[RFC PATCH v1 5/9] dwarf: Implement DWARF support for modules
madvenka at linux.microsoft.com
madvenka at linux.microsoft.com
Thu Apr 7 13:25:14 PDT 2022
From: "Madhavan T. Venkataraman" <madvenka at linux.microsoft.com>
When a module is loaded, allocate and initialize its struct dwarf_info. When
a module is unloaded, free the same.
Add code in dwarf_lookup() to look up a given address in modules, if vmlinux
does not contain the address.
Signed-off-by: Madhavan T. Venkataraman <madvenka at linux.microsoft.com>
---
include/linux/dwarf.h | 18 ++++++++++
include/linux/module.h | 3 ++
kernel/dwarf_fp.c | 71 ++++++++++++++++++++++++++++++++++---
kernel/module.c | 31 ++++++++++++++++
tools/include/linux/dwarf.h | 18 ++++++++++
5 files changed, 136 insertions(+), 5 deletions(-)
diff --git a/include/linux/dwarf.h b/include/linux/dwarf.h
index 3df15e79003c..aa44a414b0b6 100644
--- a/include/linux/dwarf.h
+++ b/include/linux/dwarf.h
@@ -11,6 +11,7 @@
#define _LINUX_DWARF_H
#include <linux/types.h>
+#include <linux/module.h>
/*
* objtool generates two special sections that contain DWARF information that
@@ -54,11 +55,28 @@ struct dwarf_block {
#ifdef CONFIG_DWARF_FP
extern struct dwarf_rule *dwarf_lookup(unsigned long pc);
+#ifdef CONFIG_MODULES
+extern void dwarf_module_alloc(struct module *mod,
+ struct dwarf_rule *rules, size_t rules_size,
+ unsigned long *pcs, size_t pcs_size);
+extern void dwarf_module_free(struct module *mod);
+#endif
#else
static inline struct dwarf_rule *dwarf_lookup(unsigned long pc)
{
return NULL;
}
+#ifdef CONFIG_MODULES
+static inline void dwarf_module_alloc(struct module *mod,
+ struct dwarf_rule *rules,
+ size_t rules_size,
+ unsigned long *pcs, size_t pcs_size)
+{
+}
+static inline void dwarf_module_free(struct module *mod)
+{
+}
+#endif
#endif
#endif /* _LINUX_DWARF_H */
diff --git a/include/linux/module.h b/include/linux/module.h
index c9f1200b2312..bd7c69b82808 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -538,6 +538,9 @@ struct module {
struct error_injection_entry *ei_funcs;
unsigned int num_ei_funcs;
#endif
+#ifdef CONFIG_DWARF_FP
+ void *dwarf_info;
+#endif
} ____cacheline_aligned __randomize_layout;
#ifndef MODULE_ARCH_INIT
#define MODULE_ARCH_INIT {}
diff --git a/kernel/dwarf_fp.c b/kernel/dwarf_fp.c
index bb14fbe3f3e1..07d647e828cd 100644
--- a/kernel/dwarf_fp.c
+++ b/kernel/dwarf_fp.c
@@ -164,6 +164,44 @@ static struct dwarf_info *dwarf_alloc(struct dwarf_rule *rules, int nrules,
return NULL;
}
+#ifdef CONFIG_MODULES
+
+/*
+ * Errors encountered in this function should not be fatal. All it will mean
+ * is that stack traces through the module would be considered unreliable.
+ */
+void dwarf_module_alloc(struct module *mod,
+ struct dwarf_rule *rules, size_t rules_size,
+ unsigned long *pcs, size_t pcs_size)
+{
+ int nrules, npcs;
+
+ mod->dwarf_info = NULL;
+
+ nrules = rules_size / sizeof(*rules);
+ npcs = pcs_size / sizeof(*pcs);
+ if (!nrules || npcs != nrules)
+ return;
+
+ mod->dwarf_info = dwarf_alloc(rules, nrules, pcs);
+}
+
+void dwarf_module_free(struct module *mod)
+{
+ struct dwarf_info *info;
+
+ info = mod->dwarf_info;
+ mod->dwarf_info = NULL;
+
+ if (info) {
+ kfree(info->blocks);
+ kfree(info->offsets);
+ kfree(info);
+ }
+}
+
+#endif
+
static struct dwarf_rule *dwarf_lookup_rule(struct dwarf_info *info,
unsigned long pc)
{
@@ -212,13 +250,36 @@ static struct dwarf_rule *dwarf_lookup_rule(struct dwarf_info *info,
return NULL;
}
+#ifdef CONFIG_MODULES
+
+static struct dwarf_rule *dwarf_module_lookup_rule(unsigned long pc)
+{
+ struct module *mod;
+
+ mod = __module_address(pc);
+ if (!mod || !mod->dwarf_info)
+ return NULL;
+
+ return dwarf_lookup_rule(mod->dwarf_info, pc);
+}
+
+#else
+
+static struct dwarf_rule *dwarf_module_lookup_rule(unsigned long pc)
+{
+ return NULL;
+}
+
+#endif
+
struct dwarf_rule *dwarf_lookup(unsigned long pc)
{
- /*
- * Currently, only looks up vmlinux. Support for modules will be
- * added later.
