ANDROID: staging: add debug-kinfo driver

Backup kernel information for bootloader usage.

  Specifics:
   - The kallsyms symbols for unwind_backtrace
   - Page directory pointer
   - UTS_RELEASE
   - BUILD_INFO(ro.build.fingerprint)

Bug: 170851792
Bug: 169101608
Signed-off-by: Jone Chou <jonechou@google.com>
Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: Ida76bf90315652b8debc081a010bc5720a5a186e

drivers/staging/android/Kconfig

@@ -14,6 +14,17 @@ config ASHMEM
 	  It is, in theory, a good memory allocator for low-memory devices,
 	  because it can discard shared memory units when under memory pressure.
 
+config DEBUG_KINFO
+	bool "Debug Kernel Information Support"
+	depends on KALLSYMS
+	help
+	  This supports kernel information backup for bootloader usage.
+	  Specifics:
+	   - The kallsyms symbols for unwind_backtrace
+	   - Page directory pointer
+	   - UTS_RELEASE
+	   - BUILD_INFO(ro.build.fingerprint)
+
 endif # if ANDROID
 
 endmenu

drivers/staging/android/Makefile

@@ -2,3 +2,4 @@
 ccflags-y += -I$(src)			# needed for trace events
 
 obj-$(CONFIG_ASHMEM)			+= ashmem.o
+obj-$(CONFIG_DEBUG_KINFO)	+= debug_kinfo.o

drivers/staging/android/debug_kinfo.c

@@ -0,0 +1,181 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * debug_kinfo.c - backup kernel information for bootloader usage
+ *
+ * Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
+ * Copyright 2021 Google LLC
+ */
+
+#include <linux/platform_device.h>
+#include <linux/kallsyms.h>
+#include <linux/vmalloc.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_reserved_mem.h>
+#include "debug_kinfo.h"
+
+/*
+ * These will be re-linked against their real values
+ * during the second link stage.
+ */
+extern const unsigned long kallsyms_addresses[] __weak;
+extern const int kallsyms_offsets[] __weak;
+extern const u8 kallsyms_names[] __weak;
+
+/*
+ * Tell the compiler that the count isn't in the small data section if the arch
+ * has one (eg: FRV).
+ */
+extern const unsigned int kallsyms_num_syms __weak
+__section(".rodata");
+
+extern const unsigned long kallsyms_relative_base __weak
+__section(".rodata");
+
+extern const u8 kallsyms_token_table[] __weak;
+extern const u16 kallsyms_token_index[] __weak;
+
+extern const unsigned int kallsyms_markers[] __weak;
+
+static void *all_info_addr;
+static u32 all_info_size;
+
+static void update_kernel_all_info(struct kernel_all_info *all_info)
+{
+	int index;
+	struct kernel_info *info;
+	u32 *checksum_info;
+
+	all_info->magic_number = DEBUG_KINFO_MAGIC;
+	all_info->combined_checksum = 0;
+
+	info = &(all_info->info);
+	checksum_info = (u32 *)info;
+	for (index = 0; index < sizeof(*info) / sizeof(u32); index++)
+		all_info->combined_checksum ^= checksum_info[index];
+}
+
+static int build_info_set(const char *str, const struct kernel_param *kp)
+{
+	struct kernel_all_info *all_info;
+	size_t build_info_size;
+	int ret = 0;
+
+	if (all_info_addr == 0 || all_info_size == 0) {
+		ret = -EPERM;
+		goto Exit;
+	}
+
+	all_info = (struct kernel_all_info *)all_info_addr;
+	build_info_size = sizeof(all_info->info.build_info);
+
+	memcpy(&all_info->info.build_info, str, min(build_info_size - 1, strlen(str)));
+	update_kernel_all_info(all_info);
+
+	if (strlen(str) > build_info_size) {
+		pr_warn("%s: Build info buffer (len: %zd) can't hold entire string '%s'\n",
+				__func__, build_info_size, str);
+		ret = -ENOMEM;
+	}
+
+Exit:
+	vunmap(all_info_addr);
+	return ret;
+}
+
+static const struct kernel_param_ops build_info_op = {
+	.set = build_info_set,
+};
+
+module_param_cb(build_info, &build_info_op, NULL, 0200);
+MODULE_PARM_DESC(build_info, "Write build info to field 'build_info' of debug kinfo.");
+
+static int debug_kinfo_probe(struct platform_device *pdev)
+{
+	struct device_node *mem_region;
+	struct reserved_mem *rmem;
+	struct kernel_all_info *all_info;
+	struct kernel_info *info;
+
+	mem_region = of_parse_phandle(pdev->dev.of_node, "memory-region", 0);
+	if (!mem_region) {
+		dev_warn(&pdev->dev, "no such memory-region\n");
+		return -ENODEV;
+	}
+
+	rmem = of_reserved_mem_lookup(mem_region);
+	if (!rmem) {
+		dev_warn(&pdev->dev, "no such reserved mem of node name %s\n",
+				pdev->dev.of_node->name);
+		return -ENODEV;
+	}
+
+	/* Deferred until dss.ko(dpm.o) and debug-snapshot-debug-kinfo.ko are ready */
+	if (!rmem->priv) {
+		return -EPROBE_DEFER;
+	}
+
+	if (!rmem->base || !rmem->size) {
+		dev_warn(&pdev->dev, "unexpected reserved memory\n");
+		return -EINVAL;
+	}
+
+	if (rmem->size < sizeof(struct kernel_all_info)) {
+		dev_warn(&pdev->dev, "unexpected reserved memory size\n");
+		return -EINVAL;
+	}
+
+	all_info_addr = rmem->priv;
+	all_info_size = rmem->size;
+
+	memset(all_info_addr, 0, all_info_size);
+	all_info = (struct kernel_all_info *)all_info_addr;
+	info = &(all_info->info);
+	info->enabled_all = IS_ENABLED(CONFIG_KALLSYMS_ALL);
+	info->enabled_base_relative = IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE);
+	info->enabled_absolute_percpu = IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU);
+	info->enabled_cfi_clang = IS_ENABLED(CONFIG_CFI_CLANG);
+	info->num_syms = kallsyms_num_syms;
+	info->name_len = KSYM_NAME_LEN;
+	info->bit_per_long = BITS_PER_LONG;
+	info->module_name_len = MODULE_NAME_LEN;
+	info->symbol_len = KSYM_SYMBOL_LEN;
+	info->_addresses_pa = (u64)virt_to_phys((volatile void *)kallsyms_addresses);
+	info->_relative_pa = (u64)virt_to_phys((volatile void *)kallsyms_relative_base);
+	info->_stext_pa = (u64)virt_to_phys(_stext);
+	info->_etext_pa = (u64)virt_to_phys(_etext);
+	info->_sinittext_pa = (u64)virt_to_phys(_sinittext);
+	info->_einittext_pa = (u64)virt_to_phys(_einittext);
+	info->_end_pa = (u64)virt_to_phys(_end);
+	info->_offsets_pa = (u64)virt_to_phys((volatile void *)kallsyms_offsets);
+	info->_names_pa = (u64)virt_to_phys((volatile void *)kallsyms_names);
+	info->_token_table_pa = (u64)virt_to_phys((volatile void *)kallsyms_token_table);
+	info->_token_index_pa = (u64)virt_to_phys((volatile void *)kallsyms_token_index);
+	info->_markers_pa = (u64)virt_to_phys((volatile void *)kallsyms_markers);
+	info->thread_size = THREAD_SIZE;
+	info->swapper_pg_dir_pa = (u64)virt_to_phys(swapper_pg_dir);
+	strlcpy(info->last_uts_release, init_utsname()->release, sizeof(info->last_uts_release));
+
+	update_kernel_all_info(all_info);
+
+	return 0;
+}
+
+static const struct of_device_id debug_kinfo_of_match[] = {
+	{ .compatible	= "google,debug-kinfo" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, debug_kinfo_of_match);
+
+static struct platform_driver debug_kinfo_driver = {
+	.probe = debug_kinfo_probe,
+	.driver = {
+		.name = "debug-kinfo",
+		.of_match_table = of_match_ptr(debug_kinfo_of_match),
+	},
+};
+module_platform_driver(debug_kinfo_driver);
+
+MODULE_AUTHOR("Jone Chou <jonechou@google.com>");
+MODULE_DESCRIPTION("Debug Kinfo Driver");
+MODULE_LICENSE("GPL v2");

