Commit e84ba47e authored by Dave Hansen's avatar Dave Hansen Committed by Borislav Petkov
Browse files

x86/fpu: Hook up PKRU into ptrace() 



One nice thing about having PKRU be XSAVE-managed is that it gets naturally
exposed into the XSAVE-using ABIs.  Now that XSAVE will not be used to
manage PKRU, these ABIs need to be manually enabled to deal with PKRU.

ptrace() uses copy_uabi_xstate_to_kernel() to collect the tracee's
XSTATE. As PKRU is not in the task's XSTATE buffer, use task->thread.pkru
for filling in up the ptrace buffer.

Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.508770763@linutronix.de
parent 9782a712

arch/x86/include/asm/fpu/xstate.h

+1 −1
Original line number Diff line number Diff line
@@ -139,7 +139,7 @@ enum xstate_copy_mode { 
};



struct membuf;

void copy_xstate_to_uabi_buf(struct membuf to, struct xregs_state *xsave,

void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,

			     enum xstate_copy_mode mode);



#endif

arch/x86/kernel/fpu/regset.c

+4 −6
Original line number Diff line number Diff line
@@ -78,7 +78,7 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset, 
				    sizeof(fpu->state.fxsave));

	}



	copy_xstate_to_uabi_buf(to, &fpu->state.xsave, XSTATE_COPY_FX);

	copy_xstate_to_uabi_buf(to, target, XSTATE_COPY_FX);

	return 0;

}
@@ -126,14 +126,12 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset, 
int xstateregs_get(struct task_struct *target, const struct user_regset *regset,

		struct membuf to)

{

	struct fpu *fpu = &target->thread.fpu;



	if (!cpu_feature_enabled(X86_FEATURE_XSAVE))

		return -ENODEV;



	sync_fpstate(fpu);

	sync_fpstate(&target->thread.fpu);



	copy_xstate_to_uabi_buf(to, &fpu->state.xsave, XSTATE_COPY_XSAVE);

	copy_xstate_to_uabi_buf(to, target, XSTATE_COPY_XSAVE);

	return 0;

}
@@ -336,7 +334,7 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset, 
		struct membuf mb = { .p = &fxsave, .left = sizeof(fxsave) };



		/* Handle init state optimized xstate correctly */

		copy_xstate_to_uabi_buf(mb, &fpu->state.xsave, XSTATE_COPY_FP);

		copy_xstate_to_uabi_buf(mb, target, XSTATE_COPY_FP);

		fx = &fxsave;

	} else {

		fx = &fpu->state.fxsave;

arch/x86/kernel/fpu/xstate.c

+18 −7
Original line number Diff line number Diff line
@@ -962,7 +962,7 @@ static void copy_feature(bool from_xstate, struct membuf *to, void *xstate, 
/**

 * copy_xstate_to_uabi_buf - Copy kernel saved xstate to a UABI buffer

 * @to:		membuf descriptor

 * @xsave:	The kernel xstate buffer to copy from

 * @tsk:	The task from which to copy the saved xstate

 * @copy_mode:	The requested copy mode

 *

 * Converts from kernel XSAVE or XSAVES compacted format to UABI conforming
@@ -971,10 +971,11 @@ static void copy_feature(bool from_xstate, struct membuf *to, void *xstate, 
 *

 * It supports partial copy but @to.pos always starts from zero.

 */

void copy_xstate_to_uabi_buf(struct membuf to, struct xregs_state *xsave,

void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,

			     enum xstate_copy_mode copy_mode)

{

	const unsigned int off_mxcsr = offsetof(struct fxregs_state, mxcsr);

	struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;

	struct xregs_state *xinit = &init_fpstate.xsave;

	struct xstate_header header;

	unsigned int zerofrom;
@@ -1048,11 +1049,21 @@ void copy_xstate_to_uabi_buf(struct membuf to, struct xregs_state *xsave, 
		if (zerofrom < xstate_offsets[i])

			membuf_zero(&to, xstate_offsets[i] - zerofrom);



		if (i == XFEATURE_PKRU) {

			struct pkru_state pkru = {0};

			/*

			 * PKRU is not necessarily up to date in the

			 * thread's XSAVE buffer.  Fill this part from the

			 * per-thread storage.

			 */

			pkru.pkru = tsk->thread.pkru;

			membuf_write(&to, &pkru, sizeof(pkru));

		} else {

			copy_feature(header.xfeatures & BIT_ULL(i), &to,

				     __raw_xsave_addr(xsave, i),

				     __raw_xsave_addr(xinit, i),

				     xstate_sizes[i]);



		}

		/*

		 * Keep track of the last copied state in the non-compacted

		 * target buffer for gap zeroing.