diff mbox series

[v2,3/7] powerpc/build: move got, toc, plt, branch_lt sections to read-only

Message ID 20220916040755.2398112-4-npiggin@gmail.com (mailing list archive)
State Accepted
Headers show
Series powerpc: build / linker improvements | expand

Commit Message

Nicholas Piggin Sept. 16, 2022, 4:07 a.m. UTC 
This moves linker-related tables from .data to read-only area.
Relocations are performed at early boot time before memory is protected,
after which there should be no modifications required.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/vmlinux.lds.S | 42 ++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 15 deletions(-)

Comments

kernel test robot Sept. 17, 2022, 8:15 p.m. UTC | #1 
Hi Nicholas,

I love your patch! Yet something to improve:

[auto build test ERROR on powerpc/next]
[also build test ERROR on linus/master v6.0-rc5 next-20220916]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Nicholas-Piggin/powerpc-build-linker-improvements/20220916-121310
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc-microwatt_defconfig (https://download.01.org/0day-ci/archive/20220918/202209180437.4U3soljK-lkp@intel.com/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 791a7ae1ba3efd6bca96338e10ffde557ba83920)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install powerpc cross compiling tool for clang build
        # apt-get install binutils-powerpc-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/6c034c08f8d0addb6fecba38c9c428b1c4df7c29
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Nicholas-Piggin/powerpc-build-linker-improvements/20220916-121310
        git checkout 6c034c08f8d0addb6fecba38c9c428b1c4df7c29
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> ld.lld: error: ./arch/powerpc/kernel/vmlinux.lds:46: { expected, but got SPECIAL
   >>>  .got : AT(ADDR(.got) - (0xc0000000 -0x00000000)) SPECIAL {
   >>>                                                   ^
Michael Ellerman Sept. 19, 2022, 5:39 a.m. UTC | #2 
kernel test robot <lkp@intel.com> writes:
> Hi Nicholas,
>
> I love your patch! Yet something to improve:
>
> [auto build test ERROR on powerpc/next]
> [also build test ERROR on linus/master v6.0-rc5 next-20220916]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Nicholas-Piggin/powerpc-build-linker-improvements/20220916-121310
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
> config: powerpc-microwatt_defconfig (https://download.01.org/0day-ci/archive/20220918/202209180437.4U3soljK-lkp@intel.com/config)
> compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 791a7ae1ba3efd6bca96338e10ffde557ba83920)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install powerpc cross compiling tool for clang build
>         # apt-get install binutils-powerpc-linux-gnu
>         # https://github.com/intel-lab-lkp/linux/commit/6c034c08f8d0addb6fecba38c9c428b1c4df7c29
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Nicholas-Piggin/powerpc-build-linker-improvements/20220916-121310
>         git checkout 6c034c08f8d0addb6fecba38c9c428b1c4df7c29
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash
                                                    ^^^^^

> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):
>
>>> ld.lld: error: ./arch/powerpc/kernel/vmlinux.lds:46: { expected, but got SPECIAL
>    >>>  .got : AT(ADDR(.got) - (0xc0000000 -0x00000000)) SPECIAL {
>    >>>                                                   ^

I guess SPECIAL is a binutils ld ism?

I can't find it documented anywhere.

Presumably we can just not use it, given we never did before?

