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Message-ID: <20250530000044.341911-1-dylanbhatch@google.com>
Date: Fri, 30 May 2025 00:00:44 +0000
From: Dylan Hatch <dylanbhatch@...gle.com>
To: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
Ard Biesheuvel <ardb@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>, Song Liu <song@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Dylan Hatch <dylanbhatch@...gle.com>, Roman Gushchin <roman.gushchin@...ux.dev>,
Toshiyuki Sato <fj6611ie@...jp.fujitsu.com>
Subject: [PATCH v5] arm64/module: Use text-poke API for late relocations.
To enable late module patching, livepatch modules need to be able to
apply some of their relocations well after being loaded. In this
scenario however, the livepatch module text and data is already RX-only,
so special treatment is needed to make the late relocations possible. To
do this, use the text-poking API for these late relocations.
This patch is partially based off commit 88fc078a7a8f6 ("x86/module: Use
text_poke() for late relocations").
Signed-off-by: Dylan Hatch <dylanbhatch@...gle.com>
Acked-by: Song Liu <song@...nel.org>
---
arch/arm64/kernel/module.c | 110 ++++++++++++++++++++++---------------
1 file changed, 66 insertions(+), 44 deletions(-)
diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
index 06bb680bfe975..93e6d63074afe 100644
--- a/arch/arm64/kernel/module.c
+++ b/arch/arm64/kernel/module.c
@@ -23,6 +23,7 @@
#include <asm/insn.h>
#include <asm/scs.h>
#include <asm/sections.h>
+#include <asm/text-patching.h>
enum aarch64_reloc_op {
RELOC_OP_NONE,
@@ -48,7 +49,26 @@ static u64 do_reloc(enum aarch64_reloc_op reloc_op, __le32 *place, u64 val)
return 0;
}
-static int reloc_data(enum aarch64_reloc_op op, void *place, u64 val, int len)
+static void write_data(void *place, s64 *sval, size_t len, struct module *me)
+{
+ if (me->state == MODULE_STATE_UNFORMED)
+ memcpy(place, sval, len);
+ else
+ aarch64_insn_copy(place, sval, len);
+}
+
+static void write_insn(__le32 *place, u32 insn, struct module *me)
+{
+ __le32 le = cpu_to_le32(insn);
+
+ if (me->state == MODULE_STATE_UNFORMED)
+ *place = le;
+ else
+ aarch64_insn_copy(place, &le, sizeof(le));
+}
+
+static int reloc_data(enum aarch64_reloc_op op, void *place, u64 val, int len,
+ struct module *me)
{
s64 sval = do_reloc(op, place, val);
@@ -66,7 +86,7 @@ static int reloc_data(enum aarch64_reloc_op op, void *place, u64 val, int len)
switch (len) {
case 16:
- *(s16 *)place = sval;
+ write_data(place, &sval, sizeof(s16), me);
switch (op) {
case RELOC_OP_ABS:
if (sval < 0 || sval > U16_MAX)
@@ -82,7 +102,7 @@ static int reloc_data(enum aarch64_reloc_op op, void *place, u64 val, int len)
}
break;
case 32:
- *(s32 *)place = sval;
+ write_data(place, &sval, sizeof(s32), me);
switch (op) {
case RELOC_OP_ABS:
if (sval < 0 || sval > U32_MAX)
@@ -98,7 +118,7 @@ static int reloc_data(enum aarch64_reloc_op op, void *place, u64 val, int len)
}
break;
case 64:
- *(s64 *)place = sval;
+ write_data(place, &sval, sizeof(s64), me);
break;
default:
pr_err("Invalid length (%d) for data relocation\n", len);
@@ -113,7 +133,8 @@ enum aarch64_insn_movw_imm_type {
};
static int reloc_insn_movw(enum aarch64_reloc_op op, __le32 *place, u64 val,
- int lsb, enum aarch64_insn_movw_imm_type imm_type)
+ int lsb, enum aarch64_insn_movw_imm_type imm_type,
+ struct module *me)
{
u64 imm;
s64 sval;
@@ -145,7 +166,7 @@ static int reloc_insn_movw(enum aarch64_reloc_op op, __le32 *place, u64 val,
