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[XEN PATCH v7 05/51] x86/mm: avoid building multiple .o from a single .c file

  • To: <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Anthony PERARD <anthony.perard@xxxxxxxxxx>
  • Date: Tue, 24 Aug 2021 11:49:52 +0100
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  • Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>
  • Delivery-date: Tue, 24 Aug 2021 10:51:12 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
This replace the use of a single .c file use for multiple .o file by
creating multiple .c file including the first one.

There's quite a few issues with trying to build more than one object
file from a single source file: there's is a duplication of the make
rules to generate those targets; there is an additional ".file" symbol
added in order to differentiate between the object files; and the
tools/symbols have an heuristic to try to pick up the right ".file".

This patch adds new .c source file which avoid the need to add a
second ".file" symbol and thus avoid the need to deal with those
issues.

Also remove __OBJECT_FILE__ from $(CC) command line as it isn't used
anywhere anymore. And remove the macro "build-intermediate" since the
generic rules for single targets can be used.

And rename the objects in mm/hap/ to remove the extra "level".

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---

Notes:
    v7:
    - rename hap/guest_walk_${level}level.c to hap/guest_walk_${level}.c
    
    v6:
    - new patch
      to replace both from v5:
        xen,symbols: rework file symbols selection
        build: use if_changed to build mm/*/guest_%.o
    
    The changes in the patch for symbols.c was too complicated to explain,
    and I probably didn't realize one important fact about the tool: it deal
    with all *.o been concatenated to each other, without a way to figure
    out which symbol belong to which original file, and certainly no way to
    figure out if there's more than one ".file" symbol to choose from beside
    some fragile heuristic.

 xen/Makefile                       | 11 -----------
 xen/Rules.mk                       |  2 +-
 xen/arch/x86/mm/Makefile           |  9 ---------
 xen/arch/x86/mm/guest_walk.c       |  3 ---
 xen/arch/x86/mm/guest_walk_2.c     |  2 ++
 xen/arch/x86/mm/guest_walk_3.c     |  2 ++
 xen/arch/x86/mm/guest_walk_4.c     |  2 ++
 xen/arch/x86/mm/hap/Makefile       | 15 +++------------
 xen/arch/x86/mm/hap/guest_walk.c   |  3 ---
 xen/arch/x86/mm/hap/guest_walk_2.c |  2 ++
 xen/arch/x86/mm/hap/guest_walk_3.c |  2 ++
 xen/arch/x86/mm/hap/guest_walk_4.c |  2 ++
 xen/arch/x86/mm/shadow/Makefile    |  9 ---------
 xen/arch/x86/mm/shadow/guest_2.c   |  2 ++
 xen/arch/x86/mm/shadow/guest_3.c   |  2 ++
 xen/arch/x86/mm/shadow/guest_4.c   |  2 ++
 xen/arch/x86/mm/shadow/multi.c     |  3 ---
 xen/tools/symbols.c                | 18 ++----------------
 18 files changed, 24 insertions(+), 67 deletions(-)
 create mode 100644 xen/arch/x86/mm/guest_walk_2.c
 create mode 100644 xen/arch/x86/mm/guest_walk_3.c
 create mode 100644 xen/arch/x86/mm/guest_walk_4.c
 create mode 100644 xen/arch/x86/mm/hap/guest_walk_2.c
 create mode 100644 xen/arch/x86/mm/hap/guest_walk_3.c
 create mode 100644 xen/arch/x86/mm/hap/guest_walk_4.c
 create mode 100644 xen/arch/x86/mm/shadow/guest_2.c
 create mode 100644 xen/arch/x86/mm/shadow/guest_3.c
 create mode 100644 xen/arch/x86/mm/shadow/guest_4.c

diff --git a/xen/Makefile b/xen/Makefile
index 4ceb02d37441..f35a4d84f7cd 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -482,17 +482,6 @@ _MAP:
 %/: FORCE
        $(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in.o built_in_bin.o
 
-build-intermediate = $(eval $(call build-intermediate-closure,$(1)))
-define build-intermediate-closure
-$(1): FORCE
-       $(MAKE) -f $(BASEDIR)/Rules.mk -C $$(@D) $$(@F)
-endef
-
-$(foreach base,arch/x86/mm/guest_walk_% \
-               arch/x86/mm/hap/guest_walk_%level \
-               arch/x86/mm/shadow/guest_%, \
-    $(foreach ext,o i s,$(call build-intermediate,$(base).$(ext))))
-
 .PHONY: cloc
 cloc:
        $(eval tmpfile := $(shell mktemp))
diff --git a/xen/Rules.mk b/xen/Rules.mk
index 3f61682ceab7..48ae519d0153 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -139,7 +139,7 @@ cpp_flags = $(filter-out -Wa$(comma)% -flto,$(1))
 # Calculation of flags, first the generic flags, then the arch specific flags,
 # and last the flags modified for a target or a directory.
 
