[PATCH v7 02/11] arm64/sframe: Read vmlinux .sframe header

[Dylan Hatch <dylanbhatch@google.com>]

From: Josh Poimboeuf <jpoimboe@kernel.org>

In preparation for unwinding kernel space stacks with sframe, add basic
sframe compile infrastructure and support for reading the .sframe
section header. Add init_sframe_table() to read the vmlinux .sframe
header at boot.

[ Jens Remus: Add support for SFrame V3.  Add support for PC-relative
FDE function start offset.  Cleanup includes and indentation. ]

[ Dylan Hatch: Repurpose patch for arm64 vmlinux. ]

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Indu Bhagat <ibhagatgnu@gmail.com>
Co-developed-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
Co-developed-by: Dylan Hatch <dylanbhatch@google.com>
Signed-off-by: Dylan Hatch <dylanbhatch@google.com>

---

This patch is adapted from commit c7db518447c6 ("unwind_user/sframe: Add
support for reading .sframe headers"), and includes the header/init
portions of v6 patch "sframe: Allow kernelspace sframe sections" in this
series.

Changes include:
 - kernel/unwind/sframe* is repurposed exclusively for kernel .sframe
   sections, under CONFIG_UNWIND_SFRAME_LOOKUP.
 - Replaced copy_from_user() with direct memory pointer access when
   reading the SFrame header.
 - (sashiko) Moved header size check to take place before any header
   fields are checked, to ensure safe memory access. Also dropped the
   (header + auxiliary) size helper, since non-zero auxiliary size is
   not currently supported.
 - Dropped unused userspace section tracking functions
   sframe_add_section(), sframe_remove_section(), free_section()
 - Dropped text_start/text_end section fields, since kernel/module
   section boundaries can be examined directly without saving.
 - Squashed in changes adding vmlinux-tracking kernel_sfsec and
   init_sframe_table(), to read vmlinux .sframe header at boot time.
---
 MAINTAINERS               |  1 +
 arch/arm64/kernel/setup.c |  2 +
 include/linux/sframe.h    | 32 ++++++++++++++++
 kernel/unwind/Makefile    |  3 +-
 kernel/unwind/sframe.c    | 80 +++++++++++++++++++++++++++++++++++++++
 kernel/unwind/sframe.h    | 78 ++++++++++++++++++++++++++++++++++++++
 6 files changed, 195 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/sframe.h
 create mode 100644 kernel/unwind/sframe.c
 create mode 100644 kernel/unwind/sframe.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 6c1c95979e437..eaa691abd7a2e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -28519,6 +28519,7 @@ M:	Josh Poimboeuf <jpoimboe@kernel.org>
 M:	Steven Rostedt <rostedt@goodmis.org>
 S:	Maintained
 F:	arch/*/include/asm/unwind_sframe.h
+F:	include/linux/sframe.h
 F:	include/linux/unwind*.h
 F:	kernel/unwind/
 
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 29c6100f0c50b..84983df605ed5 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -32,6 +32,7 @@
 #include <linux/sched/task.h>
 #include <linux/scs.h>
 #include <linux/mm.h>
+#include <linux/sframe.h>
 
 #include <asm/acpi.h>
 #include <asm/fixmap.h>
@@ -373,6 +374,7 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
 			"This indicates a broken bootloader or old kernel\n",
 			boot_args[1], boot_args[2], boot_args[3]);
 	}
+	init_sframe_table();
 }
 
