Messages in this thread Patch in this message |  | | From | "Chang S. Bae" <> | Subject | [PATCH v5 13/28] x86/fpu/xstate: Update the xstate context copy function to support dynamic states | Date | Sun, 23 May 2021 12:32:44 -0700 |
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ptrace() and signal return paths use xstate context copy functions. They allow callers to read (or write) xstate values in the target's buffer. With dynamic user states, a component's position in the buffer may vary and the initial value is not always stored in init_fpstate.
Change the helpers to find a component's offset accordingly.
When copying an initial value, explicitly check the init_fpstate coverage. If not found, reset the memory in the destination. Otherwise, copy values from init_fpstate.
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Reviewed-by: Len Brown <len.brown@intel.com> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v3: * Cleaned up the code change with more comments. * Removed 'no functional change' in the changelog. (Borislav Petkov)
Changes from v2: * Updated the changelog with task->fpu removed. (Borislav Petkov) --- arch/x86/kernel/fpu/xstate.c | 69 ++++++++++++++++++++++++++++-------- 1 file changed, 55 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 9d3cd9775b76..299373669a5d 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -301,7 +301,7 @@ void fpstate_sanitize_xstate(struct fpu *fpu) * in a special way already: */ feature_bit = 0x2; - xfeatures = (xfeatures_mask_user() & ~xfeatures) >> 2; + xfeatures = (xfeatures_mask_user() & fpu->state_mask & ~xfeatures) >> feature_bit; /* * Update all the remaining memory layouts according to their @@ -310,12 +310,19 @@ void fpstate_sanitize_xstate(struct fpu *fpu) */ while (xfeatures) { if (xfeatures & 0x1) { - int offset = xstate_comp_offsets[feature_bit]; + int offset = get_xstate_comp_offset(fpu->state_mask, feature_bit); int size = xstate_sizes[feature_bit]; - memcpy((void *)fx + offset, - (void *)&init_fpstate.xsave + offset, - size); + /* + * init_fpstate does not include the dynamic user states + * as having initial values with zeros. + */ + if (xfeatures_mask_user_dynamic & BIT_ULL(feature_bit)) + memset((void *)fx + offset, 0, size); + else + memcpy((void *)fx + offset, + (void *)&init_fpstate.xsave + offset, + size); } xfeatures >>= 1; @@ -1297,15 +1304,31 @@ static void fill_gap(struct membuf *to, unsigned *last, unsigned offset) { if (*last >= offset) return; - membuf_write(to, (void *)&init_fpstate.xsave + *last, offset - *last); + + /* + * Copy initial data. + * + * init_fpstate buffer has the minimum size as excluding the dynamic user + * states. But their initial values are zeros. + */ + if (offset <= get_xstate_config(XSTATE_MIN_SIZE)) + membuf_write(to, (void *)&init_fpstate.xsave + *last, offset - *last); + else + membuf_zero(to, offset - *last); *last = offset; } +/* + * @from: If NULL, copy zeros. + */ static void copy_part(struct membuf *to, unsigned *last, unsigned offset, unsigned size, void *from) { fill_gap(to, last, offset); - membuf_write(to, from, size); + if (from) + membuf_write(to, from, size); + else + membuf_zero(to, size); *last = offset + size; } @@ -1357,15 +1380,27 @@ void copy_xstate_to_kernel(struct membuf to, struct fpu *fpu) sizeof(header), &header); for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) { + u64 mask = BIT_ULL(i); + void *src; + + if (!(xfeatures_mask_user() & mask)) + continue; + /* - * Copy only in-use xstates: + * Copy states if used. Otherwise, copy the initial data. */ - if ((header.xfeatures >> i) & 1) { - void *src = __raw_xsave_addr(fpu, i); - copy_part(&to, &last, xstate_offsets[i], - xstate_sizes[i], src); - } + if (header.xfeatures & mask) + src = __raw_xsave_addr(fpu, i); + else + /* + * init_fpstate buffer does not include the dynamic + * user state data as having initial values with zeros. + */ + src = (xfeatures_mask_user_dynamic & mask) ? + NULL : (void *)&init_fpstate.xsave + last; + + copy_part(&to, &last, xstate_offsets[i], xstate_sizes[i], src); } fill_gap(&to, &last, size); @@ -1398,6 +1433,9 @@ int copy_kernel_to_xstate(struct fpu *fpu, const void *kbuf) if (hdr.xfeatures & mask) { void *dst = __raw_xsave_addr(fpu, i); + if (!dst) + continue; + offset = xstate_offsets[i]; size = xstate_sizes[i]; @@ -1455,6 +1493,9 @@ int copy_user_to_xstate(struct fpu *fpu, const void __user *ubuf) if (hdr.xfeatures & mask) { void *dst = __raw_xsave_addr(fpu, i); + if (!dst) + continue; + offset = xstate_offsets[i]; size = xstate_sizes[i]; @@ -1535,7 +1576,7 @@ void copy_supervisor_to_kernel(struct fpu *fpu) continue; /* Move xfeature 'i' into its normal location */ - memmove(xbuf + xstate_comp_offsets[i], + memmove(xbuf + get_xstate_comp_offset(fpu->state_mask, i), xbuf + xstate_supervisor_only_offsets[i], xstate_sizes[i]); } -- 2.17.1
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