Re: [PATCH v4 4/4] LoongArch: Support modules with new relocation types
From: Youling Tang
Date: Tue Aug 09 2022 - 07:31:40 EST
Hi, Ruoyao
On 07/29/2022 04:42 PM, Xi Ruoyao wrote:
If GAS 2.40 and/or GCC 13 is used to build the kernel, the modules will
contain R_LARCH_B26, R_LARCH_PCALA_HI20, R_LARCH_PCALA_LO12,
R_LARCH_GOT_PC_HI20, and R_LARCH_GOT_PC_LO12 relocations. Support them
in the module loader to allow a kernel built with latest toolchain
capable to load the modules.
Signed-off-by: Xi Ruoyao <xry111@xxxxxxxxxxx>
---
arch/loongarch/include/asm/elf.h | 37 +++++++++++
arch/loongarch/kernel/module-sections.c | 12 +++-
arch/loongarch/kernel/module.c | 85 +++++++++++++++++++++++++
3 files changed, 132 insertions(+), 2 deletions(-)
diff --git a/arch/loongarch/include/asm/elf.h b/arch/loongarch/include/asm/elf.h
index 5f3ff4781fda..7af0cebf28d7 100644
--- a/arch/loongarch/include/asm/elf.h
+++ b/arch/loongarch/include/asm/elf.h
@@ -74,6 +74,43 @@
#define R_LARCH_SUB64 56
#define R_LARCH_GNU_VTINHERIT 57
#define R_LARCH_GNU_VTENTRY 58
+#define R_LARCH_B16 64
+#define R_LARCH_B21 65
+#define R_LARCH_B26 66
+#define R_LARCH_ABS_HI20 67
+#define R_LARCH_ABS_LO12 68
+#define R_LARCH_ABS64_LO20 69
+#define R_LARCH_ABS64_HI12 70
ARCH_REL_TYPE_ABS should add the corresponding absolute relocation type
with the new relocation type added. Maybe we should add R_LARCH_ABS* in
arch/loongarch/vdso/Makefile?
Thanks,
Youling
+#define R_LARCH_PCALA_HI20 71
+#define R_LARCH_PCALA_LO12 72
+#define R_LARCH_PCALA64_LO20 73
+#define R_LARCH_PCALA64_HI12 74
+#define R_LARCH_GOT_PC_HI20 75
+#define R_LARCH_GOT_PC_LO12 76
+#define R_LARCH_GOT64_PC_LO20 77
+#define R_LARCH_GOT64_PC_HI12 78
+#define R_LARCH_GOT_HI20 79
+#define R_LARCH_GOT_LO12 80
+#define R_LARCH_GOT64_LO20 81
+#define R_LARCH_GOT64_HI12 82
+#define R_LARCH_TLS_LE_HI20 83
+#define R_LARCH_TLS_LE_LO12 84
+#define R_LARCH_TLS_LE64_LO20 85
+#define R_LARCH_TLS_LE64_HI12 86
+#define R_LARCH_TLS_IE_PC_HI20 87
+#define R_LARCH_TLS_IE_PC_LO12 88
+#define R_LARCH_TLS_IE64_PC_LO20 89
+#define R_LARCH_TLS_IE64_PC_HI12 90
+#define R_LARCH_TLS_IE_HI20 91
+#define R_LARCH_TLS_IE_LO12 92
+#define R_LARCH_TLS_IE64_LO20 93
+#define R_LARCH_TLS_IE64_HI12 94
+#define R_LARCH_TLS_LD_PC_HI20 95
+#define R_LARCH_TLS_LD_HI20 96
+#define R_LARCH_TLS_GD_PC_HI20 97
+#define R_LARCH_TLS_GD_HI20 98
+#define R_LARCH_32_PCREL 99
+#define R_LARCH_RELAX 100
#ifndef ELF_ARCH
diff --git a/arch/loongarch/kernel/module-sections.c b/arch/loongarch/kernel/module-sections.c
index 36a77771d18c..8c0e4ad048cc 100644
--- a/arch/loongarch/kernel/module-sections.c
+++ b/arch/loongarch/kernel/module-sections.c
@@ -76,12 +76,20 @@ static void count_max_entries(Elf_Rela *relas, int num,
for (i = 0; i < num; i++) {
type = ELF_R_TYPE(relas[i].r_info);
- if (type == R_LARCH_SOP_PUSH_PLT_PCREL) {
+ switch (type) {
+ case R_LARCH_SOP_PUSH_PLT_PCREL:
+ case R_LARCH_B26:
if (!duplicate_rela(relas, i))
(*plts)++;
- } else if (type == R_LARCH_SOP_PUSH_GPREL)
+ break;
+ case R_LARCH_SOP_PUSH_GPREL:
+ case R_LARCH_GOT_PC_HI20:
if (!duplicate_rela(relas, i))
(*gots)++;
+ break;
+ default:
+ /* Do nothing. */
+ }
}
}
diff --git a/arch/loongarch/kernel/module.c b/arch/loongarch/kernel/module.c
index 3ac4fbb5f109..c7b40150e1f0 100644
--- a/arch/loongarch/kernel/module.c
