[PATCH v7 2/3] riscv: Add remaining module relocations
Emil Renner Berthing
emil.renner.berthing at canonical.com
Tue Oct 31 06:43:19 PDT 2023
Charlie Jenkins wrote:
> Add all final module relocations and add error logs explaining the ones
> that are not supported. Implement overflow checks for
> ADD/SUB/SET/ULEB128 relocations.
>
> Signed-off-by: Charlie Jenkins <charlie at rivosinc.com>
> ---
> arch/riscv/include/uapi/asm/elf.h | 5 +-
> arch/riscv/kernel/module.c | 534 ++++++++++++++++++++++++++++++++++++--
> 2 files changed, 511 insertions(+), 28 deletions(-)
>
> diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
> index d696d6610231..11a71b8533d5 100644
> --- a/arch/riscv/include/uapi/asm/elf.h
> +++ b/arch/riscv/include/uapi/asm/elf.h
> @@ -49,6 +49,7 @@ typedef union __riscv_fp_state elf_fpregset_t;
> #define R_RISCV_TLS_DTPREL64 9
> #define R_RISCV_TLS_TPREL32 10
> #define R_RISCV_TLS_TPREL64 11
> +#define R_RISCV_IRELATIVE 58
>
> /* Relocation types not used by the dynamic linker */
> #define R_RISCV_BRANCH 16
> @@ -81,7 +82,6 @@ typedef union __riscv_fp_state elf_fpregset_t;
> #define R_RISCV_ALIGN 43
> #define R_RISCV_RVC_BRANCH 44
> #define R_RISCV_RVC_JUMP 45
> -#define R_RISCV_LUI 46
> #define R_RISCV_GPREL_I 47
> #define R_RISCV_GPREL_S 48
> #define R_RISCV_TPREL_I 49
> @@ -93,6 +93,9 @@ typedef union __riscv_fp_state elf_fpregset_t;
> #define R_RISCV_SET16 55
> #define R_RISCV_SET32 56
> #define R_RISCV_32_PCREL 57
> +#define R_RISCV_PLT32 59
> +#define R_RISCV_SET_ULEB128 60
> +#define R_RISCV_SUB_ULEB128 61
>
>
> #endif /* _UAPI_ASM_RISCV_ELF_H */
> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> index a9e94e939cb5..230172ecb26e 100644
> --- a/arch/riscv/kernel/module.c
> +++ b/arch/riscv/kernel/module.c
> @@ -7,6 +7,9 @@
> #include <linux/elf.h>
> #include <linux/err.h>
> #include <linux/errno.h>
> +#include <linux/hashtable.h>
> +#include <linux/kernel.h>
> +#include <linux/log2.h>
> #include <linux/moduleloader.h>
> #include <linux/vmalloc.h>
> #include <linux/sizes.h>
> @@ -14,6 +17,27 @@
> #include <asm/alternative.h>
> #include <asm/sections.h>
>
> +struct used_bucket {
> + struct list_head head;
> + struct hlist_head *bucket;
> +};
> +
> +struct relocation_head {
> + struct hlist_node node;
> + struct list_head *rel_entry;
> + void *location;
> +};
> +
> +struct relocation_entry {
> + struct list_head head;
> + Elf_Addr value;
> + unsigned int type;
> +};
> +
> +struct hlist_head *relocation_hashtable;
> +
> +struct list_head used_buckets_list;
> +
> /*
> * The auipc+jalr instruction pair can reach any PC-relative offset
> * in the range [-2^31 - 2^11, 2^31 - 2^11)
> @@ -269,6 +293,12 @@ static int apply_r_riscv_align_rela(struct module *me, void *location,
> return -EINVAL;
> }
>
> +static int apply_r_riscv_add8_rela(struct module *me, void *location, Elf_Addr v)
> +{
> + *(u8 *)location += (u8)v;
> + return 0;
> +}
> +
> static int apply_r_riscv_add16_rela(struct module *me, void *location,
> Elf_Addr v)
> {
> @@ -290,6 +320,12 @@ static int apply_r_riscv_add64_rela(struct module *me, void *location,
> return 0;
> }
>
> +static int apply_r_riscv_sub8_rela(struct module *me, void *location, Elf_Addr v)
> +{
> + *(u8 *)location -= (u8)v;
> + return 0;
> +}
> +
> static int apply_r_riscv_sub16_rela(struct module *me, void *location,
> Elf_Addr v)
> {
> @@ -311,33 +347,470 @@ static int apply_r_riscv_sub64_rela(struct module *me, void *location,
> return 0;
> }
>
> -static int (*reloc_handlers_rela[]) (struct module *me, void *location,
