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x86/fpu: Hook up PKRU into ptrace()

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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: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.508770763@linutronix.de
This commit is contained in:
Dave Hansen 2021-06-23 14:02:19 +02:00 committed by Borislav Petkov
parent 9782a712eb
commit e84ba47e31
3 changed files with 23 additions and 14 deletions
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2
arch/x86/include/asm/fpu/xstate.h
View File

@ -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

10
arch/x86/kernel/fpu/regset.c
View File

@ -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;

25
arch/x86/kernel/fpu/xstate.c
View File

@ -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);
copy_feature(header.xfeatures & BIT_ULL(i), &to,
__raw_xsave_addr(xsave, i),
__raw_xsave_addr(xinit, i),
xstate_sizes[i]);
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.