Re: [PATCH v2 5/9] kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS
On Tue, 20 Nov 2018, Masahiro Yamada wrote:
> My main motivation of this commit is to clean up scripts/Kbuild.include
> and scripts/Makefile.build.
>
> Currently, CONFIG_TRIM_UNUSED_KSYMS works with a tricky gimmick;
> possibly exported symbols are detected by letting $(CPP) replace
> EXPORT_SYMBOL* with a special string '=== __KSYM_*===', which is
> post-processed by sed, and passed to fixdep. The extra preprocessing
> is costly, and hacking cmd_and_fixdep is ugly.
>
> I came up with a new way to find exported symbols; insert a dummy
> symbol __ksym_marker_* to each potentially exported symbol. Those
> dummy symbols are picked up by $(NM), post-processed by sed, then
> appended to .*.cmd files. I collected the post-process part to a
> new shell script scripts/gen_ksymdeps.sh for readability. The dummy
> symbols are put into the .discard.* section so that the linker
> script rips them off the final vmlinux or modules.
>
> A nice side-effect is building with CONFIG_TRIM_UNUSED_KSYMS will
> be much faster.
>
> Signed-off-by: Masahiro Yamada
Nice work.
Reviewed-by: Nicolas Pitre
> ---
>
> Changes in v2:
> - Let gen_ksymdeps.sh add dependencies to .*.cmd file directly
> - Fix typos
>
> include/asm-generic/export.h | 13 -
> include/linux/export.h | 18 +-
> scripts/Kbuild.include | 28
> scripts/Makefile.build | 7 +++
> scripts/basic/fixdep.c | 31 ---
> scripts/gen_ksymdeps.sh | 25 +
> 6 files changed, 53 insertions(+), 69 deletions(-)
> create mode 100755 scripts/gen_ksymdeps.sh
>
> diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
> index 4d73e6e..294d6ae 100644
> --- a/include/asm-generic/export.h
> +++ b/include/asm-generic/export.h
> @@ -59,16 +59,19 @@ __kcrctab_\name:
> .endm
> #undef __put
>
> -#if defined(__KSYM_DEPS__)
> -
> -#define __EXPORT_SYMBOL(sym, val, sec) === __KSYM_##sym ===
> -
> -#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
> +#if defined(CONFIG_TRIM_UNUSED_KSYMS)
>
> #include
> #include
>
> +.macro __ksym_marker sym
> + .section ".discard.ksym","a"
> +__ksym_marker_\sym:
> + .previous
> +.endm
> +
> #define __EXPORT_SYMBOL(sym, val, sec) \
> + __ksym_marker sym; \
> __cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym))
> #define __cond_export_sym(sym, val, sec, conf) \
> ___cond_export_sym(sym, val, sec, conf)
> diff --git a/include/linux/export.h b/include/linux/export.h
> index ce764a5..fd8711e 100644
> --- a/include/linux/export.h
> +++ b/include/linux/export.h
> @@ -92,22 +92,22 @@ struct kernel_symbol {
> */
> #define __EXPORT_SYMBOL(sym, sec)
>
> -#elif defined(__KSYM_DEPS__)
> +#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
> +
> +#include
>
> /*
> * For fine grained build dependencies, we want to tell the build system
> * about each possible exported symbol even if they're not actually exported.
> - * We use a string pattern that is unlikely to be valid code that the build
> - * system filters out from the preprocessor output (see ksym_dep_filter
> - * in scripts/Kbuild.include).
> + * We use a symbol pattern __ksym_marker_ that the build system
> filters
> + * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
> + * discarded in the final link stage.
> */
> -#define __EXPORT_SYMBOL(sym, sec)=== __KSYM_##sym ===
> -
> -#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
> -
> -#include
> +#define __ksym_marker(sym) \
> + static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
>
> #define __EXPORT_SYMBOL(sym, sec)\
> + __ksym_marker(sym); \
> __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
> #define __cond_export_sym(sym, sec, conf)\
> ___cond_export_sym(sym, sec, conf)
> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> index 6cf6a8b..4b943f4 100644
> --- a/scripts/Kbuild.include
> +++ b/scripts/Kbuild.include
> @@ -260,39 +260,11 @@ if_changed_dep = $(if $(strip $(any-prereq)
> $(arg-check) ), \
> @set -e; \
> $(cmd_and_fixdep), @:)
>
> -ifndef CONFIG_TRIM_UNUSED_KSYMS
> -
> cmd_and_fixdep =
> \
> $(echo-cmd) $(cmd_$(1)); \
> scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\
> rm -f $(depfile);
>
> -else
> -
> -# Filter out exported kernel symbol names from the preprocessor output.
