RISC-V: Load purgatory in kexec_file

This patch supports kexec_file to load and relocate purgatory.
It works well on riscv64 QEMU, being tested with devmem.

Signed-off-by: Li Zhengyu <lizhengyu3@huawei.com>
Link: https://lore.kernel.org/r/20220408100914.150110-7-lizhengyu3@huawei.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index 911d65d5a123c6dee89c4080d0c9c267a4b6635c..9cb85095fd459fb5e9cea5d1d6e62e8c4b076128 100644 (file)
--- a/arch/riscv/kernel/elf_kexec.c
+++ b/arch/riscv/kernel/elf_kexec.c
@@ -182,6 +182,7 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
        unsigned long new_kernel_pbase = 0UL;
        unsigned long initrd_pbase = 0UL;
        unsigned long headers_sz;
+       unsigned long kernel_start;
        void *fdt, *headers;
        struct elfhdr ehdr;
        struct kexec_buf kbuf;
@@ -196,6 +197,7 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
                             &old_kernel_pbase, &new_kernel_pbase);
        if (ret)
                goto out;
+       kernel_start = image->start;
        pr_notice("The entry point of kernel at 0x%lx\n", image->start);
 
        /* Add the kernel binary to the image */
@@ -246,6 +248,22 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
                cmdline = modified_cmdline;
        }
 
+#ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY
+       /* Add purgatory to the image */
+       kbuf.top_down = true;
+       kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+       ret = kexec_load_purgatory(image, &kbuf);
+       if (ret) {
+               pr_err("Error loading purgatory ret=%d\n", ret);
+               goto out;
+       }
+       ret = kexec_purgatory_get_set_symbol(image, "riscv_kernel_entry",
+                                            &kernel_start,
+                                            sizeof(kernel_start), 0);
+       if (ret)
+               pr_err("Error update purgatory ret=%d\n", ret);
+#endif /* CONFIG_ARCH_HAS_KEXEC_PURGATORY */
+
        /* Add the initrd to the image */
        if (initrd != NULL) {
                kbuf.buffer = initrd;
@@ -291,6 +309,139 @@ out:
        return ret ? ERR_PTR(ret) : NULL;
 }
 
