From: stsp <stsp2@yandex.ru>
To: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>,
libc-alpha@sourceware.org
Subject: Re: [PATCH 02/13] elf: switch _dl_map_segment() to anonymous mapping
Date: Wed, 29 Mar 2023 23:00:28 +0500 [thread overview]
Message-ID: <bd4d120b-0408-e5eb-893a-86409c890a90@yandex.ru> (raw)
In-Reply-To: <a9389657-68bf-6ea1-e969-96ebf02d7c26@linaro.org>
29.03.2023 22:01, Adhemerval Zanella Netto пишет:
> glibc code guidelines [1] suggest to explicit define the types, so
> 'unsigned int' here.
Fixed locally this and a few other
similar instances. Queued to v10.
> [1] https://sourceware.org/glibc/wiki/Style_and_Conventions
>
>> +
>> +#ifdef MAP_DENYWRITE
>> + /* Tell mmap() that we are mapping solib. This flag enables things
>> + like LD_PREFER_MAP_32BIT_EXEC. */
>> + map_flags |= MAP_DENYWRITE;
>> +#endif
> Why do you need o add MAP_DENYWRITE? They are complete ignored by Linux,
But its not ignored in glibc, see
sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h
Without that flag PREFER_MAP_32BIT_EXEC
test fails.
> So basically it would add another mmap on program loading. For instance, loading
> a simple empty main programs:
Yes, that's true.
Is this a problem?
> And it also slight change the mapping, using the same program:
>
> * Before:
>
> 0x7ffff7dc2000 0x7ffff7de8000 0x26000 0x0 r--p /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
> 0x7ffff7de8000 0x7ffff7f54000 0x16c000 0x26000 r-xp /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
> 0x7ffff7f54000 0x7ffff7faa000 0x56000 0x192000 r--p /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
> 0x7ffff7faa000 0x7ffff7fab000 0x1000 0x1e8000 ---p /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
> 0x7ffff7fab000 0x7ffff7faf000 0x4000 0x1e8000 r--p /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
> 0x7ffff7faf000 0x7ffff7fb1000 0x2000 0x1ec000 rw-p /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
>
> * With this patch:
>
> 0x7ffff7dc1000 0x7ffff7de7000 0x26000 0x0 r--p /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
> 0x7ffff7de7000 0x7ffff7f53000 0x16c000 0x26000 r-xp /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
> 0x7ffff7f53000 0x7ffff7fa9000 0x56000 0x192000 r--p /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
> 0x7ffff7fa9000 0x7ffff7faa000 0x1000 0x0 ---p
> 0x7ffff7faa000 0x7ffff7fae000 0x4000 0x1e8000 r--p /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
> 0x7ffff7fae000 0x7ffff7fb0000 0x2000 0x1ec000 rw-p /home/azanella/Projects/glibc/build/x86_64-linux-gnu/libc.so
Mm, was staring on this for a while,
and file offsets and perms looks the
same. What differences do you mean
exactly?
> So I am not seeing any advantage of this refactor: it slight increase the
> number of syscalls for library loading and changes the 'debuggability' of
> resulting shared library maps.
This is not a "pure refactor", but a preparation
to dlmem(). dlmem() allows the user to pre-map
the memory area (optionally), so in the subsequent
patches I first call the user's callback, and if its
not there or doesn't want to pre-map, then I call
_dl_load_segment() for doing the same thing as
a fall-back.
Do you want me to squash also that patch
into the one that actually needs it?
next prev parent reply other threads:[~2023-03-29 18:00 UTC|newest]
Thread overview: 107+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-18 16:50 [PATCH v9 0/13] implement dlmem() function Stas Sergeev
2023-03-18 16:50 ` [PATCH 01/13] elf: strdup() l_name if no realname [BZ #30100] Stas Sergeev
2023-03-29 13:54 ` Adhemerval Zanella Netto
2023-03-29 14:12 ` stsp
2023-03-29 14:19 ` Adhemerval Zanella Netto
2023-03-29 14:28 ` stsp
2023-03-29 14:30 ` Adhemerval Zanella Netto
2023-03-29 14:33 ` stsp
2023-03-18 16:50 ` [PATCH 02/13] elf: switch _dl_map_segment() to anonymous mapping Stas Sergeev
