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Subject[PATCH 03/11] RISC-V: Support GOT_HI20/CALL_PLT relocation type in kernel module
Date
For CALL_PLT, emit the plt entry only when offset is more than 32-bit.

For PCREL_LO12, it uses the location of corresponding HI20 to
get the address of external symbol. It should check the HI20 type
is the PCREL_HI20 or GOT_HI20, because sometime the location will
have two or more relocation types.
For example:
0: 00000797 auipc a5,0x0
0: R_RISCV_ALIGN *ABS*
0: R_RISCV_GOT_HI20 SYMBOL
4: 0007b783 ld a5,0(a5) # 0 <SYMBOL>
4: R_RISCV_PCREL_LO12_I .L0
4: R_RISCV_RELAX *ABS*

Signed-off-by: Zong Li <zong@andestech.com>
---
arch/riscv/kernel/module.c | 61 ++++++++++++++++++++++++++++++++++++++--------
1 file changed, 51 insertions(+), 10 deletions(-)

diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
index e0f05034fc21..242d3a14c210 100644
--- a/arch/riscv/kernel/module.c
+++ b/arch/riscv/kernel/module.c
@@ -92,6 +92,28 @@ static int apply_r_riscv_pcrel_lo12_s_rela(struct module *me, u32 *location,
return 0;
}

+static int apply_r_riscv_got_hi20_rela(struct module *me, u32 *location,
+ Elf_Addr v)
+{
+ s64 offset = (void *)v - (void *)location;
+ s32 hi20;
+
+ /* Always emit the got entry */
+ if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
+ offset = module_emit_got_entry(me, v);
+ offset = (void *)offset - (void *)location;
+ } else {
+ pr_err(
+ "%s: can not generate the GOT entry for symbol = %016llx from PC = %p\n",
+ me->name, v, location);
+ return -EINVAL;
+ }
+
+ hi20 = (offset + 0x800) & 0xfffff000;
+ *location = (*location & 0xfff) | hi20;
+ return 0;
+}
+
static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
Elf_Addr v)
{
@@ -100,10 +122,16 @@ static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
u32 hi20, lo12;

if (offset != fill_v) {
- pr_err(
- "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
- me->name, v, location);
- return -EINVAL;
+ /* Only emit the plt entry if offset over 32-bit range */
+ if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
+ offset = module_emit_plt_entry(me, v);
+ offset = (void *)offset - (void *)location;
+ } else {
+ pr_err(
+ "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
+ me->name, v, location);
+ return -EINVAL;
+ }
}

hi20 = (offset + 0x800) & 0xfffff000;
@@ -127,6 +155,7 @@ static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
[R_RISCV_PCREL_HI20] = apply_r_riscv_pcrel_hi20_rela,
[R_RISCV_PCREL_LO12_I] = apply_r_riscv_pcrel_lo12_i_rela,
[R_RISCV_PCREL_LO12_S] = apply_r_riscv_pcrel_lo12_s_rela,
+ [R_RISCV_GOT_HI20] = apply_r_riscv_got_hi20_rela,
[R_RISCV_CALL_PLT] = apply_r_riscv_call_plt_rela,
[R_RISCV_RELAX] = apply_r_riscv_relax_rela,
};
@@ -184,25 +213,37 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
u64 hi20_loc =
sechdrs[sechdrs[relsec].sh_info].sh_addr
+ rel[j].r_offset;
- /* Find the corresponding HI20 PC-relative relocation entry */
- if (hi20_loc == sym->st_value) {
+ u32 hi20_type = ELF_RISCV_R_TYPE(rel[j].r_info);
+
+ /* Find the corresponding HI20 relocation entry */
+ if (hi20_loc == sym->st_value
+ && (hi20_type == R_RISCV_PCREL_HI20
+ || hi20_type == R_RISCV_GOT_HI20)) {
+ s32 hi20, lo12;
Elf_Sym *hi20_sym =
(Elf_Sym *)sechdrs[symindex].sh_addr
+ ELF_RISCV_R_SYM(rel[j].r_info);
u64 hi20_sym_val =
hi20_sym->st_value
+ rel[j].r_addend;
+
/* Calculate lo12 */
- s64 offset = hi20_sym_val - hi20_loc;
- s32 hi20 = (offset + 0x800) & 0xfffff000;
- s32 lo12 = offset - hi20;
+ u64 offset = hi20_sym_val - hi20_loc;
+ if (hi20_type == R_RISCV_GOT_HI20) {
+ offset = module_emit_got_entry(
+ me, hi20_sym_val);
+ offset = offset - hi20_loc;
+ }
+ hi20 = (offset + 0x800) & 0xfffff000;
+ lo12 = offset - hi20;
v = lo12;
+
break;
}
}
if (j == sechdrs[relsec].sh_size / sizeof(*rel)) {
pr_err(
- "%s: Can not find HI20 PC-relative relocation information\n",
+ "%s: Can not find HI20 relocation information\n",
me->name);
return -EINVAL;
}
--
2.16.1
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