We were relying on GNU ld's ability to re-link executable files in order to extract our VDSO symbols. This behavior was deemed a bug as of binutils-2.35 (specifically the binutils-gdb commit a87e1817a4 ("Have the linker fail if any attempt to link in an executable is made."), but as that has been backported to at least Debian's binutils-2.34 in may manifest in other places.
The previous version of this was a bit of a mess: we were linking a static executable version of the VDSO, containing only a subset of the input symbols, which we then linked into the kernel. This worked, but certainly wasn't a supported path through the toolchain. Instead this new version parses the textual output of nm to produce a symbol table. Both rely on near-zero addresses being linkable, but as we rely on weak undefined symbols being linkable elsewhere I don't view this as a major issue.
Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API") Cc: clang-built-linux@googlegroups.com Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt palmerdabbelt@google.com
---
Changes since v2 20201019235630.762886-1-palmerdabbelt@google.com:
* Uses $(srctree)/$(src) to allow for out-of-tree builds.
Changes since v1 20201017002500.503011-1-palmerdabbelt@google.com:
* Uses $(NM) instead of $(CROSS_COMPILE)nm. We use the $(CROSS_COMPILE) form elsewhere in this file, but we'll fix that later. * Removed the unnecesary .map file creation.
--- arch/riscv/kernel/vdso/.gitignore | 1 + arch/riscv/kernel/vdso/Makefile | 17 ++++++++--------- arch/riscv/kernel/vdso/so2s.sh | 6 ++++++ 3 files changed, 15 insertions(+), 9 deletions(-) create mode 100755 arch/riscv/kernel/vdso/so2s.sh
diff --git a/arch/riscv/kernel/vdso/.gitignore b/arch/riscv/kernel/vdso/.gitignore index 11ebee9e4c1d..3a19def868ec 100644 --- a/arch/riscv/kernel/vdso/.gitignore +++ b/arch/riscv/kernel/vdso/.gitignore @@ -1,3 +1,4 @@ # SPDX-License-Identifier: GPL-2.0-only vdso.lds *.tmp +vdso-syms.S diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile index 478e7338ddc1..a8ecf102e09b 100644 --- a/arch/riscv/kernel/vdso/Makefile +++ b/arch/riscv/kernel/vdso/Makefile @@ -43,19 +43,14 @@ $(obj)/vdso.o: $(obj)/vdso.so SYSCFLAGS_vdso.so.dbg = $(c_flags) $(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso) FORCE $(call if_changed,vdsold) +SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \ + -Wl,--build-id -Wl,--hash-style=both
# We also create a special relocatable object that should mirror the symbol # table and layout of the linked DSO. With ld --just-symbols we can then # refer to these symbols in the kernel code rather than hand-coded addresses. - -SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \ - -Wl,--build-id -Wl,--hash-style=both -$(obj)/vdso-dummy.o: $(src)/vdso.lds $(obj)/rt_sigreturn.o FORCE - $(call if_changed,vdsold) - -LDFLAGS_vdso-syms.o := -r --just-symbols -$(obj)/vdso-syms.o: $(obj)/vdso-dummy.o FORCE - $(call if_changed,ld) +$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE + $(call if_changed,so2s)
# strip rule for the .so file $(obj)/%.so: OBJCOPYFLAGS := -S @@ -73,6 +68,10 @@ quiet_cmd_vdsold = VDSOLD $@ $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \ rm $@.tmp
+# Extracts +quiet_cmd_so2s = SO2S $@ + cmd_so2s = $(NM) -D $< | $(srctree)/$(src)/so2s.sh > $@ + # install commands for the unstripped file quiet_cmd_vdso_install = INSTALL $@ cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@ diff --git a/arch/riscv/kernel/vdso/so2s.sh b/arch/riscv/kernel/vdso/so2s.sh new file mode 100755 index 000000000000..3c5b43207658 --- /dev/null +++ b/arch/riscv/kernel/vdso/so2s.sh @@ -0,0 +1,6 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0+ +# Copyright 2020 Palmer Dabbelt palmerdabbelt@google.com + +sed 's!([0-9a-f]*) T ([a-z0-9_]*)@@LINUX_4.15!.global \2\n.set \2,0x\1!' \ +| grep '^.'
On Fri, Oct 23, 2020 at 10:03 PM 'Palmer Dabbelt' via Clang Built Linux clang-built-linux@googlegroups.com wrote:
We were relying on GNU ld's ability to re-link executable files in order to extract our VDSO symbols. This behavior was deemed a bug as of binutils-2.35 (specifically the binutils-gdb commit a87e1817a4 ("Have the linker fail if any attempt to link in an executable is made."), but as that has been backported to at least Debian's binutils-2.34 in may manifest in other places.
The previous version of this was a bit of a mess: we were linking a static executable version of the VDSO, containing only a subset of the input symbols, which we then linked into the kernel. This worked, but certainly wasn't a supported path through the toolchain. Instead this new version parses the textual output of nm to produce a symbol table. Both rely on near-zero addresses being linkable, but as we rely on weak undefined symbols being linkable elsewhere I don't view this as a major issue.
Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API") Cc: clang-built-linux@googlegroups.com Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt palmerdabbelt@google.com
Any way to improve the error message if/when this fails? https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/407...
