* [PATCH v3 0/3] powerpc: Add to linker script discards
@ 2018-12-10 22:28 Joel Stanley
2018-12-10 22:28 ` [PATCH v3 1/3] powerpc: Discard more sections in linker script Joel Stanley
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Joel Stanley @ 2018-12-10 22:28 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Stephen Rothwell, Alan Modra
v3 fixes up the splitting of the patches, moving the dynstr hunk from
patch 2 to patch 1.
v2 pulls in the branch_lt patch too. No changes to the first two
patches.
Joel Stanley (3):
powerpc: Discard more sections in linker script
powerpc: Discard dynsym section for !PPC32
powerpc: Discard .branch_lt section
arch/powerpc/kernel/vmlinux.lds.S | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
--
2.19.1
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH v3 1/3] powerpc: Discard more sections in linker script
2018-12-10 22:28 [PATCH v3 0/3] powerpc: Add to linker script discards Joel Stanley
@ 2018-12-10 22:28 ` Joel Stanley
2018-12-20 11:18 ` Michael Ellerman
2018-12-10 22:28 ` [PATCH v3 2/3] powerpc: Discard dynsym section for !PPC32 Joel Stanley
2018-12-10 22:28 ` [PATCH v3 3/3] powerpc: Discard .branch_lt section Joel Stanley
2 siblings, 1 reply; 6+ messages in thread
From: Joel Stanley @ 2018-12-10 22:28 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Stephen Rothwell, Alan Modra
Building the ppc64 kernel with a modern binutils results in this
warning:
powerpc64le-linux-gnu-ld: warning: orphan section `.gnu.hash' from
`linker stubs' being placed in section `.gnu.hash'
Alan Modra <amodra@gmail.com> explains:
> .gnu.hash, like .hash, is used by glibc ld.so for dynamic symbol
> lookup. I imagine you don't need either section in a kernel, so
> discarding both sounds reasonable. Likely you could discard .interp
> and .dynstr too, and .dynsym when !CONFIG_PPC32.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
See https://lore.kernel.org/lkml/CACPK8Xft3n5KkpTjN3=7_VUCXHFcK7mxvZm2Rrqu7tppcBoyOg@mail.gmail.com/T/#m58532c86cf0c7b4fb01cc1fe724e48d4c7d8e4a7
v3: Add dynstr hunk to this patch (it was incorrectly left in patch 2)
---
arch/powerpc/kernel/vmlinux.lds.S | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 434581bcd5b4..779b8b3075a1 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -273,14 +273,11 @@ SECTIONS
#endif
*(.dynsym)
}
- .dynstr : AT(ADDR(.dynstr) - LOAD_OFFSET) { *(.dynstr) }
.dynamic : AT(ADDR(.dynamic) - LOAD_OFFSET)
{
__dynamic_start = .;
*(.dynamic)
}
- .hash : AT(ADDR(.hash) - LOAD_OFFSET) { *(.hash) }
- .interp : AT(ADDR(.interp) - LOAD_OFFSET) { *(.interp) }
.rela.dyn : AT(ADDR(.rela.dyn) - LOAD_OFFSET)
{
__rela_dyn_start = .;
@@ -388,5 +385,8 @@ SECTIONS
*(.gnu.version*)
*(.gnu.attributes)
*(.eh_frame)
+ *(.hash .gnu.hash)
+ *(.interp)
+ *(.dynstr)
}
}
--
2.19.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH v3 1/3] powerpc: Discard more sections in linker script
2018-12-10 22:28 ` [PATCH v3 1/3] powerpc: Discard more sections in linker script Joel Stanley
@ 2018-12-20 11:18 ` Michael Ellerman
0 siblings, 0 replies; 6+ messages in thread
From: Michael Ellerman @ 2018-12-20 11:18 UTC (permalink / raw)
To: Joel Stanley, linuxppc-dev; +Cc: Stephen Rothwell, Alan Modra
Joel Stanley <joel@jms.id.au> writes:
> Building the ppc64 kernel with a modern binutils results in this
> warning:
>
> powerpc64le-linux-gnu-ld: warning: orphan section `.gnu.hash' from
> `linker stubs' being placed in section `.gnu.hash'
>
> Alan Modra <amodra@gmail.com> explains:
>
> > .gnu.hash, like .hash, is used by glibc ld.so for dynamic symbol
> > lookup. I imagine you don't need either section in a kernel, so
> > discarding both sounds reasonable. Likely you could discard .interp
> > and .dynstr too, and .dynsym when !CONFIG_PPC32.
