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Message-Id: <20220606061633.539208-1-i@maskray.me> Date: Sun, 5 Jun 2022 23:16:33 -0700 From: Fangrui Song <i@...kray.me> To: musl@...ts.openwall.com Cc: Fangrui Song <i@...kray.me> Subject: [PATCH] ldso: support DT_RELR relative relocation format 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
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