Re: [PATCH v2 1/8] linux-user: test, don't assert addr != test in pgb_reserved_va

[Laurent Vivier]

Le 15/09/2020 à 15:43, Alex Bennée a écrit :
> On older kernels which don't implement MAP_FIXED_NOREPLACE the kernel
> may still fail to give us the address we asked for despite having
> already probed the map for a valid hole. Asserting isn't particularly
> useful to the user so let us move the check up and expand the
> error_report a little to give them a fighting chance of working around
> the problem.
> 
> Ameliorates: ee94743034
> Cc: Bug 1895080 <1895080@bugs.launchpad.net>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>  linux-user/elfload.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 4961e6119e24..f6022fd70493 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -2331,14 +2331,13 @@ static void pgb_reserved_va(const char *image_name, 
> abi_ulong guest_loaddr,
>      assert(guest_base != 0);
>      test = g2h(0);
>      addr = mmap(test, reserved_va, PROT_NONE, flags, -1, 0);
> -    if (addr == MAP_FAILED) {
> +    if (addr == MAP_FAILED || addr != test) {
>          error_report("Unable to reserve 0x%lx bytes of virtual address "
> -                     "space (%s) for use as guest address space (check your "
> -                     "virtual memory ulimit setting or reserve less "
> -                     "using -R option)", reserved_va, strerror(errno));
> +                     "space at %p (%s) for use as guest address space (check 
> your"
> +                     "virtual memory ulimit setting, min_mmap_addr or 
> reserve less "
> +                     "using -R option)", reserved_va, test, strerror(errno));
>          exit(EXIT_FAILURE);
>      }
> -    assert(addr == test);
>  }
>  
>  void probe_guest_base(const char *image_name, abi_ulong guest_loaddr,
> 

Reviewed-by: Laurent Vivier <laurent@vivier.eu>