> -# See also __KSYM_DEPS__ in include/linux/export.h.
> -# We disable the depfile generation here, so as not to overwrite the existing
> -# depfile while fixdep is parsing it.
>
Re: [PATCH v2 5/9] kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS
On Tue, 20 Nov 2018, Masahiro Yamada wrote:
> My main motivation of this commit is to clean up scripts/Kbuild.include
> and scripts/Makefile.build.
>
> Currently, CONFIG_TRIM_UNUSED_KSYMS works with a tricky gimmick;
> possibly exported symbols are detected by letting $(CPP) replace
> EXPORT_SYMBOL* with a special string '=== __KSYM_*===', which is
> post-processed by sed, and passed to fixdep. The extra preprocessing
> is costly, and hacking cmd_and_fixdep is ugly.
>
> I came up with a new way to find exported symbols; insert a dummy
> symbol __ksym_marker_* to each potentially exported symbol. Those
> dummy symbols are picked up by $(NM), post-processed by sed, then
> appended to .*.cmd files. I collected the post-process part to a
> new shell script scripts/gen_ksymdeps.sh for readability. The dummy
> symbols are put into the .discard.* section so that the linker
> script rips them off the final vmlinux or modules.
>
> A nice side-effect is building with CONFIG_TRIM_UNUSED_KSYMS will
> be much faster.
>
> Signed-off-by: Masahiro Yamada
Nice work.
Reviewed-by: Nicolas Pitre
> ---
>
> Changes in v2:
> - Let gen_ksymdeps.sh add dependencies to .*.cmd file directly
> - Fix typos
>
> include/asm-generic/export.h | 13 -
> include/linux/export.h | 18 +-
> scripts/Kbuild.include | 28
> scripts/Makefile.build | 7 +++
> scripts/basic/fixdep.c | 31 ---
> scripts/gen_ksymdeps.sh | 25 +
> 6 files changed, 53 insertions(+), 69 deletions(-)
> create mode 100755 scripts/gen_ksymdeps.sh
>
> diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
> index 4d73e6e..294d6ae 100644
> --- a/include/asm-generic/export.h
> +++ b/include/asm-generic/export.h
> @@ -59,16 +59,19 @@ __kcrctab_\name:
> .endm
> #undef __put
>
> -#if defined(__KSYM_DEPS__)
> -
> -#define __EXPORT_SYMBOL(sym, val, sec) === __KSYM_##sym ===
> -
> -#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
> +#if defined(CONFIG_TRIM_UNUSED_KSYMS)
>
> #include
> #include
>
> +.macro __ksym_marker sym
> + .section ".discard.ksym","a"
> +__ksym_marker_\sym:
> + .previous
> +.endm
> +
> #define __EXPORT_SYMBOL(sym, val, sec) \
> + __ksym_marker sym; \
> __cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym))
> #define __cond_export_sym(sym, val, sec, conf) \
> ___cond_export_sym(sym, val, sec, conf)
> diff --git a/include/linux/export.h b/include/linux/export.h
> index ce764a5..fd8711e 100644
> --- a/include/linux/export.h
> +++ b/include/linux/export.h
> @@ -92,22 +92,22 @@ struct kernel_symbol {
> */
> #define __EXPORT_SYMBOL(sym, sec)
>
> -#elif defined(__KSYM_DEPS__)
> +#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
> +
> +#include
>
> /*
> * For fine grained build dependencies, we want to tell the build system
> * about each possible exported symbol even if they're not actually exported.
> - * We use a string pattern that is unlikely to be valid code that the build
> - * system filters out from the preprocessor output (see ksym_dep_filter
> - * in scripts/Kbuild.include).
> + * We use a symbol pattern __ksym_marker_ that the build system
> filters
> + * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
> + * discarded in the final link stage.
> */
> -#define __EXPORT_SYMBOL(sym, sec)=== __KSYM_##sym ===
> -
> -#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
> -
> -#include
> +#define __ksym_marker(sym) \
> + static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
>
> #define __EXPORT_SYMBOL(sym, sec)\
> + __ksym_marker(sym); \
> __cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
> #define __cond_export_sym(sym, sec, conf)\
> ___cond_export_sym(sym, sec, conf)
> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> index 6cf6a8b..4b943f4 100644
> --- a/scripts/Kbuild.include
> +++ b/scripts/Kbuild.include
> @@ -260,39 +260,11 @@ if_changed_dep = $(if $(strip $(any-prereq)
> $(arg-check) ), \
> @set -e; \
> $(cmd_and_fixdep), @:)
>
> -ifndef CONFIG_TRIM_UNUSED_KSYMS
> -
> cmd_and_fixdep =
> \
> $(echo-cmd) $(cmd_$(1)); \
> scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\
> rm -f $(depfile);
>
> -else
> -
> -# Filter out exported kernel symbol names from the preprocessor output.
