[RFC PATCH v2 14/20] objtool: arm64: Add unwind hint support

madvenka
2022-05-24T00:18:16Z

Implement the unwind hint macros for ARM64. Define the unwind hint types
as well.

Process the unwind hints section for dynamic FP validation for ARM64.

Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
---
arch/arm64/include/asm/unwind_hints.h | 104 ++++++++++++++++++++
include/linux/objtool.h | 6 ++
tools/arch/arm64/include/asm/unwind_hints.h | 104 ++++++++++++++++++++
tools/include/linux/objtool.h | 6 ++
tools/objtool/Build | 1 +
tools/objtool/arch/arm64/decode.c | 20 ++++
tools/objtool/arch/arm64/orc.c | 6 ++
tools/objtool/fpv.c | 4 +
tools/objtool/include/objtool/endianness.h | 1 +
tools/objtool/sync-check.sh | 1 +
tools/objtool/unwind_hints.c | 16 +--
11 files changed, 263 insertions(+), 6 deletions(-)
create mode 100644 arch/arm64/include/asm/unwind_hints.h
create mode 100644 tools/arch/arm64/include/asm/unwind_hints.h

diff --git a/arch/arm64/include/asm/unwind_hints.h b/arch/arm64/include/asm/unwind_hints.h
new file mode 100644
index 000000000000..fb1b924d85bc
--- /dev/null
+++ b/arch/arm64/include/asm/unwind_hints.h
@@ -0,0 +1,104 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _ASM_ARM64_UNWIND_HINTS_H
+#define _ASM_ARM64_UNWIND_HINTS_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+
+/*
+ * This struct is used by asm and inline asm code to manually annotate the
+ * CFI for an instruction. We have to use s16 instead of s8 for some of these
+ * fields as 8-bit fields are not relocated by some assemblers.
+ */
+struct unwind_hint {
+ u32 ip;
+ s16 sp_offset;
+ s16 sp_reg;
+ s16 type;
+ s16 end;
+};
+
+#endif
+
+#include <linux/objtool.h>
+
+#include "orc_types.h"
+
+#ifdef CONFIG_STACK_VALIDATION
+
+#ifndef __ASSEMBLY__
+
+#define UNWIND_HINT(sp_reg, sp_offset, type, end) \
+ "987: \n\t" \
+ ".pushsection .discard.unwind_hints\n\t" \
+ /* struct unwind_hint */ \
+ ".long 987b - .\n\t" \
+ ".short " __stringify(sp_offset) "\n\t" \
+ ".short " __stringify(sp_reg) "\n\t" \
+ ".short " __stringify(type) "\n\t" \
+ ".short " __stringify(end) "\n\t" \
+ ".popsection\n\t"
+
+#else /* __ASSEMBLY__ */
+
+/*
+ * There are points in ASM code where it is useful to unwind through even
+ * though the ASM code itself may be unreliable from an unwind perspective.
+ * E.g., interrupt and exception handlers.
+ *
+ * These macros provide hints to objtool to compute the CFI information at
+ * such instructions.
+ */
+.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
+.Lunwind_hint_pc_\@:
+ .pushsection .discard.unwind_hints
+ /* struct unwind_hint */
+ .long .Lunwind_hint_pc_\@ - .
+ .short \sp_offset
+ .short \sp_reg
+ .short \type
+ .short \end
+ .popsection
+.endm
+
+#endif /* __ASSEMBLY__ */
+
+#else /* !CONFIG_STACK_VALIDATION */
+
+#ifndef __ASSEMBLY__
+
+#define UNWIND_HINT(sp_reg, sp_offset, type, end) \
+ "\n\t"
+#else
+.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
+.endm
+#endif
+
+#endif /* CONFIG_STACK_VALIDATION */
+#ifdef __ASSEMBLY__
+
+.macro UNWIND_HINT_FTRACE, offset
+ .set sp_reg, ORC_REG_SP
+ .set sp_offset, \offset
+ .set type, UNWIND_HINT_TYPE_FTRACE
+ UNWIND_HINT sp_reg=sp_reg sp_offset=sp_offset type=type
+.endm
+
+.macro UNWIND_HINT_REGS, offset
+ .set sp_reg, ORC_REG_SP
+ .set sp_offset, \offset
+ .set type, UNWIND_HINT_TYPE_REGS
+ UNWIND_HINT sp_reg=sp_reg sp_offset=sp_offset type=type
+.endm
+
+.macro UNWIND_HINT_IRQ, offset
+ .set sp_reg, ORC_REG_SP
+ .set sp_offset, \offset
+ .set type, UNWIND_HINT_TYPE_IRQ_STACK
+ UNWIND_HINT sp_reg=sp_reg sp_offset=sp_offset type=type
+.endm
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_ARM64_UNWIND_HINTS_H */
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 00bb449777d0..c28e3cff3b83 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -15,11 +15,17 @@
*
* UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
* Useful for code which doesn't have an ELF function annotation.
+ *
+ * UNWIND_HINT_TYPE_FTRACE: Used to unwind through an ftrace callsite.
+ *
+ * UNWIND_HINT_TYPE_IRQ_STACK: Used to unwind through the IRQ stack.
*/
#define UNWIND_HINT_TYPE_CALL 0
#define UNWIND_HINT_TYPE_REGS 1
#define UNWIND_HINT_TYPE_REGS_PARTIAL 2
#define UNWIND_HINT_TYPE_FUNC 3
+#define UNWIND_HINT_TYPE_FTRACE 4
+#define UNWIND_HINT_TYPE_IRQ_STACK 5

