Hi Dmitry,
Dmitriy Chestnykh wrote,
> Can you test please a new version of the patch?
> I have wrapped DL_RELOCATE_RELR() with #if !define(__FDPIC__).
That worked now even for FDPIC toolchains.
Thanks.
Applied and pushed,
best regards
Waldemar
>
> From f805b20fac1c77a3aa021825701ba36735cf3060 Mon Sep 17 00:00:00 2001
> From: Dmitry Chestnykh <dm.chestn...@gmail.com>
> Date: Tue, 6 Feb 2024 09:13:41 +0300
> Subject: [PATCH v3] ld.so: Add support of DT_RELR relocation format.
>
> Nowadays modern libcs like Glibc and musl currently
> support processing of RELATIVE relocations compressed
> with DT_RELR format. However I have noticed that uClibc-ng
> doesn't support this feature and if the source will be linked with
> `-Wl,-z,pack-relative-relos` (bfd) or `-Wl,--pack-dyn-relocs=relr`
> (lld) then ld.so cannot properly load the produced DSO.
> This patch is intended to fix this issue and adds applying
> of DT_RELR relative relocation.
>
> Signed-off-by: Dmitry Chestnykh <dm.chestn...@gmail.com>
> ---
> include/elf.h | 8 ++++-
> ldso/include/dl-elf.h | 41 ++++++++++++++++++++++++++
> ldso/ldso/dl-elf.c | 5 ++++
> ldso/ldso/dl-startup.c | 5 ++++
> libc/misc/internals/reloc_static_pie.c | 3 ++
> 5 files changed, 61 insertions(+), 1 deletion(-)
>
> diff --git a/include/elf.h b/include/elf.h
> index b7edbade2..c2efa9978 100644
> --- a/include/elf.h
> +++ b/include/elf.h
> @@ -60,6 +60,9 @@ typedef uint16_t Elf64_Section;
> typedef Elf32_Half Elf32_Versym;
> typedef Elf64_Half Elf64_Versym;
>
> +/* Type for relative relocations in DT_RELR format */
> +typedef Elf32_Word Elf32_Relr;
> +typedef Elf64_Xword Elf64_Relr;
>
> /* The ELF file header. This appears at the start of every ELF file. */
>
> @@ -818,7 +821,10 @@ typedef struct
> #define DT_ENCODING 32 /* Start of encoded range */
> #define DT_PREINIT_ARRAY 32 /* Array with addresses of preinit
> fct*
> /
> #define DT_PREINIT_ARRAYSZ 33 /* size in bytes of DT_PREINIT_ARRAY
> */
> -#define DT_NUM 34 /* Number used */
> +#define DT_RELRSZ 35 /* Size in bytes, of DT_RELR table */
> +#define DT_RELR 36 /* Address of Relr relocs */
> +#define DT_RELRENT 37 /* Size in bytes of one DT_RELR entry
> *
> /
> +#define DT_NUM 38 /* Number used */
> #define DT_LOOS 0x6000000d /* Start of OS-specific */
> #define DT_HIOS 0x6ffff000 /* End of OS-specific */
> #define DT_LOPROC 0x70000000 /* Start of processor-specific */
> diff --git a/ldso/include/dl-elf.h b/ldso/include/dl-elf.h
> index 2b99958d9..7d514c0f5 100644
> --- a/ldso/include/dl-elf.h
> +++ b/ldso/include/dl-elf.h
> @@ -250,5 +250,46 @@ unsigned int __dl_parse_dynamic_info(ElfW(Dyn) *dpnt,
> unsigned long dynamic_info
> (((X) & PF_W) ? PROT_WRITE : 0) | \
> (((X) & PF_X) ? PROT_EXEC : 0))
>
> +/* FDPIC ABI don't use relative relocations */
> +#if !defined(__FDPIC__)
> +/* Apply relocations in DT_RELR format */
> +#define DL_DO_RELOCATE_RELR(load_addr, relr_start, relr_end) \
> + do { \
> + const ElfW(Relr) *relr = 0; \
> + ElfW(Addr) *reloc_addr = 0; \
> + for (relr = relr_start; relr < relr_end; relr++) { \
> + ElfW(Relr) relr_entry = *relr; \
> + if (!(relr_entry & 1)) \
> + { \
> + reloc_addr = (ElfW(Addr) *)
> DL_RELOC_ADDR(load_addr, relr_entry); \
> + *reloc_addr =
> (ElfW(Addr))DL_RELOC_ADDR
> (load_addr, reloc_addr); \
> + reloc_addr++; \
> + } \
> + else \
> + { \