- */
- return dwarf_lookup_rule(vmlinux_dwarf_info, pc);
+ struct dwarf_rule *rule;
+
+ rule = dwarf_lookup_rule(vmlinux_dwarf_info, pc);
+ if (!rule)
+ rule = dwarf_module_lookup_rule(pc);
+ return rule;
}
static int __init dwarf_init_feature(void)
diff --git a/kernel/module.c b/kernel/module.c
index 84a9141a5e15..d9b73995b70a 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -59,6 +59,7 @@
#include <linux/audit.h>
#include <uapi/linux/module.h>
#include "module-internal.h"
+#include <linux/dwarf.h>
#define CREATE_TRACE_POINTS
#include <trace/events/module.h>
@@ -2153,6 +2154,7 @@ void __weak module_arch_freeing_init(struct module *mod)
}
static void cfi_cleanup(struct module *mod);
+static void module_dwarf_free(struct module *mod);
/* Free a module, remove from lists, etc. */
static void free_module(struct module *mod)
@@ -2175,6 +2177,9 @@ static void free_module(struct module *mod)
/* Arch-specific cleanup. */
module_arch_cleanup(mod);
+ /* Dwarf cleanup. */
+ module_dwarf_free(mod);
+
/* Module unload stuff */
module_unload_free(mod);
@@ -3946,6 +3951,7 @@ static int unknown_module_param_cb(char *param, char *val, const char *modname,
}
static void cfi_init(struct module *mod);
+static void module_dwarf_init(struct module *mod, struct load_info *info);
/*
* Allocate and load the module: note that size of section 0 is always
@@ -4074,6 +4080,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
if (err < 0)
goto free_modinfo;
+ module_dwarf_init(mod, info);
+
flush_module_icache(mod);
/* Setup CFI for the module. */
@@ -4154,6 +4162,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
kfree(mod->args);
free_arch_cleanup:
cfi_cleanup(mod);
+ module_dwarf_free(mod);
module_arch_cleanup(mod);
free_modinfo:
free_modinfo(mod);
@@ -4542,6 +4551,28 @@ static void cfi_cleanup(struct module *mod)
#endif
}
+static void module_dwarf_init(struct module *mod, struct load_info *info)
+{
+ Elf_Shdr *dwarf_rules, *dwarf_pcs;
+
+ dwarf_rules = &info->sechdrs[find_sec(info, ".dwarf_rules")];
+ dwarf_pcs = &info->sechdrs[find_sec(info, ".dwarf_pcs")];
+
+ if (!dwarf_rules || !dwarf_pcs)
+ return;
+
+ dwarf_module_alloc(mod,
+ (void *) dwarf_rules->sh_addr,
+ dwarf_rules->sh_size,
+ (void *) dwarf_pcs->sh_addr,
+ dwarf_pcs->sh_size);
+}
+
+static void module_dwarf_free(struct module *mod)
+{
+ dwarf_module_free(mod);
+}
+
/* Maximum number of characters written by module_flags() */
#define MODULE_FLAGS_BUF_SIZE (TAINT_FLAGS_COUNT + 4)
diff --git a/tools/include/linux/dwarf.h b/tools/include/linux/dwarf.h
index 3df15e79003c..aa44a414b0b6 100644
--- a/tools/include/linux/dwarf.h
+++ b/tools/include/linux/dwarf.h
@@ -11,6 +11,7 @@
#define _LINUX_DWARF_H
#include <linux/types.h>
+#include <linux/module.h>
/*
* objtool generates two special sections that contain DWARF information that
@@ -54,11 +55,28 @@ struct dwarf_block {
#ifdef CONFIG_DWARF_FP
extern struct dwarf_rule *dwarf_lookup(unsigned long pc);
+#ifdef CONFIG_MODULES
+extern void dwarf_module_alloc(struct module *mod,
+ struct dwarf_rule *rules, size_t rules_size,
+ unsigned long *pcs, size_t pcs_size);
+extern void dwarf_module_free(struct module *mod);
+#endif
#else
static inline struct dwarf_rule *dwarf_lookup(unsigned long pc)
{
return NULL;
}
+#ifdef CONFIG_MODULES
+static inline void dwarf_module_alloc(struct module *mod,
+ struct dwarf_rule *rules,
+ size_t rules_size,
+ unsigned long *pcs, size_t pcs_size)
+{
+}
+static inline void dwarf_module_free(struct module *mod)
+{
+}
+#endif
#endif
#endif /* _LINUX_DWARF_H */
--
2.25.1
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