From: Dave Martin <Dave.Martin@xxxxxxx>
[ 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@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
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;
--
2.15.1