> + for (long int i = 0; (relr_entry >>=
> 1)
> != 0; ++i) { \
> + if ((relr_entry & 1) != 0) \
> + reloc_addr[i] = (ElfW
> (Addr))DL_RELOC_ADDR(load_addr, reloc_addr[i]); \
> + } \
> + reloc_addr += CHAR_BIT * sizeof(ElfW
> (Relr)) - 1; \
> + } \
> + } \
> + } while (0);
> +
> +/* The macro to prepare data for the above DL_DO_RELOCATE_RELR */
> +#define DL_RELOCATE_RELR(dyn) \
> + do { \
> + if (dyn->dynamic_info[DT_RELRENT]) \
> + _dl_assert(dyn->dynamic_info[DT_RELRENT] ==
> sizeof(ElfW(Relr))); \
> + if (dyn->dynamic_info[DT_RELR] && \
> + dyn->dynamic_info[DT_RELRSZ]) { \
> + ElfW(Relr) *relr_start = (ElfW(Relr) *)((ElfW
> (Addr))dyn->loadaddr + (ElfW(Addr))dyn->dynamic_info[DT_RELR]); \
> + ElfW(Relr) *relr_end = (ElfW(Relr) *)((const
> char *)relr_start + dyn->dynamic_info[DT_RELRSZ]); \
> + _dl_if_debug_dprint("Relocating DT_RELR in %s:
> start:%p, end:%p\n", \
> + dyn->libname, (void *)
> relr_start, (void *)relr_end); \
> + DL_DO_RELOCATE_RELR(dyn->loadaddr, relr_start,
> relr_end); \
> + } \
> + } while (0);
> +#endif /* __FDPIC__ */
>
> #endif /* _DL_ELF_H */
> diff --git a/ldso/ldso/dl-elf.c b/ldso/ldso/dl-elf.c
> index 8210a012e..27907d355 100644
> --- a/ldso/ldso/dl-elf.c
> +++ b/ldso/ldso/dl-elf.c
> @@ -1027,6 +1027,11 @@ int _dl_fixup(struct dyn_elf *rpnt, struct r_scope_elem
> *scope, int now_flag)
> return goof;
> }
>
> +#if !defined(__FDPIC__)
> + /* Process DT_RELR relative relocations */
> + DL_RELOCATE_RELR(tpnt);
> +#endif
> +
> reloc_size = tpnt->dynamic_info[DT_RELOC_TABLE_SIZE];
> /* On some machines, notably SPARC & PPC, DT_REL* includes DT_JMPREL in its
> range. Note that according to the ELF spec, this is completely legal! */
> diff --git a/ldso/ldso/dl-startup.c b/ldso/ldso/dl-startup.c
> index 989711fcc..d80ee75ea 100644
> --- a/ldso/ldso/dl-startup.c
> +++ b/ldso/ldso/dl-startup.c
> @@ -264,6 +264,11 @@ DL_START(unsigned long args)
> that once we are done, we have considerably more flexibility. */
> SEND_EARLY_STDERR_DEBUG("About to do library loader relocations\n");
>
> +#if !defined(__FDPIC__)
> + /* Process DT_RELR relative relocations */
> + DL_RELOCATE_RELR(tpnt);
> +#endif
> +
> {
> int indx;
> #if defined(ELF_MACHINE_PLTREL_OVERLAP)
> diff --git a/libc/misc/internals/reloc_static_pie.c b/libc/misc/internals/
> reloc_static_pie.c
> index ab1923024..81af7d666 100644
> --- a/libc/misc/internals/reloc_static_pie.c
> +++ b/libc/misc/internals/reloc_static_pie.c
> @@ -53,6 +53,9 @@ reloc_static_pie(ElfW(Addr) load_addr)
> PERFORM_BOOTSTRAP_GOT(tpnt);
> #endif
>
> +#if !defined(__FDPIC__)
> + DL_RELOCATE_RELR(tpnt);
> +#endif
>
> #if defined(ELF_MACHINE_PLTREL_OVERLAP)
> # define INDX_MAX 1
> --
> 2.43.0
>
> ср, 7 февр. 2024 г. в 12:20, Waldemar Brodkorb <w...@openadk.org>:
>
> Hi Dmitry,
> Dmitriy Chestnykh wrote,
>
> > But I know that FDPIC ABIs don't use relative relocations because FDPIC
> don't
> > have single base address.
> > Probably I can detect whether the toolchain is FDPIC by some predefined
> > compiler macroses and wrap DL_RELOCATE_RELR with
> > #ifndef FDPIC
> > #endif.
> > Would this be a suitable solution?
>
> Yes, __FDPIC__ is defined.
>
> best regards
> Waldemar
>
>
_______________________________________________
devel mailing list -- devel@uclibc-ng.org
To unsubscribe send an email to devel-le...@uclibc-ng.org
