this resolves DT_RELR relocations in non-ldso objects. generic-abi pre-standard for DT_RELR: https://groups.google.com/g/generic-abi/c/bX460iggiKg FreeBSD rtld added DT_RELR support in 2021-08. glibc added DT_RELR support in 2022-04. Since ld.lld 7, --pack-dyn-relocs=relr can generate DT_RELR. Since binutils 2.38, GNU ld's x86 and powerpc64 ports supports -z pack-relative-relocs to generate DT_RELR. ld.lld 15 also has the option. --- Changes from https://www.openwall.com/lists/musl/2019/03/06/3 * rename some variables * decode_vec: add `if (v[0] < 8*sizeof(long))` --- include/elf.h | 8 ++++++-- ldso/dynlink.c | 20 +++++++++++++++++++- src/internal/dynlink.h | 2 +- 3 files changed, 26 insertions(+), 4 deletions(-) diff --git a/include/elf.h b/include/elf.h index 86e2f0bb..9e980a29 100644 --- a/include/elf.h +++ b/include/elf.h @@ -385,7 +385,8 @@ typedef struct { #define SHT_PREINIT_ARRAY 16 #define SHT_GROUP 17 #define SHT_SYMTAB_SHNDX 18 -#define SHT_NUM 19 +#define SHT_RELR 19 +#define SHT_NUM 20 #define SHT_LOOS 0x60000000 #define SHT_GNU_ATTRIBUTES 0x6ffffff5 #define SHT_GNU_HASH 0x6ffffff6 @@ -754,7 +755,10 @@ typedef struct { #define DT_PREINIT_ARRAY 32 #define DT_PREINIT_ARRAYSZ 33 #define DT_SYMTAB_SHNDX 34 -#define DT_NUM 35 +#define DT_RELRSZ 35 +#define DT_RELR 36 +#define DT_RELRENT 37 +#define DT_NUM 38 #define DT_LOOS 0x6000000d #define DT_HIOS 0x6ffff000 #define DT_LOPROC 0x70000000 diff --git a/ldso/dynlink.c b/ldso/dynlink.c index 5b9c8be4..a50ef00a 100644 --- a/ldso/dynlink.c +++ b/ldso/dynlink.c @@ -208,7 +208,8 @@ static void decode_vec(size_t *v, size_t *a, size_t cnt) size_t i; for (i=0; i<cnt; i++) a[i] = 0; for (; v[0]; v+=2) if (v[0]-1<cnt-1) { - a[0] |= 1UL<<v[0]; + if (v[0] < 8*sizeof(long)) + a[0] |= 1UL<<v[0]; a[v[0]] = v[1]; } } @@ -513,6 +514,22 @@ static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stri } } +static void do_relr_relocs(struct dso *dso, size_t *relr, size_t relr_size) { + unsigned char *base = dso->base; + size_t *reloc_addr; + for (; relr_size; relr++, relr_size-=sizeof(size_t)) + if ((relr[0]&1) == 0) { + reloc_addr = laddr(dso, relr[0]); + *reloc_addr++ += (size_t)base; + } else { + int i = 0; + for (size_t bitmap=relr[0]; (bitmap>>=1); i++) + if (bitmap&1) + reloc_addr[i] += (size_t)base; + reloc_addr += 8*sizeof(size_t)-1; + } +} + static void redo_lazy_relocs() { struct dso *p = lazy_head, *next; @@ -1355,6 +1372,7 @@ static void reloc_all(struct dso *p) 2+(dyn[DT_PLTREL]==DT_RELA)); do_relocs(p, laddr(p, dyn[DT_REL]), dyn[DT_RELSZ], 2); do_relocs(p, laddr(p, dyn[DT_RELA]), dyn[DT_RELASZ], 3); + do_relr_relocs(p, laddr(p, dyn[DT_RELR]), dyn[DT_RELRSZ]); if (head != &ldso && p->relro_start != p->relro_end && mprotect(laddr(p, p->relro_start), p->relro_end-p->relro_start, PROT_READ) diff --git a/src/internal/dynlink.h b/src/internal/dynlink.h index 51c0639f..830354eb 100644 --- a/src/internal/dynlink.h +++ b/src/internal/dynlink.h @@ -93,7 +93,7 @@ struct fdpic_dummy_loadmap { #endif #define AUX_CNT 32 -#define DYN_CNT 32 +#define DYN_CNT 37 typedef void (*stage2_func)(unsigned char *, size_t *); -- 2.36.1
On 2022-06-05, Fangrui Song wrote:
>this resolves DT_RELR relocations in non-ldso objects.
