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Unverified Commit 71e909c0 authored by Maciej W. Rozycki's avatar Maciej W. Rozycki Committed by James Hogan
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MIPS: ptrace: Expose FIR register through FP regset 



Correct commit 7aeb753b ("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: 7aeb753b ("MIPS: Implement task_user_regset_view.")
Signed-off-by: default avatarJames Hogan <jhogan@kernel.org>
Signed-off-by: default avatarMaciej 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: default avatarJames Hogan <jhogan@kernel.org>
parent c60128ce

arch/mips/kernel/ptrace.c

+16 −2
Original line number Diff line number Diff line
@@ -463,7 +463,7 @@ static int fpr_get_msa(struct task_struct *target, 
/*

 * 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,
@@ -471,6 +471,7 @@ static int fpr_get(struct task_struct *target, 
		   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))
@@ -483,6 +484,12 @@ static int fpr_get(struct task_struct *target, 
	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;

}
@@ -531,7 +538,8 @@ static int fpr_set_msa(struct task_struct *target, 
/*

 * 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
@@ -545,6 +553,7 @@ static int fpr_set(struct task_struct *target, 
		   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;
@@ -572,6 +581,11 @@ static int fpr_set(struct task_struct *target, 
		ptrace_setfcr31(target, fcr31);

	}



	if (count > 0)

		err = user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf,

						fir_pos,

						fir_pos + sizeof(u32));



	return err;

}