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riscv: Resolve symbols directly for symbols with STO_RISCV_VARIANT_CC.

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In some cases, we do not want to go through the resolver for function
calls. For example, functions with vector arguments will use vector
registers to pass arguments. In the resolver, we do not save/restore the
vector argument registers for lazy binding efficiency. To avoid ruining
the vector arguments, functions with vector arguments will not go
through the resolver.

To achieve the goal, we will annotate the function symbols with
STO_RISCV_VARIANT_CC flag and add DT_RISCV_VARIANT_CC tag in the dynamic
section. In the first pass on PLT relocations, we do not set up to call
_dl_runtime_resolve. Instead, we resolve the functions directly.

Signed-off-by: Hsiangkai Wang <kai.wang@sifive.com>
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://inbox.sourceware.org/libc-alpha/20230314162512.35802-1-kito.cheng@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Hsiangkai Wang
2023-03-15 00:25:12 +08:00
committed by Palmer Dabbelt
parent 2fa7fd1af7
commit 117e8b341c
4 changed files with 60 additions and 0 deletions
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26
sysdeps/riscv/dl-machine.h
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@ -53,6 +53,9 @@
|| (__WORDSIZE == 64 && (type) == R_RISCV_TLS_TPREL64))) \
| (ELF_RTYPE_CLASS_COPY * ((type) == R_RISCV_COPY)))
//* Translate a processor specific dynamic tag to the index in l_info array. */
#define DT_RISCV(x) (DT_RISCV_##x - DT_LOPROC + DT_NUM)
/* Return nonzero iff ELF header is compatible with the running host. */
static inline int __attribute_used__
elf_machine_matches_host (const ElfW(Ehdr) *ehdr)
@ -281,6 +284,29 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
/* Check for unexpected PLT reloc type. */
if (__glibc_likely (r_type == R_RISCV_JUMP_SLOT))
{
if (__glibc_unlikely (map->l_info[DT_RISCV (VARIANT_CC)] != NULL))
{
/* Check the symbol table for variant CC symbols. */
const Elf_Symndx symndx = ELFW(R_SYM) (reloc->r_info);
const ElfW(Sym) *symtab =
(const void *)D_PTR (map, l_info[DT_SYMTAB]);
const ElfW(Sym) *sym = &symtab[symndx];
if (__glibc_unlikely (sym->st_other & STO_RISCV_VARIANT_CC))
{
/* Avoid lazy resolution of variant CC symbols. */
const struct r_found_version *version = NULL;
if (map->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
{
const ElfW(Half) *vernum =
(const void *)D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);
version = &map->l_versions[vernum[symndx] & 0x7fff];
}
elf_machine_rela (map, scope, reloc, sym, version, reloc_addr,
skip_ifunc);
return;
}
}
if (__glibc_unlikely (map->l_mach.plt == 0))
{
if (l_addr)