>
>generic-abi pre-standard for DT_RELR:
>https://groups.google.com/g/generic-abi/c/bX460iggiKg
>FreeBSD rtld added DT_RELR support in 2021-08.
>glibc added DT_RELR support in 2022-04.
>
>Since ld.lld 7, --pack-dyn-relocs=relr can generate DT_RELR.
>Since binutils 2.38, GNU ld's x86 and powerpc64 ports supports -z
>pack-relative-relocs to generate DT_RELR. ld.lld 15 also has the option.
Ping
On Wed, Jun 22, 2022 at 7:12 PM Fangrui Song <i@maskray.me> wrote:
>
> On 2022-06-05, Fangrui Song wrote:
> >this resolves DT_RELR relocations in non-ldso objects.
> >
> >generic-abi pre-standard for DT_RELR:
> >https://groups.google.com/g/generic-abi/c/bX460iggiKg
> >FreeBSD rtld added DT_RELR support in 2021-08.
> >glibc added DT_RELR support in 2022-04.
> >
> >Since ld.lld 7, --pack-dyn-relocs=relr can generate DT_RELR.
> >Since binutils 2.38, GNU ld's x86 and powerpc64 ports supports -z
> >pack-relative-relocs to generate DT_RELR. ld.lld 15 also has the option.
>
> Ping
Ping^2
On Sun, Jun 05, 2022 at 11:16:33PM -0700, Fangrui Song wrote: > this resolves DT_RELR relocations in non-ldso objects. > > generic-abi pre-standard for DT_RELR: > https://groups.google.com/g/generic-abi/c/bX460iggiKg > FreeBSD rtld added DT_RELR support in 2021-08. > glibc added DT_RELR support in 2022-04. > > Since ld.lld 7, --pack-dyn-relocs=relr can generate DT_RELR. > Since binutils 2.38, GNU ld's x86 and powerpc64 ports supports -z > pack-relative-relocs to generate DT_RELR. ld.lld 15 also has the option. > > --- > Changes from https://www.openwall.com/lists/musl/2019/03/06/3 > * rename some variables > * decode_vec: add `if (v[0] < 8*sizeof(long))` > --- > include/elf.h | 8 ++++++-- > ldso/dynlink.c | 20 +++++++++++++++++++- > src/internal/dynlink.h | 2 +- > 3 files changed, 26 insertions(+), 4 deletions(-) > > diff --git a/include/elf.h b/include/elf.h > index 86e2f0bb..9e980a29 100644 > --- a/include/elf.h > +++ b/include/elf.h > @@ -385,7 +385,8 @@ typedef struct { > #define SHT_PREINIT_ARRAY 16 > #define SHT_GROUP 17 > #define SHT_SYMTAB_SHNDX 18 > -#define SHT_NUM 19 > +#define SHT_RELR 19 > +#define SHT_NUM 20 > #define SHT_LOOS 0x60000000 > #define SHT_GNU_ATTRIBUTES 0x6ffffff5 > #define SHT_GNU_HASH 0x6ffffff6 > @@ -754,7 +755,10 @@ typedef struct { > #define DT_PREINIT_ARRAY 32 > #define DT_PREINIT_ARRAYSZ 33 > #define DT_SYMTAB_SHNDX 34 > -#define DT_NUM 35 > +#define DT_RELRSZ 35 > +#define DT_RELR 36 > +#define DT_RELRENT 37 > +#define DT_NUM 38 > #define DT_LOOS 0x6000000d > #define DT_HIOS 0x6ffff000 > #define DT_LOPROC 0x70000000 > diff --git a/ldso/dynlink.c b/ldso/dynlink.c > index 5b9c8be4..a50ef00a 100644 > --- a/ldso/dynlink.c > +++ b/ldso/dynlink.c > @@ -208,7 +208,8 @@ static void decode_vec(size_t *v, size_t *a, size_t cnt) > size_t i; > for (i=0; i<cnt; i++) a[i] = 0; > for (; v[0]; v+=2) if (v[0]-1<cnt-1) { > - a[0] |= 1UL<<v[0]; > + if (v[0] < 8*sizeof(long)) > + a[0] |= 1UL<<v[0]; > a[v[0]] = v[1]; > } > } > @@ -513,6 +514,22 @@ static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stri > } > } > > +static void do_relr_relocs(struct dso *dso, size_t *relr, size_t