From: Fangrui Song <maskray@google.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: libc-alpha@sourceware.org,
Adhemerval Zanella <adhemerval.zanella@linaro.org>
Subject: Re: [PATCH v11 4/7] elf: Properly handle zero DT_RELA/DT_REL values
Date: Fri, 22 Apr 2022 15:39:15 -0700 [thread overview]
Message-ID: <20220422223915.6xzoovbwxr7tdcyv@google.com> (raw)
In-Reply-To: <20220422190139.2615492-5-hjl.tools@gmail.com>
On 2022-04-22, H.J. Lu wrote:
>With DT_RELR, there may be no relocations in DT_RELA/DT_REL and their
>entry values are zero. Don't relocate DT_RELA/DT_REL and update the
>combined relocation start address if their entry values are zero.
>---
> elf/dynamic-link.h | 6 +++++-
> elf/get-dynamic-info.h | 24 ++++++++++++++++++------
> 2 files changed, 23 insertions(+), 7 deletions(-)
>
>diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h
>index 019088f248..debbb8c9f7 100644
>--- a/elf/dynamic-link.h
>+++ b/elf/dynamic-link.h
>@@ -84,7 +84,9 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
> __typeof (((ElfW(Dyn) *) 0)->d_un.d_val) nrelative; int lazy; } \
> ranges[2] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 } }; \
> \
>- if ((map)->l_info[DT_##RELOC]) \
>+ /* With DT_RELR, DT_RELA/DT_REL can have zero value. */ \
>+ if ((map)->l_info[DT_##RELOC] != NULL \
>+ && (map)->l_info[DT_##RELOC]->d_un.d_ptr != 0) \
> { \
> ranges[0].start = D_PTR ((map), l_info[DT_##RELOC]); \
> ranges[0].size = (map)->l_info[DT_##RELOC##SZ]->d_un.d_val; \
>@@ -98,6 +100,8 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
> ElfW(Addr) start = D_PTR ((map), l_info[DT_JMPREL]); \
> ElfW(Addr) size = (map)->l_info[DT_PLTRELSZ]->d_un.d_val; \
> \
>+ if (ranges[0].start == 0) \
>+ ranges[0].start = start; \
> if (ranges[0].start + ranges[0].size == (start + size)) \
> ranges[0].size -= size; \
> if (!(do_lazy) \
>diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
>index 6c2a3a12b1..0314baf020 100644
>--- a/elf/get-dynamic-info.h
>+++ b/elf/get-dynamic-info.h
>@@ -75,24 +75,36 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
>
> # define ADJUST_DYN_INFO(tag) \
> do \
>- if (info[tag] != NULL) \
>- info[tag]->d_un.d_ptr += l_addr; \
>+ { \
>+ if (info[tag] != NULL) \
>+ info[tag]->d_un.d_ptr += l_addr; \
>+ } \
> while (0)
>
> ADJUST_DYN_INFO (DT_HASH);
> ADJUST_DYN_INFO (DT_PLTGOT);
> ADJUST_DYN_INFO (DT_STRTAB);
> ADJUST_DYN_INFO (DT_SYMTAB);
>+ ADJUST_DYN_INFO (DT_RELR);
>+ ADJUST_DYN_INFO (DT_JMPREL);
>+ ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
>+ ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
>+# undef ADJUST_DYN_INFO
>+
>+ /* DT_RELA/DT_REL are mandatory. But they may have zero value if
>+ there is DT_RELR. Don't relocate them if they are zero. */
>+# define ADJUST_DYN_INFO(tag) \
>+ do \
>+ if (info[tag] != NULL && info[tag]->d_un.d_ptr != 0) \
>+ info[tag]->d_un.d_ptr += l_addr; \
>+ while (0)
>+
> # if ! ELF_MACHINE_NO_RELA
> ADJUST_DYN_INFO (DT_RELA);
> # endif
> # if ! ELF_MACHINE_NO_REL
> ADJUST_DYN_INFO (DT_REL);
> # endif
>- ADJUST_DYN_INFO (DT_RELR);
>- ADJUST_DYN_INFO (DT_JMPREL);
>- ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
>- ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
> # undef ADJUST_DYN_INFO
> }
> if (info[DT_PLTREL] != NULL)
>--
>2.35.1
>
LG, Thanks
Reviewed-by: Fangrui Song <maskray@google.com>
next prev parent reply other threads:[~2022-04-22 22:39 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-22 19:01 [PATCH v11 0/7] Support DT_RELR relative relocation format H.J. Lu
2022-04-22 19:01 ` [PATCH v11 1/7] elf: Define DT_RELR related macros and types H.J. Lu
2022-04-22 22:36 ` Fangrui Song
2022-04-22 19:01 ` [PATCH v11 2/7] Add GLIBC_ABI_DT_RELR for DT_RELR support H.J. Lu
2022-04-22 22:37 ` Fangrui Song
2022-04-22 19:01 ` [PATCH v11 3/7] elf: Support DT_RELR relative relocation format [BZ #27924] H.J. Lu
2022-04-22 19:01 ` [PATCH v11 4/7] elf: Properly handle zero DT_RELA/DT_REL values H.J. Lu
2022-04-22 22:39 ` Fangrui Song [this message]
2022-04-22 19:01 ` [PATCH v11 5/7] elf: Add more DT_RELR tests H.J. Lu
2022-04-22 19:01 ` [PATCH v11 6/7] Add --disable-default-dt-relr H.J. Lu
2022-04-22 22:43 ` Fangrui Song
2022-04-22 19:01 ` [PATCH v11 7/7] NEWS: Mention DT_RELR support H.J. Lu
2022-04-22 22:40 ` Fangrui Song
2022-04-25 17:23 ` [PATCH v11 0/7] Support DT_RELR relative relocation format Adhemerval Zanella
2022-04-26 15:39 ` H.J. Lu
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