drivers/staging/android/debug_kinfo.h

@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * debug_kinfo.h - backup kernel information for bootloader usage
+ *
+ * Copyright 2021 Google LLC
+ */
+
+#ifndef DEBUG_KINFO_H
+#define DEBUG_KINFO_H
+
+#include <linux/utsname.h>
+
+#define BUILD_INFO_LEN		256
+#define DEBUG_KINFO_MAGIC	0xCCEEDDFF
+
+/*
+ * Header structure must be byte-packed, since the table is provided to
+ * bootloader.
+ */
+struct kernel_info {
+	/* For kallsyms */
+	__u8 enabled_all;
+	__u8 enabled_base_relative;
+	__u8 enabled_absolute_percpu;
+	__u8 enabled_cfi_clang;
+	__u32 num_syms;
+	__u16 name_len;
+	__u16 bit_per_long;
+	__u16 module_name_len;
+	__u16 symbol_len;
+	__u64 _addresses_pa;
+	__u64 _relative_pa;
+	__u64 _stext_pa;
+	__u64 _etext_pa;
+	__u64 _sinittext_pa;
+	__u64 _einittext_pa;
+	__u64 _end_pa;
+	__u64 _offsets_pa;
+	__u64 _names_pa;
+	__u64 _token_table_pa;
+	__u64 _token_index_pa;
+	__u64 _markers_pa;
+
+	/* For frame pointer */
+	__u32 thread_size;
+
+	/* For virt_to_phys */
+	__u64 swapper_pg_dir_pa;
+
+	/* For linux banner */
+	__u8 last_uts_release[__NEW_UTS_LEN];
+
+	/* Info of running build */
+	__u8 build_info[BUILD_INFO_LEN];
+} __packed;
+
+struct kernel_all_info {
+	__u32 magic_number;
+	__u32 combined_checksum;
+	struct kernel_info info;
+} __packed;
+
+#endif // DEBUG_KINFO_H