/* Update the instruction with the new encoding. */
insn = aarch64_insn_encode_immediate(AARCH64_INSN_IMM_16, insn, imm);
- *place = cpu_to_le32(insn);
+ write_insn(place, insn, me);
if (imm > U16_MAX)
return -ERANGE;
@@ -154,7 +175,8 @@ static int reloc_insn_movw(enum aarch64_reloc_op op, __le32 *place, u64 val,
}
static int reloc_insn_imm(enum aarch64_reloc_op op, __le32 *place, u64 val,
- int lsb, int len, enum aarch64_insn_imm_type imm_type)
+ int lsb, int len, enum aarch64_insn_imm_type imm_type,
+ struct module *me)
{
u64 imm, imm_mask;
s64 sval;
@@ -170,7 +192,7 @@ static int reloc_insn_imm(enum aarch64_reloc_op op, __le32 *place, u64 val,
/* Update the instruction's immediate field. */
insn = aarch64_insn_encode_immediate(imm_type, insn, imm);
- *place = cpu_to_le32(insn);
+ write_insn(place, insn, me);
/*
* Extract the upper value bits (including the sign bit) and
@@ -189,17 +211,17 @@ static int reloc_insn_imm(enum aarch64_reloc_op op, __le32 *place, u64 val,
}
static int reloc_insn_adrp(struct module *mod, Elf64_Shdr *sechdrs,
- __le32 *place, u64 val)
+ __le32 *place, u64 val, struct module *me)
{
u32 insn;
if (!is_forbidden_offset_for_adrp(place))
return reloc_insn_imm(RELOC_OP_PAGE, place, val, 12, 21,
- AARCH64_INSN_IMM_ADR);
+ AARCH64_INSN_IMM_ADR, me);
/* patch ADRP to ADR if it is in range */
if (!reloc_insn_imm(RELOC_OP_PREL, place, val & ~0xfff, 0, 21,
- AARCH64_INSN_IMM_ADR)) {
+ AARCH64_INSN_IMM_ADR, me)) {
insn = le32_to_cpu(*place);
insn &= ~BIT(31);
} else {
@@ -211,7 +233,7 @@ static int reloc_insn_adrp(struct module *mod, Elf64_Shdr *sechdrs,
AARCH64_INSN_BRANCH_NOLINK);
}
- *place = cpu_to_le32(insn);
+ write_insn(place, insn, me);
return 0;
}
@@ -255,23 +277,23 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
/* Data relocations. */
case R_AARCH64_ABS64:
overflow_check = false;
- ovf = reloc_data(RELOC_OP_ABS, loc, val, 64);
+ ovf = reloc_data(RELOC_OP_ABS, loc, val, 64, me);
break;
case R_AARCH64_ABS32:
- ovf = reloc_data(RELOC_OP_ABS, loc, val, 32);
+ ovf = reloc_data(RELOC_OP_ABS, loc, val, 32, me);
break;
case R_AARCH64_ABS16:
- ovf = reloc_data(RELOC_OP_ABS, loc, val, 16);
+ ovf = reloc_data(RELOC_OP_ABS, loc, val, 16, me);
break;
case R_AARCH64_PREL64:
overflow_check = false;
- ovf = reloc_data(RELOC_OP_PREL, loc, val, 64);
+ ovf = reloc_data(RELOC_OP_PREL, loc, val, 64, me);
break;
case R_AARCH64_PREL32:
- ovf = reloc_data(RELOC_OP_PREL, loc, val, 32);
+ ovf = reloc_data(RELOC_OP_PREL, loc, val, 32, me);
break;
case R_AARCH64_PREL16:
- ovf = reloc_data(RELOC_OP_PREL, loc, val, 16);
+ ovf = reloc_data(RELOC_OP_PREL, loc, val, 16, me);
break;
/* MOVW instruction relocations. */
@@ -280,88 +302,88 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
fallthrough;
case R_AARCH64_MOVW_UABS_G0:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, me);
break;
case R_AARCH64_MOVW_UABS_G1_NC:
overflow_check = false;
fallthrough;
case R_AARCH64_MOVW_UABS_G1:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, me);
break;
case R_AARCH64_MOVW_UABS_G2_NC:
overflow_check = false;
fallthrough;
case R_AARCH64_MOVW_UABS_G2:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, me);
break;
case R_AARCH64_MOVW_UABS_G3:
/* We're using the top bits so we can't overflow. */
overflow_check = false;
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 48,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, me);
break;
