build updates

Direct banches from code below __end_interrupts to code above __end_interrupts when built with CONFIG_RELOCATABLE are disallowed because they will break when the kernel is not located at 0.

Sample output:

    WARNING: Unrelocated relative branches
    c000000000000118 bl-> 0xc000000000038fb8 <pnv_restore_hyp_resource>
    c00000000000013c b-> 0xc0000000001068a4 <kvm_start_guest>
    c000000000000148 b-> 0xc00000000003919c <pnv_wakeup_loss>
    c00000000000014c b-> 0xc00000000003923c <pnv_wakeup_noloss>
    c0000000000005a4 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>
    c000000000001af0 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>
    c000000000001b24 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>
    c000000000001b58 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>

Signed-off-by Nicholas Piggin <[email protected]>

---

Quoted 16 lines · Nicholas Piggin

Direct banches from code below __end_interrupts to code above __end_interrupts when built with CONFIG_RELOCATABLE are disallowed because they will break when the kernel is not located at 0.

Sample output:

    WARNING: Unrelocated relative branches
    c000000000000118 bl-> 0xc000000000038fb8 <pnv_restore_hyp_resource>
    c00000000000013c b-> 0xc0000000001068a4 <kvm_start_guest>
    c000000000000148 b-> 0xc00000000003919c <pnv_wakeup_loss>
    c00000000000014c b-> 0xc00000000003923c <pnv_wakeup_noloss>
    c0000000000005a4 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>
    c000000000001af0 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>
    c000000000001b24 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>
    c000000000001b58 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>

Quoted 2 lines

Signed-off-by Nicholas Piggin <[email protected]>

---

If this is the same script I gave you, you can add my SOB line as well

Direct banches from code below __end_interrupts to code above __end_interrupts when built with CONFIG_RELOCATABLE are disallowed because they will break when the kernel is not located at 0.

Sample output:

    WARNING: Unrelocated relative branches
    c000000000000118 bl-> 0xc000000000038fb8 <pnv_restore_hyp_resource>
    c00000000000013c b-> 0xc0000000001068a4 <kvm_start_guest>
    c000000000000148 b-> 0xc00000000003919c <pnv_wakeup_loss>
    c00000000000014c b-> 0xc00000000003923c <pnv_wakeup_noloss>
    c0000000000005a4 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>
    c000000000001af0 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>
    c000000000001b24 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>
    c000000000001b58 b-> 0xc000000000106ffc <kvmppc_interrupt_hv>

Signed-off-by Nicholas Piggin <[email protected]>

---
 arch/powerpc/Makefile.postlink           |  9 ++++-
 arch/powerpc/tools/unrel_branch_check.sh | 56 ++++++++++++++++++++++++++++++++

arch/powerpc/tools/head_check.sh new file +7 -0

+# Copyright =C2=A9 2016 IBM Corporation
+
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version
+# 2 of the License, or (at your option) any later version.
+

Quoted 6 lines · Nicholas Piggin

arch/powerpc/Makefile.postlink +0 -0

index 1725e64..b8fe12b 100644
@@ -24,6 +27,9 @@ endif
 

arch/powerpc/Makefile.postlink endif · line 30

Quoted 3 lines

arch/powerpc/Makefile.postlink +1 -0

 vmlinux: FORCE
 	@true
+ifeq ($(CONFIG_PPC64),y)  

You can just use:

ifdef CONFIG_PPC64

Quoted 8 lines

arch/powerpc/Makefile.postlink +2 -0

+	$(call cmd,head_check)
+endif
 ifeq ($(CONFIG_RELOCATABLE),y)
 	$(call if_changed,relocs_check)
 endif

@@ -32,6 +38,7 @@ endif
 	@true
 

arch/powerpc/Makefile.postlink endif · line 42

Quoted 3 lines

arch/powerpc/Makefile.postlink +1 -0

 clean:
+	rm -f .tmp_symbols.txt
 	@true  

We shouldn't need the true anymore should we?

Quoted 4 lines

arch/powerpc/tools/head_check.sh new file +0 -1

new file mode 100755
index 0000000..9635fe7
--- /dev/null

arch/powerpc/tools/head_check.sh line 1

Quoted 3 lines

+++ b/arch/powerpc/tools/head_check.sh

arch/powerpc/tools/head_check.sh new file +1 -0

@@ -0,0 +1,69 @@
+#!/bin/sh  

We run this explicitly via $(CONFIG_SHELL), so having a shebang here is redundant and also a little confusing. I added "-x" here, to turn on tracing, but it doesn't take effect, so I think better to just drop the line. If anyone wants to run it manually they can just pass it to sh.

Quoted 18 lines

arch/powerpc/tools/head_check.sh new file +17 -0

+# Copyright © 2016 IBM Corporation
+
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version
+# 2 of the License, or (at your option) any later version.
+
+# This script checks the head of a vmlinux for linker stubs that
+# break our placement of fixed-location code for 64-bit.
+
+# based on relocs_check.pl
+# Copyright © 2009 IBM Corporation
+
+# READ THIS
+#
+# If the build dies here, it's likely code in head_64.S or nearby is
+# referencing labels it can't reach, which results in the linker inserting

arch/powerpc/tools/head_check.sh line 29

Quoted 10 lines

arch/powerpc/tools/head_check.sh new file +10 -0

+# stubs without the assembler's knowledge. This can move code around in ways
+# that break the fixed location placement stuff (head-64.h). To debug,
+# disassemble the vmlinux and look for branch stubs (long_branch, plt_branch
+# etc) in the fixed section region (0 - 0x8000ish). Check what places are
+# calling those stubs.
+#
+# Linker stubs use the TOC pointer, so even if fixed section code could
+# tolerate them being inserted into head code, they can't be allowed in low
+# level entry code (boot, interrupt vectors, etc) until r2 is set up. This
+# could cause the kernel to die in early boot.  