> - Elf_Addr v) = {
> - [R_RISCV_32] = apply_r_riscv_32_rela,
> - [R_RISCV_64] = apply_r_riscv_64_rela,
> - [R_RISCV_BRANCH] = apply_r_riscv_branch_rela,
> - [R_RISCV_JAL] = apply_r_riscv_jal_rela,
> - [R_RISCV_RVC_BRANCH] = apply_r_riscv_rvc_branch_rela,
> - [R_RISCV_RVC_JUMP] = apply_r_riscv_rvc_jump_rela,
> - [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_HI20] = apply_r_riscv_hi20_rela,
> - [R_RISCV_LO12_I] = apply_r_riscv_lo12_i_rela,
> - [R_RISCV_LO12_S] = apply_r_riscv_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_CALL] = apply_r_riscv_call_rela,
> - [R_RISCV_RELAX] = apply_r_riscv_relax_rela,
> - [R_RISCV_ALIGN] = apply_r_riscv_align_rela,
> - [R_RISCV_ADD16] = apply_r_riscv_add16_rela,
> - [R_RISCV_ADD32] = apply_r_riscv_add32_rela,
> - [R_RISCV_ADD64] = apply_r_riscv_add64_rela,
> - [R_RISCV_SUB16] = apply_r_riscv_sub16_rela,
> - [R_RISCV_SUB32] = apply_r_riscv_sub32_rela,
> - [R_RISCV_SUB64] = apply_r_riscv_sub64_rela,
> +static int dynamic_linking_not_supported(struct module *me, void *location,
> + Elf_Addr v)
> +{
> + pr_err("%s: Dynamic linking not supported in kernel modules PC = %p\n",
> + me->name, location);
> + return -EINVAL;
> +}
> +
> +static int tls_not_supported(struct module *me, void *location, Elf_Addr v)
> +{
> + pr_err("%s: Thread local storage not supported in kernel modules PC = %p\n",
> + me->name, location);
> + return -EINVAL;
> +}
> +
> +static int apply_r_riscv_sub6_rela(struct module *me, void *location, Elf_Addr v)
> +{
> + *(u8 *)location = (*(u8 *)location - ((u8)v & 0x3F)) & 0x3F;
> + return 0;
> +}
> +
> +static int apply_r_riscv_set6_rela(struct module *me, void *location, Elf_Addr v)
> +{
> + *(u8 *)location = ((*(u8 *)location & 0xc0) | ((u8)v & 0x3F));
Most of these casts are simple enough for here and above I'd consider
something like this for readability:
u8 *byte = location;
u8 value = v;
*byte = (*byte & 0xc0) | (value & 0x3f)
The compiler should generate the same code.
> + return 0;
> +}
> +
> +static int apply_r_riscv_set8_rela(struct module *me, void *location, Elf_Addr v)
> +{
> + *(u8 *)location = (u8)v;
> + return 0;
> +}
> +
> +static int apply_r_riscv_set16_rela(struct module *me, void *location,
> + Elf_Addr v)
> +{
> + *(u16 *)location = (u16)v;
> + return 0;
> +}
> +
> +static int apply_r_riscv_set32_rela(struct module *me, void *location,
> + Elf_Addr v)
> +{
> + *(u32 *)location = (u32)v;
> + return 0;
> +}
> +
> +static int apply_r_riscv_32_pcrel_rela(struct module *me, void *location,
> + Elf_Addr v)
> +{
> + *(u32 *)location = v - (unsigned long)location;
> + return 0;
> +}
> +
> +static int apply_r_riscv_plt32_rela(struct module *me, void *location,
> + Elf_Addr v)
> +{
> + ptrdiff_t offset = (void *)v - location;
> +
> + if (!riscv_insn_valid_32bit_offset(offset)) {
> + /* Only emit the plt entry if offset over 32-bit range */
> + if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
> + offset = (void *)module_emit_plt_entry(me, v) - location;
> + } else {
> + pr_err("%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
> + me->name, (long long)v, location);
> + return -EINVAL;
> + }
> + }
> +
> + *(u32 *)location = (u32)offset;
> + return 0;
> +}
> +
> +static int apply_r_riscv_set_uleb128(struct module *me, void *location, Elf_Addr v)
> +{
> + *(long *)location = v;
> + return 0;
> +}
> +
> +static int apply_r_riscv_sub_uleb128(struct module *me, void *location, Elf_Addr v)
> +{
> + *(long *)location -= v;
> + return 0;
> +}
> +
> +/*
> + * Relocations defined in the riscv-elf-psabi-doc.