Changes since v2 20201019235630.762886-1-palmerdabbelt@google.com:
- Uses $(srctree)/$(src) to allow for out-of-tree builds.
Changes since v1 20201017002500.503011-1-palmerdabbelt@google.com:
- Uses $(NM) instead of $(CROSS_COMPILE)nm. We use the $(CROSS_COMPILE) form elsewhere in this file, but we'll fix that later.
- Removed the unnecesary .map file creation.
arch/riscv/kernel/vdso/.gitignore | 1 + arch/riscv/kernel/vdso/Makefile | 17 ++++++++--------- arch/riscv/kernel/vdso/so2s.sh | 6 ++++++ 3 files changed, 15 insertions(+), 9 deletions(-) create mode 100755 arch/riscv/kernel/vdso/so2s.sh
diff --git a/arch/riscv/kernel/vdso/.gitignore b/arch/riscv/kernel/vdso/.gitignore index 11ebee9e4c1d..3a19def868ec 100644 --- a/arch/riscv/kernel/vdso/.gitignore +++ b/arch/riscv/kernel/vdso/.gitignore @@ -1,3 +1,4 @@ # SPDX-License-Identifier: GPL-2.0-only vdso.lds *.tmp +vdso-syms.S diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile index 478e7338ddc1..a8ecf102e09b 100644 --- a/arch/riscv/kernel/vdso/Makefile +++ b/arch/riscv/kernel/vdso/Makefile @@ -43,19 +43,14 @@ $(obj)/vdso.o: $(obj)/vdso.so SYSCFLAGS_vdso.so.dbg = $(c_flags) $(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso) FORCE $(call if_changed,vdsold) +SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
-Wl,--build-id -Wl,--hash-style=both# We also create a special relocatable object that should mirror the symbol # table and layout of the linked DSO. With ld --just-symbols we can then # refer to these symbols in the kernel code rather than hand-coded addresses.
-SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
-Wl,--build-id -Wl,--hash-style=both-$(obj)/vdso-dummy.o: $(src)/vdso.lds $(obj)/rt_sigreturn.o FORCE
$(call if_changed,vdsold)-LDFLAGS_vdso-syms.o := -r --just-symbols -$(obj)/vdso-syms.o: $(obj)/vdso-dummy.o FORCE
$(call if_changed,ld)+$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE
$(call if_changed,so2s)# strip rule for the .so file $(obj)/%.so: OBJCOPYFLAGS := -S @@ -73,6 +68,10 @@ quiet_cmd_vdsold = VDSOLD $@ $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \ rm $@.tmp
+# Extracts +quiet_cmd_so2s = SO2S $@
cmd_so2s = $(NM) -D $< | $(srctree)/$(src)/so2s.sh > $@# install commands for the unstripped file quiet_cmd_vdso_install = INSTALL $@ cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@ diff --git a/arch/riscv/kernel/vdso/so2s.sh b/arch/riscv/kernel/vdso/so2s.sh new file mode 100755 index 000000000000..3c5b43207658 --- /dev/null +++ b/arch/riscv/kernel/vdso/so2s.sh @@ -0,0 +1,6 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0+ +# Copyright 2020 Palmer Dabbelt palmerdabbelt@google.com
+sed 's!([0-9a-f]*) T ([a-z0-9_]*)@@LINUX_4.15!.global \2\n.set \2,0x\1!' \
+| grep '^.'
2.29.0.rc1.297.gfa9743e501-goog
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On Mon, 26 Oct 2020 12:48:08 PDT (-0700), Nick Desaulniers wrote:
On Fri, Oct 23, 2020 at 10:03 PM 'Palmer Dabbelt' via Clang Built Linux clang-built-linux@googlegroups.com wrote:
We were relying on GNU ld's ability to re-link executable files in order to extract our VDSO symbols. This behavior was deemed a bug as of binutils-2.35 (specifically the binutils-gdb commit a87e1817a4 ("Have the linker fail if any attempt to link in an executable is made."), but as that has been backported to at least Debian's binutils-2.34 in may manifest in other places.
The previous version of this was a bit of a mess: we were linking a static executable version of the VDSO, containing only a subset of the input symbols, which we then linked into the kernel. This worked, but certainly wasn't a supported path through the toolchain. Instead this new version parses the textual output of nm to produce a symbol table. Both rely on near-zero addresses being linkable, but as we rely on weak undefined symbols being linkable elsewhere I don't view this as a major issue.
Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API") Cc: clang-built-linux@googlegroups.com Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt palmerdabbelt@google.com
Any way to improve the error message if/when this fails? https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/407...
