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

[dave.martin@linaro.org (Dave Martin)]

On Mon, Sep 19, 2011 at 10:00 AM, 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>

Looks reasonable.

Tixy, could it make sense for that definition of
kallsyms_lookup_funcptr to migrate into the kernel headers?  I had the
impression that you might also have used this in some places, if it
had been available.

Cheers
---Dave

> ---
> ?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
>
>



-- 
Dave Martin <dave.martin at linaro.org>
Linaro Kernel Working Group

--
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