Re: [PATCH v8 2/3] riscv: Add remaining module relocations
From: Charlie Jenkins
Date: Wed Nov 01 2023 - 13:12:09 EST
On Wed, Nov 01, 2023 at 03:44:30PM +0100, Emil Renner Berthing wrote:
> 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@xxxxxxxxxxxx>
> > ---
> > arch/riscv/include/uapi/asm/elf.h | 5 +-
> > arch/riscv/kernel/module.c | 503 +++++++++++++++++++++++++++++++++++---
> > 2 files changed, 476 insertions(+), 32 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..0f5d41eaa596 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 +17,39 @@
> > #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 relocation_handlers {
> > + int (*reloc_handler)(struct module *me, void *location, Elf_Addr v);
> > + bool accumulate_relocations;
> > + int (*accumulate_handler)(struct module *me, void *location,
> > + long buffer);
> > +};
> > +
> > +unsigned int initialize_relocation_hashtable(unsigned int num_relocations);
> > +void process_accumulated_relocations(struct module *me);
> > +int add_relocation_to_accumulate(struct module *me, int type, void *location,
> > + unsigned int hashtable_bits, Elf_Addr v);
> > +
> > +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)
> > @@ -35,7 +71,7 @@ static int riscv_insn_rmw(void *location, u32 keep, u32 set)
> > insn &= keep;
> > insn |= set;
> >
> > - parcel[0] = cpu_to_le32(insn);
> > + parcel[0] = cpu_to_le16(insn);
> > parcel[1] = cpu_to_le16(insn >> 16);
> > return 0;
> > }
> > @@ -43,8 +79,12 @@ static int riscv_insn_rmw(void *location, u32 keep, u32 set)
> > static int riscv_insn_rvc_rmw(void *location, u16 keep, u16 set)
> > {
> > u16 *parcel = location;
> > + u16 insn = le16_to_cpu(*parcel);
> >
> > - *parcel = cpu_to_le16((le16_to_cpu(*parcel) & keep) | set);
> > + insn &= keep;
> > + insn |= set;
> > +
> > + *parcel = cpu_to_le16(insn);
> > return 0;
> > }
>
> I think you meant to squash these two chunks into the previous patch.
>
> >
> > @@ -269,6 +309,12 @@ 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 +336,12 @@ 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 +363,415 @@ 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 *byte = location;
> > + u8 value = v;
> > +
> > + *byte = (*byte - (value & 0x3f)) & 0x3f;
> > + return 0;
> > +}
> > +
> > +static int apply_r_riscv_set6_rela(struct module *me, void *location, Elf_Addr v)
> > +{
> > + u8 *byte = location;
> > + u8 value = v;
> > +
> > + *byte = (*byte & 0xc0) | (value & 0x3f);
> > + 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;
>
> nit: in other reviews i've been told to use uintptr_t when casting pointers to
> an unsigned integer.
>
Okay will do.
> > + 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;
> > +}
> > +
> > +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)
> > +{
> > + u8 *byte = location;
> > + u8 value = buffer;
> > +
> > + if (buffer > 0x3f) {
> > + pr_err("%s: value %ld out of range for 6-bit relocation.\n",
> > + me->name, buffer);
> > + return -EINVAL;
> > + }
> > +
> > + *byte = (*byte & 0xc0) | (value & 0x3f);
> > + return 0;
> > +}
> > +
> > +static int apply_8_bit_accumulation(struct module *me, void *location, long buffer)
> > +{
> > + if (buffer > U8_MAX) {
> > + 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_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_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.
> > + */
> > + u8 *p = location;
> > +
> > + while (buffer != 0) {
> > + u8 value = buffer & 0x7f;
> > +
> > + buffer >>= 7;
> > + value |= (!!buffer) << 7;
> > +
> > + *p++ = value;
> > + }
> > + return 0;
> > +}
> > +
> > +/*
> > + * Relocations defined in the riscv-elf-psabi-doc.
> > + * This handles static linking only.
> > + */
> > +static struct relocation_handlers reloc_handlers[] = {
>
> I don't see anywhere this table is written to. Can we maybe make it const?