relr_size) { > + unsigned char *base = dso->base; > + size_t *reloc_addr; > + for (; relr_size; relr++, relr_size-=sizeof(size_t)) > + if ((relr[0]&1) == 0) { > + reloc_addr = laddr(dso, relr[0]); > + *reloc_addr++ += (size_t)base; > + } else { > + int i = 0; > + for (size_t bitmap=relr[0]; (bitmap>>=1); i++) > + if (bitmap&1) > + reloc_addr[i] += (size_t)base; > + reloc_addr += 8*sizeof(size_t)-1; > + } > +} > + As written, this code is assuming !FDPIC, so should probably be conditional on that. However I think it can be written not to make this assumption, as: *reloc_addr = laddr(dso, *reloc_addr); reloc_addr++; instead of: *reloc_addr++ += base; and likewise in the second instance. The laddr() macro exists specifically to abstract translating "addresss in space of ELF image" to "address as mapped in memory" which I think is the intended semantic here. Is that correct? > static void redo_lazy_relocs() > { > struct dso *p = lazy_head, *next; > @@ -1355,6 +1372,7 @@ static void reloc_all(struct dso *p) > 2+(dyn[DT_PLTREL]==DT_RELA)); > do_relocs(p, laddr(p, dyn[DT_REL]), dyn[DT_RELSZ], 2); > do_relocs(p, laddr(p, dyn[DT_RELA]), dyn[DT_RELASZ], 3); > + do_relr_relocs(p, laddr(p, dyn[DT_RELR]), dyn[DT_RELRSZ]); > > if (head != &ldso && p->relro_start != p->relro_end && > mprotect(laddr(p, p->relro_start), p->relro_end-p->relro_start, PROT_READ) > diff --git a/src/internal/dynlink.h b/src/internal/dynlink.h > index 51c0639f..830354eb 100644 > --- a/src/internal/dynlink.h > +++ b/src/internal/dynlink.h > @@ -93,7 +93,7 @@ struct fdpic_dummy_loadmap { > #endif > > #define AUX_CNT 32 > -#define DYN_CNT 32 > +#define DYN_CNT 37 I was concerned about the decode_vec [0] slot bitmask usage, but you addressed that, and I've checked for other instances that might be wrong but couldn't find any, so I think it's okay. Rich
On 2022-08-02, Rich Felker wrote: >On Sun, Jun 05, 2022 at 11:16:33PM -0700, Fangrui Song wrote: >> this resolves DT_RELR relocations in non-ldso objects. >> >> generic-abi pre-standard for DT_RELR: >> https://groups.google.com/g/generic-abi/c/bX460iggiKg >> FreeBSD rtld added DT_RELR support in 2021-08. >> glibc added DT_RELR support in 2022-04. >> >> Since ld.lld 7, --pack-dyn-relocs=relr can generate DT_RELR. >> Since binutils 2.38, GNU ld's x86 and powerpc64 ports supports -z >> pack-relative-relocs to generate DT_RELR. ld.lld 15 also has the option. >> >> --- >> Changes from https://www.openwall.com/lists/musl/2019/03/06/3 >> * rename some variables >> * decode_vec: add `if (v[0] < 8*sizeof(long))` >> --- >> include/elf.h | 8 ++++++-- >> ldso/dynlink.c | 20 +++++++++++++++++++- >> src/internal/dynlink.h | 2 +- >> 3 files changed, 26 insertions(+), 4 deletions(-) >> >> diff --git a/include/elf.h b/include/elf.h >> index 86e2f0bb..9e980a29 100644 >> --- a/include/elf.h >> +++ b/include/elf.h >> @@ -385,7 +385,8 @@ typedef struct { >> #define SHT_PREINIT_ARRAY 16 >> #define SHT_GROUP 17 >> #define SHT_SYMTAB_SHNDX 18 >> -#define SHT_NUM 19 >> +#define SHT_RELR 19 >> +#define SHT_NUM 20 >> #define SHT_LOOS 0x60000000 >> #define SHT_GNU_ATTRIBUTES 0x6ffffff5 >> #define SHT_GNU_HASH 