> -# See also __KSYM_DEPS__ in include/linux/export.h.
> -# We disable the depfile generation here, so as not to overwrite the existing
> -# depfile while fixdep is parsing it.
>
[PATCH v2 5/9] kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS
My main motivation of this commit is to clean up scripts/Kbuild.include
and scripts/Makefile.build.
Currently, CONFIG_TRIM_UNUSED_KSYMS works with a tricky gimmick;
possibly exported symbols are detected by letting $(CPP) replace
EXPORT_SYMBOL* with a special string '=== __KSYM_*===', which is
post-processed by sed, and passed to fixdep. The extra preprocessing
is costly, and hacking cmd_and_fixdep is ugly.
I came up with a new way to find exported symbols; insert a dummy
symbol __ksym_marker_* to each potentially exported symbol. Those
dummy symbols are picked up by $(NM), post-processed by sed, then
appended to .*.cmd files. I collected the post-process part to a
new shell script scripts/gen_ksymdeps.sh for readability. The dummy
symbols are put into the .discard.* section so that the linker
script rips them off the final vmlinux or modules.
A nice side-effect is building with CONFIG_TRIM_UNUSED_KSYMS will
be much faster.
Signed-off-by: Masahiro Yamada
---
Changes in v2:
- Let gen_ksymdeps.sh add dependencies to .*.cmd file directly
- Fix typos
include/asm-generic/export.h | 13 -
include/linux/export.h | 18 +-
scripts/Kbuild.include | 28
scripts/Makefile.build | 7 +++
scripts/basic/fixdep.c | 31 ---
scripts/gen_ksymdeps.sh | 25 +
6 files changed, 53 insertions(+), 69 deletions(-)
create mode 100755 scripts/gen_ksymdeps.sh
diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
index 4d73e6e..294d6ae 100644
--- a/include/asm-generic/export.h
+++ b/include/asm-generic/export.h
@@ -59,16 +59,19 @@ __kcrctab_\name:
.endm
#undef __put
-#if defined(__KSYM_DEPS__)
-
-#define __EXPORT_SYMBOL(sym, val, sec) === __KSYM_##sym ===
-
-#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
+#if defined(CONFIG_TRIM_UNUSED_KSYMS)
#include
#include
+.macro __ksym_marker sym
+ .section ".discard.ksym","a"
+__ksym_marker_\sym:
+.previous
+.endm
+
#define __EXPORT_SYMBOL(sym, val, sec) \
+ __ksym_marker sym; \
__cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym))
#define __cond_export_sym(sym, val, sec, conf) \
___cond_export_sym(sym, val, sec, conf)
diff --git a/include/linux/export.h b/include/linux/export.h
index ce764a5..fd8711e 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -92,22 +92,22 @@ struct kernel_symbol {
*/
#define __EXPORT_SYMBOL(sym, sec)
-#elif defined(__KSYM_DEPS__)
+#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
+
+#include
/*
* For fine grained build dependencies, we want to tell the build system
* about each possible exported symbol even if they're not actually exported.
- * We use a string pattern that is unlikely to be valid code that the build
- * system filters out from the preprocessor output (see ksym_dep_filter
- * in scripts/Kbuild.include).
+ * We use a symbol pattern __ksym_marker_ that the build system filters
+ * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
+ * discarded in the final link stage.
*/
-#define __EXPORT_SYMBOL(sym, sec) === __KSYM_##sym ===
-
-#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
-
-#include
+#define __ksym_marker(sym) \
+ static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
#define __EXPORT_SYMBOL(sym, sec) \
+ __ksym_marker(sym); \
__cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
#define __cond_export_sym(sym, sec, conf) \
___cond_export_sym(sym, sec, conf)
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 6cf6a8b..4b943f4 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -260,39 +260,11 @@ if_changed_dep = $(if $(strip $(any-prereq) $(arg-check)
), \
@set -e; \
$(cmd_and_fixdep), @:)
-ifndef CONFIG_TRIM_UNUSED_KSYMS
-
cmd_and_fixdep = \
$(echo-cmd) $(cmd_$(1)); \
scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\
rm -f $(depfile);
-else
-
-# Filter out exported kernel symbol names from the preprocessor output.
-# See also __KSYM_DEPS__ in include/linux/export.h.
-# We disable the depfile generation here, so as not to overwrite the existing
-# depfile while fixdep is parsing it.
