lkml.org 
[lkml]   [2018]   [Apr]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH AUTOSEL for 4.9 121/293] arm64: ptrace: Fix VFP register dumping in compat coredumps
    Date
    From: Dave Martin <Dave.Martin@arm.com>

    [ Upstream commit af66b2d88a76574d55e81d712292abd34beb6178 ]

    Currently, VFP registers are omitted from coredumps for compat
    processes, due to a bug in the REGSET_COMPAT_VFP regset
    implementation.

    compat_vfp_get() needs to transfer non-contiguous data from
    thread_struct.fpsimd_state, and uses put_user() to handle the
    offending trailing word (FPSCR). This fails when copying to a
    kernel address (i.e., kbuf && !ubuf), which is what happens when
    dumping core. As a result, the ELF coredump core code silently
    omits the NT_ARM_VFP note from the dump.

    It would be possible to work around this with additional special
    case code for the put_user(), but since user_regset_copyout() is
    explicitly designed to handle this scenario it is cleaner to port
    the put_user() to a user_regset_copyout() call, which this patch
    does.

    Signed-off-by: Dave Martin <Dave.Martin@arm.com>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    arch/arm64/kernel/ptrace.c | 11 +++++++----
    1 file changed, 7 insertions(+), 4 deletions(-)

    diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
    index d1fd560b3a2a..5c78b64369cf 100644
    --- a/arch/arm64/kernel/ptrace.c
    +++ b/arch/arm64/kernel/ptrace.c
    @@ -896,7 +896,7 @@ static int compat_vfp_get(struct task_struct *target,
    {
    struct user_fpsimd_state *uregs;
    compat_ulong_t fpscr;
    - int ret;
    + int ret, vregs_end_pos;

    uregs = &target->thread.fpsimd_state.user_fpsimd;

    @@ -904,13 +904,16 @@ static int compat_vfp_get(struct task_struct *target,
    * The VFP registers are packed into the fpsimd_state, so they all sit
    * nicely together for us. We just need to create the fpscr separately.
    */
    - ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, uregs, 0,
    - VFP_STATE_SIZE - sizeof(compat_ulong_t));
    + vregs_end_pos = VFP_STATE_SIZE - sizeof(compat_ulong_t);
    + ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, uregs,
    + 0, vregs_end_pos);

    if (count && !ret) {
    fpscr = (uregs->fpsr & VFP_FPSCR_STAT_MASK) |
    (uregs->fpcr & VFP_FPSCR_CTRL_MASK);
    - ret = put_user(fpscr, (compat_ulong_t *)ubuf);
    +
    + ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, &fpscr,
    + vregs_end_pos, VFP_STATE_SIZE);
    }

    return ret;
    --
    2.15.1
    \
     
     \ /
      Last update: 2018-04-09 04:21    [W:2.852 / U:0.432 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site