+++ b/arch/loongarch/kernel/module.c
@@ -291,6 +291,86 @@ static int apply_r_larch_add_sub(struct module *mod, u32 *location, Elf_Addr v,
}
}
+static int apply_r_larch_b26(struct module *mod, u32 *location, Elf_Addr v,
+ s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+ ptrdiff_t offset = (void *)v - (void *)location;
+ union loongarch_instruction *insn = (union loongarch_instruction *)location;
+
+ if (offset >= SZ_128M)
+ v = module_emit_plt_entry(mod, v);
+
+ if (offset < -SZ_128M)
+ v = module_emit_plt_entry(mod, v);
+
+ offset = (void *)v - (void *)location;
+
+ if (offset & 3) {
+ pr_err("module %s: jump offset = 0x%llx unaligned! dangerous R_LARCH_B26 (%u) relocation\n",
+ mod->name, (long long)offset, type);
+ return -ENOEXEC;
+ }
+
+ if (!signed_imm_check(offset, 28)) {
+ pr_err("module %s: jump offset = 0x%llx overflow! dangerous R_LARCH_B26 (%u) relocation\n",
+ mod->name, (long long)offset, type);
+ return -ENOEXEC;
+ }
+
+ offset >>= 2;
+ insn->reg0i26_format.immediate_l = offset & 0xffff;
+ insn->reg0i26_format.immediate_h = (offset >> 16) & 0x3ff;
+ return 0;
+}
+
+static int apply_r_larch_pcala_hi20(struct module *mod, u32 *location,
+ Elf_Addr v, s64 *rela_stack, size_t *rela_stack_top,
+ unsigned int type)
+{
+ ptrdiff_t offset = (void *)((v + 0x800) & ~0xfff) -
+ (void *)((Elf_Addr)location & ~0xfff);
+ union loongarch_instruction *insn = (union loongarch_instruction *)location;
+
+ if (!signed_imm_check(offset, 32)) {
+ pr_err("module %s: PCALA offset = 0x%llx does not fit in 32-bit signed and is unsupported by kernel! dangerous %s (%u) relocation\n",
+ mod->name, (long long)offset, __func__, type);
+ return -ENOEXEC;
+ }
+
+ insn->reg1i20_format.immediate = (offset >> 12) & 0xfffff;
+ return 0;
+}
+
+static int apply_r_larch_got_pc_hi20(struct module *mod, u32 *location,
+ Elf_Addr v, s64 *rela_stack, size_t *rela_stack_top,
+ unsigned int type)
+{
+ Elf_Addr got = module_emit_got_entry(mod, v);
+
+ return apply_r_larch_pcala_hi20(mod, location, got, rela_stack,
+ rela_stack_top, type);
+}
+
+static int apply_r_larch_pcala_lo12(struct module *mod, u32 *location,
+ Elf_Addr v, s64 *rela_stack, size_t *rela_stack_top,
+ unsigned int type)
+{
+ union loongarch_instruction *insn = (union loongarch_instruction *)location;
+
+ insn->reg2i12_format.immediate = v & 0xfff;
+ return 0;
+}
+
+static int apply_r_larch_got_pc_lo12(struct module *mod, u32 *location,
+ Elf_Addr v, s64 *rela_stack, size_t *rela_stack_top,
+ unsigned int type)
+{
+ Elf_Addr got = module_emit_got_entry(mod, v);
+
+ return apply_r_larch_pcala_lo12(mod, location, got, rela_stack,
+ rela_stack_top, type);
+}
+
/*
* reloc_handlers_rela() - Apply a particular relocation to a module
* @mod: the module to apply the reloc to
@@ -321,6 +401,11 @@ static reloc_rela_handler reloc_rela_handlers[] = {
[R_LARCH_SOP_SUB ... R_LARCH_SOP_IF_ELSE] = apply_r_larch_sop,
[R_LARCH_SOP_POP_32_S_10_5 ... R_LARCH_SOP_POP_32_U] = apply_r_larch_sop_imm_field,
[R_LARCH_ADD32 ... R_LARCH_SUB64] = apply_r_larch_add_sub,
+ [R_LARCH_B26] = apply_r_larch_b26,
+ [R_LARCH_PCALA_HI20] = apply_r_larch_pcala_hi20,
+ [R_LARCH_PCALA_LO12] = apply_r_larch_pcala_lo12,
+ [R_LARCH_GOT_PC_HI20] = apply_r_larch_got_pc_hi20,
+ [R_LARCH_GOT_PC_LO12] = apply_r_larch_got_pc_lo12,
};
int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,