Can you add:

# Turn this on if you want more debug output:

# set -x

arch/powerpc/tools/head_check.sh line 40

Quoted 12 lines

arch/powerpc/tools/head_check.sh new file +11 -0

+
+if [ $# -lt 2 ]; then
+	echo "$0 [path to nm] [path to vmlinux]" 1>&2
+	exit 1
+fi
+
+# Have Kbuild supply the path to nm so we handle cross compilation.
+nm="$1"
+vmlinux="$2"
+
+nm "$vmlinux" | grep -e " T _stext$" -e " t start_first_256B$" -e " a text_start$" -e " t start_text$" -m4 > .tmp_symbols.txt  

You don't use $nm there.

arch/powerpc/tools/head_check.sh line 51

Quoted 11 lines

arch/powerpc/tools/head_check.sh new file +11 -0

+
+
+vma=$(cat .tmp_symbols.txt | grep " T _stext$" | cut -d' ' -f1)
+
+expected_start_head_addr=$vma
+
+start_head_addr=$(cat .tmp_symbols.txt | grep " t start_first_256B$" | cut -d' ' -f1)
+
+if [ "$start_head_addr" != "$expected_start_head_addr" ]; then
+	echo "ERROR: head code starts at $start_head_addr, should be 0"
+	echo "ERROR: see comments in arch/powerpc/tools/head_check.sh"  

This is blowing up for me with ppc64e_defconfig.

It says:

ERROR: start_text address is c000000000001100, should be c000000000000200

Quoted 13 lines · On Tue, 15 Nov 2016 11:55:26 +1100 Michael Ellerman <[email protected]> wrote:

arch/powerpc/tools/head_check.sh line 1

Quoted 7 lines · Nicholas Piggin

arch/powerpc/tools/head_check.sh new file +1 -0

new file mode 100755
index 0000000..9635fe7
@@ -0,0 +1,69 @@
+#!/bin/sh  

We run this explicitly via $(CONFIG_SHELL), so having a shebang here is redundant and also a little confusing. I added "-x" here, to turn on tracing, but it doesn't take effect, so I think better to just drop the line. If anyone wants to run it manually they can just pass it to sh.

Okay. How about relocs_check.sh? I just started by copying that.

Quoted 2 lines

# Turn this on if you want more debug output:

# set -x

Can do, same question applies for relocs_check.sh

Enable thin archives build for powerpc when COMPILE_TEST is set. Thin archives are explained in this commit:

a5967db9af51a84f5e181600954714a9e4c69f1f

Hi Nick,

Quoted 1 line · On Wed, 19 Oct 2016 14:15:59 +1100 Nicholas Piggin <[email protected]> wrote:

Quoted 4 lines

Enable thin archives build for powerpc when COMPILE_TEST is set. Thin archives are explained in this commit:

a5967db9af51a84f5e181600954714a9e4c69f1f

This reference should be like this:

a5967db9af51 ("kbuild: allow architectures to use thin archives instead of ld -r")

Enable thin archives build for powerpc when COMPILE_TEST is set. Thin archives are explained in this commit:

a5967db9af51a84f5e181600954714a9e4c69f1f

This is a gradual way to introduce the option to testers.

Quoted 6 lines · Nicholas Piggin

Enable thin archives build for powerpc when COMPILE_TEST is set. Thin archives are explained in this commit:

a5967db9af51a84f5e181600954714a9e4c69f1f

This is a gradual way to introduce the option to testers.

I think I'd rather this was actually a user-selectable option, eg.

config USE_THIN_ARCHIVES
bool "Build the kernel using thin archives" default n
select THIN_ARCHIVES
help
Build the kernel using thin archives. If you're unsure say N.

Enable thin archives build for powerpc when COMPILE_TEST is set. Thin archives are explained in this commit:

a5967db9af51a84f5e181600954714a9e4c69f1f

This is a gradual way to introduce the option to testers.

Some change to the way we invoke ar is required so it can be used by scripts/link-vmlinux.sh.

Signed-off-by Stephen Rothwell <[email protected]>

Signed-off-by Nicholas Piggin <[email protected]>

This is cruft to work around allmodconfig build breakage.

Signed-off-by Nicholas Piggin <[email protected]>

[*] Building allyesconfig still requires KALLSYMS_EXTRA_PASS=1, which
I'm yet to look into.

Quoted 2 lines · On Wed, 19 Oct 2016 14:15:53 +1100 Nicholas Piggin <[email protected]> wrote:

[*] Building allyesconfig still requires KALLSYMS_EXTRA_PASS=1, which
I'm yet to look into.

Oh, it's because the kallsyms payload increases kernel image size and that causes more linker stubs to be generated, which have symbols, which go into kallsyms... What a nightmare.

We can use --no-emit-stub-syms, but it's kind of nice to have names for things.