cheers
Nicholas Piggin Sept. 20, 2022, 10:50 a.m. UTC | #3 
On Mon Sep 19, 2022 at 3:39 PM AEST, Michael Ellerman wrote:
> kernel test robot <lkp@intel.com> writes:
> > Hi Nicholas,
> >
> > I love your patch! Yet something to improve:
> >
> > [auto build test ERROR on powerpc/next]
> > [also build test ERROR on linus/master v6.0-rc5 next-20220916]
> > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > And when submitting patch, we suggest to use '--base' as documented in
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> >
> > url:    https://github.com/intel-lab-lkp/linux/commits/Nicholas-Piggin/powerpc-build-linker-improvements/20220916-121310
> > base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
> > config: powerpc-microwatt_defconfig (https://download.01.org/0day-ci/archive/20220918/202209180437.4U3soljK-lkp@intel.com/config)
> > compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 791a7ae1ba3efd6bca96338e10ffde557ba83920)
> > reproduce (this is a W=1 build):
> >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> >         chmod +x ~/bin/make.cross
> >         # install powerpc cross compiling tool for clang build
> >         # apt-get install binutils-powerpc-linux-gnu
> >         # https://github.com/intel-lab-lkp/linux/commit/6c034c08f8d0addb6fecba38c9c428b1c4df7c29
> >         git remote add linux-review https://github.com/intel-lab-lkp/linux
> >         git fetch --no-tags linux-review Nicholas-Piggin/powerpc-build-linker-improvements/20220916-121310
> >         git checkout 6c034c08f8d0addb6fecba38c9c428b1c4df7c29
> >         # save the config file
> >         mkdir build_dir && cp config build_dir/.config
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash
>                                                     ^^^^^
>
> > If you fix the issue, kindly add following tag where applicable
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> > All errors (new ones prefixed by >>):
> >
> >>> ld.lld: error: ./arch/powerpc/kernel/vmlinux.lds:46: { expected, but got SPECIAL
> >    >>>  .got : AT(ADDR(.got) - (0xc0000000 -0x00000000)) SPECIAL {
> >    >>>                                                   ^
>
> I guess SPECIAL is a binutils ld ism?
>
> I can't find it documented anywhere.
>
> Presumably we can just not use it, given we never did before?

Yeah that's what it is, oops I just took it from the linker script.

I think we can drop it, I think it selects either old or new plt
sections that are created with --secure-plt, I guess depending on
some link options and copmatibility concerns. Doesn't look like
ppc32 uses --secure-plt.

Thanks,
Nick
diff mbox series

Patch

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 607b17b1e785..16c4389d498d 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -131,6 +131,10 @@  SECTIONS
 	/* Read-only data */
 	RO_DATA(PAGE_SIZE)
 
+	.branch_lt : AT(ADDR(.branch_lt) - LOAD_OFFSET) {
+		*(.branch_lt)
+	}
+
 #ifdef CONFIG_PPC32
 	.got1 : AT(ADDR(.got1) - LOAD_OFFSET) {
 		*(.got1)
@@ -140,7 +144,30 @@  SECTIONS
 		*(.got2)
 		__got2_end = .;
 	}
+	.got : AT(ADDR(.got) - LOAD_OFFSET) SPECIAL {
+		*(.got)
+		*(.got.plt)
+	}
+	.plt : AT(ADDR(.plt) - LOAD_OFFSET) SPECIAL {
+		/* XXX: is .plt (and .got.plt) required? */
+		*(.plt)
+	}
+
 #else /* CONFIG_PPC32 */
+	.toc1 : AT(ADDR(.toc1) - LOAD_OFFSET) {
+		*(.toc1)
+	}
+
+	.got : AT(ADDR(.got) - LOAD_OFFSET) ALIGN(256) {
+		*(.got)
+#ifndef CONFIG_RELOCATABLE
+		__prom_init_toc_start = .;
+		arch/powerpc/kernel/prom_init.o*(.toc)
+		__prom_init_toc_end = .;
+#endif
+		*(.toc)
+	}
+
 	SOFT_MASK_TABLE(8)
 	RESTART_TABLE(8)
 
@@ -327,26 +354,11 @@  SECTIONS
 		*(.data.rel*)
 		*(SDATA_MAIN)
 		*(.sdata2)
-		*(.got.plt) *(.got)
-		*(.plt)
-		*(.branch_lt)
 	}
 #else
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {
 		DATA_DATA
 		*(.data.rel*)
-		*(.toc1)
-		*(.branch_lt)
-	}
-
-	.got : AT(ADDR(.got) - LOAD_OFFSET) ALIGN(256) {
-		*(.got)
-#ifndef CONFIG_RELOCATABLE
-		__prom_init_toc_start = .;
-		arch/powerpc/kernel/prom_init.o*(.toc)
-		__prom_init_toc_end = .;
-#endif
-		*(.toc)
 	}
 #endif