Probably, but I can't get that command to actually run this stuff. I tried pulling the commands, but I'm getting some weirdness
$ rm -f arch/riscv/kernel/vdso/vdso-syms.S $ make ARCH=riscv defconfig $ make -j2 AR=llvm-ar 'CC=clang' 'HOSTCC=clang' HOSTLD=ld KCFLAGS=-Wno-implicit-fallthrough LD=riscv64-linux-gnu-ld LLVM_IAS=1 NM=llvm-nm OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-size READELF=llvm-readelf STRIP=llvm-strip ARCH=riscv Image SYNC include/config/auto.conf.cmd HOSTCC scripts/basic/fixdep HOSTCC scripts/kconfig/conf.o HOSTCC scripts/kconfig/confdata.o HOSTCC scripts/kconfig/expr.o HOSTCC scripts/kconfig/lexer.lex.o HOSTCC scripts/kconfig/parser.tab.o HOSTCC scripts/kconfig/preprocess.o HOSTCC scripts/kconfig/symbol.o HOSTCC scripts/kconfig/util.o HOSTLD scripts/kconfig/conf * * Restart config... * * * Memory initialization * Initialize kernel stack variables at function entry
- no automatic initialization (weakest) (INIT_STACK_NONE)
2. 0xAA-init everything on the stack (strongest) (INIT_STACK_ALL_PATTERN) (NEW) 3. zero-init everything on the stack (strongest and safest) (INIT_STACK_ALL_ZERO) (NEW) choice[1-3?]: Enable heap memory zeroing on allocation by default (INIT_ON_ALLOC_DEFAULT_ON) [N/y/?] n Enable heap memory zeroing on free by default (INIT_ON_FREE_DEFAULT_ON) [N/y/?] n HOSTCC scripts/dtc/dtc.o HOSTCC scripts/dtc/flattree.o HOSTCC scripts/dtc/fstree.o HOSTCC scripts/dtc/data.o HOSTCC scripts/dtc/livetree.o HOSTCC scripts/dtc/treesource.o HOSTCC scripts/dtc/srcpos.o HOSTCC scripts/dtc/checks.o HOSTCC scripts/dtc/util.o HOSTCC scripts/dtc/dtc-lexer.lex.o HOSTCC scripts/dtc/dtc-parser.tab.o HOSTLD scripts/dtc/dtc HOSTCC scripts/kallsyms CC scripts/mod/empty.o HOSTCC scripts/mod/mk_elfconfig error: invalid value 'medany' in '-mcode-model medany' make[1]: *** [scripts/Makefile.build:283: scripts/mod/empty.o] Error 1 make[1]: *** Waiting for unfinished jobs.... make: *** [Makefile:1199: prepare0] Error 2
I have no idea where the space in '-mcode-model medany' comes from.
Does this fail in general for LLVM, or is the issue just the error message? I've put this on fixes assuming it's just the error message, but LMK if it's actually not working in which case I won't send it out as I don't want to break stuff that was working.
Either way I'd be happy to fix it if I can reproduce it. I always just guess at regexes until they work for me, so I bet there's something subtly different in LLVM. This splits out the calls, which might be enough to sort it out (I've fixed the comment on fixes):
diff --git a/arch/riscv/kernel/vdso/.gitignore b/arch/riscv/kernel/vdso/.gitignore index 3a19def868ec..88206dd8b472 100644 --- a/arch/riscv/kernel/vdso/.gitignore +++ b/arch/riscv/kernel/vdso/.gitignore @@ -2,3 +2,4 @@ vdso.lds *.tmp vdso-syms.S +vdso-syms.nm diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile index a8ecf102e09b..fe5c969a6bf4 100644 --- a/arch/riscv/kernel/vdso/Makefile +++ b/arch/riscv/kernel/vdso/Makefile @@ -49,8 +49,11 @@ SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \ # We also create a special relocatable object that should mirror the symbol # table and layout of the linked DSO. With ld --just-symbols we can then # refer to these symbols in the kernel code rather than hand-coded addresses. -$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE - $(call if_changed,so2s) +$(obj)/vdso-syms.nm: $(obj)/vdso.so + $(call if_changed,nm_d) + +$(obj)/vdso-syms.S: $(obj)/vdso-syms.nm + $(call if_changed,nm2s)
# strip rule for the .so file $(obj)/%.so: OBJCOPYFLAGS := -S @@ -68,9 +71,13 @@ quiet_cmd_vdsold = VDSOLD $@ $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \ rm $@.tmp
-# Extracts -quiet_cmd_so2s = SO2S $@ - cmd_so2s = $(NM) -D $< | $(srctree)/$(src)/so2s.sh > $@ +# Extracts symbol offsets from the VDSO, converting them into an assembly file +# that contains the same symbols at the same offsets. +quiet_cmd_nm_d = NM -D $@ + cmd_nm_d = $(NM) -D $< > $@ + +quiet_cmd_nm2s = SYMS2S $@ + cmd_nm2s = cat $< | $(srctree)/$(src)/so2s.sh > $@
# install commands for the unstripped file quiet_cmd_vdso_install = INSTALL $@
For reference, here's the output of nmo for me:
$ cat arch/riscv/kernel/vdso/vdso-syms.nm 0000000000000000 A LINUX_4.15 00000000000009e0 T __vdso_clock_getres@@LINUX_4.15 000000000000080a T __vdso_clock_gettime@@LINUX_4.15 0000000000000a48 T __vdso_flush_icache@@LINUX_4.15 0000000000000a3c T __vdso_getcpu@@LINUX_4.15 0000000000000916 T __vdso_gettimeofday@@LINUX_4.15 0000000000000800 T __vdso_rt_sigreturn@@LINUX_4.15
Changes since v2 20201019235630.762886-1-palmerdabbelt@google.com:
- Uses $(srctree)/$(src) to allow for out-of-tree builds.
