On 9/1/20 10:25 PM, Nick Desaulniers wrote:
Rather than invoke the compiler as the driver, use the linker. That way
we can check --orphan-handling=warn support correctly, as cc-ldoption
was removed in
commit 055efab3120b ("kbuild: drop support for cc-ldoption").
Requires dropping the .got section. I couldn't find how it was used in
the vdso32.
Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan
sections")
Link:
https://lore.kernel.org/lkml/cakwvodnn3wxydjomvnveyd_njwrku3fabwt_bs92duihhyw...@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulni...@google.com>
---
Not sure removing .got is a good idea or not. Otherwise I observe the
following link error:
powerpc-linux-gnu-ld: warning: orphan section `.got' from
`arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.got'
powerpc-linux-gnu-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc-linux-gnu-ld: final link failed: bad value
sigtramp.c doesn't mention anything from the GOT AFAICT, and doesn't
look like it contains relocations that do, so I'm not sure where
references to _GLOBAL_OFFSET_TABLE_ are coming from.
I'm getting the same but only when building for PPC64.
I don't get any reference to sigtramp.o though:
CALL scripts/checksyscalls.sh
CALL scripts/atomic/check-atomics.sh
VDSO32A arch/powerpc/kernel/vdso32/sigtramp.o
VDSO32A arch/powerpc/kernel/vdso32/gettimeofday.o
VDSO32A arch/powerpc/kernel/vdso32/datapage.o
VDSO32A arch/powerpc/kernel/vdso32/cacheflush.o
VDSO32A arch/powerpc/kernel/vdso32/note.o
VDSO32A arch/powerpc/kernel/vdso32/getcpu.o
LD arch/powerpc/kernel/vdso32/vdso32.so.dbg
powerpc64-linux-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc64-linux-ld: final link failed: Bad value
(GCC 8.1, Binutils 2.30)
So it seems that the got section is being created by the linker. Don't
know why though.
With GCC 10.1, binutils 2.34 I get:
LDS arch/powerpc/kernel/vdso32/vdso32.lds
VDSO32A arch/powerpc/kernel/vdso32/sigtramp.o
VDSO32A arch/powerpc/kernel/vdso32/gettimeofday.o
VDSO32A arch/powerpc/kernel/vdso32/datapage.o
VDSO32A arch/powerpc/kernel/vdso32/cacheflush.o
VDSO32A arch/powerpc/kernel/vdso32/note.o
VDSO32A arch/powerpc/kernel/vdso32/getcpu.o
LD arch/powerpc/kernel/vdso32/vdso32.so.dbg
powerpc64-linux-ld: warning: orphan section `.branch_lt' from
`arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.branch_lt'
powerpc64-linux-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc64-linux-ld: final link failed: bad value
I can't see any .branch_lt section when objdumping sigtramp.o or any
other .o
When I move sigtramp.o at the end of the definition of obj-vdso32 in
Makefile, I then get:
powerpc64-linux-ld: warning: orphan section `.branch_lt' from
`arch/powerpc/kernel/vdso32/gettimeofday.o' being placed in section
`.branch_lt'
powerpc64-linux-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc64-linux-ld: final link failed: bad value
gettimeofday.o now being the first object in obj-vdso32
Christophe
arch/powerpc/kernel/vdso32/Makefile | 7 +++++--
arch/powerpc/kernel/vdso32/vdso32.lds.S | 3 ++-
2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kernel/vdso32/Makefile
b/arch/powerpc/kernel/vdso32/Makefile
index 87ab1152d5ce..611a5951945a 100644
--- a/arch/powerpc/kernel/vdso32/Makefile
+++ b/arch/powerpc/kernel/vdso32/Makefile
@@ -27,6 +27,9 @@ UBSAN_SANITIZE := n
ccflags-y := -shared -fno-common -fno-builtin -nostdlib \
-Wl,-soname=linux-vdso32.so.1 -Wl,--hash-style=both
asflags-y := -D__VDSO32__ -s
+ldflags-y := -shared -soname linux-vdso32.so.1 \
+ $(call ld-option, --eh-frame-hdr) \
+ $(call ld-option, --orphan-handling=warn) -T
obj-y += vdso32_wrapper.o
extra-y += vdso32.lds
@@ -49,8 +52,8 @@ $(obj-vdso32): %.o: %.S FORCE
$(call if_changed_dep,vdso32as)
# actual build commands
-quiet_cmd_vdso32ld = VDSO32L $@
- cmd_vdso32ld = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ $(call
cc-ldoption, -Wl$(comma)--orphan-handling=warn) -Wl,-T$(filter %.lds,$^)
$(filter %.o,$^)
+quiet_cmd_vdso32ld = LD $@
+ cmd_vdso32ld = $(cmd_ld)
quiet_cmd_vdso32as = VDSO32A $@
cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) -c -o $@ $<
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 4c985467a668..0ccdebad18b8 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -61,7 +61,6 @@ SECTIONS
.fixup : { *(.fixup) }
.dynamic : { *(.dynamic) } :text :dynamic
- .got : { *(.got) } :text
.plt : { *(.plt) }
_end = .;
@@ -108,7 +107,9 @@ SECTIONS
.debug_varnames 0 : { *(.debug_varnames) }
/DISCARD/ : {
+ *(.got)
*(.note.GNU-stack)
+ *(.branch_lt)
*(.data .data.* .gnu.linkonce.d.* .sdata*)
*(.bss .sbss .dynbss .dynsbss)
*(.glink .iplt .plt .rela*)
