Re: [PATCH 1/1] arch/powerpc: Don't assume start_text & head_end align

From: Christophe Leroy
Date: Thu Sep 08 2022 - 02:42:49 EST




Le 13/03/2019 à 04:38, Alastair D'Silva a écrit :
From: Alastair D'Silva <alastair@xxxxxxxxxxx>

When building LTO kernels, the start_text symbol is not guaranteed to mark
the end of the head section.

Instead, look explicitly for __head_end.

Could you please give more details ?

Have you encountered a problem ?

From commit c494adefef9f ("powerpc/64: Tool to check head sections location sanity"), I understand that we want to make sure text_start is where it is, not that __head_end is.

Thanks
Christophe



Signed-off-by: Alastair D'Silva <alastair@xxxxxxxxxxx>
---
arch/powerpc/tools/head_check.sh | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/tools/head_check.sh b/arch/powerpc/tools/head_check.sh
index ad9e57209aa4..1b0f634038c3 100644
--- a/arch/powerpc/tools/head_check.sh
+++ b/arch/powerpc/tools/head_check.sh
@@ -44,7 +44,7 @@ nm="$1"
vmlinux="$2"
# gcc-4.6-era toolchain make _stext an A (absolute) symbol rather than T
-$nm "$vmlinux" | grep -e " [TA] _stext$" -e " t start_first_256B$" -e " a text_start$" -e " t start_text$" -m4 > .tmp_symbols.txt
+$nm "$vmlinux" | grep -e " [TA] _stext$" -e " t start_first_256B$" -e " a text_start$" -e " T __head_end$" -m4 > .tmp_symbols.txt
vma=$(cat .tmp_symbols.txt | grep -e " [TA] _stext$" | cut -d' ' -f1)
@@ -63,12 +63,12 @@ fi
top_vma=$(echo $vma | cut -d'0' -f1)
-expected_start_text_addr=$(cat .tmp_symbols.txt | grep " a text_start$" | cut -d' ' -f1 | sed "s/^0/$top_vma/")
+expected_head_end_addr=$(cat .tmp_symbols.txt | grep " a text_start$" | cut -d' ' -f1 | sed "s/^0/$top_vma/")
-start_text_addr=$(cat .tmp_symbols.txt | grep " t start_text$" | cut -d' ' -f1)
+head_end_addr=$(cat .tmp_symbols.txt | grep " T __head_end$" | cut -d' ' -f1)
-if [ "$start_text_addr" != "$expected_start_text_addr" ]; then
- echo "ERROR: start_text address is $start_text_addr, should be $expected_start_text_addr"
+if [ "$head_end_addr" != "$expected_head_end_addr" ]; then
+ echo "ERROR: __head_end address is $head_end_addr, should be $expected_head_end_addr"
echo "ERROR: try to enable LD_HEAD_STUB_CATCH config option"
echo "ERROR: see comments in arch/powerpc/tools/head_check.sh"