[PATCH v3 4/8] sframe: Provide PC lookup for vmlinux .sframe section.

[Dylan Hatch]

With SFRAME_UNWINDER, read in the .sframe section at boot. This provides
unwind data as an alternative/supplement to frame pointer-based
unwinding.

Signed-off-by: Dylan Hatch <dylanbhatch at google.com>
---
 arch/arm64/kernel/setup.c |  2 ++
 include/linux/sframe.h    | 14 ++++++++++++++
 kernel/unwind/sframe.c    | 39 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+)

diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 23c05dc7a8f2..4a633bc7aefb 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>
@@ -375,6 +376,7 @@ 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
index 673b9edfc921..905775c3fde2 100644
--- a/include/linux/sframe.h
+++ b/include/linux/sframe.h
@@ -109,4 +109,18 @@ static inline int sframe_find_user(unsigned long ip, struct unwind_frame *frame)
 
 #endif /* CONFIG_HAVE_UNWIND_USER_SFRAME */
 
+#ifdef CONFIG_SFRAME_UNWINDER
+
+void __init init_sframe_table(void);
+void sframe_module_init(struct module *mod, void *sframe, size_t sframe_size,
+			void *text, size_t text_size);
+
+extern int sframe_find_kernel(unsigned long ip, struct unwind_frame *frame);
+
+#else
+
+static inline void __init init_sframe_table(void) {}
+
+#endif /* CONFIG_SFRAME_UNWINDER */
+
 #endif /* _LINUX_SFRAME_H */
diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
index cad4384dfb4f..321d0615aec7 100644
--- a/kernel/unwind/sframe.c
+++ b/kernel/unwind/sframe.c
@@ -13,10 +13,23 @@
 #include <linux/string_helpers.h>
 #include <linux/sframe.h>
 #include <asm/unwind_sframe.h>
+#ifdef CONFIG_SFRAME_UNWINDER
+#include <linux/kallsyms.h>
+#endif
 
 #include "sframe.h"
 #include "sframe_debug.h"
 
+#ifdef CONFIG_SFRAME_UNWINDER
+
+extern char __start_sframe_header[];
+extern char __stop_sframe_header[];
+
+static bool sframe_init __ro_after_init;
+static struct sframe_section kernel_sfsec __ro_after_init;
+
+#endif /* CONFIG_SFRAME_UNWINDER */
+
 struct sframe_fde_internal {
 	unsigned long	func_addr;
 	u32		func_size;
@@ -930,3 +943,29 @@ void sframe_free_mm(struct mm_struct *mm)
 }
 
 #endif /* CONFIG_HAVE_UNWIND_USER_SFRAME */
+
+#ifdef CONFIG_SFRAME_UNWINDER
+
+int sframe_find_kernel(unsigned long ip, struct unwind_frame *frame)
+{
+	if (!frame || !sframe_init)
+		return -EINVAL;
+
+	return  __sframe_find(&kernel_sfsec, ip, frame);
+}
+
+void __init init_sframe_table(void)
+{
+	kernel_sfsec.sec_type		= SFRAME_KERNEL;
+	kernel_sfsec.sframe_start	= (unsigned long)__start_sframe_header;
+	kernel_sfsec.sframe_end		= (unsigned long)__stop_sframe_header;
+	kernel_sfsec.text_start		= (unsigned long)_stext;
+	kernel_sfsec.text_end		= (unsigned long)_etext;
+
+	if (WARN_ON(sframe_read_header(&kernel_sfsec)))
+		return;
+
+	sframe_init = true;
+}
+
+#endif /* CONFIG_SFRAME_UNWINDER */
-- 
2.53.0.1213.gd9a14994de-goog