 static inline bool cpu_can_disable(unsigned int cpu)
diff --git a/include/linux/sframe.h b/include/linux/sframe.h
new file mode 100644
index 0000000000000..54e5cb76cb92c
--- /dev/null
+++ b/include/linux/sframe.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_SFRAME_H
+#define _LINUX_SFRAME_H
+
+#include <linux/init.h>
+
+#ifdef CONFIG_UNWIND_SFRAME_LOOKUP
+
+struct sframe_section {
+	unsigned long	sframe_start;
+	unsigned long	sframe_end;
+
+	unsigned long	fdes_start;
+	unsigned long	fres_start;
+	unsigned long	fres_end;
+	unsigned int	num_fdes;
+
+	signed char	ra_off;
+	signed char	fp_off;
+};
+
+extern struct sframe_section kernel_sfsec __ro_after_init;
+
+void __init init_sframe_table(void);
+
+#else /* !CONFIG_UNWIND_SFRAME_LOOKUP */
+
+static inline void __init init_sframe_table(void) {}
+
+#endif /* CONFIG_UNWIND_SFRAME_LOOKUP */
+
+#endif /* _LINUX_SFRAME_H */
diff --git a/kernel/unwind/Makefile b/kernel/unwind/Makefile
index eae37bea54fdb..c5f9f8124564e 100644
--- a/kernel/unwind/Makefile
+++ b/kernel/unwind/Makefile
@@ -1 +1,2 @@
- obj-$(CONFIG_UNWIND_USER)	+= user.o deferred.o
+ obj-$(CONFIG_UNWIND_USER)		+= user.o deferred.o
+ obj-$(CONFIG_UNWIND_SFRAME_LOOKUP)	+= sframe.o
diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
new file mode 100644
index 0000000000000..5f49f05e6226d
--- /dev/null
+++ b/kernel/unwind/sframe.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Kernel sframe access functions
+ */
+
+#define pr_fmt(fmt)	"sframe: " fmt
+
+#include <linux/mm.h>
+#include <linux/string_helpers.h>
+#include <linux/sframe.h>
+#include <asm/sections.h>
+
+#include "sframe.h"
+
+static bool sframe_init __ro_after_init;
+struct sframe_section kernel_sfsec __ro_after_init;
+
+static int sframe_read_header(struct sframe_section *sec)
+{
+	unsigned long header_end, fdes_start, fdes_end, fres_start, fres_end;
+	struct sframe_header *shdr;
+	unsigned int num_fdes;
+
+	header_end = sec->sframe_start + sizeof(struct sframe_header);
+	if (header_end >= sec->sframe_end) {
+		pr_debug("header struct doesn't fit in section\n");
+		return -EINVAL;
+	}
+
+	shdr = (struct sframe_header *)sec->sframe_start;
+
+	if (shdr->preamble.magic != SFRAME_MAGIC ||
+	    shdr->preamble.version != SFRAME_VERSION_3 ||
+	    !(shdr->preamble.flags & SFRAME_F_FDE_SORTED) ||
+	    !(shdr->preamble.flags & SFRAME_F_FDE_FUNC_START_PCREL) ||
+	    shdr->auxhdr_len) {
+		pr_debug("bad/unsupported sframe header\n");
+		return -EINVAL;
+	}
+
+	if (!shdr->num_fdes || !shdr->num_fres) {
+		pr_debug("no fde/fre entries\n");
+		return -EINVAL;
+	}
+
+	num_fdes   = shdr->num_fdes;
+	fdes_start = header_end + shdr->fdes_off;
+	fdes_end   = fdes_start + (num_fdes * sizeof(struct sframe_fde_v3));
+
+	fres_start = header_end + shdr->fres_off;
