[PATCH 5.10 046/148] objtool: Handle __sanitize_cov*() tail calls

Greg Kroah-Hartman
2022-07-23T10:00:46Z

From: Peter Zijlstra <peterz@infradead.org>

commit f56dae88a81fded66adf2bea9922d1d98d1da14f upstream.

Turns out the compilers also generate tail calls to __sanitize_cov*(),
make sure to also patch those out in noinstr code.

Fixes: 0f1441b44e82 ("objtool: Fix noinstr vs KCOV")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20210624095147.818783799@infradead.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
[bwh: Backported to 5.10:
- objtool doesn't have any mcount handling
- Write the NOPs as hex literals since we can't use <asm/nops.h>]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/objtool/arch.h | 1
tools/objtool/arch/x86/decode.c | 20 ++++++
tools/objtool/check.c | 123 +++++++++++++++++++++-------------------
3 files changed, 86 insertions(+), 58 deletions(-)

--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -83,6 +83,7 @@ unsigned long arch_jump_destination(stru
unsigned long arch_dest_reloc_offset(int addend);

const char *arch_nop_insn(int len);
+const char *arch_ret_insn(int len);

int arch_decode_hint_reg(u8 sp_reg, int *base);

--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -586,6 +586,26 @@ const char *arch_nop_insn(int len)
return nops[len-1];
}

+#define BYTE_RET 0xC3
+
+const char *arch_ret_insn(int len)
+{
+ static const char ret[5][5] = {
+ { BYTE_RET },
+ { BYTE_RET, 0x90 },
+ { BYTE_RET, 0x66, 0x90 },
+ { BYTE_RET, 0x0f, 0x1f, 0x00 },
+ { BYTE_RET, 0x0f, 0x1f, 0x40, 0x00 },
+ };
+
+ if (len < 1 || len > 5) {
+ WARN("invalid RET size: %d\n", len);
+ return NULL;
+ }
+
+ return ret[len-1];
+}
+
/* asm/alternative.h ? */

#define ALTINSTR_FLAG_INV (1 << 15)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -860,6 +860,60 @@ static struct reloc *insn_reloc(struct o
return insn->reloc;
}

+static void remove_insn_ops(struct instruction *insn)
+{
+ struct stack_op *op, *tmp;
+
+ list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
+ list_del(&op->list);
+ free(op);
+ }
+}
+
+static void add_call_dest(struct objtool_file *file, struct instruction *insn,
+ struct symbol *dest, bool sibling)
+{
+ struct reloc *reloc = insn_reloc(file, insn);
+
+ insn->call_dest = dest;
+ if (!dest)
+ return;
+
+ if (insn->call_dest->static_call_tramp) {
+ list_add_tail(&insn->call_node,
+ &file->static_call_list);
+ }
+
+ /*
+ * Many compilers cannot disable KCOV with a function attribute
+ * so they need a little help, NOP out any KCOV calls from noinstr
+ * text.
+ */
+ if (insn->sec->noinstr &&
+ !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {
+ if (reloc) {
+ reloc->type = R_NONE;
+ elf_write_reloc(file->elf, reloc);
+ }
+
+ elf_write_insn(file->elf, insn->sec,
+ insn->offset, insn->len,
+ sibling ? arch_ret_insn(insn->len)
+ : arch_nop_insn(insn->len));
+
+ insn->type = sibling ? INSN_RETURN : INSN_NOP;
+ }
+
+ /*
+ * Whatever stack impact regular CALLs have, should be undone
+ * by the RETURN of the called function.
+ *
+ * Annotated intra-function calls retain the stack_ops but
+ * are converted to JUMP, see read_intra_function_calls().
+ */
+ remove_insn_ops(insn);
+}
+
/*
* Find the destination instructions for all jumps.
*/
@@ -898,11 +952,7 @@ static int add_jump_destinations(struct
continue;
} else if (insn->func) {
/* internal or external sibling call (with reloc) */
- insn->call_dest = reloc->sym;
- if (insn->call_dest->static_call_tramp) {
- list_add_tail(&insn->call_node,
- &file->static_call_list);
- }
+ add_call_dest(file, insn, reloc->sym, true);
continue;
} else if (reloc->sym->sec->idx) {
dest_sec = reloc->sym->sec;
@@ -958,13 +1008,8 @@ static int add_jump_destinations(struct

} else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
insn->jump_dest->offset == insn->jump_dest->func->offset) {
-
/* internal sibling call (without reloc) */
- insn->call_dest = insn->jump_dest->func;
- if (insn->call_dest->static_call_tramp) {
- list_add_tail(&insn->call_node,
- &file->static_call_list);
- }
+ add_call_dest(file, insn, insn->jump_dest->func, true);
}
}
}
@@ -972,16 +1017,6 @@ static int add_jump_destinations(struct
return 0;
}

-static void remove_insn_ops(struct instruction *insn)
-{
- struct stack_op *op, *tmp;
-
- list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
- list_del(&op->list);
- free(op);
- }
-}
-
static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
{
struct symbol *call_dest;
@@ -1000,6 +1035,7 @@ static int add_call_destinations(struct
{
struct instruction *insn;
unsigned long dest_off;
+ struct symbol *dest;
struct reloc *reloc;

for_each_insn(file, insn) {
@@ -1009,7 +1045,9 @@ static int add_call_destinations(struct
reloc = insn_reloc(file, insn);
if (!reloc) {
dest_off = arch_jump_destination(insn);
- insn->call_dest = find_call_destination(insn->sec, dest_off);
+ dest = find_call_destination(insn->sec, dest_off);
+
+ add_call_dest(file, insn, dest, false);

if (insn->ignore)
continue;
@@ -1027,9 +1065,8 @@ static int add_call_destinations(struct

} else if (reloc->sym->type == STT_SECTION) {
dest_off = arch_dest_reloc_offset(reloc->addend);
- insn->call_dest = find_call_destination(reloc->sym->sec,
- dest_off);
- if (!insn->call_dest) {
+ dest = find_call_destination(reloc->sym->sec, dest_off);
+ if (!dest) {
WARN_FUNC("can't find call dest symbol at %s+0x%lx",
insn->sec, insn->offset,
reloc->sym->sec->name,
@@ -1037,6 +1074,8 @@ static int add_call_destinations(struct
return -1;
}

+ add_call_dest(file, insn, dest, false);
+
} else if (arch_is_retpoline(reloc->sym)) {
/*
* Retpoline calls are really dynamic calls in
@@ -1052,39 +1091,7 @@ static int add_call_destinations(struct
continue;

} else
- insn->call_dest = reloc->sym;
-
- if (insn->call_dest && insn->call_dest->static_call_tramp) {
- list_add_tail(&insn->call_node,
- &file->static_call_list);
- }
-
- /*
- * Many compilers cannot disable KCOV with a function attribute
- * so they need a little help, NOP out any KCOV calls from noinstr
- * text.
- */
- if (insn->sec->noinstr &&
- !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {
- if (reloc) {
- reloc->type = R_NONE;
- elf_write_reloc(file->elf, reloc);
- }
-
- elf_write_insn(file->elf, insn->sec,
- insn->offset, insn->len,
- arch_nop_insn(insn->len));
- insn->type = INSN_NOP;
- }
-
- /*
- * Whatever stack impact regular CALLs have, should be undone
- * by the RETURN of the called function.
- *
- * Annotated intra-function calls retain the stack_ops but
- * are converted to JUMP, see read_intra_function_calls().
- */
- remove_insn_ops(insn);
+ add_call_dest(file, insn, reloc->sym, false);
}

return 0;