case R_AARCH64_MOVW_SABS_G0:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, me);
break;
case R_AARCH64_MOVW_SABS_G1:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, me);
break;
case R_AARCH64_MOVW_SABS_G2:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, me);
break;
case R_AARCH64_MOVW_PREL_G0_NC:
overflow_check = false;
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, me);
break;
case R_AARCH64_MOVW_PREL_G0:
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, me);
break;
case R_AARCH64_MOVW_PREL_G1_NC:
overflow_check = false;
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, me);
break;
case R_AARCH64_MOVW_PREL_G1:
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, me);
break;
case R_AARCH64_MOVW_PREL_G2_NC:
overflow_check = false;
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, me);
break;
case R_AARCH64_MOVW_PREL_G2:
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, me);
break;
case R_AARCH64_MOVW_PREL_G3:
/* We're using the top bits so we can't overflow. */
overflow_check = false;
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 48,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, me);
break;
/* Immediate instruction relocations. */
case R_AARCH64_LD_PREL_LO19:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
- AARCH64_INSN_IMM_19);
+ AARCH64_INSN_IMM_19, me);
break;
case R_AARCH64_ADR_PREL_LO21:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 0, 21,
- AARCH64_INSN_IMM_ADR);
+ AARCH64_INSN_IMM_ADR, me);
break;
case R_AARCH64_ADR_PREL_PG_HI21_NC:
overflow_check = false;
fallthrough;
case R_AARCH64_ADR_PREL_PG_HI21:
- ovf = reloc_insn_adrp(me, sechdrs, loc, val);
+ ovf = reloc_insn_adrp(me, sechdrs, loc, val, me);
if (ovf && ovf != -ERANGE)
return ovf;
break;
@@ -369,46 +391,46 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
case R_AARCH64_LDST8_ABS_LO12_NC:
overflow_check = false;
ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 0, 12,
- AARCH64_INSN_IMM_12);
+ AARCH64_INSN_IMM_12, me);
break;
case R_AARCH64_LDST16_ABS_LO12_NC:
overflow_check = false;
ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 1, 11,
- AARCH64_INSN_IMM_12);
+ AARCH64_INSN_IMM_12, me);
break;
case R_AARCH64_LDST32_ABS_LO12_NC:
overflow_check = false;
ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 2, 10,
- AARCH64_INSN_IMM_12);
+ AARCH64_INSN_IMM_12, me);
break;
case R_AARCH64_LDST64_ABS_LO12_NC:
overflow_check = false;
ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 3, 9,
- AARCH64_INSN_IMM_12);
+ AARCH64_INSN_IMM_12, me);
break;
case R_AARCH64_LDST128_ABS_LO12_NC:
overflow_check = false;
ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 4, 8,
- AARCH64_INSN_IMM_12);
+ AARCH64_INSN_IMM_12, me);
break;
case R_AARCH64_TSTBR14:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 14,
- AARCH64_INSN_IMM_14);
+ AARCH64_INSN_IMM_14, me);
break;
case R_AARCH64_CONDBR19:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
- AARCH64_INSN_IMM_19);
+ AARCH64_INSN_IMM_19, me);
break;
case R_AARCH64_JUMP26:
case R_AARCH64_CALL26:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26,
- AARCH64_INSN_IMM_26);
+ AARCH64_INSN_IMM_26, me);
if (ovf == -ERANGE) {
val = module_emit_plt_entry(me, sechdrs, loc, &rel[i], sym);
if (!val)
return -ENOEXEC;
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2,
- 26, AARCH64_INSN_IMM_26);
+ 26, AARCH64_INSN_IMM_26, me);
}
break;
--
2.49.0.1204.g71687c7c1d-goog
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