This adds configurable sysenter support on x86. This saves about 5k on
small systems.
$ size vmlinux-baseline vmlinux
text data bss dec hex filename
2920821 523232 190652 3634705 377611 vmlinux-baseline
2920558 518376 190652 3629586 376212 vmlinux
Signed-off-by: Matt Mackall <[email protected]>
Index: 2.6.15-misc/arch/i386/kernel/Makefile
===================================================================
--- 2.6.15-misc.orig/arch/i386/kernel/Makefile 2005-12-28 14:51:45.000000000 -0600
+++ 2.6.15-misc/arch/i386/kernel/Makefile 2005-12-28 14:51:46.000000000 -0600
@@ -31,7 +31,7 @@ obj-$(CONFIG_X86_NUMAQ) += numaq.o
obj-$(CONFIG_X86_SUMMIT_NUMA) += summit.o
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_MODULES) += module.o
-obj-y += sysenter.o vsyscall.o
+obj-$(CONFIG_SYSENTER) += sysenter.o vsyscall.o
obj-$(CONFIG_ACPI_SRAT) += srat.o
obj-$(CONFIG_HPET_TIMER) += time_hpet.o
obj-$(CONFIG_EFI) += efi.o efi_stub.o
Index: 2.6.15-misc/include/asm-i386/elf.h
===================================================================
--- 2.6.15-misc.orig/include/asm-i386/elf.h 2005-12-28 14:36:59.000000000 -0600
+++ 2.6.15-misc/include/asm-i386/elf.h 2005-12-28 14:51:47.000000000 -0600
@@ -134,11 +134,13 @@ extern int dump_task_extended_fpu (struc
#define VSYSCALL_ENTRY ((unsigned long) &__kernel_vsyscall)
extern void __kernel_vsyscall;
+#ifdef CONFIG_SYSENTER
#define ARCH_DLINFO \
do { \
NEW_AUX_ENT(AT_SYSINFO, VSYSCALL_ENTRY); \
NEW_AUX_ENT(AT_SYSINFO_EHDR, VSYSCALL_BASE); \
} while (0)
+#endif
/*
* These macros parameterize elf_core_dump in fs/binfmt_elf.c to write out
Index: 2.6.15-misc/init/Kconfig
===================================================================
--- 2.6.15-misc.orig/init/Kconfig 2005-12-28 14:51:45.000000000 -0600
+++ 2.6.15-misc/init/Kconfig 2005-12-28 14:51:47.000000000 -0600
@@ -352,6 +352,14 @@ config VM86
XFree86 to initialize some video cards via BIOS. Disabling this
option saves about 6k.
+config SYSENTER
+ depends X86
+ default y
+ bool "Enable syscalls via sysenter" if EMBEDDED
+ help
+ Disabling this feature removes sysenter handling as well as
+ vsyscall fixmaps.
+
config CC_OPTIMIZE_FOR_SIZE
bool "Optimize for size"
default y if ARM || H8300
Index: 2.6.15-misc/include/asm-i386/processor.h
===================================================================
--- 2.6.15-misc.orig/include/asm-i386/processor.h 2005-12-28 14:51:44.000000000 -0600
+++ 2.6.15-misc/include/asm-i386/processor.h 2005-12-28 14:51:41.000000000 -0600
@@ -709,8 +709,14 @@ extern void select_idle_routine(const st
#define cache_line_size() (boot_cpu_data.x86_cache_alignment)
extern unsigned long boot_option_idle_override;
+
+#ifdef CONFIG_SYSENTER
extern void enable_sep_cpu(void);
extern int sysenter_setup(void);
+#else
+#define enable_sep_cpu()
+static inline int sysenter_setup(void) { return 0; }
+#endif
#ifdef CONFIG_MTRR
extern void mtrr_ap_init(void);
--
Mathematics is the supreme nostalgia of our time.
* Matt Mackall <[email protected]> wrote:
> This adds configurable sysenter support on x86. This saves about 5k on
> small systems.
note that this also turns off vsyscalls. Right now vsyscalls are mostly
about sysenter support, but that's not fundamentally so. 4k of the 5k
savings come from the turn-off-vsyscalls portion.
Ingo
On Thu, Dec 29, 2005 at 09:48:58AM +0100, Ingo Molnar wrote:
>
> * Matt Mackall <[email protected]> wrote:
>
> > This adds configurable sysenter support on x86. This saves about 5k on
> > small systems.
>
> note that this also turns off vsyscalls. Right now vsyscalls are mostly
> about sysenter support, but that's not fundamentally so. 4k of the 5k
> savings come from the turn-off-vsyscalls portion.
Yes, this patch would more properly be CONFIG_VSYSCALL.
--
Mathematics is the supreme nostalgia of our time.
> It's under CONFIG_EMBEDDED. Think uclibc. Think systems without
> interactive shells.
Interactive or not has absolutely nothing to do with this. And other
libcs have the same issues wrt to backtraces. And finally, there is
unfortunately no way to prevent somebody from using glibc on an
"embedded" kernel and I have no interest in getting "bug reports" caused
by this kind of user error.
--
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
On Thu, Dec 29, 2005 at 07:04:42PM -0800, Ulrich Drepper wrote:
> > It's under CONFIG_EMBEDDED. Think uclibc. Think systems without
> > interactive shells.
>
> Interactive or not has absolutely nothing to do with this.
Ok, let me be explicit: think systems with absolutely no facility for
recording or displaying a backtrace.
> And other
> libcs have the same issues wrt to backtraces.
As far as I'm aware, uclibc has no vdso support, so it might as well
not exist for systems using it.
--
Mathematics is the supreme nostalgia of our time.
Matt Mackall wrote:
> Ok, let me be explicit: think systems with absolutely no facility for
> recording or displaying a backtrace.
You don't know much about unwinding, do you? The same information is
needed for C++ exception handling, thread cancellation, etc. Now go on
and tell me you don't need this either.
> As far as I'm aware, uclibc has no vdso support, so it might as well
> not exist for systems using it.
And I told you that the support which magically makes all this sometimes
work without the unwind info in the vdso will sooner or later break.
Then whatever other libc is out there has to get vdso support to be able
to function correctly.
--
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
On Thu, 2005-12-29 at 20:03 -0800, Ulrich Drepper wrote:
> Matt Mackall wrote:
> > Ok, let me be explicit: think systems with absolutely no facility for
> > recording or displaying a backtrace.
>
> You don't know much about unwinding, do you? The same information is
> needed for C++ exception handling, thread cancellation, etc. Now go on
> and tell me you don't need this either.
On (presumbly small) embedded devices?
Please be serious.
Bernd
--
Firmix Software GmbH http://www.firmix.at/
mobil: +43 664 4416156 fax: +43 1 7890849-55
Embedded Linux Development and Services