[PATCH] 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.chestnykh@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
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.chestnykh@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
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Hello Waldemar, currently i haven't any ideas but i will check this ASAP
and fix the issue.
ср, 7 февр. 2024 г. в 11:53, Waldemar Brodkorb <wbx@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.chestnykh@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-leave@uclibc-ng.org
> >
>
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 <wbx@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.chestnykh@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-leave@uclibc-ng.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
Can you test please a new version of the patch?
I have wrapped DL_RELOCATE_RELR() with #if !define(__FDPIC__).
From f805b20fac1c77a3aa021825701ba36735cf3060 Mon Sep 17 00:00:00 2001
From: Dmitry Chestnykh <dm.chestnykh@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.chestnykh@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 <wbx@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
>
>
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.chestnykh@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.chestnykh@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 <wbx@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
participants (3)
-
Dmitriy Chestnykh -
Dmitry Chestnykh
-
Waldemar Brodkorb