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Commit efdb4167 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
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scripts/faddr2line: Fix "size mismatch" error 



I'm not sure how we missed this problem before.  When I take a function
address and size from an oops and give it to faddr2line, it usually
complains about a size mismatch:

  $ scripts/faddr2line ~/k/vmlinux write_sysrq_trigger+0x51/0x60
  skipping write_sysrq_trigger address at 0xffffffff815731a1 due to size mismatch (0x60 != 83)
  no match for write_sysrq_trigger+0x51/0x60

The problem is caused by differences in how kallsyms and faddr2line
determine a function's size.

kallsyms calculates a function's size by parsing the output of 'nm -n'
and subtracting the next function's address from the current function's
address.  This means that nop instructions after the end of the function
are included in the size.

In contrast, faddr2line reads the size from the symbol table, which does
*not* include the ending nops in the function's size.

Change faddr2line to calculate the size from the output of 'nm -n' to be
consistent with kallsyms and oops outputs.

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/bd313ed7c4003f6b1fda63e825325c44a9d837de.1477405374.git.jpoimboe@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 5e25d5bd

scripts/faddr2line

+21 −12
Original line number Diff line number Diff line
@@ -105,9 +105,18 @@ __faddr2line() { 
	# In rare cases there might be duplicates.

	while read symbol; do

		local fields=($symbol)

		local sym_base=0x${fields[1]}

		local sym_size=${fields[2]}

		local sym_type=${fields[3]}

		local sym_base=0x${fields[0]}

		local sym_type=${fields[1]}

		local sym_end=0x${fields[3]}



		# calculate the size

		local sym_size=$(($sym_end - $sym_base))

		if [[ -z $sym_size ]] || [[ $sym_size -le 0 ]]; then

			warn "bad symbol size: base: $sym_base end: $sym_end"

			DONE=1

			return

		fi

		sym_size=0x$(printf %x $sym_size)



		# calculate the address

		local addr=$(($sym_base + $offset))
@@ -116,26 +125,26 @@ __faddr2line() { 
			DONE=1

			return

		fi

		local hexaddr=0x$(printf %x $addr)

		addr=0x$(printf %x $addr)



		# weed out non-function symbols

		if [[ $sym_type != "FUNC" ]]; then

		if [[ $sym_type != t ]] && [[ $sym_type != T ]]; then

			[[ $print_warnings = 1 ]] &&

				echo "skipping $func address at $hexaddr due to non-function symbol"

				echo "skipping $func address at $addr due to non-function symbol of type '$sym_type'"

			continue

		fi



		# if the user provided a size, make sure it matches the symbol's size

		if [[ -n $size ]] && [[ $size -ne $sym_size ]]; then

			[[ $print_warnings = 1 ]] &&

				echo "skipping $func address at $hexaddr due to size mismatch ($size != $sym_size)"

				echo "skipping $func address at $addr due to size mismatch ($size != $sym_size)"

			continue;

		fi



		# make sure the provided offset is within the symbol's range

		if [[ $offset -gt $sym_size ]]; then

			[[ $print_warnings = 1 ]] &&

				echo "skipping $func address at $hexaddr due to size mismatch ($offset > $sym_size)"

				echo "skipping $func address at $addr due to size mismatch ($offset > $sym_size)"

			continue

		fi
@@ -143,12 +152,12 @@ __faddr2line() { 
		[[ $FIRST = 0 ]] && echo

		FIRST=0



		local hexsize=0x$(printf %x $sym_size)

		echo "$func+$offset/$hexsize:"

		addr2line -fpie $objfile $hexaddr | sed "s; $dir_prefix\(\./\)*; ;"

		# pass real address to addr2line

		echo "$func+$offset/$sym_size:"

		addr2line -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;"

		DONE=1



	done < <(readelf -sW $objfile | awk -v f=$func '$8 == f {print}')

	done < <(nm -n $objfile | awk -v fn=$func '$3 == fn { found=1; line=$0; start=$1; next } found == 1 { found=0; print line, $1 }')

}



[[ $# -lt 2 ]] && usage