4.9-stable review patch. If anyone has any objections, please let me know.
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From: Maciej W. Rozycki macro@mips.com
commit 71e909c0cdad28a1df1fa14442929e68615dee45 upstream.
Correct commit 7aeb753b5353 ("MIPS: Implement task_user_regset_view.") and expose the FIR register using the unused 4 bytes at the end of the NT_PRFPREG regset. Without that register included clients cannot use the PTRACE_GETREGSET request to retrieve the complete FPU register set and have to resort to one of the older interfaces, either PTRACE_PEEKUSR or PTRACE_GETFPREGS, to retrieve the missing piece of data. Also the register is irreversibly missing from core dumps.
This register is architecturally hardwired and read-only so the write path does not matter. Ignore data supplied on writes then.
Fixes: 7aeb753b5353 ("MIPS: Implement task_user_regset_view.") Signed-off-by: James Hogan jhogan@kernel.org Signed-off-by: Maciej W. Rozycki macro@mips.com Cc: Ralf Baechle ralf@linux-mips.org Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org # 3.13+ Patchwork: https://patchwork.linux-mips.org/patch/19273/ Signed-off-by: James Hogan jhogan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/mips/kernel/ptrace.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)
--- a/arch/mips/kernel/ptrace.c +++ b/arch/mips/kernel/ptrace.c @@ -483,7 +483,7 @@ static int fpr_get_msa(struct task_struc /* * Copy the floating-point context to the supplied NT_PRFPREG buffer. * Choose the appropriate helper for general registers, and then copy - * the FCSR register separately. + * the FCSR and FIR registers separately. */ static int fpr_get(struct task_struct *target, const struct user_regset *regset, @@ -491,6 +491,7 @@ static int fpr_get(struct task_struct *t void *kbuf, void __user *ubuf) { const int fcr31_pos = NUM_FPU_REGS * sizeof(elf_fpreg_t); + const int fir_pos = fcr31_pos + sizeof(u32); int err;
if (sizeof(target->thread.fpu.fpr[0]) == sizeof(elf_fpreg_t)) @@ -503,6 +504,12 @@ static int fpr_get(struct task_struct *t err = user_regset_copyout(&pos, &count, &kbuf, &ubuf, &target->thread.fpu.fcr31, fcr31_pos, fcr31_pos + sizeof(u32)); + if (err) + return err; + + err = user_regset_copyout(&pos, &count, &kbuf, &ubuf, + &boot_cpu_data.fpu_id, + fir_pos, fir_pos + sizeof(u32));
return err; } @@ -551,7 +558,8 @@ static int fpr_set_msa(struct task_struc /* * Copy the supplied NT_PRFPREG buffer to the floating-point context. * Choose the appropriate helper for general registers, and then copy - * the FCSR register separately. + * the FCSR register separately. Ignore the incoming FIR register + * contents though, as the register is read-only. * * We optimize for the case where `count % sizeof(elf_fpreg_t) == 0', * which is supposed to have been guaranteed by the kernel before @@ -565,6 +573,7 @@ static int fpr_set(struct task_struct *t const void *kbuf, const void __user *ubuf) { const int fcr31_pos = NUM_FPU_REGS * sizeof(elf_fpreg_t); + const int fir_pos = fcr31_pos + sizeof(u32); u32 fcr31; int err;
@@ -592,6 +601,11 @@ static int fpr_set(struct task_struct *t ptrace_setfcr31(target, fcr31); }
+ if (count > 0) + err = user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf, + fir_pos, + fir_pos + sizeof(u32)); + return err; }