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riscv: Avoid unaligned access when relocating modules
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With the C-extension regular 32bit instructions are not
necessarily aligned on 4-byte boundaries. RISC-V instructions
are in fact an ordered list of 16bit little-endian
"parcels", so access the instruction as such.

This should also make the code work in case someone builds
a big-endian RISC-V machine.

Signed-off-by: Emil Renner Berthing <[email protected]>
Signed-off-by: Charlie Jenkins <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>
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@esmil @palmer-dabbelt
esmil authored and palmer-dabbelt committed Nov 7, 2023
1 parent 0bb80ec commit 8cbe0ac
Showing 1 changed file with 81 additions and 76 deletions.
157 changes: 81 additions & 76 deletions arch/riscv/kernel/module.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,68 +27,90 @@ static bool riscv_insn_valid_32bit_offset(ptrdiff_t val)
#endif
}

static int apply_r_riscv_32_rela(struct module *me, u32 *location, Elf_Addr v)
static int riscv_insn_rmw(void *location, u32 keep, u32 set)
{
u16 *parcel = location;
u32 insn = (u32)le16_to_cpu(parcel[0]) | (u32)le16_to_cpu(parcel[1]) << 16;

insn &= keep;
insn |= set;

parcel[0] = cpu_to_le16(insn);
parcel[1] = cpu_to_le16(insn >> 16);
return 0;
}

static int riscv_insn_rvc_rmw(void *location, u16 keep, u16 set)
{
u16 *parcel = location;
u16 insn = le16_to_cpu(*parcel);

insn &= keep;
insn |= set;

*parcel = cpu_to_le16(insn);
return 0;
}

static int apply_r_riscv_32_rela(struct module *me, void *location, Elf_Addr v)
{
if (v != (u32)v) {
pr_err("%s: value %016llx out of range for 32-bit field\n",
me->name, (long long)v);
return -EINVAL;
}
*location = v;
*(u32 *)location = v;
return 0;
}

static int apply_r_riscv_64_rela(struct module *me, u32 *location, Elf_Addr v)
static int apply_r_riscv_64_rela(struct module *me, void *location, Elf_Addr v)
{
*(u64 *)location = v;
return 0;
}

static int apply_r_riscv_branch_rela(struct module *me, u32 *location,
static int apply_r_riscv_branch_rela(struct module *me, void *location,
Elf_Addr v)
{
ptrdiff_t offset = (void *)v - (void *)location;
ptrdiff_t offset = (void *)v - location;
u32 imm12 = (offset & 0x1000) << (31 - 12);
u32 imm11 = (offset & 0x800) >> (11 - 7);
u32 imm10_5 = (offset & 0x7e0) << (30 - 10);
u32 imm4_1 = (offset & 0x1e) << (11 - 4);

*location = (*location & 0x1fff07f) | imm12 | imm11 | imm10_5 | imm4_1;
return 0;
return riscv_insn_rmw(location, 0x1fff07f, imm12 | imm11 | imm10_5 | imm4_1);
}

static int apply_r_riscv_jal_rela(struct module *me, u32 *location,
static int apply_r_riscv_jal_rela(struct module *me, void *location,
Elf_Addr v)
{
ptrdiff_t offset = (void *)v - (void *)location;
ptrdiff_t offset = (void *)v - location;
u32 imm20 = (offset & 0x100000) << (31 - 20);
u32 imm19_12 = (offset & 0xff000);
u32 imm11 = (offset & 0x800) << (20 - 11);
u32 imm10_1 = (offset & 0x7fe) << (30 - 10);

*location = (*location & 0xfff) | imm20 | imm19_12 | imm11 | imm10_1;
return 0;
return riscv_insn_rmw(location, 0xfff, imm20 | imm19_12 | imm11 | imm10_1);
}

static int apply_r_riscv_rvc_branch_rela(struct module *me, u32 *location,
static int apply_r_riscv_rvc_branch_rela(struct module *me, void *location,
Elf_Addr v)
{
ptrdiff_t offset = (void *)v - (void *)location;
ptrdiff_t offset = (void *)v - location;
u16 imm8 = (offset & 0x100) << (12 - 8);
u16 imm7_6 = (offset & 0xc0) >> (6 - 5);
u16 imm5 = (offset & 0x20) >> (5 - 2);
u16 imm4_3 = (offset & 0x18) << (12 - 5);
u16 imm2_1 = (offset & 0x6) << (12 - 10);

