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Re: [PATCH for-8.1 v10 10/14] util/selfmap: Rewrite using qemu/interval-
From: |
Ilya Leoshkevich |
Subject: |
Re: [PATCH for-8.1 v10 10/14] util/selfmap: Rewrite using qemu/interval-tree.h |
Date: |
Thu, 10 Aug 2023 23:31:00 +0200 |
User-agent: |
Evolution 3.48.4 (3.48.4-1.fc38) |
On Mon, 2023-08-07 at 11:17 -0700, Richard Henderson wrote:
> On 8/7/23 09:37, Richard Henderson wrote:
> > We will want to be able to search the set of mappings.
> > For this patch, the two users iterate the tree in order.
> >
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> > include/qemu/selfmap.h | 20 ++++----
> > linux-user/elfload.c | 14 +++--
> > linux-user/syscall.c | 15 +++---
> > util/selfmap.c | 114 +++++++++++++++++++++++++-----------
> > -----
> > 4 files changed, 96 insertions(+), 67 deletions(-)
>
> I should note that, for 8.2, this will enable a rewrite of
> open_self_maps_1 so that it
> does not require page-by-page checking of page_get_flags.
>
> My idea is that open_self_maps_1 would use walk_memory_regions to see
> all guest memory
> regions. The per-region callback would cross-check with the host-
> region interval tree to
> find the dev+inode+path.
>
> Cc Ilya and Helge, since there are two outstanding changes to
> open_self_maps.
>
>
> r~
My outstanding change should not be sensitive to this; it should be
possible to put it in both before or after the rewrite.
I really like this idea though, since I looked into ppc64le and there
printing maps is quite broken: it's not just that QEMU can't determine
the names of the mapped files, but also a number of regions are simply
missing. This also affects core dumps generated by GDB attached to
gdbstub.
For example, cat /proc/self/maps has the following internal page
layout:
start end size prot
0000000010000000-000000001000d000 000000000000d000 r-x
000000001000d000-0000000010010000 0000000000003000 ---
0000000010010000-000000001001f000 000000000000f000 r--
000000001001f000-0000000010020000 0000000000001000 r--
0000000010020000-0000000010021000 0000000000001000 rw-
0000100000000000-0000100000010000 0000000000010000 ---
0000100000010000-0000100000810000 0000000000800000 rw-
0000100000810000-0000100000830000 0000000000020000 r-x
0000100000830000-000010000083d000 000000000000d000 r-x
000010000083d000-0000100000840000 0000000000003000 ---
0000100000840000-000010000084f000 000000000000f000 r--
000010000084f000-0000100000850000 0000000000001000 r--
0000100000850000-0000100000851000 0000000000001000 rw-
0000100000851000-0000100000852000 0000000000001000 rw-
0000100000860000-0000100000861000 0000000000001000 r-x
0000100000880000-0000100000a50000 00000000001d0000 r-x
0000100000a50000-0000100000a60000 0000000000010000 r--
0000100000a60000-0000100000a70000 0000000000010000 rw-
0000100000a70000-0000100000b70000 0000000000100000 rw-
0000100000b70000-000010000742d000 00000000068bd000 r--
00007fffb22b0000-00007fffb22e0000 0000000000030000 rw-
but prints only:
100000000000-100000010000 ---p 00000000 00:00 0
100000010000-100000810000 rw-p 00000000 00:00 0
[stack]
100000810000-100000830000 r-xp 00000000 fd:00 3049136
/usr/lib64/ld-2.17.so
100000880000-100000a50000 r-xp 00000000 fd:00 3017372
/usr/lib64/libc-2.17.so
100000a50000-100000a60000 r--p 001c0000 fd:00 3017372
/usr/lib64/libc-2.17.so
100000a60000-100000a70000 rw-p 001d0000 fd:00 3017372
/usr/lib64/libc-2.17.so
100000a70000-100000b70000 rw-p 00000000 00:00 0
7fffb22b0000-7fffb22e0000 rw-p 00000000 00:00 0
I don't see a good way to prevent page_check_range() from rejecting
most of the mappings with the current code structure, but I think that
after the proposed rewrite it should begin to just work.
Re: [PATCH for-8.1 v10 10/14] util/selfmap: Rewrite using qemu/interval-tree.h, Michael Tokarev, 2023/08/08
[PATCH for-8.1 v10 06/14] linux-user: Adjust initial brk when interpreter is close to executable, Richard Henderson, 2023/08/07
[PATCH for-8.1 v10 07/14] linux-user: Do not adjust image mapping for host page size, Richard Henderson, 2023/08/07
[PATCH for-8.1 v10 08/14] linux-user: Do not adjust zero_bss for host page size, Richard Henderson, 2023/08/07
[PATCH for-8.1 v10 04/14] linux-user: Use MAP_FIXED_NOREPLACE for initial image mmap, Richard Henderson, 2023/08/07