The toolchain problem described in commit f6537f2f0eba
(scripts/kallsyms: filter symbols not in kernel address space) makes it
necessary to filter out some kernel symbols from /proc/kallsyms to make
perf happy.
For that to work correctly the address used to filter should be just
below the kernel text segment. Depending on kernel configuration
CONFIG_PAGE_OFFSET is not the right address to use. See the comments
introduced by this commit for the glory details.
Fixes: b9b32bf70f2f (ARM: use linker magic for vectors and vector stubs)
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
---
Hello,
note I'm not entirely sure if the diagnose "toolchain problem" is right.
That's what Arnd suggested in #armlinux. So maybe the commit log wants
some fixing.
This is probably stable material as 7122c3e9154b and f6537f2f0eba were
considered for stable, too. As b9b32bf70f2f has a stable annotation,
too, maybe older stable kernel also need fixing.
Other than that I wonder if "--page-offset" is a misnomer. Better use
"--kernel-start"? I didn't do this change here because patches for
stable should be minimal. But maybe it's worth a followup patch?
Best regards
Uwe
scripts/link-vmlinux.sh | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 2dcb37736d84..493b4ccdf5fc 100644
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -82,8 +82,24 @@ kallsyms()
kallsymopt="${kallsymopt} --all-symbols"
fi
- if [ -n "${CONFIG_ARM}" ] && [ -n "${CONFIG_PAGE_OFFSET}" ]; then
- kallsymopt="${kallsymopt} --page-offset=$CONFIG_PAGE_OFFSET"
+ if [ -n "${CONFIG_ARM}" ]; then
+ # There are some ARM toolchains that generate some internal
+ # symbols that then appear in /proc/kallsyms and these disturbe
+ # perf. So filter out all symbols below PAGE_OFFSET.
+ # ARM is a bit complicated here. The page-offset isn't
+ # completely determined in Kconfig as of 3.14-rc. Without MMU
+ # it's not CONFIG_PAGE_OFFSET that is used but (indirectly)
+ # CONFIG_DRAM_BASE. But for XIP we want the XIP PHYS_ADDR
+ # though.
+ if [ -n "${CONFIG_XIP_PHYS_ADDR}" ]; then
+ page_offset="${CONFIG_XIP_PHYS_ADDR}"
+ elif [ -z "${CONFIG_MMU}" ]; then
+ page_offset="${CONFIG_DRAM_BASE}"
+ else
+ page_offset="$CONFIG_PAGE_OFFSET"
+ fi
+
+ kallsymopt="${kallsymopt} --page-offset=$page_offset"
fi
local aflags="${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
--
1.8.5.3
--
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