Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
On Sat, Feb 14, 2009 at 08:57:02PM +0100, Sam Ravnborg wrote:
[...]
--- a/Makefile
+++ b/Makefile
@@ -525,8 +525,6 @@ else
KBUILD_CFLAGS+= -O2
endif
-include $(srctree)/arch/$(SRCARCH)/Makefile
-
ifneq (CONFIG_FRAME_WARN,0)
KBUILD_CFLAGS += $(call
cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
@@ -555,6 +553,8 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
+include $(srctree)/arch/$(SRCARCH)/Makefile
+
# arch Makefile may override CC so keep this after arch Makefile is
included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC)
-print-file-name=include)
CHECKFLAGS += $(NOSTDINC_FLAGS)
--
this patch is really for Sam to judge - Cc:-ed him.
If we move the include further down then the following:
# Force gcc to behave correct even for buggy distributions
# Arch Makefiles may override this setting
KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
will most likely fail.
Hm... I don't get it, the comment says that the arch may override
this setting, but currently it may not, since arch makefile is
included before this line. So my patch also fixes this bug, no?
Or arches supposed to overwrite cc-option behaviour? Hm..
There is an interesting commit:
commit e06b8b98da071f7dd78fb7822991694288047df0
Author: Sam Ravnborg s...@ravnborg.org
Date: Wed Feb 13 22:43:28 2008 +0100
kbuild: allow -fstack-protector to take effect
[...]
--- a/Makefile
+++ b/Makefile
@@ -507,6 +507,10 @@ else
KBUILD_CFLAGS += -O2
endif
+# Force gcc to behave correct even for buggy distributions
+# Arch Makefiles may override this setting
+KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
+
include $(srctree)/arch/$(SRCARCH)/Makefile
ifdef CONFIG_FRAME_POINTER
@@ -525,9 +529,6 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
-# Force gcc to behave correct even for buggy distributions
-KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
-
# arch Makefile may override CC so keep this after arch Makefile is included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
CHECKFLAGS += $(NOSTDINC_FLAGS)
^^ Which does the same (wrt fno-stack-protector) as the patch I
sent, i.e. includes arch Makefile later.
But then, this commit reverted things back (w/o your Ack):
commit bef5b54bd7bf8117c75cb943d64549134c6d9a1f
Author: Ralf Baechle r...@linux-mips.org
Date: Wed Jul 16 13:02:24 2008 +0100
Fix MIPS cross-compile problem
[...]
Signed-off-by: Ralf Baechle r...@linux-mips.org
Signed-off-by: Linus Torvalds torva...@linux-foundation.org
[...]
--- a/Makefile
+++ b/Makefile
@@ -508,6 +508,8 @@ else
KBUILD_CFLAGS += -O2
endif
+include $(srctree)/arch/$(SRCARCH)/Makefile
+
ifneq (CONFIG_FRAME_WARN,0)
KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
@@ -516,8 +518,6 @@ endif
# Arch Makefiles may override this setting
KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
-include $(srctree)/arch/$(SRCARCH)/Makefile
-
ifdef CONFIG_FRAME_POINTER
KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
else
:-?
--
Anton Vorontsov
email: cbouatmai...@gmail.com
irc://irc.freenode.net/bd2
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Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
On Mon, Feb 16, 2009 at 05:20:01PM +0300, Anton Vorontsov wrote:
On Sat, Feb 14, 2009 at 08:57:02PM +0100, Sam Ravnborg wrote:
[...]
--- a/Makefile
+++ b/Makefile
@@ -525,8 +525,6 @@ else
KBUILD_CFLAGS += -O2
endif
-include $(srctree)/arch/$(SRCARCH)/Makefile
-
ifneq (CONFIG_FRAME_WARN,0)
KBUILD_CFLAGS += $(call
cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
@@ -555,6 +553,8 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
+include $(srctree)/arch/$(SRCARCH)/Makefile
+
# arch Makefile may override CC so keep this after arch Makefile is
included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC)
-print-file-name=include)
CHECKFLAGS += $(NOSTDINC_FLAGS)
--
this patch is really for Sam to judge - Cc:-ed him.
If we move the include further down then the following:
# Force gcc to behave correct even for buggy distributions
# Arch Makefiles may override this setting
KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
will most likely fail.
Hm... I don't get it, the comment says that the arch may override
this setting, but currently it may not, since arch makefile is
included before this line. So my patch also fixes this bug, no?
Or arches supposed to overwrite cc-option behaviour? Hm..
