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 55909b2208cc..183f39384e4c 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -792,7 +792,7 @@ 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;
@@ -800,13 +800,16 @@ 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;