[ltt-dev] [PATCH V1] ARM: Set bit 0 for thumb mode in kallsyms_lookup_name returned address

[Mathieu Desnoyers]

* Avik Sil (avik.sil at linaro.org) wrote:
> This patch fixes the undefined instruction oops due to execution
> of thumb-2 code in ARM mode. The zero bit in the symbol address
> returned by kallsyms_lookup_name is not set, leading to switching
> to ARM mode that generates oops while executing thumb-2 code. For
> detailed discussion, see [1].
> [1] http://lists.casi.polymtl.ca/pipermail/ltt-dev/2011-September/005176.html
> 
> v1:
> 	- include wrapper function kallsyms_lookup_funcptr as suggested
> 	by Dave Martin
> 
> Signed-off-by: Avik Sil <avik.sil at linaro.org>

Merged, thanks!

Mathieu

> ---
>  lttng-context-prio.c |    3 ++-
>  wrapper/ftrace.h     |    5 +++--
>  wrapper/kallsyms.h   |   28 ++++++++++++++++++++++++++++
>  wrapper/splice.c     |    3 ++-
>  wrapper/vmalloc.h    |    3 ++-
>  5 files changed, 37 insertions(+), 5 deletions(-)
>  create mode 100644 wrapper/kallsyms.h
> 
> diff --git a/lttng-context-prio.c b/lttng-context-prio.c
> index ad1c42f..1ee3a54 100644
> --- a/lttng-context-prio.c
> +++ b/lttng-context-prio.c
> @@ -13,6 +13,7 @@
>  #include "ltt-events.h"
>  #include "wrapper/ringbuffer/frontend_types.h"
>  #include "wrapper/vmalloc.h"
> +#include "wrapper/kallsyms.h"
>  #include "ltt-tracer.h"
>  
>  static
> @@ -20,7 +21,7 @@ int (*wrapper_task_prio_sym)(struct task_struct *t);
>  
>  int wrapper_task_prio_init(void)
>  {
> -	wrapper_task_prio_sym = (void *) kallsyms_lookup_name("task_prio");
> +	wrapper_task_prio_sym = (void *) kallsyms_lookup_funcptr("task_prio");
>  	if (!wrapper_task_prio_sym) {
>  		printk(KERN_WARNING "LTTng: task_prio symbol lookup failed.\n");
>  		return -EINVAL;
> diff --git a/wrapper/ftrace.h b/wrapper/ftrace.h
> index 9c18cc5..ace33c5 100644
> --- a/wrapper/ftrace.h
> +++ b/wrapper/ftrace.h
> @@ -16,6 +16,7 @@
>  #ifdef CONFIG_KALLSYMS
>  
>  #include <linux/kallsyms.h>
> +#include "kallsyms.h"
>  
>  static inline
>  int wrapper_register_ftrace_function_probe(char *glob,
> @@ -24,7 +25,7 @@ int wrapper_register_ftrace_function_probe(char *glob,
>  	int (*register_ftrace_function_probe_sym)(char *glob,
>  			struct ftrace_probe_ops *ops, void *data);
>  
> -	register_ftrace_function_probe_sym = (void *) kallsyms_lookup_name("register_ftrace_function_probe");
> +	register_ftrace_function_probe_sym = (void *) kallsyms_lookup_funcptr("register_ftrace_function_probe");
>  	if (register_ftrace_function_probe_sym) {
>  		return register_ftrace_function_probe_sym(glob, ops, data);
>  	} else {
> @@ -40,7 +41,7 @@ void wrapper_unregister_ftrace_function_probe(char *glob,
>  	void (*unregister_ftrace_function_probe_sym)(char *glob,
>  			struct ftrace_probe_ops *ops, void *data);
>  
> -	unregister_ftrace_function_probe_sym = (void *) kallsyms_lookup_name("unregister_ftrace_function_probe");
> +	unregister_ftrace_function_probe_sym = (void *) kallsyms_lookup_funcptr("unregister_ftrace_function_probe");
>  	if (unregister_ftrace_function_probe_sym) {
>  		unregister_ftrace_function_probe_sym(glob, ops, data);
>  	} else {
> diff --git a/wrapper/kallsyms.h b/wrapper/kallsyms.h
> new file mode 100644
> index 0000000..bb45f38
> --- /dev/null
> +++ b/wrapper/kallsyms.h
> @@ -0,0 +1,28 @@
> +#ifndef _LTT_WRAPPER_KALLSYMS_H
> +#define _LTT_WRAPPER_KALLSYMS_H
> +
> +/*
> + * Copyright (C) 2011 Avik Sil (avik.sil at linaro.org)
> + *
> + * wrapper around kallsyms_lookup_name. Implements arch-dependent code for
> + * arches where the address of the start of the function body is different
> + * from the pointer which can be used to call the function, e.g. ARM THUMB2.
> + *
> + * Dual LGPL v2.1/GPL v2 license.
> + */
> +
> +static inline
> +unsigned long kallsyms_lookup_funcptr(const char *name)
> +{
> +	unsigned long addr;
> +
> +	addr = kallsyms_lookup_name(name);
> +#ifdef CONFIG_ARM
> +#ifdef CONFIG_THUMB2_KERNEL
> +	if (addr)
> +		addr |= 1; /* set bit 0 in address for thumb mode */
> +#endif
> +#endif
> +	return addr;
> +}
> +#endif /* _LTT_WRAPPER_KALLSYMS_H */
> diff --git a/wrapper/splice.c b/wrapper/splice.c
> index edc499c..ba224ee 100644
> --- a/wrapper/splice.c
> +++ b/wrapper/splice.c
> @@ -13,6 +13,7 @@
>  #include <linux/kallsyms.h>
>  #include <linux/fs.h>
>  #include <linux/splice.h>
> +#include "kallsyms.h"
>  
>  static
>  ssize_t (*splice_to_pipe_sym)(struct pipe_inode_info *pipe,
> @@ -22,7 +23,7 @@ ssize_t wrapper_splice_to_pipe(struct pipe_inode_info *pipe,
>  			       struct splice_pipe_desc *spd)
>  {
>  	if (!splice_to_pipe_sym)
> -		splice_to_pipe_sym = (void *) kallsyms_lookup_name("splice_to_pipe");
> +		splice_to_pipe_sym = (void *) kallsyms_lookup_funcptr("splice_to_pipe"); 
>  	if (splice_to_pipe_sym) {
>  		return splice_to_pipe_sym(pipe, spd);
>  	} else {
> diff --git a/wrapper/vmalloc.h b/wrapper/vmalloc.h
> index 7d87855..765f2ad 100644
> --- a/wrapper/vmalloc.h
> +++ b/wrapper/vmalloc.h
> @@ -14,13 +14,14 @@
>  #ifdef CONFIG_KALLSYMS
>  
>  #include <linux/kallsyms.h>
> +#include "kallsyms.h"
>  
>  static inline
>  void wrapper_vmalloc_sync_all(void)
>  {
>  	void (*vmalloc_sync_all_sym)(void);
>  
> -	vmalloc_sync_all_sym = (void *) kallsyms_lookup_name("vmalloc_sync_all");
> +	vmalloc_sync_all_sym = (void *) kallsyms_lookup_funcptr("vmalloc_sync_all");
>  	if (vmalloc_sync_all_sym) {
>  		vmalloc_sync_all_sym();
>  	} else {
> -- 
> 1.7.0.4
> 
> 
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> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com