> + * This handles static linking only.
> + */
> +static int (*reloc_handlers_rela[])(struct module *me, void *location,
> + Elf_Addr v) = {
> + [R_RISCV_32] = apply_r_riscv_32_rela,
> + [R_RISCV_64] = apply_r_riscv_64_rela,
> + [R_RISCV_RELATIVE] = dynamic_linking_not_supported,
> + [R_RISCV_COPY] = dynamic_linking_not_supported,
> + [R_RISCV_JUMP_SLOT] = dynamic_linking_not_supported,
> + [R_RISCV_TLS_DTPMOD32] = dynamic_linking_not_supported,
> + [R_RISCV_TLS_DTPMOD64] = dynamic_linking_not_supported,
> + [R_RISCV_TLS_DTPREL32] = dynamic_linking_not_supported,
> + [R_RISCV_TLS_DTPREL64] = dynamic_linking_not_supported,
> + [R_RISCV_TLS_TPREL32] = dynamic_linking_not_supported,
> + [R_RISCV_TLS_TPREL64] = dynamic_linking_not_supported,
> + /* 12-15 undefined */
> + [R_RISCV_BRANCH] = apply_r_riscv_branch_rela,
> + [R_RISCV_JAL] = apply_r_riscv_jal_rela,
> + [R_RISCV_CALL] = apply_r_riscv_call_rela,
> + [R_RISCV_CALL_PLT] = apply_r_riscv_call_plt_rela,
> + [R_RISCV_GOT_HI20] = apply_r_riscv_got_hi20_rela,
> + [R_RISCV_TLS_GOT_HI20] = tls_not_supported,
> + [R_RISCV_TLS_GD_HI20] = tls_not_supported,
> + [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_HI20] = apply_r_riscv_hi20_rela,
> + [R_RISCV_LO12_I] = apply_r_riscv_lo12_i_rela,
> + [R_RISCV_LO12_S] = apply_r_riscv_lo12_s_rela,
> + [R_RISCV_TPREL_HI20] = tls_not_supported,
> + [R_RISCV_TPREL_LO12_I] = tls_not_supported,
> + [R_RISCV_TPREL_LO12_S] = tls_not_supported,
> + [R_RISCV_TPREL_ADD] = tls_not_supported,
> + [R_RISCV_ADD8] = apply_r_riscv_add8_rela,
> + [R_RISCV_ADD16] = apply_r_riscv_add16_rela,
> + [R_RISCV_ADD32] = apply_r_riscv_add32_rela,
> + [R_RISCV_ADD64] = apply_r_riscv_add64_rela,
> + [R_RISCV_SUB8] = apply_r_riscv_sub8_rela,
> + [R_RISCV_SUB16] = apply_r_riscv_sub16_rela,
> + [R_RISCV_SUB32] = apply_r_riscv_sub32_rela,
> + [R_RISCV_SUB64] = apply_r_riscv_sub64_rela,
> + /* 41-42 reserved for future standard use */
> + [R_RISCV_ALIGN] = apply_r_riscv_align_rela,
> + [R_RISCV_RVC_BRANCH] = apply_r_riscv_rvc_branch_rela,
> + [R_RISCV_RVC_JUMP] = apply_r_riscv_rvc_jump_rela,
> + /* 46-50 reserved for future standard use */
> + [R_RISCV_RELAX] = apply_r_riscv_relax_rela,
> + [R_RISCV_SUB6] = apply_r_riscv_sub6_rela,
> + [R_RISCV_SET6] = apply_r_riscv_set6_rela,
> + [R_RISCV_SET8] = apply_r_riscv_set8_rela,
> + [R_RISCV_SET16] = apply_r_riscv_set16_rela,
> + [R_RISCV_SET32] = apply_r_riscv_set32_rela,
> + [R_RISCV_32_PCREL] = apply_r_riscv_32_pcrel_rela,
> + [R_RISCV_IRELATIVE] = dynamic_linking_not_supported,
> + [R_RISCV_PLT32] = apply_r_riscv_plt32_rela,