*(u16 *)location = (*(u16 *)location & 0xe383) |
imm8 | imm7_6 | imm5 | imm4_3 | imm2_1;
return 0;
return riscv_insn_rvc_rmw(location, 0xe383,
imm8 | imm7_6 | imm5 | imm4_3 | imm2_1);
}

static int apply_r_riscv_rvc_jump_rela(struct module *me, u32 *location,
static int apply_r_riscv_rvc_jump_rela(struct module *me, void *location,
Elf_Addr v)
{
ptrdiff_t offset = (void *)v - (void *)location;
ptrdiff_t offset = (void *)v - location;
u16 imm11 = (offset & 0x800) << (12 - 11);
u16 imm10 = (offset & 0x400) >> (10 - 8);
u16 imm9_8 = (offset & 0x300) << (12 - 11);
Expand All @@ -98,16 +120,14 @@ static int apply_r_riscv_rvc_jump_rela(struct module *me, u32 *location,
u16 imm4 = (offset & 0x10) << (12 - 5);
u16 imm3_1 = (offset & 0xe) << (12 - 10);

*(u16 *)location = (*(u16 *)location & 0xe003) |
imm11 | imm10 | imm9_8 | imm7 | imm6 | imm5 | imm4 | imm3_1;
return 0;
return riscv_insn_rvc_rmw(location, 0xe003,
imm11 | imm10 | imm9_8 | imm7 | imm6 | imm5 | imm4 | imm3_1);
}

static int apply_r_riscv_pcrel_hi20_rela(struct module *me, u32 *location,
static int apply_r_riscv_pcrel_hi20_rela(struct module *me, void *location,
Elf_Addr v)
{
ptrdiff_t offset = (void *)v - (void *)location;
s32 hi20;
ptrdiff_t offset = (void *)v - location;

if (!riscv_insn_valid_32bit_offset(offset)) {
pr_err(
Expand All @@ -116,23 +136,20 @@ static int apply_r_riscv_pcrel_hi20_rela(struct module *me, u32 *location,
return -EINVAL;
}

hi20 = (offset + 0x800) & 0xfffff000;
*location = (*location & 0xfff) | hi20;
return 0;
return riscv_insn_rmw(location, 0xfff, (offset + 0x800) & 0xfffff000);
}

static int apply_r_riscv_pcrel_lo12_i_rela(struct module *me, u32 *location,
static int apply_r_riscv_pcrel_lo12_i_rela(struct module *me, void *location,
Elf_Addr v)
{
/*
* v is the lo12 value to fill. It is calculated before calling this
* handler.
*/
*location = (*location & 0xfffff) | ((v & 0xfff) << 20);
return 0;
return riscv_insn_rmw(location, 0xfffff, (v & 0xfff) << 20);
}

static int apply_r_riscv_pcrel_lo12_s_rela(struct module *me, u32 *location,
static int apply_r_riscv_pcrel_lo12_s_rela(struct module *me, void *location,
Elf_Addr v)
{
/*
Expand All @@ -142,82 +159,72 @@ static int apply_r_riscv_pcrel_lo12_s_rela(struct module *me, u32 *location,
u32 imm11_5 = (v & 0xfe0) << (31 - 11);
u32 imm4_0 = (v & 0x1f) << (11 - 4);

*location = (*location & 0x1fff07f) | imm11_5 | imm4_0;
return 0;
return riscv_insn_rmw(location, 0x1fff07f, imm11_5 | imm4_0);
}

static int apply_r_riscv_hi20_rela(struct module *me, u32 *location,
static int apply_r_riscv_hi20_rela(struct module *me, void *location,
Elf_Addr v)
{
s32 hi20;

if (IS_ENABLED(CONFIG_CMODEL_MEDLOW)) {
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;
}

hi20 = ((s32)v + 0x800) & 0xfffff000;
*location = (*location & 0xfff) | hi20;
return 0;
return riscv_insn_rmw(location, 0xfff, ((s32)v + 0x800) & 0xfffff000);
}

static int apply_r_riscv_lo12_i_rela(struct module *me, u32 *location,
static int apply_r_riscv_lo12_i_rela(struct module *me, void *location,
Elf_Addr v)
{
/* Skip medlow checking because of filtering by HI20 already */
s32 hi20 = ((s32)v + 0x800) & 0xfffff000;
s32 lo12 = ((s32)v - hi20);
*location = (*location & 0xfffff) | ((lo12 & 0xfff) << 20);
return 0;

return riscv_insn_rmw(location, 0xfffff, (lo12 & 0xfff) << 20);
}

static int apply_r_riscv_lo12_s_rela(struct module *me, u32 *location,
static int apply_r_riscv_lo12_s_rela(struct module *me, void *location,
Elf_Addr v)
{
/* Skip medlow checking because of filtering by HI20 already */
s32 hi20 = ((s32)v + 0x800) & 0xfffff000;
s32 lo12 = ((s32)v - hi20);
u32 imm11_5 = (lo12 & 0xfe0) << (31 - 11);
u32 imm4_0 = (lo12 & 0x1f) << (11 - 4);
*location = (*location & 0x1fff07f) | imm11_5 | imm4_0;
return 0;

return riscv_insn_rmw(location, 0x1fff07f, imm11_5 | imm4_0);
}

static int apply_r_riscv_got_hi20_rela(struct module *me, u32 *location,
static int apply_r_riscv_got_hi20_rela(struct module *me, void *location,
Elf_Addr v)
{
ptrdiff_t offset = (void *)v - (void *)location;
s32 hi20;
ptrdiff_t offset = (void *)v - location;