Changes since v1 20201017002500.503011-1-palmerdabbelt@google.com:
- Uses $(NM) instead of $(CROSS_COMPILE)nm. We use the $(CROSS_COMPILE) form elsewhere in this file, but we'll fix that later.
- Removed the unnecesary .map file creation.
arch/riscv/kernel/vdso/.gitignore | 1 + arch/riscv/kernel/vdso/Makefile | 17 ++++++++--------- arch/riscv/kernel/vdso/so2s.sh | 6 ++++++ 3 files changed, 15 insertions(+), 9 deletions(-) create mode 100755 arch/riscv/kernel/vdso/so2s.sh
diff --git a/arch/riscv/kernel/vdso/.gitignore b/arch/riscv/kernel/vdso/.gitignore index 11ebee9e4c1d..3a19def868ec 100644 --- a/arch/riscv/kernel/vdso/.gitignore +++ b/arch/riscv/kernel/vdso/.gitignore @@ -1,3 +1,4 @@ # SPDX-License-Identifier: GPL-2.0-only vdso.lds *.tmp +vdso-syms.S diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile index 478e7338ddc1..a8ecf102e09b 100644 --- a/arch/riscv/kernel/vdso/Makefile +++ b/arch/riscv/kernel/vdso/Makefile @@ -43,19 +43,14 @@ $(obj)/vdso.o: $(obj)/vdso.so SYSCFLAGS_vdso.so.dbg = $(c_flags) $(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso) FORCE $(call if_changed,vdsold) +SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
-Wl,--build-id -Wl,--hash-style=both# We also create a special relocatable object that should mirror the symbol # table and layout of the linked DSO. With ld --just-symbols we can then # refer to these symbols in the kernel code rather than hand-coded addresses.
-SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
-Wl,--build-id -Wl,--hash-style=both-$(obj)/vdso-dummy.o: $(src)/vdso.lds $(obj)/rt_sigreturn.o FORCE
$(call if_changed,vdsold)-LDFLAGS_vdso-syms.o := -r --just-symbols -$(obj)/vdso-syms.o: $(obj)/vdso-dummy.o FORCE
$(call if_changed,ld)+$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE
$(call if_changed,so2s)# strip rule for the .so file $(obj)/%.so: OBJCOPYFLAGS := -S @@ -73,6 +68,10 @@ quiet_cmd_vdsold = VDSOLD $@ $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \ rm $@.tmp
+# Extracts +quiet_cmd_so2s = SO2S $@
cmd_so2s = $(NM) -D $< | $(srctree)/$(src)/so2s.sh > $@# install commands for the unstripped file quiet_cmd_vdso_install = INSTALL $@ cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@ diff --git a/arch/riscv/kernel/vdso/so2s.sh b/arch/riscv/kernel/vdso/so2s.sh new file mode 100755 index 000000000000..3c5b43207658 --- /dev/null +++ b/arch/riscv/kernel/vdso/so2s.sh @@ -0,0 +1,6 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0+ +# Copyright 2020 Palmer Dabbelt palmerdabbelt@google.com
+sed 's!([0-9a-f]*) T ([a-z0-9_]*)@@LINUX_4.15!.global \2\n.set \2,0x\1!' \
+| grep '^.'
2.29.0.rc1.297.gfa9743e501-goog
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On Thu, Nov 05, 2020 at 08:42:22PM -0800, 'Palmer Dabbelt' via Clang Built Linux wrote:
On Mon, 26 Oct 2020 12:48:08 PDT (-0700), Nick Desaulniers wrote:
On Fri, Oct 23, 2020 at 10:03 PM 'Palmer Dabbelt' via Clang Built Linux clang-built-linux@googlegroups.com wrote:
We were relying on GNU ld's ability to re-link executable files in order to extract our VDSO symbols. This behavior was deemed a bug as of binutils-2.35 (specifically the binutils-gdb commit a87e1817a4 ("Have the linker fail if any attempt to link in an executable is made."), but as that has been backported to at least Debian's binutils-2.34 in may manifest in other places.
The previous version of this was a bit of a mess: we were linking a static executable version of the VDSO, containing only a subset of the input symbols, which we then linked into the kernel. This worked, but certainly wasn't a supported path through the toolchain. Instead this new version parses the textual output of nm to produce a symbol table. Both rely on near-zero addresses being linkable, but as we rely on weak undefined symbols being linkable elsewhere I don't view this as a major issue.
Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API") Cc: clang-built-linux@googlegroups.com Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt palmerdabbelt@google.com
Any way to improve the error message if/when this fails? https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/407...
Probably, but I can't get that command to actually run this stuff. I tried pulling the commands, but I'm getting some weirdness
$ rm -f arch/riscv/kernel/vdso/vdso-syms.S $ make ARCH=riscv defconfig $ make -j2 AR=llvm-ar 'CC=clang' 'HOSTCC=clang' HOSTLD=ld KCFLAGS=-Wno-implicit-fallthrough LD=riscv64-linux-gnu-ld LLVM_IAS=1 NM=llvm-nm OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-size READELF=llvm-readelf STRIP=llvm-strip ARCH=riscv Image
This command is simpler and reproduces it for me locally on next-20201105.
$ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- LD=riscv64-linux-gnu-ld LLVM=1 distclean defconfig Image clang-12: warning: argument unused during compilation: '-no-pie' [-Wunused-command-line-argument] make[4]: *** [arch/riscv/kernel/vdso/Makefile:53: arch/riscv/kernel/vdso/vdso-syms.S] Error 1 make[4]: *** Deleting file 'arch/riscv/kernel/vdso/vdso-syms.S' make[4]: Target '__build' not remade because of errors. make[3]: *** [scripts/Makefile.build:500: arch/riscv/kernel/vdso] Error 2 make[3]: Target '__build' not remade because of errors. make[2]: *** [scripts/Makefile.build:500: arch/riscv/kernel] Error 2 make[2]: Target '__build' not remade because of errors. make[1]: *** [Makefile:1797: arch/riscv] Error 2 make[1]: Target 'Image' not remade because of errors. make: *** [Makefile:335: __build_one_by_one] Error 2 make: Target 'distclean' not remade because of errors. make: Target 'defconfig' not remade because of errors. make: Target 'Image' not remade because of errors.
<snip>
diff --git a/arch/riscv/kernel/vdso/.gitignore b/arch/riscv/kernel/vdso/.gitignore index 3a19def868ec..88206dd8b472 100644 --- a/arch/riscv/kernel/vdso/.gitignore +++ b/arch/riscv/kernel/vdso/.gitignore @@ -2,3 +2,4 @@ vdso.lds *.tmp vdso-syms.S +vdso-syms.nm diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile index a8ecf102e09b..fe5c969a6bf4 100644 --- a/arch/riscv/kernel/vdso/Makefile +++ b/arch/riscv/kernel/vdso/Makefile @@ -49,8 +49,11 @@ SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \ # We also create a special relocatable object that should mirror the symbol # table and layout of the linked DSO. With ld --just-symbols we can then # refer to these symbols in the kernel code rather than hand-coded addresses. -$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE
- $(call if_changed,so2s)
+$(obj)/vdso-syms.nm: $(obj)/vdso.so
- $(call if_changed,nm_d)
+$(obj)/vdso-syms.S: $(obj)/vdso-syms.nm
- $(call if_changed,nm2s)
# strip rule for the .so file $(obj)/%.so: OBJCOPYFLAGS := -S @@ -68,9 +71,13 @@ quiet_cmd_vdsold = VDSOLD $@ $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \ rm $@.tmp
-# Extracts -quiet_cmd_so2s = SO2S $@
cmd_so2s = $(NM) -D $< | $(srctree)/$(src)/so2s.sh > $@+# Extracts symbol offsets from the VDSO, converting them into an assembly file +# that contains the same symbols at the same offsets. +quiet_cmd_nm_d = NM -D $@
cmd_nm_d = $(NM) -D $< > $@+quiet_cmd_nm2s = SYMS2S $@
cmd_nm2s = cat $< | $(srctree)/$(src)/so2s.sh > $@# install commands for the unstripped file quiet_cmd_vdso_install = INSTALL $@
For reference, here's the output of nmo for me:
$ cat arch/riscv/kernel/vdso/vdso-syms.nm 0000000000000000 A LINUX_4.15 00000000000009e0 T __vdso_clock_getres@@LINUX_4.15 000000000000080a T __vdso_clock_gettime@@LINUX_4.15 0000000000000a48 T __vdso_flush_icache@@LINUX_4.15 0000000000000a3c T __vdso_getcpu@@LINUX_4.15 0000000000000916 T __vdso_gettimeofday@@LINUX_4.15 0000000000000800 T __vdso_rt_sigreturn@@LINUX_4.15
This diff does not solve the issue for me with the above command.
Cheers, Nathan
On Thu, 05 Nov 2020 20:59:02 PST (-0800), natechancellor@gmail.com wrote:
On Thu, Nov 05, 2020 at 08:42:22PM -0800, 'Palmer Dabbelt' via Clang Built Linux wrote:
On Mon, 26 Oct 2020 12:48:08 PDT (-0700), Nick Desaulniers wrote:
On Fri, Oct 23, 2020 at 10:03 PM 'Palmer Dabbelt' via Clang Built Linux clang-built-linux@googlegroups.com wrote:
We were relying on GNU ld's ability to re-link executable files in order to extract our VDSO symbols. This behavior was deemed a bug as of binutils-2.35 (specifically the binutils-gdb commit a87e1817a4 ("Have the linker fail if any attempt to link in an executable is made."), but as that has been backported to at least Debian's binutils-2.34 in may manifest in other places.
The previous version of this was a bit of a mess: we were linking a static executable version of the VDSO, containing only a subset of the input symbols, which we then linked into the kernel. This worked, but certainly wasn't a supported path through the toolchain. Instead this new version parses the textual output of nm to produce a symbol table. Both rely on near-zero addresses being linkable, but as we rely on weak undefined symbols being linkable elsewhere I don't view this as a major issue.
Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API") Cc: clang-built-linux@googlegroups.com Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt palmerdabbelt@google.com
Any way to improve the error message if/when this fails? https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/407...