> + [R_RISCV_SET_ULEB128] = apply_r_riscv_set_uleb128,
> + [R_RISCV_SUB_ULEB128] = apply_r_riscv_sub_uleb128,
> + /* 62-191 reserved for future standard use */
> + /* 192-255 nonstandard ABI extensions */
> +};
> +
> +static bool accumulate_relocations[] = {
> + [R_RISCV_32] = false,
> + [R_RISCV_64] = false,
> + [R_RISCV_RELATIVE] = false,
> + [R_RISCV_COPY] = false,
> + [R_RISCV_JUMP_SLOT] = false,
> + [R_RISCV_TLS_DTPMOD32] = false,
> + [R_RISCV_TLS_DTPMOD64] = false,
> + [R_RISCV_TLS_DTPREL32] = false,
> + [R_RISCV_TLS_DTPREL64] = false,
> + [R_RISCV_TLS_TPREL32] = false,
> + [R_RISCV_TLS_TPREL64] = false,
> + /* 12-15 undefined */
> + [R_RISCV_BRANCH] = false,
> + [R_RISCV_JAL] = false,
> + [R_RISCV_CALL] = false,
> + [R_RISCV_CALL_PLT] = false,
> + [R_RISCV_GOT_HI20] = false,
> + [R_RISCV_TLS_GOT_HI20] = false,
> + [R_RISCV_TLS_GD_HI20] = false,
> + [R_RISCV_PCREL_HI20] = false,
> + [R_RISCV_PCREL_LO12_I] = false,
> + [R_RISCV_PCREL_LO12_S] = false,
> + [R_RISCV_HI20] = false,
> + [R_RISCV_LO12_I] = false,
> + [R_RISCV_LO12_S] = false,
> + [R_RISCV_TPREL_HI20] = false,
> + [R_RISCV_TPREL_LO12_I] = false,
> + [R_RISCV_TPREL_LO12_S] = false,
> + [R_RISCV_TPREL_ADD] = false,
> + [R_RISCV_ADD8] = true,
> + [R_RISCV_ADD16] = true,
> + [R_RISCV_ADD32] = true,
> + [R_RISCV_ADD64] = true,
> + [R_RISCV_SUB8] = true,
> + [R_RISCV_SUB16] = true,
> + [R_RISCV_SUB32] = true,
> + [R_RISCV_SUB64] = true,
> + /* 41-42 reserved for future standard use */
> + [R_RISCV_ALIGN] = false,
> + [R_RISCV_RVC_BRANCH] = false,
> + [R_RISCV_RVC_JUMP] = false,
> + /* 46-50 reserved for future standard use */
> + [R_RISCV_RELAX] = false,
> + [R_RISCV_SUB6] = true,
> + [R_RISCV_SET6] = true,
> + [R_RISCV_SET8] = true,
> + [R_RISCV_SET16] = true,
> + [R_RISCV_SET32] = true,
> + [R_RISCV_32_PCREL] = false,
> + [R_RISCV_IRELATIVE] = false,
> + [R_RISCV_PLT32] = false,
> + [R_RISCV_SET_ULEB128] = true,
> + [R_RISCV_SUB_ULEB128] = true,
> + /* 62-191 reserved for future standard use */
> + /* 192-255 nonstandard ABI extensions */
> +};
> +
> +static int accumulation_not_supported(struct module *me, void *location, long buffer)
> +{
> + pr_err("%s: Internal error. Only ADD/SUB/SET/ULEB128 should be accumulated.", me->name);
> + return -EINVAL;
> +}
> +
> +static int apply_6_bit_accumulation(struct module *me, void *location, long buffer)
> +{
> + if (buffer != (buffer & 0x3F)) {
It may be a matter of taste, but I'd find something like this easier to read:
if (buffer > 0x3f) {
To me that more directly conveys that you're just checking if any if the higher
bits are set.