/* Always emit the got entry */
if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
offset = module_emit_got_entry(me, v);
offset = (void *)offset - (void *)location;
offset = (void *)module_emit_got_entry(me, v) - location;
} else {
pr_err(
"%s: can not generate the GOT entry for symbol = %016llx from PC = %p\n",
me->name, (long long)v, location);
return -EINVAL;
}

hi20 = (offset + 0x800) & 0xfffff000;
*location = (*location & 0xfff) | hi20;
return 0;
return riscv_insn_rmw(location, 0xfff, (offset + 0x800) & 0xfffff000);
}

static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
static int apply_r_riscv_call_plt_rela(struct module *me, void *location,
Elf_Addr v)
{
ptrdiff_t offset = (void *)v - (void *)location;
ptrdiff_t offset = (void *)v - location;
u32 hi20, lo12;

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 = module_emit_plt_entry(me, v);
offset = (void *)offset - (void *)location;
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",
Expand All @@ -228,15 +235,14 @@ static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,

hi20 = (offset + 0x800) & 0xfffff000;
lo12 = (offset - hi20) & 0xfff;
*location = (*location & 0xfff) | hi20;
*(location + 1) = (*(location + 1) & 0xfffff) | (lo12 << 20);
return 0;
riscv_insn_rmw(location, 0xfff, hi20);
return riscv_insn_rmw(location + 4, 0xfffff, lo12 << 20);
}

static int apply_r_riscv_call_rela(struct module *me, u32 *location,
static int apply_r_riscv_call_rela(struct module *me, void *location,
Elf_Addr v)
{
ptrdiff_t offset = (void *)v - (void *)location;
ptrdiff_t offset = (void *)v - location;
u32 hi20, lo12;

if (!riscv_insn_valid_32bit_offset(offset)) {
Expand All @@ -248,18 +254,17 @@ static int apply_r_riscv_call_rela(struct module *me, u32 *location,

hi20 = (offset + 0x800) & 0xfffff000;
lo12 = (offset - hi20) & 0xfff;
*location = (*location & 0xfff) | hi20;
*(location + 1) = (*(location + 1) & 0xfffff) | (lo12 << 20);
return 0;
riscv_insn_rmw(location, 0xfff, hi20);
return riscv_insn_rmw(location + 4, 0xfffff, lo12 << 20);
}

static int apply_r_riscv_relax_rela(struct module *me, u32 *location,
static int apply_r_riscv_relax_rela(struct module *me, void *location,
Elf_Addr v)
{
return 0;
}

static int apply_r_riscv_align_rela(struct module *me, u32 *location,
static int apply_r_riscv_align_rela(struct module *me, void *location,
Elf_Addr v)
{
pr_err(
Expand All @@ -268,49 +273,49 @@ static int apply_r_riscv_align_rela(struct module *me, u32 *location,
return -EINVAL;
}

static int apply_r_riscv_add16_rela(struct module *me, u32 *location,
static int apply_r_riscv_add16_rela(struct module *me, void *location,
Elf_Addr v)
{
*(u16 *)location += (u16)v;
return 0;
}

static int apply_r_riscv_add32_rela(struct module *me, u32 *location,
static int apply_r_riscv_add32_rela(struct module *me, void *location,
Elf_Addr v)
{
*(u32 *)location += (u32)v;
return 0;
}

static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
static int apply_r_riscv_add64_rela(struct module *me, void *location,
Elf_Addr v)
{
*(u64 *)location += (u64)v;
return 0;
}

static int apply_r_riscv_sub16_rela(struct module *me, u32 *location,
static int apply_r_riscv_sub16_rela(struct module *me, void *location,
Elf_Addr v)
{
*(u16 *)location -= (u16)v;
return 0;
}

static int apply_r_riscv_sub32_rela(struct module *me, u32 *location,
static int apply_r_riscv_sub32_rela(struct module *me, void *location,
Elf_Addr v)
{
*(u32 *)location -= (u32)v;
return 0;
}

static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
static int apply_r_riscv_sub64_rela(struct module *me, void *location,
Elf_Addr v)
{
*(u64 *)location -= (u64)v;
return 0;
}

static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
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,
Expand Down Expand Up @@ -342,9 +347,9 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
struct module *me)
{
Elf_Rela *rel = (void *) sechdrs[relsec].sh_addr;
int (*handler)(struct module *me, u32 *location, Elf_Addr v);
int (*handler)(struct module *me, void *location, Elf_Addr v);
Elf_Sym *sym;
u32 *location;
void *location;
unsigned int i, type;
Elf_Addr v;
int res;
Expand Down

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