There is an interesting commit:
commit e06b8b98da071f7dd78fb7822991694288047df0
Author: Sam Ravnborg s...@ravnborg.org
Date: Wed Feb 13 22:43:28 2008 +0100
kbuild: allow -fstack-protector to take effect
[...]
--- a/Makefile
+++ b/Makefile
@@ -507,6 +507,10 @@ else
KBUILD_CFLAGS += -O2
endif
+# Force gcc to behave correct even for buggy distributions
+# Arch Makefiles may override this setting
+KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
+
include $(srctree)/arch/$(SRCARCH)/Makefile
ifdef CONFIG_FRAME_POINTER
@@ -525,9 +529,6 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
-# Force gcc to behave correct even for buggy distributions
-KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
-
# arch Makefile may override CC so keep this after arch Makefile is included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
CHECKFLAGS += $(NOSTDINC_FLAGS)
^^ Which does the same (wrt fno-stack-protector) as the patch I
sent, i.e. includes arch Makefile later.
But then, this commit reverted things back (w/o your Ack):
commit bef5b54bd7bf8117c75cb943d64549134c6d9a1f
Author: Ralf Baechle r...@linux-mips.org
Date: Wed Jul 16 13:02:24 2008 +0100
Fix MIPS cross-compile problem
[...]
Signed-off-by: Ralf Baechle r...@linux-mips.org
Signed-off-by: Linus Torvalds torva...@linux-foundation.org
Ok, I think I got it. It seems that Ralf was using this feature
of arch/mips/Makefile:
ifneq ($(SUBARCH),$(ARCH))
ifeq ($(CROSS_COMPILE),)
CROSS_COMPILE := $(call cc-cross-prefix, $(tool-archpref)-linux-
$(tool-archpref)-linux-gnu- $(tool-archpref)-unknown-linux-gnu-)
endif
endif
There are few arches that have auto detection of CROSS_COMPILE
variable: mips, m68k, parisc, xtensa, h8300 and blackfin.
So `normal' arches don't have any chance to overwrite the flags
because of the few offenders above. ;-)
[...]
--- a/Makefile
+++ b/Makefile
@@ -508,6 +508,8 @@ else
KBUILD_CFLAGS += -O2
endif
+include $(srctree)/arch/$(SRCARCH)/Makefile
+
ifneq (CONFIG_FRAME_WARN,0)
KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
@@ -516,8 +518,6 @@ endif
# Arch Makefiles may override this setting
KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
-include $(srctree)/arch/$(SRCARCH)/Makefile
-
ifdef CONFIG_FRAME_POINTER
KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
else
--
Anton Vorontsov
email: cbouatmai...@gmail.com
irc://irc.freenode.net/bd2
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Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
On Mon, Feb 16, 2009 at 05:20:01PM +0300, Anton Vorontsov wrote:
[...]
But then, this commit reverted things back (w/o your Ack):
commit bef5b54bd7bf8117c75cb943d64549134c6d9a1f
Author: Ralf Baechle r...@linux-mips.org
Date: Wed Jul 16 13:02:24 2008 +0100
Fix MIPS cross-compile problem
[...]
Signed-off-by: Ralf Baechle r...@linux-mips.org
Signed-off-by: Linus Torvalds torva...@linux-foundation.org
[...]
--- a/Makefile
+++ b/Makefile
@@ -508,6 +508,8 @@ else
KBUILD_CFLAGS += -O2
endif
+include $(srctree)/arch/$(SRCARCH)/Makefile
+
ifneq (CONFIG_FRAME_WARN,0)
KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
@@ -516,8 +518,6 @@ endif
# Arch Makefiles may override this setting
KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
-include $(srctree)/arch/$(SRCARCH)/Makefile
-
ifdef CONFIG_FRAME_POINTER
KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
else
Btw, I wonder if x86's CONFIG_CC_STACKPROTECTOR is a no-op since
v2.6.27-rc1? Seems like it is.
--
Anton Vorontsov
email: cbouatmai...@gmail.com
irc://irc.freenode.net/bd2
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Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
* Anton Vorontsov avoront...@ru.mvista.com wrote:
On Mon, Feb 16, 2009 at 05:20:01PM +0300, Anton Vorontsov wrote:
[...]
But then, this commit reverted things back (w/o your Ack):
commit bef5b54bd7bf8117c75cb943d64549134c6d9a1f
Author: Ralf Baechle r...@linux-mips.org
Date: Wed Jul 16 13:02:24 2008 +0100
Fix MIPS cross-compile problem
[...]
