On 10/06/2016 07:18 AM, Mark Wielaard wrote:
> Having a symbol in an allocated symbol table (like .dynsym) that
> points to an unallocated section is wrong. Traditionally strip
> has removed such symbols if they are section or group symbols.
> But removing a real symbol from an allocate symbol table is hard
> and probably a mistake. Really removing it means rewriting the
> dynamic segment and hash sections. Since we don't do that, don't
> remove the symbol (and corrupt the ELF file). Do warn and set
> the symbol section to SHN_UNDEF.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1380961
>
> Signed-off-by: Mark Wielaard <m...@redhat.com>
Works for me. On the test from bugzilla, I get the expected warning:
strip: Cannot remove symbol [1550] from allocated symbol table [3]
but ldd is perfectly happy with the result.
I also tried it with a manual "objcopy -R .rustc" beforehand, which I
will probably do in the rpm to prevent that section from even being
saved to debuginfo -- just discard it entirely. Strip still works with
the same warning and a working result.
> ---
> src/ChangeLog | 5 +++++
> src/strip.c | 35 ++++++++++++++++++++++++-----------
> 2 files changed, 29 insertions(+), 11 deletions(-)
>
> diff --git a/src/ChangeLog b/src/ChangeLog
> index e5b3b20..70d11f2 100644
> --- a/src/ChangeLog
> +++ b/src/ChangeLog
> @@ -1,3 +1,8 @@
> +2016-10-06 Mark Wielaard <m...@redhat.com>
> +
> + * strip.c (handle_elf): Don't remove real symbols from allocated
> + symbol tables.
> +
> 2016-08-25 Mark Wielaard <m...@redhat.com>
>
> * strip.c (handle_elf): Recompress with ELF_CHF_FORCE.
> diff --git a/src/strip.c b/src/strip.c
> index da093e9..819b67e 100644
> --- a/src/strip.c
> +++ b/src/strip.c
> @@ -1341,15 +1341,12 @@ handle_elf (int fd, Elf *elf, const char *prefix,
> const char *fname,
>
> /* Get the full section index, if necessary from the
> XINDEX table. */
> - if (sym->st_shndx != SHN_XINDEX)
> - sec = shdr_info[sym->st_shndx].idx;
> - else
> - {
> - elf_assert (shndxdata != NULL
> - && shndxdata->d_buf != NULL);
> -
> - sec = shdr_info[xshndx].idx;
> - }
> + if (sym->st_shndx == SHN_XINDEX)
> + elf_assert (shndxdata != NULL
> + && shndxdata->d_buf != NULL);
> + size_t sidx = (sym->st_shndx != SHN_XINDEX
> + ? sym->st_shndx : xshndx);
> + sec = shdr_info[sidx].idx;
>
> if (sec != 0)
> {
> @@ -1387,6 +1384,24 @@ handle_elf (int fd, Elf *elf, const char *prefix,
> const char *fname,
> shdr_info[cnt].shdr.sh_info = destidx - 1;
> }
> }
> + else if ((shdr_info[cnt].shdr.sh_flags & SHF_ALLOC) != 0
> + && GELF_ST_TYPE (sym->st_info) != STT_SECTION
> + && shdr_info[sidx].shdr.sh_type != SHT_GROUP)
> + {
> + /* Removing a real symbol from an allocated
> + symbol table is hard and probably a
> + mistake. Really removing it means
> + rewriting the dynamic segment and hash
> + sections. Just warn and set the symbol
> + section to UNDEF. */
> + error (0, 0,
> + gettext ("Cannot remove symbol [%zd] from
> allocated symbol table [%zd]"), inner, cnt);
> + sym->st_shndx = SHN_UNDEF;
> + if (gelf_update_sym (shdr_info[cnt].data, destidx,
> + sym) == 0)
> + INTERNAL_ERROR (fname);
> + shdr_info[cnt].newsymidx[inner] = destidx++;
> + }
> else if (debug_fname != NULL
> && shdr_info[cnt].debug_data == NULL)
> /* The symbol points to a section that is discarded
> @@ -1394,8 +1409,6 @@ handle_elf (int fd, Elf *elf, const char *prefix, const
> char *fname,
> this is a section or group signature symbol
> for a section which has been removed. */
> {
> - size_t sidx = (sym->st_shndx != SHN_XINDEX
> - ? sym->st_shndx : xshndx);
> elf_assert (GELF_ST_TYPE (sym->st_info) == STT_SECTION
> || ((shdr_info[sidx].shdr.sh_type
> == SHT_GROUP)
>
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