>
> > + [R_RISCV_32] = { apply_r_riscv_32_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_64] = { apply_r_riscv_64_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_RELATIVE] = { dynamic_linking_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_COPY] = { dynamic_linking_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_JUMP_SLOT] = { dynamic_linking_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TLS_DTPMOD32] = { dynamic_linking_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TLS_DTPMOD64] = { dynamic_linking_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TLS_DTPREL32] = { dynamic_linking_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TLS_DTPREL64] = { dynamic_linking_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TLS_TPREL32] = { dynamic_linking_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TLS_TPREL64] = { dynamic_linking_not_supported, false,
> > + accumulation_not_supported },
> > + /* 12-15 undefined */
> > + [R_RISCV_BRANCH] = { apply_r_riscv_branch_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_JAL] = { apply_r_riscv_jal_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_CALL] = { apply_r_riscv_call_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_CALL_PLT] = { apply_r_riscv_call_plt_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_GOT_HI20] = { apply_r_riscv_got_hi20_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TLS_GOT_HI20] = { tls_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TLS_GD_HI20] = { tls_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_PCREL_HI20] = { apply_r_riscv_pcrel_hi20_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_PCREL_LO12_I] = { apply_r_riscv_pcrel_lo12_i_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_PCREL_LO12_S] = { apply_r_riscv_pcrel_lo12_s_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_HI20] = { apply_r_riscv_hi20_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_LO12_I] = { apply_r_riscv_lo12_i_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_LO12_S] = { apply_r_riscv_lo12_s_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TPREL_HI20] = { tls_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TPREL_LO12_I] = { tls_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TPREL_LO12_S] = { tls_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_TPREL_ADD] = { tls_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_ADD8] = { apply_r_riscv_add8_rela, true,
> > + apply_8_bit_accumulation },
> > + [R_RISCV_ADD16] = { apply_r_riscv_add16_rela, true,
> > + apply_16_bit_accumulation },
> > + [R_RISCV_ADD32] = { apply_r_riscv_add32_rela, true,
> > + apply_32_bit_accumulation },
> > + [R_RISCV_ADD64] = { apply_r_riscv_add64_rela, true,
> > + apply_64_bit_accumulation },
> > + [R_RISCV_SUB8] = { apply_r_riscv_sub8_rela, true,
> > + apply_8_bit_accumulation },
> > + [R_RISCV_SUB16] = { apply_r_riscv_sub16_rela, true,
> > + apply_16_bit_accumulation },
> > + [R_RISCV_SUB32] = { apply_r_riscv_sub32_rela, true,
> > + apply_32_bit_accumulation },
> > + [R_RISCV_SUB64] = { apply_r_riscv_sub64_rela, true,
> > + apply_64_bit_accumulation },
> > + /* 41-42 reserved for future standard use */
> > + [R_RISCV_ALIGN] = { apply_r_riscv_align_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_RVC_BRANCH] = { apply_r_riscv_rvc_branch_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_RVC_JUMP] = { apply_r_riscv_rvc_jump_rela, false,
> > + accumulation_not_supported },
> > + /* 46-50 reserved for future standard use */
> > + [R_RISCV_RELAX] = { apply_r_riscv_relax_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_SUB6] = { apply_r_riscv_sub6_rela, true,
> > + apply_6_bit_accumulation },
> > + [R_RISCV_SET6] = { apply_r_riscv_set6_rela, true,
> > + apply_6_bit_accumulation },
> > + [R_RISCV_SET8] = { apply_r_riscv_set8_rela, true,
> > + apply_8_bit_accumulation },
> > + [R_RISCV_SET16] = { apply_r_riscv_set16_rela, true,
> > + apply_16_bit_accumulation },
> > + [R_RISCV_SET32] = { apply_r_riscv_set32_rela, true,
> > + apply_32_bit_accumulation },
> > + [R_RISCV_32_PCREL] = { apply_r_riscv_32_pcrel_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_IRELATIVE] = { dynamic_linking_not_supported, false,
> > + accumulation_not_supported },
> > + [R_RISCV_PLT32] = { apply_r_riscv_plt32_rela, false,
> > + accumulation_not_supported },
> > + [R_RISCV_SET_ULEB128] = { apply_r_riscv_set_uleb128, true,
> > + apply_uleb128_accumulation },
> > + [R_RISCV_SUB_ULEB128] = { apply_r_riscv_sub_uleb128, true,
> > + 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[curr_type].reloc_handler(
> > + me, &buffer, rel_entry_iter->value);
> > + kfree(rel_entry_iter);
> > + }
> > + reloc_handlers[curr_type].accumulate_handler(
> > + 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 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);
>
> uintptr_t
>
> > +
> > + current_head = &relocation_hashtable[hash];
> > +
> > + /* 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 +783,13 @@ 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;
> > @@ -371,8 +807,8 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> >
> > type = ELF_RISCV_R_TYPE(rel[i].r_info);
> >
> > - if (type < ARRAY_SIZE(reloc_handlers_rela))
> > - handler = reloc_handlers_rela[type];
> > + if (type < ARRAY_SIZE(reloc_handlers))
> > + handler = reloc_handlers[type].reloc_handler;
> > else
> > handler = NULL;
> >
> > @@ -428,11 +864,16 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> > }
> > }
> >
> > - res = handler(me, location, v);
> > + if (reloc_handlers[type].accumulate_relocations)
>
> As far as I can tell the table above has accumulate_relocations == false if and
> only if .accumulate_handler == accumulation_not_supported. Could we maybe drop
> the bool and just check for that?
>
> Are there situations where we might end up calling
> accumulation_not_supported()? If not we could just let .accumulate_handler be
> NULL where accumulation is not supported. Then the table could be initialised
> with
>
> { reloc_handler }, // when accumulation is not supported and
> { reloc_handler, accumulate_handler }, // when it is
>
> ..and the test above would just be
>
> if (reloc_handlers[type].accumulate_handler)
>
Yes it will always be the case that accumulate_relocations == false and
it uses accumulation_not_supported. This suggestion will make the code
much cleaner.
- Charlie
> > + 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
> >
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@xxxxxxxxxxxxxxxxxxx
> > http://lists.infradead.org/mailman/listinfo/linux-riscv