Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1240050 > unrolled thread

[PATCH v2 10/36] x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm

Started byAndy Lutomirski <luto@kernel.org>
First post2015-10-06 02:50 +0200
Last post2015-10-09 15:10 +0200
Articles 3 — 3 participants

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  [PATCH v2 10/36] x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm Andy Lutomirski <luto@kernel.org> - 2015-10-06 02:50 +0200
    Re: [PATCH v2 10/36] x86/vdso: Define BUILD_VDSO while building and  emit .eh_frame in asm Ingo Molnar <mingo@kernel.org> - 2015-10-09 09:30 +0200
    [tip:x86/asm] x86/vdso:   Define BUILD_VDSO while building and emit .eh_frame in asm tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2015-10-09 15:10 +0200

#1240050 — [PATCH v2 10/36] x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm

FromAndy Lutomirski <luto@kernel.org>
Date2015-10-06 02:50 +0200
Subject[PATCH v2 10/36] x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm
Message-ID<qgoC6-715-3@gated-at.bofh.it>
For the vDSO, user code wants runtime unwind info.  Make sure that,
if we use .cfi directives, we generate it.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/entry/vdso/Makefile  |  4 ++--
 arch/x86/include/asm/dwarf2.h | 13 ++++++++++---
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 3bfb39e7b8b2..265c0ed68118 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -67,7 +67,7 @@ $(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE
 CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
        $(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
        -fno-omit-frame-pointer -foptimize-sibling-calls \
-       -DDISABLE_BRANCH_PROFILING
+       -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
 
 $(vobjs): KBUILD_CFLAGS += $(CFL)
 
@@ -131,7 +131,7 @@ targets += vdso32/vdso32.lds
 targets += vdso32/note.o vdso32/vclock_gettime.o vdso32/system_call.o
 targets += vdso32/vclock_gettime.o
 
-KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS))
+KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS)) -DBUILD_VDSO
 $(obj)/vdso32.so.dbg: KBUILD_AFLAGS = $(KBUILD_AFLAGS_32)
 $(obj)/vdso32.so.dbg: asflags-$(CONFIG_X86_64) += -m32
 
diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
index de1cdaf4d743..09133ba032b3 100644
--- a/arch/x86/include/asm/dwarf2.h
+++ b/arch/x86/include/asm/dwarf2.h
@@ -36,15 +36,22 @@
 #endif
 
 #if defined(CONFIG_AS_CFI_SECTIONS) && defined(__ASSEMBLY__)
+#ifndef BUILD_VDSO
 	/*
 	 * Emit CFI data in .debug_frame sections, not .eh_frame sections.
 	 * The latter we currently just discard since we don't do DWARF
 	 * unwinding at runtime.  So only the offline DWARF information is
-	 * useful to anyone.  Note we should not use this directive if this
-	 * file is used in the vDSO assembly, or if vmlinux.lds.S gets
-	 * changed so it doesn't discard .eh_frame.
+	 * useful to anyone.  Note we should not use this directive if
+	 * vmlinux.lds.S gets changed so it doesn't discard .eh_frame.
 	 */
 	.cfi_sections .debug_frame
+#else
+	 /*
+	  * For the vDSO, emit both runtime unwind information and debug
+	  * symbols for the .dbg file.
+	  */
+	.cfi_sections .eh_frame, .debug_frame
+#endif
 #endif
 
 #else
-- 
2.4.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [next] | [standalone]

#1243082 — Re: [PATCH v2 10/36] x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm

FromIngo Molnar <mingo@kernel.org>
Date2015-10-09 09:30 +0200
SubjectRe: [PATCH v2 10/36] x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm
Message-ID<qhAhP-3Jz-5@gated-at.bofh.it>
In reply to#1240050
* Andy Lutomirski <luto@kernel.org> wrote:

