[Dwarf-discuss] Incorrect dwarf information?

[Jun Koi]

Hello,

I am using dwarfdump to analyze the Linux kernel compiled with gcc. A
function named tty_read() has prototype like below:

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

And dwardump returns the below information:

..............
<1><42653>      DW_TAG_subprogram
                DW_AT_sibling               <42825>
                DW_AT_name                  tty_read
                DW_AT_decl_file             1 drivers/char/tty_io.c
                DW_AT_decl_line             1269
                DW_AT_prototyped            yes(1)
                DW_AT_type                  <635>
                DW_AT_low_pc                0xc0200950
                DW_AT_high_pc               0xc0200a14
                DW_AT_frame_base            DW_OP_reg5
<2><42680>      DW_TAG_formal_parameter
                DW_AT_name                  file
                DW_AT_decl_file             1 drivers/char/tty_io.c
                DW_AT_decl_line             1267
                DW_AT_type                  <11014>
                DW_AT_location              <loclist with 4 entries follows>
                        [ 0]<lowpc=0xc0200950><highpc=0xc0200983>DW_OP_fbreg 8
                        [ 1]<lowpc=0xc0200983><highpc=0xc0200993>DW_OP_reg6
                        [ 2]<lowpc=0xc0200993><highpc=0xc0200998>DW_OP_fbreg 8
                        [ 3]<lowpc=0xc0200998><highpc=0xc0200a14>DW_OP_reg6
<2><42696>      DW_TAG_formal_parameter
                DW_AT_name                  buf
                DW_AT_decl_file             1 drivers/char/tty_io.c
                DW_AT_decl_line             1267
                DW_AT_type                  <258>
                DW_AT_location              DW_OP_reg0
........