Signed-off-by: Ralf Baechle r...@linux-mips.org
Signed-off-by: Linus Torvalds torva...@linux-foundation.org
[...]
--- a/Makefile
+++ b/Makefile
@@ -508,6 +508,8 @@ else
KBUILD_CFLAGS += -O2
endif
+include $(srctree)/arch/$(SRCARCH)/Makefile
+
ifneq (CONFIG_FRAME_WARN,0)
KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
@@ -516,8 +518,6 @@ endif
# Arch Makefiles may override this setting
KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
-include $(srctree)/arch/$(SRCARCH)/Makefile
-
ifdef CONFIG_FRAME_POINTER
KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
else
Btw, I wonder if x86's CONFIG_CC_STACKPROTECTOR is a no-op since
v2.6.27-rc1? Seems like it is.
that's fixed and merged up for 2.6.30.
Ingo
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Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
There are few arches that have auto detection of CROSS_COMPILE variable: mips, m68k, parisc, xtensa, h8300 and blackfin. So `normal' arches don't have any chance to overwrite the flags because of the few offenders above. ;-) We also have archs where we add options to gcc that may impact for example -fno-stack-protector. We had a bug in x86 in this area for a while. So the only sane thing is to only add the most generic options to KBUILD_CFLAGS before we include the arch specific part. And we can then add the conditional options later - like the KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector) in this case. We learned a few lessons in this area over time as your history digging also showed. Sam ___ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
* Benjamin Herrenschmidt b...@kernel.crashing.org wrote: On Sat, 2009-02-14 at 23:03 +0100, Ingo Molnar wrote: So the question is: even with FRAME_POINTERS disabled on PPC, is __builtin_return_address(1)/(2) reliable, and is save_stack_trace() fast? (i.e. can it walk down the stack frame efficiently, or does it have to scan the full kernel stack) I.e. does PPC have all the material advantages of frame pointers? Yes, we do. We effectively have frame pointers in fact, they may only be omitted in leaf functions but then gcc __builtin_return_address() knows how to handle that afaik. So basically we want to define FRAME_POINTERS on PPC, but do not want the -fno-omit-frame-pointers flag. Originally (many moons ago) FRAME_POINTER _was_ just the toplevel Makefile detail, but these days we've got a handful of secondary uses as well, expressing the reliability of backtraces in essence. We could split the whole option (affecting lots of files), or we could zap that compiler flag in the PPC case - it is only PPC that worries about this anyway. Ingo ___ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
On Wed, Feb 04, 2009 at 10:26:12PM +0100, Ingo Molnar wrote:
* Anton Vorontsov avoront...@ru.mvista.com wrote:
This patch gives arches more freedom on overwriting CFLAGS, specifically
on PowerPC we want to remove -fno-omit-frame-pointer flag.
Signed-off-by: Anton Vorontsov avoront...@ru.mvista.com
---
Makefile |4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index 7715b2c..d1ba93f 100644
--- a/Makefile
+++ b/Makefile
@@ -525,8 +525,6 @@ else
KBUILD_CFLAGS += -O2
endif
-include $(srctree)/arch/$(SRCARCH)/Makefile
-
ifneq (CONFIG_FRAME_WARN,0)
KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
@@ -555,6 +553,8 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
+include $(srctree)/arch/$(SRCARCH)/Makefile
+
# arch Makefile may override CC so keep this after arch Makefile is
included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC)
-print-file-name=include)
CHECKFLAGS += $(NOSTDINC_FLAGS)
--
this patch is really for Sam to judge - Cc:-ed him.
If we move the include further down then the following:
# Force gcc to behave correct even for buggy distributions
# Arch Makefiles may override this setting
KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
will most likely fail.
If popwerpc needs to get rid of -fno-omit-frame-pointer then
we need a way to express this at KConfig level and NOT by doing
some tricks with CFLAGS.
Sam
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Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
On Wed, Feb 11, 2009 at 02:51:34PM +1100, Benjamin Herrenschmidt wrote: On Wed, 2009-02-04 at 22:26 +0100, Ingo Molnar wrote: +include $(srctree)/arch/$(SRCARCH)/Makefile + # arch Makefile may override CC so keep this after arch Makefile is included NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) CHECKFLAGS += $(NOSTDINC_FLAGS) -- this patch is really for Sam to judge - Cc:-ed him. Sam ? I have a few more powerpc patches depending on that one... so I'd like to know if it's totally doomed or not :-) See my answer to the mail from Ingo. We really need to do this on Kconfig level it at all possible. Sam ___ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
* Sam Ravnborg s...@ravnborg.org wrote:
On Wed, Feb 04, 2009 at 10:26:12PM +0100, Ingo Molnar wrote:
* Anton Vorontsov avoront...@ru.mvista.com wrote:
This patch gives arches more freedom on overwriting CFLAGS, specifically
on PowerPC we want to remove -fno-omit-frame-pointer flag.
