riscv32:
> ../qemu.git/linux-user/elfload.c:2341: pgb_reserved_va: Assertion `addr ==
> test' failed.
>   ) = 103
>
>   The source code is in the function pgb_reserved_va (linux-
>   user/elfload.c). I think mmap cannot guarantee that the returned
>   pointer (test) equals to the parameter of addr. So is this a bug to
>   assert (addr == test)?
>
>   Attached configure script and test ELF file.
>
>   Thanks.
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/qemu/+bug/1895080/+subscriptions
>

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1895080

Title:
  pgb_reserved_va: Assertion `addr == test' failed

Status in QEMU:
  New

Bug description:
  This problem occurs on CentOS-7.5 (64-bit) with qemu-5.1.0, qemu head
  (commit 9435a8b3dd35f1f926f1b9127e8a906217a5518a) for riscv32-linux-
  user.

  Firstly, compile fails:
  Compiling C object libqemu-riscv32-linux-user.fa.p/linux-user_strace.c.o
  ../qemu.git/linux-user/strace.c:1210:18: error: ‘FALLOC_FL_KEEP_SIZE’ 
undeclared here (not in a function)
       FLAG_GENERIC(FALLOC_FL_KEEP_SIZE),

  I have to add below include to linux-user/strace.c
  diff --git a/linux-user/strace.c b/linux-user/strace.c
  index 11fea14fba..22e51d4a8a 100644
  --- a/linux-user/strace.c
  +++ b/linux-user/strace.c
  @@ -7,6 +7,7 @@
   #include <sys/mount.h>
   #include <arpa/inet.h>
   #include <netinet/tcp.h>
  +#include <linux/falloc.h>
   #include <linux/if_packet.h>
   #include <linux/netlink.h>
   #include <sched.h>

  Then trying qemu-riscv32 with a simple ELF, I get:
  linux-user/elfload.c:2341: pgb_reserved_va: Assertion `addr == test' failed.

  strace shows that:
  mmap(0x1000, 4294963200, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, 
-1, 0) = 0x10000
  write(2, "qemu-riscv32: ../qemu.git/linux-"..., 103qemu-riscv32: 
../qemu.git/linux-user/elfload.c:2341: pgb_reserved_va: Assertion `addr == 
test' failed.
  ) = 103

  The source code is in the function pgb_reserved_va (linux-
  user/elfload.c). I think mmap cannot guarantee that the returned
  pointer (test) equals to the parameter of addr. So is this a bug to
  assert (addr == test)?

  Attached configure script and test ELF file.

  Thanks.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1895080/+subscriptions