> For the vDSO, user code wants runtime unwind info.  Make sure that,
> if we use .cfi directives, we generate it.
> 
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
>  arch/x86/entry/vdso/Makefile  |  4 ++--
>  arch/x86/include/asm/dwarf2.h | 13 ++++++++++---
>  2 files changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
> index 3bfb39e7b8b2..265c0ed68118 100644
> --- a/arch/x86/entry/vdso/Makefile
> +++ b/arch/x86/entry/vdso/Makefile
> @@ -67,7 +67,7 @@ $(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE
>  CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
>         $(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
>         -fno-omit-frame-pointer -foptimize-sibling-calls \
> -       -DDISABLE_BRANCH_PROFILING
> +       -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
>  
>  $(vobjs): KBUILD_CFLAGS += $(CFL)
>  
> @@ -131,7 +131,7 @@ targets += vdso32/vdso32.lds
>  targets += vdso32/note.o vdso32/vclock_gettime.o vdso32/system_call.o
>  targets += vdso32/vclock_gettime.o
>  
> -KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS))
> +KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS)) -DBUILD_VDSO
>  $(obj)/vdso32.so.dbg: KBUILD_AFLAGS = $(KBUILD_AFLAGS_32)
>  $(obj)/vdso32.so.dbg: asflags-$(CONFIG_X86_64) += -m32
>  
> diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
> index de1cdaf4d743..09133ba032b3 100644
> --- a/arch/x86/include/asm/dwarf2.h
> +++ b/arch/x86/include/asm/dwarf2.h
> @@ -36,15 +36,22 @@
>  #endif
>  
>  #if defined(CONFIG_AS_CFI_SECTIONS) && defined(__ASSEMBLY__)
> +#ifndef BUILD_VDSO
>  	/*
>  	 * Emit CFI data in .debug_frame sections, not .eh_frame sections.
>  	 * The latter we currently just discard since we don't do DWARF
>  	 * unwinding at runtime.  So only the offline DWARF information is
> -	 * useful to anyone.  Note we should not use this directive if this
> -	 * file is used in the vDSO assembly, or if vmlinux.lds.S gets
> -	 * changed so it doesn't discard .eh_frame.
> +	 * useful to anyone.  Note we should not use this directive if
> +	 * vmlinux.lds.S gets changed so it doesn't discard .eh_frame.
>  	 */
>  	.cfi_sections .debug_frame
> +#else
> +	 /*
> +	  * For the vDSO, emit both runtime unwind information and debug
> +	  * symbols for the .dbg file.
> +	  */
> +	.cfi_sections .eh_frame, .debug_frame
> +#endif
>  #endif

So it's exactly such hacks why I dislike the old CFI code:

1)

Emitting assembler directives from .h files is just disgusting. What's wrong with 
adding it to the .c file, so that it becomes obvious to everyone what's going on? 
Or if it's possible, do it in the build command line - the vDSO is built in a 
different way anyway.

2)

Could we require that to build the vDSO you need CFI capable tooling? All other 
tooling is probably on very ancient systems which can live with only having the 
vsyscall and the regular int80 entry methods, or something like that.

So could you please clean this all up instead of reintroducing old hacks? I'll 
apply the patches and see how well they work to move things forward, but this part 
is disgusting and needs to be resolved.

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [prev] | [next] | [standalone]

#1243325 — [tip:x86/asm] x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm

Fromtip-bot for Andy Lutomirski <tipbot@zytor.com>
Date2015-10-09 15:10 +0200
Subject[tip:x86/asm] x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm
Message-ID<qhFAR-30e-1@gated-at.bofh.it>
In reply to#1240050
Commit-ID:  f24f910884277aa6824bbc2dda4b5d0418d45c28
Gitweb:     http://git.kernel.org/tip/f24f910884277aa6824bbc2dda4b5d0418d45c28
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Mon, 5 Oct 2015 17:47:58 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 9 Oct 2015 09:41:05 +0200

x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm

For the vDSO, user code wants runtime unwind info.  Make sure
that, if we use .cfi directives, we generate it.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/16e29ad8855e6508197000d8c41f56adb00d7580.1444091584.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/entry/vdso/Makefile  |  4 ++--
 arch/x86/include/asm/dwarf2.h | 13 ++++++++++---
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 3bfb39e..265c0ed 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -67,7 +67,7 @@ $(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE
 CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
        $(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
        -fno-omit-frame-pointer -foptimize-sibling-calls \
-       -DDISABLE_BRANCH_PROFILING
+       -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
 
 $(vobjs): KBUILD_CFLAGS += $(CFL)
 
@@ -131,7 +131,7 @@ targets += vdso32/vdso32.lds
 targets += vdso32/note.o vdso32/vclock_gettime.o vdso32/system_call.o
 targets += vdso32/vclock_gettime.o
 
-KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS))
+KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS)) -DBUILD_VDSO
 $(obj)/vdso32.so.dbg: KBUILD_AFLAGS = $(KBUILD_AFLAGS_32)
 $(obj)/vdso32.so.dbg: asflags-$(CONFIG_X86_64) += -m32
 
diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
index de1cdaf..09133ba 100644
--- a/arch/x86/include/asm/dwarf2.h
+++ b/arch/x86/include/asm/dwarf2.h
@@ -36,15 +36,22 @@
 #endif
 
 #if defined(CONFIG_AS_CFI_SECTIONS) && defined(__ASSEMBLY__)
+#ifndef BUILD_VDSO
 	/*
 	 * Emit CFI data in .debug_frame sections, not .eh_frame sections.
 	 * The latter we currently just discard since we don't do DWARF
 	 * unwinding at runtime.  So only the offline DWARF information is
-	 * useful to anyone.  Note we should not use this directive if this
-	 * file is used in the vDSO assembly, or if vmlinux.lds.S gets
-	 * changed so it doesn't discard .eh_frame.
+	 * useful to anyone.  Note we should not use this directive if
+	 * vmlinux.lds.S gets changed so it doesn't discard .eh_frame.
 	 */
 	.cfi_sections .debug_frame
+#else
+	 /*
+	  * For the vDSO, emit both runtime unwind information and debug
+	  * symbols for the .dbg file.
+	  */
+	.cfi_sections .eh_frame, .debug_frame
+#endif
 #endif
 
 #else
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web