Signed-off-by: Anton Vorontsov avoront...@ru.mvista.com
---
Makefile |4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index 7715b2c..d1ba93f 100644
--- a/Makefile
+++ b/Makefile
@@ -525,8 +525,6 @@ else
KBUILD_CFLAGS+= -O2
endif
-include $(srctree)/arch/$(SRCARCH)/Makefile
-
ifneq (CONFIG_FRAME_WARN,0)
KBUILD_CFLAGS += $(call
cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
endif
@@ -555,6 +553,8 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
+include $(srctree)/arch/$(SRCARCH)/Makefile
+
# arch Makefile may override CC so keep this after arch Makefile is
included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC)
-print-file-name=include)
CHECKFLAGS += $(NOSTDINC_FLAGS)
--
this patch is really for Sam to judge - Cc:-ed him.
If we move the include further down then the following:
# Force gcc to behave correct even for buggy distributions
# Arch Makefiles may override this setting
KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
will most likely fail.
ah, ok. (I long ago made the mental note of dont change the toplevel Makefile
if you can avoid it - this reinforces that.)
If popwerpc needs to get rid of -fno-omit-frame-pointer then
we need a way to express this at KConfig level and NOT by doing
some tricks with CFLAGS.
Here is what we have in the toplevel Makefile at the moment:
ifdef CONFIG_FRAME_POINTER
KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
else
KBUILD_CFLAGS += -fomit-frame-pointer
endif
My original suggestion (more than a week ago) was to make PPC always
select FRAME_POINTERS.
It was pointed out that -fno-omit-frame-pointers (i.e.: generate frame
pointers) not only makes the code less optimal on PPC, but it can also be
miscompiled.
But instrumentation really needs to know whether __builtin_return_address(1)
[etc] is reliable, whether stack tracing is fast - and other details - and PPC
is the odd one out.
So the question is: even with FRAME_POINTERS disabled on PPC, is
__builtin_return_address(1)/(2) reliable, and is save_stack_trace() fast? (i.e.
can it walk down the stack frame efficiently, or does it have to scan the full
kernel stack) I.e. does PPC have all the material advantages of frame pointers?
Ingo
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Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
On Sat, 2009-02-14 at 23:03 +0100, Ingo Molnar wrote: So the question is: even with FRAME_POINTERS disabled on PPC, is __builtin_return_address(1)/(2) reliable, and is save_stack_trace() fast? (i.e. can it walk down the stack frame efficiently, or does it have to scan the full kernel stack) I.e. does PPC have all the material advantages of frame pointers? Yes, we do. We effectively have frame pointers in fact, they may only be omitted in leaf functions but then gcc __builtin_return_address() knows how to handle that afaik. Cheers, Ben. ___ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
On Wed, 2009-02-11 at 14:23 +0100, Ingo Molnar wrote: * Benjamin Herrenschmidt b...@kernel.crashing.org wrote: On Wed, 2009-02-04 at 22:26 +0100, Ingo Molnar wrote: +include $(srctree)/arch/$(SRCARCH)/Makefile + # arch Makefile may override CC so keep this after arch Makefile is included NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) CHECKFLAGS += $(NOSTDINC_FLAGS) -- this patch is really for Sam to judge - Cc:-ed him. Sam ? I have a few more powerpc patches depending on that one... so I'd like to know if it's totally doomed or not :-) Well, toplevel Makefile changes are not to be taken lightly :-) Looks good to me but it's handy to have Sam's Ack on it too. Someone on IRC said that Sam is on vacation. This could take a while for an ACK. -- Steve ___ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
Re: [PATCH 1/3] Makefile: Include arch Makefiles as late as possible
On Wed, 2009-02-04 at 22:26 +0100, Ingo Molnar wrote: +include $(srctree)/arch/$(SRCARCH)/Makefile + # arch Makefile may override CC so keep this after arch Makefile is included NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) CHECKFLAGS += $(NOSTDINC_FLAGS) -- this patch is really for Sam to judge - Cc:-ed him. Sam ? I have a few more powerpc patches depending on that one... so I'd like to know if it's totally doomed or not :-) Cheers, Ben. ___ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
