From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: "H.J. Lu" <hjl.tools@gmail.com>, libc-alpha@sourceware.org
Cc: Florian Weimer <fweimer@redhat.com>
Subject: Re: [PATCH v7 1/4] elf: Properly align all PT_LOAD segments [BZ #28676]
Date: Tue, 18 Jan 2022 14:48:58 -0300 [thread overview]
Message-ID: <0a5eb87b-9a3c-6b3b-a82c-58e872e7e42f@linaro.org> (raw)
In-Reply-To: <20220103230433.1907240-2-hjl.tools@gmail.com>
On 03/01/2022 20:04, H.J. Lu wrote:
> Linker may set p_align of a PT_LOAD segment larger than p_align of the
> first PT_LOAD segment to satisfy a section alignment:
>
> Elf file type is DYN (Shared object file)
> Entry point 0x0
> There are 10 program headers, starting at offset 64
>
> Program Headers:
> Type Offset VirtAddr PhysAddr
> FileSiz MemSiz Flags Align
> LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000
> 0x0000000000000834 0x0000000000000834 R E 0x1000
> LOAD 0x0000000000000e00 0x0000000000001e00 0x0000000000001e00
> 0x0000000000000230 0x0000000000000230 RW 0x1000
> LOAD 0x0000000000400000 0x0000000000400000 0x0000000000400000
> 0x0000000000000004 0x0000000000000008 RW 0x400000
> ...
>
> Section to Segment mapping:
> Segment Sections...
> 00 .note.gnu.property .note.gnu.build-id .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .plt.got .text .fini .rodata .eh_frame_hdr .eh_frame
> 01 .init_array .fini_array .data.rel.ro .dynamic .got .got.plt
> 02 .data .bss
>
> We should align the first PT_LOAD segment to the maximum p_align of all
> PT_LOAD segments, similar to the kernel commit:
>
> commit ce81bb256a224259ab686742a6284930cbe4f1fa
> Author: Chris Kennelly <ckennelly@google.com>
> Date: Thu Oct 15 20:12:32 2020 -0700
>
> fs/binfmt_elf: use PT_LOAD p_align values for suitable start address
> ---
> elf/dl-load.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/elf/dl-load.c b/elf/dl-load.c
> index ddc4295ef5..109bed3fb5 100644
> --- a/elf/dl-load.c
> +++ b/elf/dl-load.c
> @@ -1101,6 +1101,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
> size_t nloadcmds = 0;
> bool has_holes = false;
> bool empty_dynamic = false;
> + ElfW(Addr) p_align_max = 0;
>
> /* The struct is initialized to zero so this is not necessary:
> l->l_ld = 0;
> @@ -1146,7 +1147,9 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
> c->mapend = ALIGN_UP (ph->p_vaddr + ph->p_filesz, GLRO(dl_pagesize));
> c->dataend = ph->p_vaddr + ph->p_filesz;
> c->allocend = ph->p_vaddr + ph->p_memsz;
> - c->mapalign = ph->p_align;
> + /* Remember the maximum p_align. */
> + if (ph->p_align > p_align_max)
> + p_align_max = ph->p_align;
> c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
>
> /* Determine whether there is a gap between the last segment
Kernel also skips non-power of two alignment as invalid, should we do the same
to consider the max alignment?
> @@ -1221,6 +1224,10 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
> goto lose;
> }
>
> + /* Align all PT_LOAD segments to the maximum p_align. */
> + for (size_t i = 0; i < nloadcmds; i++)
> + loadcmds[i].mapalign = p_align_max;
> +
> /* dlopen of an executable is not valid because it is not possible
> to perform proper relocations, handle static TLS, or run the
> ELF constructors. For PIE, the check needs the dynamic
next prev parent reply other threads:[~2022-01-18 17:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-03 23:04 [PATCH v7 0/4] Properly align all PT_LOAD segments with tests H.J. Lu
2022-01-03 23:04 ` [PATCH v7 1/4] elf: Properly align all PT_LOAD segments [BZ #28676] H.J. Lu
2022-01-18 17:48 ` Adhemerval Zanella [this message]
2022-01-18 21:46 ` H.J. Lu
2022-01-03 23:04 ` [PATCH v7 2/4] elf: Add a test for PT_LOAD segments with mixed p_align " H.J. Lu
2022-01-18 16:25 ` Adhemerval Zanella
2022-01-18 21:53 ` H.J. Lu
2022-01-03 23:04 ` [PATCH v7 3/4] elf: Add a test for PT_LOAD segments with p_align == 1 [BZ #28688] H.J. Lu
2022-01-18 16:32 ` Adhemerval Zanella
2022-01-18 16:36 ` Adhemerval Zanella
2022-01-18 21:55 ` H.J. Lu
2022-01-03 23:04 ` [PATCH v7 4/4] elf: Add a test for PT_LOAD segments with invalid p_align " H.J. Lu
2022-01-18 18:05 ` Adhemerval Zanella
2022-01-18 21:50 ` H.J. Lu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=0a5eb87b-9a3c-6b3b-a82c-58e872e7e42f@linaro.org \
--to=adhemerval.zanella@linaro.org \
--cc=fweimer@redhat.com \
--cc=hjl.tools@gmail.com \
--cc=libc-alpha@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).