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Date: Wed, 20 Jan 2021 18:37:52 +0100
From: Julien Thierry <jthierry@...hat.com>
To: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc: catalin.marinas@....com, will@...nel.org, ardb@...nel.org,
masahiroy@...nel.org, keescook@...omium.org,
michal.lkml@...kovi.net, jpoimboe@...hat.com, peterz@...radead.org,
mark.rutland@....com, broonie@...nel.org,
linux-efi@...r.kernel.org, linux-hardening@...r.kernel.org,
Julien Thierry <jthierry@...hat.com>
Subject: [RFC PATCH 09/17] objtool: arm64: Decode LDR instructions
Load literal instructions can generate constants inside code sections.
Record the locations of the constants in order to be able to remove
their corresponding "struct instruction".
Signed-off-by: Julien Thierry <jthierry@...hat.com>
---
tools/objtool/arch/arm64/decode.c | 86 ++++++++++++++++++++++++++++
tools/objtool/arch/x86/decode.c | 5 ++
tools/objtool/check.c | 3 +
tools/objtool/include/objtool/arch.h | 3 +
4 files changed, 97 insertions(+)
diff --git a/tools/objtool/arch/arm64/decode.c b/tools/objtool/arch/arm64/decode.c
index 1087ede67bcd..b4d4d5b051b0 100644
--- a/tools/objtool/arch/arm64/decode.c
+++ b/tools/objtool/arch/arm64/decode.c
@@ -30,6 +30,73 @@ static unsigned long sign_extend(unsigned long x, int nbits)
return ((~0UL + (sign_bit ^ 1)) << nbits) | x;
}
+struct insn_loc {
+ const struct section *sec;
+ unsigned long offset;
+ struct hlist_node hnode;
+ bool ignorable;
+};
+
+DEFINE_HASHTABLE(invalid_insns, 16);
+
+static int record_invalid_insn(const struct section *sec,
+ unsigned long offset,
+ bool ignore)
+{
+ struct insn_loc *loc;
+ struct hlist_head *l;
+
+ l = &invalid_insns[hash_min(offset, HASH_BITS(invalid_insns))];
+ if (!hlist_empty(l)) {
+ loc = hlist_entry(l->first, struct insn_loc, hnode);
+ loc->ignorable |= ignore;
+ return 0;
+ }
+
+ loc = malloc(sizeof(*loc));
+ if (!loc) {
+ WARN("malloc failed");
+ return -1;
+ }
+
+ loc->sec = sec;
+ loc->offset = offset;
+ loc->ignorable = ignore;
+
+ hash_add(invalid_insns, &loc->hnode, loc->offset);
+
+ return 0;
+}
+
+int arch_post_process_instructions(struct objtool_file *file)
+{
+ struct hlist_node *tmp;
+ struct insn_loc *loc;
+ unsigned int bkt;
+ int res = 0;
+
+ hash_for_each_safe(invalid_insns, bkt, tmp, loc, hnode) {
+ struct instruction *insn;
+
+ insn = find_insn(file, (struct section *) loc->sec, loc->offset);
+ if (insn) {
+ if (loc->ignorable) {
+ list_del(&insn->list);
+ hash_del(&insn->hash);
+ free(insn);
+ } else {
+ WARN_FUNC("can't decode instruction", insn->sec, insn->offset);
+ return -1;
+ }
+ }
+
+ hash_del(&loc->hnode);
+ free(loc);
+ }
+
+ return res;
+}
+
bool arch_callee_saved_reg(unsigned char reg)
{
switch (reg) {
@@ -359,6 +426,25 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
case AARCH64_INSN_CLS_LDST:
if (arm_decode_load_store(insn, type, immediate, ops_list))
break;
+ if (aarch64_insn_is_ldr_lit(insn)) {
+ long pc_offset;
+
+ pc_offset = insn & GENMASK(23, 5);
+ /* Sign extend and multiply by 4 */
+ pc_offset = (pc_offset << (64 - 23));
+ pc_offset = ((pc_offset >> (64 - 23)) >> 5) << 2;
+
+ if (record_invalid_insn(sec, offset + pc_offset, true))
+ return -1;
+
+ /* 64-bit literal */
+ if (insn & BIT(30)) {
+ if (record_invalid_insn(sec,
+ offset + pc_offset + 4,
+ true))
+ return -1;
+ }
+ }
*type = INSN_OTHER;
break;
default:
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 6baa22732ca6..e76d987ce3c7 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -549,6 +549,11 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
return 0;
}
+int arch_post_process_instructions(struct objtool_file *file)
+{
+ return 0;
+}
+
void arch_initial_func_cfi_state(struct cfi_init_state *state)
{
int i;
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 270b507e7098..d902697a388e 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -319,6 +319,9 @@ static int decode_instructions(struct objtool_file *file)
if (stats)
printf("nr_insns: %lu\n", nr_insns);
+ if (arch_post_process_instructions(file))
+ return -1;
+
return 0;
err:
diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h
index 6ff0685f5cc5..456d0465b676 100644
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -66,6 +66,7 @@ struct stack_op {
struct list_head list;
};
+struct objtool_file;
struct instruction;
void arch_initial_func_cfi_state(struct cfi_init_state *state);
@@ -76,6 +77,8 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
unsigned long *immediate,
struct list_head *ops_list);
+int arch_post_process_instructions(struct objtool_file *file);
+
bool arch_callee_saved_reg(unsigned char reg);
unsigned long arch_jump_destination(struct instruction *insn);
--
2.25.4
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