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SubjectRe: mmotm 2018-01-04-16-19 uploaded
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On 01/05/2018 02:16 PM, Michal Hocko wrote:
> On Fri 05-01-18 12:13:17, Anshuman Khandual wrote:
>> On 01/05/2018 05:50 AM, akpm@linux-foundation.org wrote:
>>> The mm-of-the-moment snapshot 2018-01-04-16-19 has been uploaded to

[...]

>>>
>>> This tree is partially included in linux-next. To see which patches are
>>> included in linux-next, consult the `series' file. Only the patches
>>> within the #NEXT_PATCHES_START/#NEXT_PATCHES_END markers are included in
>>> linux-next.
>>>
>>> A git tree which contains the memory management portion of this tree is
>>> maintained at git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git
>> Seems like this latest snapshot mmotm-2018-01-04-16-19 has not been
>> updated in this git tree. I could not fetch not it shows up in the
>> http link below.
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git
> I will update the tree today (WIP). This is not a fully automated
> process and Andrew pushed his tree during my night ;) So be patient
> please. My tree is non-rebasing which means I cannot just throw the old
> tree away and regenerate it from scratch.
>
>> The last one mmotm-2017-12-22-17-55 seems to have some regression on
>> powerpc with respect to ELF loading of binaries (see below). Seems to
>> be related to recent MAP_FIXED_SAFE (or MAP_FIXED_NOREPLACE as seen
>> now in the code). IIUC (have not been following the series last month)
>> MAP_FIXED_NOREPLACE will fail an allocation request if the hint address
>> cannot be reserve instead of changing existing mappings.
> Correct
>
>> Is it possible
>> that ELF loading needs to be fixed at a higher level to deal with these
>> new possible mmap() failures because of MAP_FIXED_NOREPLACE ?
> Could you give us more information about the failure please. Debugging
> patch from http://lkml.kernel.org/r/20171218091302.GL16951@dhcp22.suse.cz
> should help to see what is the clashing VMA.

Seems like its re-requesting the same mapping again.

[ 23.423642] 9148 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[ 23.423706] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
[ 23.426089] 9151 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[ 23.426232] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
[ 23.429048] 9154 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[ 23.429196] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
[ 23.482766] 9164 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[ 23.482904] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
[ 23.485849] 9167 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[ 23.485945] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
[ 76.041836] 9262 (hostname): Uhuuh, elf segment at 0000000010020000 requested but the memory is mapped already
[ 76.041965] requested [10020000, 10030000] mapped [10020000, 10030000] 100073 anon
[ 76.207197] 9285 (pkg-config): Uhuuh, elf segment at 0000000010020000 requested but the memory is mapped already
[ 76.207326] requested [10020000, 10030000] mapped [10020000, 10030000] 100073 anon
[ 76.371073] 9299 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[ 76.371165] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon


I have fixed/changed the debug patch a bit


diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index d8c5657..a43eccaa 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -372,11 +372,35 @@ static unsigned long elf_map(struct file *filep, unsigned long addr,
} else
map_addr = vm_mmap(filep, addr, size, prot, type, off);

- if ((type & MAP_FIXED_NOREPLACE) && BAD_ADDR(map_addr))
+ if ((type & MAP_FIXED_NOREPLACE) && BAD_ADDR(map_addr)) {
+ struct vm_area_struct *vma;
+ unsigned long end;
+
+ if (total_size)
+ end = addr + total_size;
+ else
+ end = addr + size;
+
pr_info("%d (%s): Uhuuh, elf segment at %p requested but the memory is mapped already\n",
task_pid_nr(current), current->comm,
(void *)addr);

+ vma = find_vma(current->mm, addr);
+ if (vma && vma->vm_start <= addr) {
+ pr_info("requested [%lx, %lx] mapped [%lx, %lx] %lx ", addr, end,
+ vma->vm_start, vma->vm_end, vma->vm_flags);
+ if (!vma->vm_file) {
+ pr_cont("anon\n");
+ } else {
+ char path[512];
+ char *p = file_path(vma->vm_file, path, sizeof(path));
+ if (IS_ERR(p))
+ p = "?";
+ pr_cont("\"%s\"\n", kbasename(p));
+ }
+ dump_stack();
+ }
+ }
return(map_addr);
}



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