+	fres_end   = fres_start + shdr->fre_len;
+
+	if (fres_start < fdes_end || fres_end > sec->sframe_end) {
+		pr_debug("inconsistent fde/fre offsets\n");
+		return -EINVAL;
+	}
+
+	sec->num_fdes		= num_fdes;
+	sec->fdes_start		= fdes_start;
+	sec->fres_start		= fres_start;
+	sec->fres_end		= fres_end;
+
+	sec->ra_off		= shdr->cfa_fixed_ra_offset;
+	sec->fp_off		= shdr->cfa_fixed_fp_offset;
+
+	return 0;
+}
+
+void __init init_sframe_table(void)
+{
+	kernel_sfsec.sframe_start	= (unsigned long)__start_sframe;
+	kernel_sfsec.sframe_end		= (unsigned long)__end_sframe;
+
+	if (sframe_read_header(&kernel_sfsec)) {
+		pr_warn("invalid vmlinux SFrame header\n");
+		return;
+	}
+
+	sframe_init = true;
+}
diff --git a/kernel/unwind/sframe.h b/kernel/unwind/sframe.h
new file mode 100644
index 0000000000000..bf895107c2070
--- /dev/null
+++ b/kernel/unwind/sframe.h
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * From https://www.sourceware.org/binutils/docs/sframe-spec.html
+ */
+#ifndef _SFRAME_H
+#define _SFRAME_H
+
+#include <linux/types.h>
+
+#define SFRAME_VERSION_1			1
+#define SFRAME_VERSION_2			2
+#define SFRAME_VERSION_3			3
+#define SFRAME_MAGIC				0xdee2
+
+#define SFRAME_F_FDE_SORTED			0x1
+#define SFRAME_F_FRAME_POINTER			0x2
+#define SFRAME_F_FDE_FUNC_START_PCREL		0x4
+
+#define SFRAME_ABI_AARCH64_ENDIAN_BIG		1
+#define SFRAME_ABI_AARCH64_ENDIAN_LITTLE	2
+#define SFRAME_ABI_AMD64_ENDIAN_LITTLE		3
+
+struct sframe_preamble {
+	u16	magic;
+	u8	version;
+	u8	flags;
+} __packed;
+
+struct sframe_header {
+	struct sframe_preamble preamble;
+	u8	abi_arch;
+	s8	cfa_fixed_fp_offset;
+	s8	cfa_fixed_ra_offset;
+	u8	auxhdr_len;
+	u32	num_fdes;
+	u32	num_fres;
+	u32	fre_len;
+	u32	fdes_off;
+	u32	fres_off;
+} __packed;
+
+struct sframe_fde_v3 {
+	s64	func_start_off;
+	u32	func_size;
+	u32	fres_off;
+} __packed;
+
+struct sframe_fda_v3 {
+	u16	fres_num;
+	u8	info;
+	u8	info2;
+	u8	rep_size;
+} __packed;
+
+#define SFRAME_FDE_PCTYPE_INC			0
+#define SFRAME_FDE_PCTYPE_MASK			1
+
+#define SFRAME_AARCH64_PAUTH_KEY_A		0
+#define SFRAME_AARCH64_PAUTH_KEY_B		1
+
+#define SFRAME_V3_FDE_FRE_TYPE(info)		((info) & 0xf)
+#define SFRAME_V3_FDE_PCTYPE(info)		(((info) >> 4) & 0x1)
+#define SFRAME_V3_AARCH64_FDE_PAUTH_KEY(info)	(((info) >> 5) & 0x1)
+
+#define SFRAME_FDE_TYPE_DEFAULT			0
+
+#define SFRAME_V3_FDE_TYPE_MASK			0x1f
+#define SFRAME_V3_FDE_TYPE(info2)		((info2) & SFRAME_V3_FDE_TYPE_MASK)
+
+#define SFRAME_BASE_REG_FP			0
+#define SFRAME_BASE_REG_SP			1
+
+#define SFRAME_V3_FRE_CFA_BASE_REG_ID(info)		((info) & 0x1)
+#define SFRAME_V3_FRE_DATAWORD_COUNT(info)		(((info) >> 1) & 0xf)
+#define SFRAME_V3_FRE_DATAWORD_SIZE(info)		(((info) >> 5) & 0x3)
+#define SFRAME_V3_AARCH64_FRE_MANGLED_RA_P(info)	(((info) >> 7) & 0x1)
+
+#endif /* _SFRAME_H */
-- 
2.55.0.1082.g2b9226bbc0-goog