Probably, but I can't get that command to actually run this stuff. I tried pulling the commands, but I'm getting some weirdness
$ rm -f arch/riscv/kernel/vdso/vdso-syms.S $ make ARCH=riscv defconfig $ make -j2 AR=llvm-ar 'CC=clang' 'HOSTCC=clang' HOSTLD=ld KCFLAGS=-Wno-implicit-fallthrough LD=riscv64-linux-gnu-ld LLVM_IAS=1 NM=llvm-nm OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-size READELF=llvm-readelf STRIP=llvm-strip ARCH=riscv Image
This command is simpler and reproduces it for me locally on next-20201105.
$ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- LD=riscv64-linux-gnu-ld LLVM=1 distclean defconfig Image clang-12: warning: argument unused during compilation: '-no-pie' [-Wunused-command-line-argument] make[4]: *** [arch/riscv/kernel/vdso/Makefile:53: arch/riscv/kernel/vdso/vdso-syms.S] Error 1 make[4]: *** Deleting file 'arch/riscv/kernel/vdso/vdso-syms.S' make[4]: Target '__build' not remade because of errors. make[3]: *** [scripts/Makefile.build:500: arch/riscv/kernel/vdso] Error 2 make[3]: Target '__build' not remade because of errors. make[2]: *** [scripts/Makefile.build:500: arch/riscv/kernel] Error 2 make[2]: Target '__build' not remade because of errors. make[1]: *** [Makefile:1797: arch/riscv] Error 2 make[1]: Target 'Image' not remade because of errors. make: *** [Makefile:335: __build_one_by_one] Error 2 make: Target 'distclean' not remade because of errors. make: Target 'defconfig' not remade because of errors. make: Target 'Image' not remade because of errors.
<snip>
diff --git a/arch/riscv/kernel/vdso/.gitignore b/arch/riscv/kernel/vdso/.gitignore index 3a19def868ec..88206dd8b472 100644 --- a/arch/riscv/kernel/vdso/.gitignore +++ b/arch/riscv/kernel/vdso/.gitignore @@ -2,3 +2,4 @@ vdso.lds *.tmp vdso-syms.S +vdso-syms.nm diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile index a8ecf102e09b..fe5c969a6bf4 100644 --- a/arch/riscv/kernel/vdso/Makefile +++ b/arch/riscv/kernel/vdso/Makefile @@ -49,8 +49,11 @@ SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \ # We also create a special relocatable object that should mirror the symbol # table and layout of the linked DSO. With ld --just-symbols we can then # refer to these symbols in the kernel code rather than hand-coded addresses. -$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE
- $(call if_changed,so2s)
+$(obj)/vdso-syms.nm: $(obj)/vdso.so
- $(call if_changed,nm_d)
+$(obj)/vdso-syms.S: $(obj)/vdso-syms.nm
- $(call if_changed,nm2s)
# strip rule for the .so file $(obj)/%.so: OBJCOPYFLAGS := -S @@ -68,9 +71,13 @@ quiet_cmd_vdsold = VDSOLD $@ $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \ rm $@.tmp
-# Extracts -quiet_cmd_so2s = SO2S $@
cmd_so2s = $(NM) -D $< | $(srctree)/$(src)/so2s.sh > $@+# Extracts symbol offsets from the VDSO, converting them into an assembly file +# that contains the same symbols at the same offsets. +quiet_cmd_nm_d = NM -D $@
cmd_nm_d = $(NM) -D $< > $@+quiet_cmd_nm2s = SYMS2S $@
cmd_nm2s = cat $< | $(srctree)/$(src)/so2s.sh > $@# install commands for the unstripped file quiet_cmd_vdso_install = INSTALL $@
For reference, here's the output of nmo for me:
$ cat arch/riscv/kernel/vdso/vdso-syms.nm 0000000000000000 A LINUX_4.15 00000000000009e0 T __vdso_clock_getres@@LINUX_4.15 000000000000080a T __vdso_clock_gettime@@LINUX_4.15 0000000000000a48 T __vdso_flush_icache@@LINUX_4.15 0000000000000a3c T __vdso_getcpu@@LINUX_4.15 0000000000000916 T __vdso_gettimeofday@@LINUX_4.15 0000000000000800 T __vdso_rt_sigreturn@@LINUX_4.15
This diff does not solve the issue for me with the above command.
It wasn't really meant to solve anything, just split the commands up a touch more so we could see what's going on.
I just installed Debian's toolchain, which is LLVM 9. IIRC that's pretty ancient WRT RISC-V, so my guess is that it's just a long way from building Linux. Looks like llvm-nm on my system doesn't put the @@LINUX_4.15 after the symbol names, I think this should do it?
diff --git a/arch/riscv/kernel/vdso/so2s.sh b/arch/riscv/kernel/vdso/so2s.sh index 3c5b43207658..e64cb6d9440e 100755 --- a/arch/riscv/kernel/vdso/so2s.sh +++ b/arch/riscv/kernel/vdso/so2s.sh @@ -2,5 +2,5 @@ # SPDX-License-Identifier: GPL-2.0+ # Copyright 2020 Palmer Dabbelt palmerdabbelt@google.com
-sed 's!([0-9a-f]*) T ([a-z0-9_]*)@@LINUX_4.15!.global \2\n.set \2,0x\1!' \ +sed 's!([0-9a-f]*) T ([a-z0-9_]*)(@@LINUX_4.15)*!.global \2\n.set \2,0x\1!' \ | grep '^.'
