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RISC-V: Add section of GOT.PLT for kernel module

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Separate the function symbol address from .plt to .got.plt section.

The original plt entry has trampoline code with symbol address,
there is a 32-bit padding bwtween jar instruction and symbol address.

Extract the symbol address to .got.plt to reduce the module size.

Signed-off-by: Zong Li <zong@andestech.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
This commit is contained in:
Zong Li 2018-03-15 16:50:42 +08:00 • committed by Palmer Dabbelt
parent ab1ef68e54
commit b8bde0ef12
No known key found for this signature in database
GPG key ID: EF4CA1502CCBAB41
3 changed files with 45 additions and 17 deletions
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21
arch/riscv/kernel/module-sections.c
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@ -30,18 +30,23 @@ u64 module_emit_got_entry(struct module *mod, u64 val)
u64 module_emit_plt_entry(struct module *mod, u64 val)
{
struct mod_section *got_plt_sec = &mod->arch.got_plt;
struct got_entry *got_plt;
struct mod_section *plt_sec = &mod->arch.plt;
struct plt_entry *plt = get_plt_entry(val, plt_sec);
struct plt_entry *plt = get_plt_entry(val, plt_sec, got_plt_sec);
int i = plt_sec->num_entries;
if (plt)
return (u64)plt;
/* There is no duplicate entry, create a new one */
got_plt = (struct got_entry *)got_plt_sec->shdr->sh_addr;
got_plt[i] = emit_got_entry(val);
plt = (struct plt_entry *)plt_sec->shdr->sh_addr;
plt[i] = emit_plt_entry(val);
plt[i] = emit_plt_entry(val, (u64)&plt[i], (u64)&got_plt[i]);
plt_sec->num_entries++;
got_plt_sec->num_entries++;
BUG_ON(plt_sec->num_entries > plt_sec->max_entries);
return (u64)&plt[i];
@ -94,6 +99,8 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
mod->arch.plt.shdr = sechdrs + i;
else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got"))
mod->arch.got.shdr = sechdrs + i;
else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got.plt"))
mod->arch.got_plt.shdr = sechdrs + i;
}
if (!mod->arch.plt.shdr) {
@ -104,6 +111,10 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
pr_err("%s: module GOT section(s) missing\n", mod->name);
return -ENOEXEC;
}
if (!mod->arch.got_plt.shdr) {
pr_err("%s: module GOT.PLT section(s) missing\n", mod->name);
return -ENOEXEC;
}
/* Calculate the maxinum number of entries */
for (i = 0; i < ehdr->e_shnum; i++) {
@ -135,5 +146,11 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
mod->arch.got.num_entries = 0;
mod->arch.got.max_entries = num_gots;
mod->arch.got_plt.shdr->sh_type = SHT_NOBITS;
mod->arch.got_plt.shdr->sh_flags = SHF_ALLOC;
mod->arch.got_plt.shdr->sh_addralign = L1_CACHE_BYTES;
mod->arch.got_plt.shdr->sh_size = (num_plts + 1) * sizeof(struct got_entry);
mod->arch.got_plt.num_entries = 0;
mod->arch.got_plt.max_entries = num_plts;
return 0;
}