> + pr_err("%s: value %ld out of range for 6-bit relocation.\n",
> + me->name, buffer);
> + return -EINVAL;
> + }
> + *(u8 *)location = ((*(u8 *)location & 0xc0) | ((u8)buffer & 0x3F));
Here the casts also get a bit much.
> + return 0;
> +}
> +
> +static int apply_8_bit_accumulation(struct module *me, void *location, long buffer)
> +{
> + if (buffer != (u8)buffer) {
> + pr_err("%s: value %ld out of range for 8-bit relocation.\n",
> + me->name, buffer);
> + return -EINVAL;
> + }
> + *(u8 *)location = (u8)buffer;
> + return 0;
> +}
> +
> +static int apply_16_bit_accumulation(struct module *me, void *location, long buffer)
> +{
> + if (buffer != (u16)buffer) {
if (buffer > U16_MAX) {
> + pr_err("%s: value %ld out of range for 16-bit relocation.\n",
> + me->name, buffer);
> + return -EINVAL;
> + }
> + *(u16 *)location = (u16)buffer;
> + return 0;
> +}
> +
> +static int apply_32_bit_accumulation(struct module *me, void *location, long buffer)
> +{
> + if (buffer != (u32)buffer) {
if (buffer > U32_MAX) {
> + pr_err("%s: value %ld out of range for 32-bit relocation.\n",
> + me->name, buffer);
> + return -EINVAL;
> + }
> + *(u32 *)location = (u32)buffer;
> + return 0;
> +}
> +
> +static int apply_64_bit_accumulation(struct module *me, void *location, long buffer)
> +{
> + *(u64 *)location = (u64)buffer;
> + return 0;
> +}
> +
> +static int apply_uleb128_accumulation(struct module *me, void *location, long buffer)
> +{
> + /*
> + * ULEB128 is a variable length encoding. Encode the buffer into
> + * the ULEB128 data format.
> + */
> + while (buffer != 0) {
> + *(u8 *)location = (u8)buffer & 0x7F;
> + buffer >>= 7;
> + *(u8 *)location |= (buffer != 0) << 7;
> + location = (u8 *)location + 1;
> + }
How about something like
u8 *p = location;
while (buffer) {
u8 value = buffer & 0x7f;
buffer >>= 7;
value |= (!!buffer) << 7;
*p++ = value;
}
This sould do the same as above, but if buffer == 0 it doesn't write anything.
Is that the right thing to do?
> + return 0;
> +}
> +
> +/*
> + * Need to duplicate this a third time to capture the handlers for accumulation.
> + */
> +static int (*accumulate_handlers[])(struct module *me, void *location, long buffer) = {
> + [R_RISCV_32] = accumulation_not_supported,
> + [R_RISCV_64] = accumulation_not_supported,
> + [R_RISCV_RELATIVE] = accumulation_not_supported,
> + [R_RISCV_COPY] = accumulation_not_supported,
> + [R_RISCV_JUMP_SLOT] = accumulation_not_supported,
> + [R_RISCV_TLS_DTPMOD32] = accumulation_not_supported,
> + [R_RISCV_TLS_DTPMOD64] = accumulation_not_supported,
> + [R_RISCV_TLS_DTPREL32] = accumulation_not_supported,
> + [R_RISCV_TLS_DTPREL64] = accumulation_not_supported,
> + [R_RISCV_TLS_TPREL32] = accumulation_not_supported,
> + [R_RISCV_TLS_TPREL64] = accumulation_not_supported,
> + /* 12-15 undefined */