#ifdef CONFIG_STACK_VALIDATION

diff --git a/tools/arch/arm64/include/asm/unwind_hints.h b/tools/arch/arm64/include/asm/unwind_hints.h
new file mode 100644
index 000000000000..fb1b924d85bc
--- /dev/null
+++ b/tools/arch/arm64/include/asm/unwind_hints.h
@@ -0,0 +1,104 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _ASM_ARM64_UNWIND_HINTS_H
+#define _ASM_ARM64_UNWIND_HINTS_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+
+/*
+ * This struct is used by asm and inline asm code to manually annotate the
+ * CFI for an instruction. We have to use s16 instead of s8 for some of these
+ * fields as 8-bit fields are not relocated by some assemblers.
+ */
+struct unwind_hint {
+ u32 ip;
+ s16 sp_offset;
+ s16 sp_reg;
+ s16 type;
+ s16 end;
+};
+
+#endif
+
+#include <linux/objtool.h>
+
+#include "orc_types.h"
+
+#ifdef CONFIG_STACK_VALIDATION
+
+#ifndef __ASSEMBLY__
+
+#define UNWIND_HINT(sp_reg, sp_offset, type, end) \
+ "987: \n\t" \
+ ".pushsection .discard.unwind_hints\n\t" \
+ /* struct unwind_hint */ \
+ ".long 987b - .\n\t" \
+ ".short " __stringify(sp_offset) "\n\t" \
+ ".short " __stringify(sp_reg) "\n\t" \
+ ".short " __stringify(type) "\n\t" \
+ ".short " __stringify(end) "\n\t" \
+ ".popsection\n\t"
+
+#else /* __ASSEMBLY__ */
+
+/*
+ * There are points in ASM code where it is useful to unwind through even
+ * though the ASM code itself may be unreliable from an unwind perspective.
+ * E.g., interrupt and exception handlers.
+ *
+ * These macros provide hints to objtool to compute the CFI information at
+ * such instructions.
+ */
+.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
+.Lunwind_hint_pc_\@:
+ .pushsection .discard.unwind_hints
+ /* struct unwind_hint */
+ .long .Lunwind_hint_pc_\@ - .
+ .short \sp_offset
+ .short \sp_reg
+ .short \type
+ .short \end
+ .popsection
+.endm
+
+#endif /* __ASSEMBLY__ */
+
+#else /* !CONFIG_STACK_VALIDATION */
+
+#ifndef __ASSEMBLY__
+
+#define UNWIND_HINT(sp_reg, sp_offset, type, end) \
+ "\n\t"
+#else
+.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
+.endm
+#endif
+
+#endif /* CONFIG_STACK_VALIDATION */
+#ifdef __ASSEMBLY__
+
+.macro UNWIND_HINT_FTRACE, offset
+ .set sp_reg, ORC_REG_SP
+ .set sp_offset, \offset
+ .set type, UNWIND_HINT_TYPE_FTRACE
+ UNWIND_HINT sp_reg=sp_reg sp_offset=sp_offset type=type
+.endm
+
+.macro UNWIND_HINT_REGS, offset
+ .set sp_reg, ORC_REG_SP
+ .set sp_offset, \offset
+ .set type, UNWIND_HINT_TYPE_REGS
+ UNWIND_HINT sp_reg=sp_reg sp_offset=sp_offset type=type
+.endm
+
+.macro UNWIND_HINT_IRQ, offset
+ .set sp_reg, ORC_REG_SP
+ .set sp_offset, \offset
+ .set type, UNWIND_HINT_TYPE_IRQ_STACK
+ UNWIND_HINT sp_reg=sp_reg sp_offset=sp_offset type=type
+.endm
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_ARM64_UNWIND_HINTS_H */
diff --git a/tools/include/linux/objtool.h b/tools/include/linux/objtool.h
index 00bb449777d0..c28e3cff3b83 100644
--- a/tools/include/linux/objtool.h
+++ b/tools/include/linux/objtool.h
@@ -15,11 +15,17 @@
*
* UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
* Useful for code which doesn't have an ELF function annotation.
+ *
+ * UNWIND_HINT_TYPE_FTRACE: Used to unwind through an ftrace callsite.
+ *
+ * UNWIND_HINT_TYPE_IRQ_STACK: Used to unwind through the IRQ stack.
*/
#define UNWIND_HINT_TYPE_CALL 0
#define UNWIND_HINT_TYPE_REGS 1
#define UNWIND_HINT_TYPE_REGS_PARTIAL 2
#define UNWIND_HINT_TYPE_FUNC 3
+#define UNWIND_HINT_TYPE_FTRACE 4
+#define UNWIND_HINT_TYPE_IRQ_STACK 5