+#define RV_X(x, s, n)  (((x) >> (s)) & ((1 << (n)) - 1))
+#define RISCV_IMM_BITS 12
+#define RISCV_IMM_REACH (1LL << RISCV_IMM_BITS)
+#define RISCV_CONST_HIGH_PART(x) \
+       (((x) + (RISCV_IMM_REACH >> 1)) & ~(RISCV_IMM_REACH - 1))
+#define RISCV_CONST_LOW_PART(x) ((x) - RISCV_CONST_HIGH_PART(x))
+
+#define ENCODE_ITYPE_IMM(x) \
+       (RV_X(x, 0, 12) << 20)
+#define ENCODE_BTYPE_IMM(x) \
+       ((RV_X(x, 1, 4) << 8) | (RV_X(x, 5, 6) << 25) | \
+       (RV_X(x, 11, 1) << 7) | (RV_X(x, 12, 1) << 31))
+#define ENCODE_UTYPE_IMM(x) \
+       (RV_X(x, 12, 20) << 12)
+#define ENCODE_JTYPE_IMM(x) \
+       ((RV_X(x, 1, 10) << 21) | (RV_X(x, 11, 1) << 20) | \
+       (RV_X(x, 12, 8) << 12) | (RV_X(x, 20, 1) << 31))
+#define ENCODE_CBTYPE_IMM(x) \
+       ((RV_X(x, 1, 2) << 3) | (RV_X(x, 3, 2) << 10) | (RV_X(x, 5, 1) << 2) | \
+       (RV_X(x, 6, 2) << 5) | (RV_X(x, 8, 1) << 12))
+#define ENCODE_CJTYPE_IMM(x) \
+       ((RV_X(x, 1, 3) << 3) | (RV_X(x, 4, 1) << 11) | (RV_X(x, 5, 1) << 2) | \
+       (RV_X(x, 6, 1) << 7) | (RV_X(x, 7, 1) << 6) | (RV_X(x, 8, 2) << 9) | \
+       (RV_X(x, 10, 1) << 8) | (RV_X(x, 11, 1) << 12))
+#define ENCODE_UJTYPE_IMM(x) \
+       (ENCODE_UTYPE_IMM(RISCV_CONST_HIGH_PART(x)) | \
+       (ENCODE_ITYPE_IMM(RISCV_CONST_LOW_PART(x)) << 32))
+#define ENCODE_UITYPE_IMM(x) \
+       (ENCODE_UTYPE_IMM(x) | (ENCODE_ITYPE_IMM(x) << 32))
+
+#define CLEAN_IMM(type, x) \
+       ((~ENCODE_##type##_IMM((uint64_t)(-1))) & (x))
+
+int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
+                                    Elf_Shdr *section,
+                                    const Elf_Shdr *relsec,
+                                    const Elf_Shdr *symtab)
+{
+       const char *strtab, *name, *shstrtab;
+       const Elf_Shdr *sechdrs;
+       Elf_Rela *relas;
+       int i, r_type;
+
+       /* String & section header string table */
+       sechdrs = (void *)pi->ehdr + pi->ehdr->e_shoff;
+       strtab = (char *)pi->ehdr + sechdrs[symtab->sh_link].sh_offset;
+       shstrtab = (char *)pi->ehdr + sechdrs[pi->ehdr->e_shstrndx].sh_offset;
+
+       relas = (void *)pi->ehdr + relsec->sh_offset;
+
+       for (i = 0; i < relsec->sh_size / sizeof(*relas); i++) {
+               const Elf_Sym *sym;     /* symbol to relocate */
+               unsigned long addr;     /* final location after relocation */
+               unsigned long val;      /* relocated symbol value */
+               unsigned long sec_base; /* relocated symbol value */
+               void *loc;              /* tmp location to modify */
+
+               sym = (void *)pi->ehdr + symtab->sh_offset;
+               sym += ELF64_R_SYM(relas[i].r_info);
+
+               if (sym->st_name)
+                       name = strtab + sym->st_name;
+               else
+                       name = shstrtab + sechdrs[sym->st_shndx].sh_name;
+
+               loc = pi->purgatory_buf;
+               loc += section->sh_offset;
+               loc += relas[i].r_offset;
+
+               if (sym->st_shndx == SHN_ABS)
+                       sec_base = 0;
+               else if (sym->st_shndx >= pi->ehdr->e_shnum) {
+                       pr_err("Invalid section %d for symbol %s\n",
+                              sym->st_shndx, name);
+                       return -ENOEXEC;
+               } else
+                       sec_base = pi->sechdrs[sym->st_shndx].sh_addr;
+
+               val = sym->st_value;
+               val += sec_base;
+               val += relas[i].r_addend;
+
+               addr = section->sh_addr + relas[i].r_offset;
+
+               r_type = ELF64_R_TYPE(relas[i].r_info);
+
+               switch (r_type) {
+               case R_RISCV_BRANCH:
+                       *(u32 *)loc = CLEAN_IMM(BTYPE, *(u32 *)loc) |
+                                ENCODE_BTYPE_IMM(val - addr);
+                       break;
+               case R_RISCV_JAL:
+                       *(u32 *)loc = CLEAN_IMM(JTYPE, *(u32 *)loc) |
+                                ENCODE_JTYPE_IMM(val - addr);
+                       break;
+               /*
+                * With no R_RISCV_PCREL_LO12_S, R_RISCV_PCREL_LO12_I
+                * sym is expected to be next to R_RISCV_PCREL_HI20
+                * in purgatory relsec. Handle it like R_RISCV_CALL
+                * sym, instead of searching the whole relsec.
+                */
+               case R_RISCV_PCREL_HI20:
+               case R_RISCV_CALL:
+                       *(u64 *)loc = CLEAN_IMM(UITYPE, *(u64 *)loc) |
+                                ENCODE_UJTYPE_IMM(val - addr);
+                       break;
+               case R_RISCV_RVC_BRANCH:
+                       *(u32 *)loc = CLEAN_IMM(CBTYPE, *(u32 *)loc) |
+                                ENCODE_CBTYPE_IMM(val - addr);
+                       break;
+               case R_RISCV_RVC_JUMP:
+                       *(u32 *)loc = CLEAN_IMM(CJTYPE, *(u32 *)loc) |
+                                ENCODE_CJTYPE_IMM(val - addr);
+                       break;
+               case R_RISCV_ADD32:
+                       *(u32 *)loc += val;
+                       break;
+               case R_RISCV_SUB32:
+                       *(u32 *)loc -= val;
+                       break;
+               /* It has been applied by R_RISCV_PCREL_HI20 sym */
+               case R_RISCV_PCREL_LO12_I:
+               case R_RISCV_ALIGN:
+               case R_RISCV_RELAX:
+                       break;
+               default:
+                       pr_err("Unknown rela relocation: %d\n", r_type);
+                       return -ENOEXEC;
+               }
+       }
+       return 0;
+}
+
 const struct kexec_file_ops elf_kexec_ops = {
        .probe = kexec_elf_probe,
        .load  = elf_kexec_load,