>
> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> Signed-off-by: Joel Stanley <joel@jms.id.au>
> ---
> See https://lore.kernel.org/lkml/CACPK8Xft3n5KkpTjN3=7_VUCXHFcK7mxvZm2Rrqu7tppcBoyOg@mail.gmail.com/T/#m58532c86cf0c7b4fb01cc1fe724e48d4c7d8e4a7
>
> v3: Add dynstr hunk to this patch (it was incorrectly left in patch 2)
> ---
> arch/powerpc/kernel/vmlinux.lds.S | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
Building ppc64le_defconfig with gcc 8.1.0 / binutils 2.30, this is giving me:
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux1: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux1: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux1: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux1: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux1: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux1: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux1: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux1: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux1: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux2: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux2: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: vmlinux: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: vmlinux: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux2: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: .tmp_vmlinux2: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: vmlinux: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-nm: vmlinux: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: vmlinux: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: vmlinux: attempt to load strings from a non-string section (number 0)
WARNING: 2 bad relocations
c000000001490a50 R_PPC64_ADDR64 (null)
c000000001490a68 R_PPC64_ADDR64 (null)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: vmlinux: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: vmlinux: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: vmlinux: attempt to load strings from a non-string section (number 0)
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: vmlinux: attempt to load strings from a non-string section (number 0)
Haven't had time to dig into why yet.
cheers
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v3 2/3] powerpc: Discard dynsym section for !PPC32
2018-12-10 22:28 [PATCH v3 0/3] powerpc: Add to linker script discards Joel Stanley
2018-12-10 22:28 ` [PATCH v3 1/3] powerpc: Discard more sections in linker script Joel Stanley
@ 2018-12-10 22:28 ` Joel Stanley
2018-12-20 11:20 ` Michael Ellerman
2018-12-10 22:28 ` [PATCH v3 3/3] powerpc: Discard .branch_lt section Joel Stanley
2 siblings, 1 reply; 6+ messages in thread
From: Joel Stanley @ 2018-12-10 22:28 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Stephen Rothwell, Alan Modra
Alan Modra <amodra@gmail.com> explains:
> Likely you could discard .interp > and .dynstr too, and .dynsym when
> !CONFIG_PPC32.
Discarding of interp and dynstr happened in a previous patch. The dynsym
cleanup was a bit less straightforward, so it gets it's own patch.
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
See https://lore.kernel.org/lkml/CACPK8Xft3n5KkpTjN3=7_VUCXHFcK7mxvZm2Rrqu7tppcBoyOg@mail.gmail.com/T/#m58532c86cf0c7b4fb01cc1fe724e48d4c7d8e4a7
v3: Move dynstr hunk to patch 1 (it was incorrectly left in this patch)
---
arch/powerpc/kernel/vmlinux.lds.S | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 779b8b3075a1..2c93a420f456 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -266,13 +266,13 @@ SECTIONS
}
#ifdef CONFIG_RELOCATABLE
. = ALIGN(8);
+#ifdef CONFIG_PPC32
.dynsym : AT(ADDR(.dynsym) - LOAD_OFFSET)
{
-#ifdef CONFIG_PPC32
__dynamic_symtab = .;
-#endif
*(.dynsym)
}
+#endif
.dynamic : AT(ADDR(.dynamic) - LOAD_OFFSET)
{
__dynamic_start = .;
@@ -388,5 +388,8 @@ SECTIONS
*(.hash .gnu.hash)
*(.interp)
*(.dynstr)
+#ifndef CONFIG_PPC32
+ *(.dynsym)
+#endif
}
}
--
2.19.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH v3 2/3] powerpc: Discard dynsym section for !PPC32
2018-12-10 22:28 ` [PATCH v3 2/3] powerpc: Discard dynsym section for !PPC32 Joel Stanley
@ 2018-12-20 11:20 ` Michael Ellerman
0 siblings, 0 replies; 6+ messages in thread
From: Michael Ellerman @ 2018-12-20 11:20 UTC (permalink / raw)
To: Joel Stanley, linuxppc-dev; +Cc: Stephen Rothwell, Alan Modra
Joel Stanley <joel@jms.id.au> writes:
> Alan Modra <amodra@gmail.com> explains:
>
> > Likely you could discard .interp > and .dynstr too, and .dynsym when
> > !CONFIG_PPC32.