#ifdef CONFIG_STACK_VALIDATION

diff --git a/tools/objtool/Build b/tools/objtool/Build
index d40ee95039cf..4a57d7c7d31e 100644
--- a/tools/objtool/Build
+++ b/tools/objtool/Build
@@ -19,6 +19,7 @@ objtool-$(SUBCMD_FPV) += fpv.o
objtool-$(SUBCMD_FPV) += cfi.o
objtool-$(SUBCMD_FPV) += insn.o
objtool-$(SUBCMD_FPV) += decode.o
+objtool-$(SUBCMD_FPV) += unwind_hints.o
objtool-$(SUBCMD_FPV) += orc_gen.o
objtool-$(SUBCMD_FPV) += orc_dump.o

diff --git a/tools/objtool/arch/arm64/decode.c b/tools/objtool/arch/arm64/decode.c
index 93ef7c0811f1..d3c650ca044e 100644
--- a/tools/objtool/arch/arm64/decode.c
+++ b/tools/objtool/arch/arm64/decode.c
@@ -15,6 +15,7 @@
#include <objtool/elf.h>
#include <objtool/warn.h>
#include <arch/cfi_regs.h>
+#include <asm/orc_types.h>

/* ARM64 instructions are all 4 bytes wide. */
#define INSN_SIZE 4
@@ -60,6 +61,25 @@ unsigned long arch_jump_destination(struct instruction *insn)
return insn->offset + insn->immediate;
}

+int arch_decode_hint_reg(u8 sp_reg, int *base)
+{
+ switch (sp_reg) {
+ case ORC_REG_UNDEFINED:
+ *base = CFI_UNDEFINED;
+ break;
+ case ORC_REG_SP:
+ *base = CFI_SP;
+ break;
+ case ORC_REG_FP:
+ *base = CFI_FP;
+ break;
+ default:
+ return -1;
+ }
+
+ return 0;
+}
+
/* --------------------- miscellaneous functions --------------------------- */