-flags_nodeps = $(filter-out -Wp$(comma)-M%, $($(1)))
-ksym_dep_filter =\
- case "$(1)" in \
- cc_*_c|cpp_i_c)\
- $(CPP) $(call
[PATCH v2 5/9] kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS
My main motivation of this commit is to clean up scripts/Kbuild.include
and scripts/Makefile.build.
Currently, CONFIG_TRIM_UNUSED_KSYMS works with a tricky gimmick;
possibly exported symbols are detected by letting $(CPP) replace
EXPORT_SYMBOL* with a special string '=== __KSYM_*===', which is
post-processed by sed, and passed to fixdep. The extra preprocessing
is costly, and hacking cmd_and_fixdep is ugly.
I came up with a new way to find exported symbols; insert a dummy
symbol __ksym_marker_* to each potentially exported symbol. Those
dummy symbols are picked up by $(NM), post-processed by sed, then
appended to .*.cmd files. I collected the post-process part to a
new shell script scripts/gen_ksymdeps.sh for readability. The dummy
symbols are put into the .discard.* section so that the linker
script rips them off the final vmlinux or modules.
A nice side-effect is building with CONFIG_TRIM_UNUSED_KSYMS will
be much faster.
Signed-off-by: Masahiro Yamada
---
Changes in v2:
- Let gen_ksymdeps.sh add dependencies to .*.cmd file directly
- Fix typos
include/asm-generic/export.h | 13 -
include/linux/export.h | 18 +-
scripts/Kbuild.include | 28
scripts/Makefile.build | 7 +++
scripts/basic/fixdep.c | 31 ---
scripts/gen_ksymdeps.sh | 25 +
6 files changed, 53 insertions(+), 69 deletions(-)
create mode 100755 scripts/gen_ksymdeps.sh
diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
index 4d73e6e..294d6ae 100644
--- a/include/asm-generic/export.h
+++ b/include/asm-generic/export.h
@@ -59,16 +59,19 @@ __kcrctab_\name:
.endm
#undef __put
-#if defined(__KSYM_DEPS__)
-
-#define __EXPORT_SYMBOL(sym, val, sec) === __KSYM_##sym ===
-
-#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
+#if defined(CONFIG_TRIM_UNUSED_KSYMS)
#include
#include
+.macro __ksym_marker sym
+ .section ".discard.ksym","a"
+__ksym_marker_\sym:
+.previous
+.endm
+
#define __EXPORT_SYMBOL(sym, val, sec) \
+ __ksym_marker sym; \
__cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym))
#define __cond_export_sym(sym, val, sec, conf) \
___cond_export_sym(sym, val, sec, conf)
diff --git a/include/linux/export.h b/include/linux/export.h
index ce764a5..fd8711e 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -92,22 +92,22 @@ struct kernel_symbol {
*/
#define __EXPORT_SYMBOL(sym, sec)
-#elif defined(__KSYM_DEPS__)
+#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
+
+#include
/*
* For fine grained build dependencies, we want to tell the build system
* about each possible exported symbol even if they're not actually exported.
- * We use a string pattern that is unlikely to be valid code that the build
- * system filters out from the preprocessor output (see ksym_dep_filter
- * in scripts/Kbuild.include).
+ * We use a symbol pattern __ksym_marker_ that the build system filters
+ * from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
+ * discarded in the final link stage.
*/
-#define __EXPORT_SYMBOL(sym, sec) === __KSYM_##sym ===
-
-#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
-
-#include
+#define __ksym_marker(sym) \
+ static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
#define __EXPORT_SYMBOL(sym, sec) \
+ __ksym_marker(sym); \
__cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
#define __cond_export_sym(sym, sec, conf) \
___cond_export_sym(sym, sec, conf)
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 6cf6a8b..4b943f4 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -260,39 +260,11 @@ if_changed_dep = $(if $(strip $(any-prereq) $(arg-check)
), \
@set -e; \
$(cmd_and_fixdep), @:)
-ifndef CONFIG_TRIM_UNUSED_KSYMS
-
cmd_and_fixdep = \
$(echo-cmd) $(cmd_$(1)); \
scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\
rm -f $(depfile);
-else
-
-# Filter out exported kernel symbol names from the preprocessor output.
-# See also __KSYM_DEPS__ in include/linux/export.h.
-# We disable the depfile generation here, so as not to overwrite the existing
-# depfile while fixdep is parsing it.
-flags_nodeps = $(filter-out -Wp$(comma)-M%, $($(1)))
-ksym_dep_filter =\
- case "$(1)" in \
- cc_*_c|cpp_i_c)\
- $(CPP) $(call