-c_flags = -MMD -MP -MF $(@D)/.$(@F).d $(XEN_CFLAGS) '-D__OBJECT_FILE__="$@"'
+c_flags = -MMD -MP -MF $(@D)/.$(@F).d $(XEN_CFLAGS)
 a_flags = -MMD -MP -MF $(@D)/.$(@F).d $(XEN_AFLAGS)
 
 include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
diff --git a/xen/arch/x86/mm/Makefile b/xen/arch/x86/mm/Makefile
index 2818c066f76a..6b7882d992bb 100644
--- a/xen/arch/x86/mm/Makefile
+++ b/xen/arch/x86/mm/Makefile
@@ -10,12 +10,3 @@ obj-$(CONFIG_MEM_SHARING) += mem_sharing.o
 obj-y += p2m.o
 obj-$(CONFIG_HVM) += p2m-ept.o p2m-pod.o p2m-pt.o
 obj-y += paging.o
-
-guest_walk_%.o: guest_walk.c Makefile
-       $(CC) $(c_flags) -DGUEST_PAGING_LEVELS=$* -c $< -o $@
-
-guest_walk_%.i: guest_walk.c Makefile
-       $(CPP) $(call cpp_flags,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -c $< -o $@
-
-guest_walk_%.s: guest_walk.c Makefile
-       $(CC) $(filter-out -Wa$(comma)%,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -S 
$< -o $@
diff --git a/xen/arch/x86/mm/guest_walk.c b/xen/arch/x86/mm/guest_walk.c
index 30d83cf1e0e6..b9f607272c39 100644
--- a/xen/arch/x86/mm/guest_walk.c
+++ b/xen/arch/x86/mm/guest_walk.c
@@ -21,9 +21,6 @@
  * along with this program; If not, see <http://www.gnu.org/licenses/>.
  */
 
-/* Allow uniquely identifying static symbols in the 3 generated objects. */
-asm(".file \"" __OBJECT_FILE__ "\"");
-
 #include <xen/types.h>
 #include <xen/mm.h>
 #include <xen/paging.h>
diff --git a/xen/arch/x86/mm/guest_walk_2.c b/xen/arch/x86/mm/guest_walk_2.c
new file mode 100644
index 000000000000..defcd59bc260
--- /dev/null
+++ b/xen/arch/x86/mm/guest_walk_2.c
@@ -0,0 +1,2 @@
+#define GUEST_PAGING_LEVELS 2
+#include "guest_walk.c"
diff --git a/xen/arch/x86/mm/guest_walk_3.c b/xen/arch/x86/mm/guest_walk_3.c
new file mode 100644
index 000000000000..1c9eca37741e
--- /dev/null
+++ b/xen/arch/x86/mm/guest_walk_3.c
@@ -0,0 +1,2 @@
+#define GUEST_PAGING_LEVELS 3
+#include "guest_walk.c"
diff --git a/xen/arch/x86/mm/guest_walk_4.c b/xen/arch/x86/mm/guest_walk_4.c
new file mode 100644
index 000000000000..aa3900338a2d
--- /dev/null
+++ b/xen/arch/x86/mm/guest_walk_4.c
@@ -0,0 +1,2 @@
+#define GUEST_PAGING_LEVELS 4
+#include "guest_walk.c"
diff --git a/xen/arch/x86/mm/hap/Makefile b/xen/arch/x86/mm/hap/Makefile
index c6d296b51720..8ef54b1faa50 100644
--- a/xen/arch/x86/mm/hap/Makefile
+++ b/xen/arch/x86/mm/hap/Makefile
@@ -1,15 +1,6 @@
 obj-y += hap.o
-obj-y += guest_walk_2level.o
-obj-y += guest_walk_3level.o
-obj-y += guest_walk_4level.o
+obj-y += guest_walk_2.o
+obj-y += guest_walk_3.o
+obj-y += guest_walk_4.o
 obj-y += nested_hap.o
 obj-y += nested_ept.o
-
-guest_walk_%level.o: guest_walk.c Makefile
-       $(CC) $(c_flags) -DGUEST_PAGING_LEVELS=$* -c $< -o $@
-
-guest_walk_%level.i: guest_walk.c Makefile
-       $(CPP) $(call cpp_flags,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -c $< -o $@
-
-guest_walk_%level.s: guest_walk.c Makefile
-       $(CC) $(filter-out -Wa$(comma)%,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -S 
$< -o $@
diff --git a/xen/arch/x86/mm/hap/guest_walk.c b/xen/arch/x86/mm/hap/guest_walk.c
index f59ebc84a290..832a8058471e 100644
--- a/xen/arch/x86/mm/hap/guest_walk.c
+++ b/xen/arch/x86/mm/hap/guest_walk.c
@@ -18,9 +18,6 @@
  * this program; If not, see <http://www.gnu.org/licenses/>.
  */
 