It works for me, at least for this specific problem.
$ llvm-nm-9 -D arch/riscv/kernel/vdso/vdso.so | ./arch/riscv/kernel/vdso/so2s.sh .global __vdso_clock_getres .set __vdso_clock_getres,0x00000000000009e0 .global __vdso_clock_gettime .set __vdso_clock_gettime,0x000000000000080a .global __vdso_flush_icache .set __vdso_flush_icache,0x0000000000000a48 .global __vdso_getcpu .set __vdso_getcpu,0x0000000000000a3c .global __vdso_gettimeofday .set __vdso_gettimeofday,0x0000000000000916 .global __vdso_rt_sigreturn .set __vdso_rt_sigreturn,0x0000000000000800 $ nm -D arch/riscv/kernel/vdso/vdso.so | ./arch/riscv/kernel/vdso/so2s.sh .global __vdso_clock_getres .set __vdso_clock_getres,0x00000000000009e0 .global __vdso_clock_gettime .set __vdso_clock_gettime,0x000000000000080a .global __vdso_flush_icache .set __vdso_flush_icache,0x0000000000000a48 .global __vdso_getcpu .set __vdso_getcpu,0x0000000000000a3c .global __vdso_gettimeofday .set __vdso_gettimeofday,0x0000000000000916 .global __vdso_rt_sigreturn .set __vdso_rt_sigreturn,0x0000000000000800
Cheers, Nathan
On Thu, Nov 05, 2020 at 09:12:25PM -0800, Palmer Dabbelt wrote:
On Thu, 05 Nov 2020 20:59:02 PST (-0800), natechancellor@gmail.com wrote:
On Thu, Nov 05, 2020 at 08:42:22PM -0800, 'Palmer Dabbelt' via Clang Built Linux wrote:
On Mon, 26 Oct 2020 12:48:08 PDT (-0700), Nick Desaulniers wrote:
On Fri, Oct 23, 2020 at 10:03 PM 'Palmer Dabbelt' via Clang Built Linux clang-built-linux@googlegroups.com wrote:
We were relying on GNU ld's ability to re-link executable files in order to extract our VDSO symbols. This behavior was deemed a bug as of binutils-2.35 (specifically the binutils-gdb commit a87e1817a4 ("Have the linker fail if any attempt to link in an executable is made."), but as that has been backported to at least Debian's binutils-2.34 in may manifest in other places.
The previous version of this was a bit of a mess: we were linking a static executable version of the VDSO, containing only a subset of the input symbols, which we then linked into the kernel. This worked, but certainly wasn't a supported path through the toolchain. Instead this new version parses the textual output of nm to produce a symbol table. Both rely on near-zero addresses being linkable, but as we rely on weak undefined symbols being linkable elsewhere I don't view this as a major issue.
Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API") Cc: clang-built-linux@googlegroups.com Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt palmerdabbelt@google.com
Any way to improve the error message if/when this fails? https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/407...
Probably, but I can't get that command to actually run this stuff. I tried pulling the commands, but I'm getting some weirdness
$ rm -f arch/riscv/kernel/vdso/vdso-syms.S $ make ARCH=riscv defconfig $ make -j2 AR=llvm-ar 'CC=clang' 'HOSTCC=clang' HOSTLD=ld KCFLAGS=-Wno-implicit-fallthrough LD=riscv64-linux-gnu-ld LLVM_IAS=1 NM=llvm-nm OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-size READELF=llvm-readelf STRIP=llvm-strip ARCH=riscv Image
This command is simpler and reproduces it for me locally on next-20201105.
$ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- LD=riscv64-linux-gnu-ld LLVM=1 distclean defconfig Image clang-12: warning: argument unused during compilation: '-no-pie' [-Wunused-command-line-argument] make[4]: *** [arch/riscv/kernel/vdso/Makefile:53: arch/riscv/kernel/vdso/vdso-syms.S] Error 1 make[4]: *** Deleting file 'arch/riscv/kernel/vdso/vdso-syms.S' make[4]: Target '__build' not remade because of errors. make[3]: *** [scripts/Makefile.build:500: arch/riscv/kernel/vdso] Error 2 make[3]: Target '__build' not remade because of errors. make[2]: *** [scripts/Makefile.build:500: arch/riscv/kernel] Error 2 make[2]: Target '__build' not remade because of errors. make[1]: *** [Makefile:1797: arch/riscv] Error 2 make[1]: Target 'Image' not remade because of errors. make: *** [Makefile:335: __build_one_by_one] Error 2 make: Target 'distclean' not remade because of errors. make: Target 'defconfig' not remade because of errors. make: Target 'Image' not remade because of errors.
