From ea637639591def87a54cea811cbac796980cb30d Mon Sep 17 00:00:00 2001 From: Jie Zhang Date: Mon, 14 Dec 2009 18:00:02 -0800 Subject: nommu: fix malloc performance by adding uninitialized flag The NOMMU code currently clears all anonymous mmapped memory. While this is what we want in the default case, all memory allocation from userspace under NOMMU has to go through this interface, including malloc() which is allowed to return uninitialized memory. This can easily be a significant performance penalty. So for constrained embedded systems were security is irrelevant, allow people to avoid clearing memory unnecessarily. This also alters the ELF-FDPIC binfmt such that it obtains uninitialised memory for the brk and stack region. Signed-off-by: Jie Zhang Signed-off-by: Robin Getz Signed-off-by: Mike Frysinger Signed-off-by: David Howells Acked-by: Paul Mundt Acked-by: Greg Ungerer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- init/Kconfig | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index 54c655ce9c0..a23da9f0180 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1079,6 +1079,28 @@ config SLOB endchoice +config MMAP_ALLOW_UNINITIALIZED + bool "Allow mmapped anonymous memory to be uninitialized" + depends on EMBEDDED && !MMU + default n + help + Normally, and according to the Linux spec, anonymous memory obtained + from mmap() has it's contents cleared before it is passed to + userspace. Enabling this config option allows you to request that + mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus + providing a huge performance boost. If this option is not enabled, + then the flag will be ignored. + + This is taken advantage of by uClibc's malloc(), and also by + ELF-FDPIC binfmt's brk and stack allocator. + + Because of the obvious security issues, this option should only be + enabled on embedded devices where you control what is run in + userspace. Since that isn't generally a problem on no-MMU systems, + it is normally safe to say Y here. + + See Documentation/nommu-mmap.txt for more information. + config PROFILING bool "Profiling support (EXPERIMENTAL)" help -- cgit v1.2.3 From 196a15b4ee99f627fbc2c07e58e14aab2065fa80 Mon Sep 17 00:00:00 2001 From: H Hartley Sweeten Date: Mon, 14 Dec 2009 18:00:18 -0800 Subject: init/main.c: fix symbol shadows noise The symbol 'call' is a static symbol used for initcall_debug. This same symbol name is used locally by a couple functions and produces the following sparse warnings: warning: symbol 'call' shadows an earlier one Fix this noise by renaming the local symbols. Signed-off-by: H Hartley Sweeten Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- init/main.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) (limited to 'init') diff --git a/init/main.c b/init/main.c index 4051d75dd2d..c3db4a98b36 100644 --- a/init/main.c +++ b/init/main.c @@ -691,10 +691,10 @@ asmlinkage void __init start_kernel(void) static void __init do_ctors(void) { #ifdef CONFIG_CONSTRUCTORS - ctor_fn_t *call = (ctor_fn_t *) __ctors_start; + ctor_fn_t *fn = (ctor_fn_t *) __ctors_start; - for (; call < (ctor_fn_t *) __ctors_end; call++) - (*call)(); + for (; fn < (ctor_fn_t *) __ctors_end; fn++) + (*fn)(); #endif } @@ -755,10 +755,10 @@ extern initcall_t __initcall_start[], __initcall_end[], __early_initcall_end[]; static void __init do_initcalls(void) { - initcall_t *call; + initcall_t *fn; - for (call = __early_initcall_end; call < __initcall_end; call++) - do_one_initcall(*call); + for (fn = __early_initcall_end; fn < __initcall_end; fn++) + do_one_initcall(*fn); /* Make sure there is no pending stuff from the initcall sequence */ flush_scheduled_work(); @@ -785,10 +785,10 @@ static void __init do_basic_setup(void) static void __init do_pre_smp_initcalls(void) { - initcall_t *call; + initcall_t *fn; - for (call = __initcall_start; call < __early_initcall_end; call++) - do_one_initcall(*call); + for (fn = __initcall_start; fn < __early_initcall_end; fn++) + do_one_initcall(*fn); } static void run_init_process(char *init_filename) -- cgit v1.2.3