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Subject[PATCH 3/7] kbuild: generate an address ranges map at vmlinux link time
Date
This emits a new file, .tmp_vmlinux.ranges, which maps address
range/size pairs in vmlinux to the object files which make them up,
e.g., in part:

0x0000000000000000 0x30 arch/x86/kernel/cpu/common.o
0x0000000000001000 0x1000 arch/x86/events/intel/ds.o
0x0000000000002000 0x4000 arch/x86/kernel/irq_64.o
0x0000000000006000 0x5000 arch/x86/kernel/process.o
0x000000000000b000 0x1000 arch/x86/kernel/cpu/common.o
0x000000000000c000 0x5000 arch/x86/mm/cpu_entry_area.o
0x0000000000011000 0x10 arch/x86/kernel/espfix_64.o
0x0000000000011010 0x2 arch/x86/kernel/cpu/common.o
[...]

In my simple tests this seems to work with clang too, but if I'm not
sure how stable the format of clang's linker mapfiles is: if it turns
out not to work in some versions, the mapfile-massaging awk script added
here might need some adjustment.

Signed-off-by: Nick Alcock <nick.alcock@oracle.com>
---
scripts/link-vmlinux.sh | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 0e0f6466b18d..00ad1b4b0055 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -178,6 +178,7 @@ vmlinux_link()
objects="--whole-archive \
vmlinux.o \
--no-whole-archive \
+ -Map=.tmp_vmlinux.map \
${@}"
else
objects="--whole-archive \
@@ -186,6 +187,7 @@ vmlinux_link()
--start-group \
${KBUILD_VMLINUX_LIBS} \
--end-group \
+ -Map=.tmp_vmlinux.map \
${@}"
fi

@@ -201,6 +203,7 @@ vmlinux_link()
-Wl,--start-group \
${KBUILD_VMLINUX_LIBS} \
-Wl,--end-group \
+ -Wl,-Map=.tmp_vmlinux.map \
${@}"

${CC} ${CFLAGS_vmlinux} \
@@ -259,6 +262,19 @@ kallsyms()
{
local kallsymopt;

+ # read the linker map to identify ranges of addresses:
+ # - for each *.o file, report address, size, pathname
+ # - most such lines will have four fields
+ # - but sometimes there is a line break after the first field
+ # - start reading at "Linker script and memory map"
+ # - stop reading at ".brk"
+ ${AWK} '
+ /\.o$/ && start==1 { print $(NF-2), $(NF-1), $NF }
+ /^Linker script and memory map/ { start = 1 }
+ /^\.brk/ { exit(0) }
+ ' .tmp_vmlinux.map | sort > .tmp_vmlinux.ranges
+
+ # get kallsyms options
if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
kallsymopt="${kallsymopt} --all-symbols"
fi
--
2.32.0.255.gd9b1d14a2a
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