<snip>
diff --git a/arch/riscv/kernel/vdso/.gitignore b/arch/riscv/kernel/vdso/.gitignore index 3a19def868ec..88206dd8b472 100644 --- a/arch/riscv/kernel/vdso/.gitignore +++ b/arch/riscv/kernel/vdso/.gitignore @@ -2,3 +2,4 @@ vdso.lds *.tmp vdso-syms.S +vdso-syms.nm diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile index a8ecf102e09b..fe5c969a6bf4 100644 --- a/arch/riscv/kernel/vdso/Makefile +++ b/arch/riscv/kernel/vdso/Makefile @@ -49,8 +49,11 @@ SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \ # We also create a special relocatable object that should mirror the symbol # table and layout of the linked DSO. With ld --just-symbols we can then # refer to these symbols in the kernel code rather than hand-coded addresses. -$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE
- $(call if_changed,so2s)
+$(obj)/vdso-syms.nm: $(obj)/vdso.so
- $(call if_changed,nm_d)
+$(obj)/vdso-syms.S: $(obj)/vdso-syms.nm
- $(call if_changed,nm2s)
# strip rule for the .so file $(obj)/%.so: OBJCOPYFLAGS := -S @@ -68,9 +71,13 @@ quiet_cmd_vdsold = VDSOLD $@ $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \ rm $@.tmp
-# Extracts -quiet_cmd_so2s = SO2S $@
cmd_so2s = $(NM) -D $< | $(srctree)/$(src)/so2s.sh > $@+# Extracts symbol offsets from the VDSO, converting them into an assembly file +# that contains the same symbols at the same offsets. +quiet_cmd_nm_d = NM -D $@
cmd_nm_d = $(NM) -D $< > $@+quiet_cmd_nm2s = SYMS2S $@
cmd_nm2s = cat $< | $(srctree)/$(src)/so2s.sh > $@# install commands for the unstripped file quiet_cmd_vdso_install = INSTALL $@
For reference, here's the output of nmo for me:
$ cat arch/riscv/kernel/vdso/vdso-syms.nm 0000000000000000 A LINUX_4.15 00000000000009e0 T __vdso_clock_getres@@LINUX_4.15 000000000000080a T __vdso_clock_gettime@@LINUX_4.15 0000000000000a48 T __vdso_flush_icache@@LINUX_4.15 0000000000000a3c T __vdso_getcpu@@LINUX_4.15 0000000000000916 T __vdso_gettimeofday@@LINUX_4.15 0000000000000800 T __vdso_rt_sigreturn@@LINUX_4.15
This diff does not solve the issue for me with the above command.
It wasn't really meant to solve anything, just split the commands up a touch more so we could see what's going on.
I just installed Debian's toolchain, which is LLVM 9. IIRC that's pretty ancient WRT RISC-V, so my guess is that it's just a long way from building Linux. Looks like llvm-nm on my system doesn't put the @@LINUX_4.15 after the symbol names, I think this should do it?
diff --git a/arch/riscv/kernel/vdso/so2s.sh b/arch/riscv/kernel/vdso/so2s.sh index 3c5b43207658..e64cb6d9440e 100755 --- a/arch/riscv/kernel/vdso/so2s.sh +++ b/arch/riscv/kernel/vdso/so2s.sh @@ -2,5 +2,5 @@ # SPDX-License-Identifier: GPL-2.0+ # Copyright 2020 Palmer Dabbelt palmerdabbelt@google.com
-sed 's!([0-9a-f]*) T ([a-z0-9_]*)@@LINUX_4.15!.global \2\n.set \2,0x\1!' \ +sed 's!([0-9a-f]*) T ([a-z0-9_]*)(@@LINUX_4.15)*!.global \2\n.set \2,0x\1!' \ | grep '^.'
It works for me, at least for this specific problem.
Same here. defconfig minus CONFIG_EFI builds and boots in QEMU with that diff (plus LLVM_IAS=1 in the make command, I forgot that earlier).
Tested-by: Nathan Chancellor natechancellor@gmail.com
$ llvm-nm-9 -D arch/riscv/kernel/vdso/vdso.so | ./arch/riscv/kernel/vdso/so2s.sh .global __vdso_clock_getres .set __vdso_clock_getres,0x00000000000009e0 .global __vdso_clock_gettime .set __vdso_clock_gettime,0x000000000000080a .global __vdso_flush_icache .set __vdso_flush_icache,0x0000000000000a48 .global __vdso_getcpu .set __vdso_getcpu,0x0000000000000a3c .global __vdso_gettimeofday .set __vdso_gettimeofday,0x0000000000000916 .global __vdso_rt_sigreturn .set __vdso_rt_sigreturn,0x0000000000000800 $ nm -D arch/riscv/kernel/vdso/vdso.so | ./arch/riscv/kernel/vdso/so2s.sh .global __vdso_clock_getres .set __vdso_clock_getres,0x00000000000009e0 .global __vdso_clock_gettime .set __vdso_clock_gettime,0x000000000000080a .global __vdso_flush_icache .set __vdso_flush_icache,0x0000000000000a48 .global __vdso_getcpu .set __vdso_getcpu,0x0000000000000a3c .global __vdso_gettimeofday .set __vdso_gettimeofday,0x0000000000000916 .global __vdso_rt_sigreturn .set __vdso_rt_sigreturn,0x0000000000000800
Cheers, Nathan
linux-stable-mirror@lists.linaro.org
-
Nathan Chancellor -
Nick Desaulniers -
Palmer Dabbelt