0x6ffffff6 >> @@ -754,7 +755,10 @@ typedef struct { >> #define DT_PREINIT_ARRAY 32 >> #define DT_PREINIT_ARRAYSZ 33 >> #define DT_SYMTAB_SHNDX 34 >> -#define DT_NUM 35 >> +#define DT_RELRSZ 35 >> +#define DT_RELR 36 >> +#define DT_RELRENT 37 >> +#define DT_NUM 38 >> #define DT_LOOS 0x6000000d >> #define DT_HIOS 0x6ffff000 >> #define DT_LOPROC 0x70000000 >> diff --git a/ldso/dynlink.c b/ldso/dynlink.c >> index 5b9c8be4..a50ef00a 100644 >> --- a/ldso/dynlink.c >> +++ b/ldso/dynlink.c >> @@ -208,7 +208,8 @@ static void decode_vec(size_t *v, size_t *a, size_t cnt) >> size_t i; >> for (i=0; i<cnt; i++) a[i] = 0; >> for (; v[0]; v+=2) if (v[0]-1<cnt-1) { >> - a[0] |= 1UL<<v[0]; >> + if (v[0] < 8*sizeof(long)) >> + a[0] |= 1UL<<v[0]; >> a[v[0]] = v[1]; >> } >> } >> @@ -513,6 +514,22 @@ static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stri >> } >> } >> >> +static void do_relr_relocs(struct dso *dso, size_t *relr, size_t relr_size) { >> + unsigned char *base = dso->base; >> + size_t *reloc_addr; >> + for (; relr_size; relr++, relr_size-=sizeof(size_t)) >> + if ((relr[0]&1) == 0) { >> + reloc_addr = laddr(dso, relr[0]); >> + *reloc_addr++ += (size_t)base; >> + } else { >> + int i = 0; >> + for (size_t bitmap=relr[0]; (bitmap>>=1); i++) >> + if (bitmap&1) >> + reloc_addr[i] += (size_t)base; >> + reloc_addr += 8*sizeof(size_t)-1; >> + } >> +} >> + > >As written, this code is assuming !FDPIC, so should probably be >conditional on that. However I think it can be written not to make >this assumption, as: > > *reloc_addr = laddr(dso, *reloc_addr); > reloc_addr++; > >instead of: > > *reloc_addr++ += base; > >and likewise in the second instance. The laddr() macro exists >specifically to abstract translating "addresss in space of ELF image" >to "address as mapped in memory" which I think is the intended >semantic here. Is that correct? I have to confess I don't know much about FDPIC (I merely read a little bit about "ARM FDPIC ABI" a while ago.) DT_RELR operations should resemble REL_RELATIVE for REL/RELA. The REL_RELATIVE code does *reloc_addr = (size_t)base + addend; so I think `*reloc_addr++ += (size_t)base;` is fine. >> static void redo_lazy_relocs() >> { >> struct dso *p = lazy_head, *next; >> @@ -1355,6 +1372,7 @@ static void reloc_all(struct dso *p) >> 2+(dyn[DT_PLTREL]==DT_RELA)); >> do_relocs(p, laddr(p, dyn[DT_REL]), dyn[DT_RELSZ], 2); >> do_relocs(p, laddr(p, dyn[DT_RELA]), dyn[DT_RELASZ], 3); >> + do_relr_relocs(p, laddr(p, dyn[DT_RELR]), dyn[DT_RELRSZ]); >> >> if (head != &ldso && p->relro_start != p->relro_end && >> mprotect(laddr(p, p->relro_start), p->relro_end-p->relro_start, PROT_READ) >> diff --git a/src/internal/dynlink.h b/src/internal/dynlink.h >> index 51c0639f..830354eb 100644 >> --- a/src/internal/dynlink.h >> +++ b/src/internal/dynlink.h >> @@ -93,7 +93,7 @@ struct fdpic_dummy_loadmap { >> #endif >> >> #define AUX_CNT 32 >> -#define DYN_CNT 32 >> +#define DYN_CNT 37 > >I was concerned about the decode_vec [0] slot bitmask usage, but you >addressed that, and I've checked for other instances that might be >wrong but couldn't find any, so I think it's okay. > >Rich