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Piccoli" , Will Deacon , dianders@chromium.org, groeck@chromium.org Subject: [PATCH] kernel/trace: Add TRACING_ALLOW_PRINTK config option Date: Wed, 24 Jun 2020 16:45:24 +0800 Message-Id: <20200624084524.259560-1-drinkcat@chromium.org> X-Mailer: git-send-email 2.27.0.111.gc72c7da667-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org trace_printk is only meant as a debugging tool, and should never be compiled into production code without source code changes, as indicated by the warning that shows up on boot if any trace_printk is called: ** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE ** ** ** ** trace_printk() being used. Allocating extra memory. ** ** ** ** This means that this is a DEBUG kernel and it is ** ** unsafe for production use. ** If this option is set to n, the kernel will generate a build-time error if trace_printk is used. Signed-off-by: Nicolas Boichat --- include/linux/kernel.h | 17 ++++++++++++++++- kernel/trace/Kconfig | 9 +++++++++ 2 files changed, 25 insertions(+), 1 deletion(-) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 196607aaf653082..b6addc6ba669e85 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -721,10 +721,15 @@ do { \ #define trace_printk(fmt, ...) \ do { \ char _______STR[] = __stringify((__VA_ARGS__)); \ + \ + __static_assert( \ + IS_ENABLED(CONFIG_TRACING_ALLOW_PRINTK),\ + "trace_printk called, please enable CONFIG_TRACING_ALLOW_PRINTK."); \ + \ if (sizeof(_______STR) > 3) \ do_trace_printk(fmt, ##__VA_ARGS__); \ else \ - trace_puts(fmt); \ + do_trace_puts(fmt); \ } while (0) #define do_trace_printk(fmt, args...) \ @@ -773,6 +778,13 @@ int __trace_printk(unsigned long ip, const char *fmt, ...); */ #define trace_puts(str) ({ \ + __static_assert( \ + IS_ENABLED(CONFIG_TRACING_ALLOW_PRINTK), \ + "trace_puts called, please enable CONFIG_TRACING_ALLOW_PRINTK."); \ + do_trace_puts(str); \ +}) + +#define do_trace_puts(str) ({ \ static const char *trace_printk_fmt __used \ __attribute__((section("__trace_printk_fmt"))) = \ __builtin_constant_p(str) ? str : NULL; \ @@ -794,6 +806,9 @@ extern void trace_dump_stack(int skip); */ #define ftrace_vprintk(fmt, vargs) \ do { \ + __static_assert( \ + IS_ENABLED(CONFIG_TRACING_ALLOW_PRINTK), \ + "ftrace_vprintk called, please enable CONFIG_TRACING_ALLOW_PRINTK."); \ if (__builtin_constant_p(fmt)) { \ static const char *trace_printk_fmt __used \ __attribute__((section("__trace_printk_fmt"))) = \ diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index a4020c0b4508c99..89ffddebe1864aa 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -111,6 +111,15 @@ config GENERIC_TRACER bool select TRACING +config TRACING_ALLOW_PRINTK + bool "Allow trace_printk" + default y if DEBUG_KERNEL + depends on TRACING + help + trace_printk is only meant as a debugging tool. If this option is + set to n, the kernel will generate a build-time error if trace_printk + is used. + # # Minimum requirements an architecture has to meet for us to # be able to offer generic tracing facilities: -- 2.27.0.111.gc72c7da667-goog