• Tony Wu's avatar
    MIPS: Fix sibling call handling in get_frame_info · e7438c4b
    Tony Wu authored
    Given a function, get_frame_info() analyzes its instructions
    to figure out frame size and return address. get_frame_info()
    works as follows:
    
    1. analyze up to 128 instructions if the function size is unknown
    2. search for 'addiu/daddiu sp,sp,-immed' for frame size
    3. search for 'sw ra,offset(sp)' for return address
    4. end search when it sees jr/jal/jalr
    
    This leads to an issue when the given function is a sibling
    call, example shown as follows.
    
    801ca110 <schedule>:
    801ca110:       8f820000        lw      v0,0(gp)
    801ca114:       8c420000        lw      v0,0(v0)
    801ca118:       080726f0        j       801c9bc0 <__schedule>
    801ca11c:       00000000        nop
    
    801ca120 <io_schedule>:
    801ca120:       27bdffe8        addiu   sp,sp,-24
    801ca124:       3c028022        lui     v0,0x8022
    801ca128:       afbf0014        sw      ra,20(sp)
    
    In this case, get_frame_info() cannot properly detect schedule's
    frame info, and eventually returns io_schedule's instead.
    
    This patch adds 'j' to the end search condition to workaround
    sibling call cases.
    Signed-off-by: default avatarTony Wu <tung7970@gmail.com>
    Cc: linux-mips@linux-mips.org
    Patchwork: https://patchwork.linux-mips.org/patch/5236/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
    e7438c4b
process.c 13.1 KB