>
> Discarding of interp and dynstr happened in a previous patch. The dynsym
> cleanup was a bit less straightforward, so it gets it's own patch.
>
> Signed-off-by: Joel Stanley <joel@jms.id.au>
And with the same toolchain this gives me:
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: vmlinux: not a dynamic object
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: vmlinux: Invalid operation
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: vmlinux: not a dynamic object
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: vmlinux: Invalid operation
/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-objdump: --stop-address: bad number: 0x
cheers
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v3 3/3] powerpc: Discard .branch_lt section
2018-12-10 22:28 [PATCH v3 0/3] powerpc: Add to linker script discards Joel Stanley
2018-12-10 22:28 ` [PATCH v3 1/3] powerpc: Discard more sections in linker script Joel Stanley
2018-12-10 22:28 ` [PATCH v3 2/3] powerpc: Discard dynsym section for !PPC32 Joel Stanley
@ 2018-12-10 22:28 ` Joel Stanley
2 siblings, 0 replies; 6+ messages in thread
From: Joel Stanley @ 2018-12-10 22:28 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Stephen Rothwell, Alan Modra
When building a 32 bit powerpc kernel with Binutils 2.31.1 this warning
is emitted:
powerpc-linux-gnu-ld: warning: orphan section `.branch_lt' from
`arch/powerpc/kernel/head_44x.o' being placed in section `.branch_lt'
As of binutils commit 2d7ad24e8726 ("Support PLT16 relocs against local
symbols")[1], 32 bit targets can produce .branch_lt sections in their
output.
These sections should be empty for the kernel build so discard them for
both PPC64 and PPC32.
[1] https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commitdiff;h=2d7ad24e8726ba4c45c9e67be08223a146a837ce
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
v2: Discard instead of keep. Alan said "[discarding] can be a recipe for
finding linker bugs", so lets go with that.
---
arch/powerpc/kernel/vmlinux.lds.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 2c93a420f456..af0f81df8bb9 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -316,7 +316,6 @@ SECTIONS
DATA_DATA
*(.data.rel*)
*(.toc1)
- *(.branch_lt)
}
.opd : AT(ADDR(.opd) - LOAD_OFFSET) {
@@ -388,6 +387,7 @@ SECTIONS
*(.hash .gnu.hash)
*(.interp)
*(.dynstr)
+ *(.branch_lt)
#ifndef CONFIG_PPC32
*(.dynsym)
#endif
--
2.19.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-12-20 11:23 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2018-12-10 22:28 [PATCH v3 0/3] powerpc: Add to linker script discards Joel Stanley
2018-12-10 22:28 ` [PATCH v3 1/3] powerpc: Discard more sections in linker script Joel Stanley
2018-12-20 11:18 ` Michael Ellerman
2018-12-10 22:28 ` [PATCH v3 2/3] powerpc: Discard dynsym section for !PPC32 Joel Stanley
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2018-12-10 22:28 ` [PATCH v3 3/3] powerpc: Discard .branch_lt section Joel Stanley
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