[PATCH v2 -next 6/6] RISC-V: Load purgatory in kexec_file
Li Zhengyu
lizhengyu3 at huawei.com
Wed Mar 30 01:17:01 PDT 2022
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 at huawei.com>
---
arch/riscv/kernel/elf_kexec.c | 151 ++++++++++++++++++++++++++++++++++
1 file changed, 151 insertions(+)
diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index 911d65d5a123..9cb85095fd45 100644
--- 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 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
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,
--
2.17.1
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