2023-03-29 17:01 ` Adhemerval Zanella Netto
2023-03-29 18:00 ` stsp [this message]
2023-03-29 18:29 ` Adhemerval Zanella Netto
2023-03-29 18:46 ` stsp
2023-03-29 19:17 ` Adhemerval Zanella Netto
2023-03-29 19:43 ` stsp
2023-03-18 16:51 ` [PATCH 03/13] elf: dont pass fd to _dl_process_pt_xx Stas Sergeev
2023-03-29 17:10 ` Adhemerval Zanella Netto
2023-03-30 16:08 ` stsp
2023-03-30 20:46 ` Adhemerval Zanella Netto
2023-03-31 12:02 ` Szabolcs Nagy
2023-03-31 12:54 ` Adhemerval Zanella Netto
2023-03-31 14:04 ` stsp
2023-03-18 16:51 ` [PATCH 04/13] elf: split _dl_map_object_from_fd() into reusable parts Stas Sergeev
2023-03-18 16:51 ` [PATCH 05/13] elf: split open_verify() " Stas Sergeev
2023-03-18 16:51 ` [PATCH 06/13] elf: load elf hdr fully in open_verify() Stas Sergeev
2023-03-18 16:51 ` [PATCH 07/13] elf: convert pread64 to callback in do_open_verify() Stas Sergeev
2023-03-18 16:51 ` [PATCH 08/13] elf: convert _dl_map_segments's mmap() to a callback Stas Sergeev
2023-03-18 16:51 ` [PATCH 09/13] elf: call _dl_map_segment() via premap callback Stas Sergeev
2023-03-18 16:51 ` [PATCH 10/13] elf: convert _dl_map_object to a callback Stas Sergeev
2023-03-18 16:51 ` [PATCH 11/13] elf: split _dl_check_loaded() from _dl_map_object Stas Sergeev
2023-03-18 16:51 ` [PATCH 12/13] dlfcn,elf: implement dlmem() [BZ #11767] Stas Sergeev
2023-03-29 13:45 ` Carlos O'Donell
2023-03-29 13:51 ` stsp
2023-03-29 14:10 ` Jonathon Anderson
2023-03-29 14:20 ` stsp
2023-03-29 14:31 ` Adhemerval Zanella Netto
2023-03-29 15:01 ` stsp
2023-03-29 14:35 ` Carlos O'Donell
2023-03-29 14:50 ` stsp
2023-03-29 15:20 ` Carlos O'Donell
2023-03-29 15:34 ` stsp
2023-03-30 8:09 ` stsp
2023-03-18 16:51 ` [PATCH 13/13] dlfcn,elf: impl DLMEM_DONTREPLACE dlmem() flag Stas Sergeev
2023-03-29 12:32 ` [PATCH v9 0/13] implement dlmem() function Adhemerval Zanella Netto
2023-03-29 13:10 ` stsp
2023-03-29 13:18 ` stsp
2023-03-31 12:20 ` Szabolcs Nagy
2023-03-31 13:51 ` stsp
2023-03-31 14:49 ` Rich Felker
2023-03-31 14:56 ` stsp
2023-03-31 14:58 ` Rich Felker
2023-03-31 15:03 ` stsp
2023-03-31 14:44 ` stsp
2023-03-31 15:12 ` stsp
2023-03-31 17:12 ` Szabolcs Nagy
2023-03-31 17:36 ` stsp
2023-04-01 9:28 ` stsp
2023-04-03 10:04 ` Szabolcs Nagy
2023-04-03 10:43 ` stsp
2023-04-03 12:01 ` Szabolcs Nagy
2023-04-03 13:07 ` stsp
2023-04-05 7:29 ` stsp
2023-04-05 8:51 ` Szabolcs Nagy
2023-04-05 9:26 ` stsp
2023-04-05 9:31 ` Florian Weimer
2023-04-12 17:23 ` stsp
2023-04-12 18:00 ` stsp
2023-04-12 18:20 ` Rich Felker
2023-04-12 18:46 ` stsp
2023-04-12 19:52 ` Zack Weinberg
2023-04-12 19:07 ` stsp
2023-04-13 10:01 ` stsp
2023-04-13 12:38 ` Szabolcs Nagy
2023-04-13 15:59 ` stsp
2023-04-13 18:09 ` Adhemerval Zanella Netto
2023-04-13 18:59 ` stsp
2023-04-13 19:12 ` Adhemerval Zanella Netto
2023-04-13 19:29 ` stsp
2023-04-13 20:02 ` Adhemerval Zanella Netto
2023-04-13 20:21 ` stsp
2023-04-13 20:57 ` stsp
2023-04-14 7:07 ` stsp
2023-04-14 7:36 ` stsp
2023-04-14 11:30 ` stsp
2023-04-14 19:04 ` proof for dlmem() (Re: [PATCH v9 0/13] implement dlmem() function) stsp
2023-05-01 23:11 ` Zack Weinberg
2023-05-02 5:48 ` stsp
2023-05-08 16:00 ` stsp
2023-05-02 6:24 ` stsp
2023-05-08 15:10 ` [PATCH v9 0/13] implement dlmem() function stsp
2023-03-31 18:47 ` stsp
2023-03-31 19:00 ` stsp
2023-03-29 13:17 ` Carlos O'Donell
2023-03-29 13:26 ` stsp
2023-03-29 17:03 ` stsp
2023-03-29 18:13 ` Carlos O'Donell
2023-03-29 18:29 ` stsp
2023-03-31 11:04 ` stsp
2023-04-13 21:17 ` Carlos O'Donell
2023-04-13 21:58 ` stsp
2023-04-13 22:08 ` stsp
2023-04-13 22:50 ` stsp
2023-04-14 16:15 ` Autoconf maintenance (extremely tangential to Re: [PATCH v9 0/13] implement dlmem() function) Zack Weinberg
2023-04-14 20:24 ` Carlos O'Donell
2023-04-14 20:40 ` Zack Weinberg
2023-05-08 15:05 ` [PATCH v9 0/13] implement dlmem() function stsp
2023-05-19 7:26 ` stsp
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