-/* Allow uniquely identifying static symbols in the 3 generated objects. */
-asm(".file \"" __OBJECT_FILE__ "\"");
-
 #include <xen/domain_page.h>
 #include <xen/paging.h>
 #include <xen/sched.h>
diff --git a/xen/arch/x86/mm/hap/guest_walk_2.c 
b/xen/arch/x86/mm/hap/guest_walk_2.c
new file mode 100644
index 000000000000..defcd59bc260
--- /dev/null
+++ b/xen/arch/x86/mm/hap/guest_walk_2.c
@@ -0,0 +1,2 @@
+#define GUEST_PAGING_LEVELS 2
+#include "guest_walk.c"
diff --git a/xen/arch/x86/mm/hap/guest_walk_3.c 
b/xen/arch/x86/mm/hap/guest_walk_3.c
new file mode 100644
index 000000000000..1c9eca37741e
--- /dev/null
+++ b/xen/arch/x86/mm/hap/guest_walk_3.c
@@ -0,0 +1,2 @@
+#define GUEST_PAGING_LEVELS 3
+#include "guest_walk.c"
diff --git a/xen/arch/x86/mm/hap/guest_walk_4.c 
b/xen/arch/x86/mm/hap/guest_walk_4.c
new file mode 100644
index 000000000000..aa3900338a2d
--- /dev/null
+++ b/xen/arch/x86/mm/hap/guest_walk_4.c
@@ -0,0 +1,2 @@
+#define GUEST_PAGING_LEVELS 4
+#include "guest_walk.c"
diff --git a/xen/arch/x86/mm/shadow/Makefile b/xen/arch/x86/mm/shadow/Makefile
index fd64b4dda925..b4a1620b6920 100644
--- a/xen/arch/x86/mm/shadow/Makefile
+++ b/xen/arch/x86/mm/shadow/Makefile
@@ -5,12 +5,3 @@ obj-$(CONFIG_PV) += pv.o guest_4.o
 else
 obj-y += none.o
 endif
-
-guest_%.o: multi.c Makefile
-       $(CC) $(c_flags) -DGUEST_PAGING_LEVELS=$* -c $< -o $@
-
-guest_%.i: multi.c Makefile
-       $(CPP) $(call cpp_flags,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -c $< -o $@
-
-guest_%.s: multi.c Makefile
-       $(CC) $(filter-out -Wa$(comma)%,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -S 
$< -o $@
diff --git a/xen/arch/x86/mm/shadow/guest_2.c b/xen/arch/x86/mm/shadow/guest_2.c
new file mode 100644
index 000000000000..288b229982b0
--- /dev/null
+++ b/xen/arch/x86/mm/shadow/guest_2.c
@@ -0,0 +1,2 @@
+#define GUEST_PAGING_LEVELS 2
+#include "multi.c"
diff --git a/xen/arch/x86/mm/shadow/guest_3.c b/xen/arch/x86/mm/shadow/guest_3.c
new file mode 100644
index 000000000000..04e17b0b8adc
--- /dev/null
+++ b/xen/arch/x86/mm/shadow/guest_3.c
@@ -0,0 +1,2 @@
+#define GUEST_PAGING_LEVELS 3
+#include "multi.c"
diff --git a/xen/arch/x86/mm/shadow/guest_4.c b/xen/arch/x86/mm/shadow/guest_4.c
new file mode 100644
index 000000000000..c0c5d3cb11ad
--- /dev/null
+++ b/xen/arch/x86/mm/shadow/guest_4.c
@@ -0,0 +1,2 @@
+#define GUEST_PAGING_LEVELS 4
+#include "multi.c"
diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index 8bb028c2e2fa..7207fcf9e75f 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -20,9 +20,6 @@
  * along with this program; If not, see <http://www.gnu.org/licenses/>.
  */
 
-/* Allow uniquely identifying static symbols in the 3 generated objects. */
-asm(".file \"" __OBJECT_FILE__ "\"");
-
 #include <xen/types.h>
 #include <xen/mm.h>
 #include <xen/trace.h>
diff --git a/xen/tools/symbols.c b/xen/tools/symbols.c
index 0b124526165d..710e9785d348 100644
--- a/xen/tools/symbols.c
+++ b/xen/tools/symbols.c
@@ -84,7 +84,6 @@ static int read_symbol(FILE *in, struct sym_entry *s)
 {
        char str[500], type[20] = "";
        char *sym, stype;
-       static enum { symbol, single_source, multi_source } last;
        static char *filename;
        int rc = -1;
 
@@ -118,24 +117,11 @@ static int read_symbol(FILE *in, struct sym_entry *s)
              */
             input_format == fmt_sysv && !*type && stype == '?' && sym &&
             sym[1] && strchr("cSsoh", sym[1]) && !sym[2])) {
-               /*
-                * gas prior to binutils commit fbdf9406b0 (expected to appear
-                * in 2.27) outputs symbol table entries resulting from .file
-                * in reverse order. If we get two consecutive file symbols,
-                * prefer the first one if that names an object file or has a
-                * directory component (to cover multiply compiled files).
-                */
-               bool multi = strchr(str, '/') || (sym && sym[1] == 'o');
-
-               if (multi || last != multi_source) {
-                       free(filename);
-                       filename = *str ? strdup(str) : NULL;
-               }
-               last = multi ? multi_source : single_source;
+               free(filename);
+               filename = *str ? strdup(str) : NULL;
                goto skip_tail;
        }
 
-       last = symbol;
        rc = -1;
 
        sym = str;
-- 
Anthony PERARD

 

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