static void reg_check(unsigned int sp_check, unsigned int fp_check,
diff --git a/tools/objtool/arch/arm64/orc.c b/tools/objtool/arch/arm64/orc.c
index cef14114e1ec..fecbed12b3f1 100644
--- a/tools/objtool/arch/arm64/orc.c
+++ b/tools/objtool/arch/arm64/orc.c
@@ -57,6 +57,12 @@ const char *orc_type_name(unsigned int type)
switch (type) {
case UNWIND_HINT_TYPE_CALL:
return "call";
+ case UNWIND_HINT_TYPE_REGS:
+ return "regs";
+ case UNWIND_HINT_TYPE_FTRACE:
+ return "ftrace";
+ case UNWIND_HINT_TYPE_IRQ_STACK:
+ return "irqstack";
default:
return "?";
}
diff --git a/tools/objtool/fpv.c b/tools/objtool/fpv.c
index 52f613ae998f..346e0de787f3 100644
--- a/tools/objtool/fpv.c
+++ b/tools/objtool/fpv.c
@@ -257,6 +257,10 @@ int fpv_decode(struct objtool_file *file)

add_jump_destinations(file);

+ ret = read_unwind_hints(file);
+ if (ret)
+ return ret;
+
if (!list_empty(&file->insn_list)) {
fill = false;
walk_sections(file);
diff --git a/tools/objtool/include/objtool/endianness.h b/tools/objtool/include/objtool/endianness.h
index 10241341eff3..9a53ab421a19 100644
--- a/tools/objtool/include/objtool/endianness.h
+++ b/tools/objtool/include/objtool/endianness.h
@@ -29,6 +29,7 @@
case 8: __ret = __NEED_BSWAP ? bswap_64(val) : (val); break; \
case 4: __ret = __NEED_BSWAP ? bswap_32(val) : (val); break; \
case 2: __ret = __NEED_BSWAP ? bswap_16(val) : (val); break; \
+ case 1: __ret = (val); break; \
default: \
BUILD_BUG(); break; \
} \
diff --git a/tools/objtool/sync-check.sh b/tools/objtool/sync-check.sh
index 0d0656f6ce4a..3742d1e2585c 100755
--- a/tools/objtool/sync-check.sh
+++ b/tools/objtool/sync-check.sh
@@ -31,6 +31,7 @@ fi

if [ "$SRCARCH" = "arm64" ]; then
FILES="$FILES
+arch/arm64/include/asm/unwind_hints.h
arch/arm64/include/asm/orc_types.h
include/linux/orc_entry.h
"
diff --git a/tools/objtool/unwind_hints.c b/tools/objtool/unwind_hints.c
index d4e41c67403b..91ceea3f7fd7 100644
--- a/tools/objtool/unwind_hints.c
+++ b/tools/objtool/unwind_hints.c
@@ -16,6 +16,7 @@ int read_unwind_hints(struct objtool_file *file)
struct unwind_hint *hint;
struct instruction *insn;
struct reloc *reloc;
+ u8 sp_reg, type;
int i;

sec = find_section_by_name(file->elf, ".discard.unwind_hints");
@@ -38,6 +39,9 @@ int read_unwind_hints(struct objtool_file *file)
for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
hint = (struct unwind_hint *)sec->data->d_buf + i;

+ sp_reg = bswap_if_needed(hint->sp_reg);
+ type = bswap_if_needed(hint->type);
+
reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
if (!reloc) {
WARN("can't find reloc for unwind_hints[%d]", i);
@@ -52,7 +56,7 @@ int read_unwind_hints(struct objtool_file *file)

insn->hint = true;

- if (ibt && hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
+ if (ibt && type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);

if (sym && sym->bind == STB_GLOBAL &&
@@ -62,7 +66,7 @@ int read_unwind_hints(struct objtool_file *file)
}
}

- if (hint->type == UNWIND_HINT_TYPE_FUNC) {
+ if (type == UNWIND_HINT_TYPE_FUNC) {
insn->cfi = &func_cfi;
continue;
}
@@ -70,15 +74,15 @@ int read_unwind_hints(struct objtool_file *file)
if (insn->cfi)
cfi = *(insn->cfi);

- if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
+ if (arch_decode_hint_reg(sp_reg, &cfi.cfa.base)) {
WARN_FUNC("unsupported unwind_hint sp base reg %d",
- insn->sec, insn->offset, hint->sp_reg);
+ insn->sec, insn->offset, sp_reg);
return -1;
}

cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
- cfi.type = hint->type;
- cfi.end = hint->end;
+ cfi.type = type;
+ cfi.end = bswap_if_needed(hint->end);

insn->cfi = cfi_hash_find_or_add(&cfi);
}
--
2.25.1