> + [R_RISCV_BRANCH] = accumulation_not_supported,
> + [R_RISCV_JAL] = accumulation_not_supported,
> + [R_RISCV_CALL] = accumulation_not_supported,
> + [R_RISCV_CALL_PLT] = accumulation_not_supported,
> + [R_RISCV_GOT_HI20] = accumulation_not_supported,
> + [R_RISCV_TLS_GOT_HI20] = accumulation_not_supported,
> + [R_RISCV_TLS_GD_HI20] = accumulation_not_supported,
> + [R_RISCV_PCREL_HI20] = accumulation_not_supported,
> + [R_RISCV_PCREL_LO12_I] = accumulation_not_supported,
> + [R_RISCV_PCREL_LO12_S] = accumulation_not_supported,
> + [R_RISCV_HI20] = accumulation_not_supported,
> + [R_RISCV_LO12_I] = accumulation_not_supported,
> + [R_RISCV_LO12_S] = accumulation_not_supported,
> + [R_RISCV_TPREL_HI20] = accumulation_not_supported,
> + [R_RISCV_TPREL_LO12_I] = accumulation_not_supported,
> + [R_RISCV_TPREL_LO12_S] = accumulation_not_supported,
> + [R_RISCV_TPREL_ADD] = accumulation_not_supported,
> + [R_RISCV_ADD8] = apply_8_bit_accumulation,
> + [R_RISCV_ADD16] = apply_16_bit_accumulation,
> + [R_RISCV_ADD32] = apply_32_bit_accumulation,
> + [R_RISCV_ADD64] = apply_64_bit_accumulation,
> + [R_RISCV_SUB8] = apply_8_bit_accumulation,
> + [R_RISCV_SUB16] = apply_16_bit_accumulation,
> + [R_RISCV_SUB32] = apply_32_bit_accumulation,
> + [R_RISCV_SUB64] = apply_64_bit_accumulation,
> + /* 41-42 reserved for future standard use */
> + [R_RISCV_ALIGN] = accumulation_not_supported,
> + [R_RISCV_RVC_BRANCH] = accumulation_not_supported,
> + [R_RISCV_RVC_JUMP] = accumulation_not_supported,
> + /* 46-50 reserved for future standard use */
> + [R_RISCV_RELAX] = accumulation_not_supported,
> + [R_RISCV_SUB6] = apply_6_bit_accumulation,
> + [R_RISCV_SET6] = apply_6_bit_accumulation,
> + [R_RISCV_SET8] = apply_8_bit_accumulation,
> + [R_RISCV_SET16] = apply_16_bit_accumulation,
> + [R_RISCV_SET32] = apply_32_bit_accumulation,
> + [R_RISCV_32_PCREL] = accumulation_not_supported,
> + [R_RISCV_IRELATIVE] = accumulation_not_supported,
> + [R_RISCV_PLT32] = accumulation_not_supported,
> + [R_RISCV_SET_ULEB128] = apply_uleb128_accumulation,
> + [R_RISCV_SUB_ULEB128] = apply_uleb128_accumulation,
> + /* 62-191 reserved for future standard use */
> + /* 192-255 nonstandard ABI extensions */
> };
>
> +void process_accumulated_relocations(struct module *me)
> +{
> + /*
> + * Only ADD/SUB/SET/ULEB128 should end up here.
> + *
> + * Each bucket may have more than one relocation location. All
> + * relocations for a location are stored in a list in a bucket.
> + *
> + * Relocations are applied to a temp variable before being stored to the
> + * provided location to check for overflow. This also allows ULEB128 to
> + * properly decide how many entries are needed before storing to
> + * location. The final value is stored into location using the handler
> + * for the last relocation to an address.
