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?
ср, 7 февр. 2024 г. в 11:53, Waldemar Brodkorb <w...@openadk.org>:
> Hi Dmitry,
>
> thanks for the patch.
> Unfortunately it breaks ARM FDPIC toolchain building:
> ldso/ldso/dl-startup.c: In function '_dl_start':
> ldso/ldso/dl-startup.c:268:9: error: aggregate value used where an
> integer was expected
> 268 | DL_RELOCATE_RELR(tpnt);
> | ^~~~~~~~~~~~~~~~
>
> You could use OpenADK to produce such a toolchain.
>
> Any idea what is wrong?
>
> best regards
> Waldemar
>
> Dmitry Chestnykh wrote,
>
> > 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 | 38 ++++++++++++++++++++++++++
> > ldso/ldso/dl-elf.c | 3 ++
> > ldso/ldso/dl-startup.c | 3 ++
> > libc/misc/internals/reloc_static_pie.c | 1 +
> > 5 files changed, 52 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..10b895733 100644
> > --- a/ldso/include/dl-elf.h
> > +++ b/ldso/include/dl-elf.h
> > @@ -250,5 +250,43 @@ 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))
> >
> > +/* 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 /* _DL_ELF_H */
> > diff --git a/ldso/ldso/dl-elf.c b/ldso/ldso/dl-elf.c
> > index 8210a012e..cc42b904f 100644
> > --- a/ldso/ldso/dl-elf.c
> > +++ b/ldso/ldso/dl-elf.c
> > @@ -1027,6 +1027,9 @@ int _dl_fixup(struct dyn_elf *rpnt, struct
> r_scope_elem *scope, int now_flag)
> > return goof;
> > }
> >
> > + /* Process DT_RELR relative relocations */
> > + DL_RELOCATE_RELR(tpnt);
> > +
> > 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..674c4b7b9 100644
> > --- a/ldso/ldso/dl-startup.c
> > +++ b/ldso/ldso/dl-startup.c
> > @@ -264,6 +264,9 @@ 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");
> >
> > + /* Process DT_RELR relative relocations */
> > + DL_RELOCATE_RELR(tpnt);
> > +
> > {
> > 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..7ad80f97b 100644
> > --- a/libc/misc/internals/reloc_static_pie.c
> > +++ b/libc/misc/internals/reloc_static_pie.c
> > @@ -53,6 +53,7 @@ reloc_static_pie(ElfW(Addr) load_addr)
> > PERFORM_BOOTSTRAP_GOT(tpnt);
> > #endif
> >
> > + DL_RELOCATE_RELR(tpnt);
> >
> > #if defined(ELF_MACHINE_PLTREL_OVERLAP)
> > # define INDX_MAX 1
> > --
> > 2.43.0
> >
> > _______________________________________________
> > devel mailing list -- devel@uclibc-ng.org
> > To unsubscribe send an email to devel-le...@uclibc-ng.org
> >
>
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