Messages in this thread Patch in this message | | | Date | Mon, 23 May 2011 22:01:23 +0200 (CEST) | From | John Kacur <> | Subject | Re: [PATCH] kernel: Fix ftrace.c compiler warning when calling ftrace_nop_replace() |
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On Mon, 23 May 2011, Steven Rostedt wrote:
> On Sun, 2011-05-22 at 18:36 -0700, H. Peter Anvin wrote: > > On 05/22/2011 06:19 PM, Eduardo Silva wrote: > > > the function ftrace_nop_replace() returns a 'static const unsigned char *' > > > value, so when the caller perform a direct assignment to a > > > 'static unsigned char *', the compiler raise the following warning message: > > > > > > ftrace.c:308:6: warning: assignment discards qualifiers from pointer target type > > > ftrace.c:318:6: warning: assignment discards qualifiers from pointer target type > > > > > > Adding the proper casts the message goes away. > > > > > > Signed-off-by: Eduardo Silva <edsiper@gmail.com> > > > > This quiets a warning of something that potentially looks like a real > > bug. Perhaps "new" should be const? > > Although there is no real bug here, I hate these "hide the warning" > patches. > > The real solution is to change all the users into const *. This should > be doable as the new and old pointers are not modified. > > And remember: > > char *changes; > const char *no_changes; > > no_changes = changes; /* is OK! (no compiler warnings) */ > > changes = no_changes; /* is not OK. (compiler will warn). */ > > -- Steve
The following needs some testing, just compile tested for now.
From 71d6e5971cc90a03fd2d7bf8aaa2b81932bd0c7c Mon Sep 17 00:00:00 2001 From: John Kacur <jkacur@redhat.com> Date: Mon, 23 May 2011 21:24:27 +0200 Subject: [PATCH] ftrace: Change unsigned char *new, *old to const MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
This removes the warning: arch/x86/kernel/ftrace.c: In function ‘ftrace_make_nop’: /arch/x86/kernel/ftrace.c:308: warning: assignment discards qualifiers from pointer target type
Steven Rostedt suggested to make these pointers const pointers.
This patch assumes that https://patchwork.kernel.org/patch/798172/ is applied first.
Reported-by: Eduardo Silva <edsiper@gmail.com> Signed-off-by: John Kacur <jkacur@redhat.com> --- arch/x86/kernel/ftrace.c | 12 ++++++------ 1 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 0ba15a6..e4f23d1 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -123,7 +123,7 @@ static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr) static atomic_t nmi_running = ATOMIC_INIT(0); static int mod_code_status; /* holds return value of text write */ static void *mod_code_ip; /* holds the IP to write to */ -static void *mod_code_newcode; /* holds the text to write to the IP */ +static const void *mod_code_newcode; /* holds the text to write to the IP */ static unsigned nmi_wait_count; static atomic_t nmi_update_count = ATOMIC_INIT(0); @@ -225,7 +225,7 @@ within(unsigned long addr, unsigned long start, unsigned long end) } static int -do_ftrace_mod_code(unsigned long ip, void *new_code) +do_ftrace_mod_code(unsigned long ip, const void *new_code) { /* * On x86_64, kernel text mappings are mapped read-only with @@ -266,8 +266,8 @@ static const unsigned char *ftrace_nop_replace(void) } static int -ftrace_modify_code(unsigned long ip, unsigned char *old_code, - unsigned char *new_code) +ftrace_modify_code(unsigned long ip, const unsigned char *old_code, + const unsigned char *new_code) { unsigned char replaced[MCOUNT_INSN_SIZE]; @@ -301,7 +301,7 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code, int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { - unsigned char *new, *old; + const unsigned char *new, *old; unsigned long ip = rec->ip; old = ftrace_call_replace(ip, addr); @@ -312,7 +312,7 @@ int ftrace_make_nop(struct module *mod, int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { - unsigned char *new, *old; + const unsigned char *new, *old; unsigned long ip = rec->ip; old = ftrace_nop_replace(); -- 1.7.2.3
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