> + *
> + * Three layers of indexing:
> + * - Each of the buckets in use
> + * - Groups of relocations in each bucket by location address
> + * - Each relocation entry for a location address
> + */
> + struct used_bucket *bucket_iter;
> + struct relocation_head *rel_head_iter;
> + struct relocation_entry *rel_entry_iter;
> + int curr_type;
> + void *location;
> + long buffer;
> +
> + list_for_each_entry(bucket_iter, &used_buckets_list, head) {
> + hlist_for_each_entry(rel_head_iter, bucket_iter->bucket, node) {
> + buffer = 0;
> + location = rel_head_iter->location;
> + list_for_each_entry(rel_entry_iter, rel_head_iter->rel_entry, head) {
> + curr_type = rel_entry_iter->type;
> + reloc_handlers_rela[curr_type](me, &buffer, rel_entry_iter->value);
> + kfree(rel_entry_iter);
> + }
> + accumulate_handlers[curr_type](me, location, buffer);
> + kfree(rel_head_iter);
> + }
> + kfree(bucket_iter);
> + }
> +
> + kfree(relocation_hashtable);
> +}
> +
> +int add_relocation_to_accumulate(struct module *me, int type, void *location,
> + unsigned int hashtable_bits, Elf_Addr v)
> +{
> + struct relocation_entry *entry;
> + struct relocation_head *rel_head;
> + struct hlist_head *current_head;
> + struct hlist_node *first;
> + struct used_bucket *bucket;
> + unsigned long hash;
> +
> + entry = kmalloc(sizeof(*entry), GFP_KERNEL);
> + INIT_LIST_HEAD(&entry->head);
> + entry->type = type;
> + entry->value = v;
> +
> + hash = hash_min((unsigned long)location, hashtable_bits);
> +
> + current_head = &relocation_hashtable[hash];
> + first = current_head->first;
> +
> + /* Find matching location (if any) */
> + bool found = false;
> + struct relocation_head *rel_head_iter;
> +
> + hlist_for_each_entry(rel_head_iter, current_head, node) {
> + if (rel_head_iter->location == location) {
> + found = true;
> + rel_head = rel_head_iter;
> + break;
> + }
> + }
> +
> + if (!found) {
> + rel_head = kmalloc(sizeof(*rel_head), GFP_KERNEL);
> + rel_head->rel_entry =
> + kmalloc(sizeof(struct list_head), GFP_KERNEL);
> + INIT_LIST_HEAD(rel_head->rel_entry);
> + rel_head->location = location;
> + INIT_HLIST_NODE(&rel_head->node);
> + if (!current_head->first) {
> + bucket =
> + kmalloc(sizeof(struct used_bucket), GFP_KERNEL);
> + INIT_LIST_HEAD(&bucket->head);
> + bucket->bucket = current_head;
> + list_add(&bucket->head, &used_buckets_list);
> + }
> + hlist_add_head(&rel_head->node, current_head);
> + }
> +
> + /* Add relocation to head of discovered rel_head */
> + list_add_tail(&entry->head, rel_head->rel_entry);
> +
> + return 0;
> +}
> +
> +unsigned int initialize_relocation_hashtable(unsigned int num_relocations)
> +{
> + /* Can safely assume that bits is not greater than sizeof(long) */
> + unsigned long hashtable_size = roundup_pow_of_two(num_relocations);
> + unsigned int hashtable_bits = ilog2(hashtable_size);
> +
> + /*
> + * Double size of hashtable if num_relocations * 1.25 is greater than
> + * hashtable_size.
> + */
> + int should_double_size = ((num_relocations + (num_relocations >> 2)) > (hashtable_size));
> +
> + hashtable_bits += should_double_size;
> +
> + hashtable_size <<= should_double_size;
> +
> + relocation_hashtable = kmalloc_array(hashtable_size,
> + sizeof(*relocation_hashtable),
> + GFP_KERNEL);
> + __hash_init(relocation_hashtable, hashtable_size);
> +
> + INIT_LIST_HEAD(&used_buckets_list);
> +
> + return hashtable_bits;
> +}
> +
> int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> unsigned int symindex, unsigned int relsec,
> struct module *me)
> @@ -349,11 +822,13 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> unsigned int i, type;
> Elf_Addr v;
> int res;
> + unsigned int num_relocations = sechdrs[relsec].sh_size / sizeof(*rel);
> + unsigned int hashtable_bits = initialize_relocation_hashtable(num_relocations);
>
> pr_debug("Applying relocate section %u to %u\n", relsec,
> sechdrs[relsec].sh_info);
>
> - for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
> + for (i = 0; i < num_relocations; i++) {
> /* This is where to make the change */
> location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
> + rel[i].r_offset;
> @@ -428,11 +903,16 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> }
> }
>
> - res = handler(me, location, v);
> + if (accumulate_relocations[type])
> + res = add_relocation_to_accumulate(me, type, location, hashtable_bits, v);
> + else
> + res = handler(me, location, v);
> if (res)
> return res;
> }
>
> + process_accumulated_relocations(me);
> +
> return 0;
> }
>
>
> --
> 2.34.1
>
>
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