sparc64: Fix userspace FPU register corruptions.

If we have a series of events from userpsace, with %fprs=FPRS_FEF,
like follows:

ETRAP
	ETRAP
		VIS_ENTRY(fprs=0x4)
		VIS_EXIT
		RTRAP (kernel FPU restore with fpu_saved=0x4)
	RTRAP

We will not restore the user registers that were clobbered by the FPU
using kernel code in the inner-most trap.

Traps allocate FPU save slots in the thread struct, and FPU using
sequences save the "dirty" FPU registers only.

This works at the initial trap level because all of the registers
get recorded into the top-level FPU save area, and we'll return
to userspace with the FPU disabled so that any FPU use by the user
will take an FPU disabled trap wherein we'll load the registers
back up properly.

But this is not how trap returns from kernel to kernel operate.

The simplest fix for this bug is to always save all FPU register state
for anything other than the top-most FPU save area.

Getting rid of the optimized inner-slot FPU saving code ends up
making VISEntryHalf degenerate into plain VISEntry.

Longer term we need to do something smarter to reinstate the partial
save optimizations.  Perhaps the fundament error is having trap entry
and exit allocate FPU save slots and restore register state.  Instead,
the VISEntry et al. calls should be doing that work.

This bug is about two decades old.

Reported-by: James Y Knight <jyknight@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/sparc/include/asm/visasm.h b/arch/sparc/include/asm/visasm.h
index 1f0aa2024e94be341efc079f58145a2e70909052..6424249d5f785e698c4283677c1b975668393478 100644 (file)
--- a/arch/sparc/include/asm/visasm.h
+++ b/arch/sparc/include/asm/visasm.h
@@ -28,16 +28,10 @@
  * Must preserve %o5 between VISEntryHalf and VISExitHalf */
 
 #define VISEntryHalf                                   \
-       rd              %fprs, %o5;                     \
-       andcc           %o5, FPRS_FEF, %g0;             \
-       be,pt           %icc, 297f;                     \
-        sethi          %hi(298f), %g7;                 \
-       sethi           %hi(VISenterhalf), %g1;         \
-       jmpl            %g1 + %lo(VISenterhalf), %g0;   \
-        or             %g7, %lo(298f), %g7;            \
-       clr             %o5;                            \
-297:   wr              %o5, FPRS_FEF, %fprs;           \
-298:
+       VISEntry
+
+#define VISExitHalf                                    \
+       VISExit
 
 #define VISEntryHalfFast(fail_label)                   \
        rd              %fprs, %o5;                     \
@@ -47,7 +41,7 @@
        ba,a,pt         %xcc, fail_label;               \
 297:   wr              %o5, FPRS_FEF, %fprs;
 
-#define VISExitHalf                                    \
+#define VISExitHalfFast                                        \
        wr              %o5, 0, %fprs;
 
 #ifndef __ASSEMBLY__

diff --git a/arch/sparc/lib/NG4memcpy.S b/arch/sparc/lib/NG4memcpy.S
index 140527a20e7df03cc0a0dd9e6a3438f44b432177..83aeeb1dffdb3b4c29293d5924cd5259e2269ce5 100644 (file)
--- a/arch/sparc/lib/NG4memcpy.S
+++ b/arch/sparc/lib/NG4memcpy.S
@@ -240,8 +240,11 @@ FUNC_NAME: /* %o0=dst, %o1=src, %o2=len */
        add             %o0, 0x40, %o0
        bne,pt          %icc, 1b
         LOAD(prefetch, %g1 + 0x200, #n_reads_strong)
+#ifdef NON_USER_COPY
+       VISExitHalfFast
+#else
        VISExitHalf
-
+#endif
        brz,pn          %o2, .Lexit
         cmp            %o2, 19
        ble,pn          %icc, .Lsmall_unaligned

diff --git a/arch/sparc/lib/VISsave.S b/arch/sparc/lib/VISsave.S
index b320ae9e2e2e8b27c7184f58ddc640b4adf6fdda..a063d84336d6384a03d7ddd8a5143f0909801ed8 100644 (file)
--- a/arch/sparc/lib/VISsave.S
+++ b/arch/sparc/lib/VISsave.S
@@ -44,9 +44,8 @@ vis1: ldub            [%g6 + TI_FPSAVED], %g3
 
         stx            %g3, [%g6 + TI_GSR]
 2:     add             %g6, %g1, %g3
-       cmp             %o5, FPRS_DU
-       be,pn           %icc, 6f
-        sll            %g1, 3, %g1
+       mov             FPRS_DU | FPRS_DL | FPRS_FEF, %o5
+       sll             %g1, 3, %g1
        stb             %o5, [%g3 + TI_FPSAVED]
        rd              %gsr, %g2
        add             %g6, %g1, %g3
@@ -80,65 +79,3 @@ vis1:        ldub            [%g6 + TI_FPSAVED], %g3
        .align          32
 80:    jmpl            %g7 + %g0, %g0
         nop
-
-6:     ldub            [%g3 + TI_FPSAVED], %o5
-       or              %o5, FPRS_DU, %o5
-       add             %g6, TI_FPREGS+0x80, %g2
-       stb             %o5, [%g3 + TI_FPSAVED]
-
-       sll             %g1, 5, %g1
-       add             %g6, TI_FPREGS+0xc0, %g3
-       wr              %g0, FPRS_FEF, %fprs
-       membar          #Sync
-       stda            %f32, [%g2 + %g1] ASI_BLK_P
-       stda            %f48, [%g3 + %g1] ASI_BLK_P
-       membar          #Sync
-       ba,pt           %xcc, 80f
-        nop
-
-       .align          32
-80:    jmpl            %g7 + %g0, %g0
-        nop
-
-       .align          32
-VISenterhalf:
-       ldub            [%g6 + TI_FPDEPTH], %g1
-       brnz,a,pn       %g1, 1f
-        cmp            %g1, 1
-       stb             %g0, [%g6 + TI_FPSAVED]
-       stx             %fsr, [%g6 + TI_XFSR]
-       clr             %o5
-       jmpl            %g7 + %g0, %g0
-        wr             %g0, FPRS_FEF, %fprs
-
-1:     bne,pn          %icc, 2f
-        srl            %g1, 1, %g1
-       ba,pt           %xcc, vis1
-        sub            %g7, 8, %g7
-2:     addcc           %g6, %g1, %g3
-       sll             %g1, 3, %g1
-       andn            %o5, FPRS_DU, %g2
-       stb             %g2, [%g3 + TI_FPSAVED]
-
-       rd              %gsr, %g2
-       add             %g6, %g1, %g3
-       stx             %g2, [%g3 + TI_GSR]
-       add             %g6, %g1, %g2
-       stx             %fsr, [%g2 + TI_XFSR]
-       sll             %g1, 5, %g1
-3:     andcc           %o5, FPRS_DL, %g0
-       be,pn           %icc, 4f
-        add            %g6, TI_FPREGS, %g2
-
-       add             %g6, TI_FPREGS+0x40, %g3
-       membar          #Sync
-       stda            %f0, [%g2 + %g1] ASI_BLK_P
-       stda            %f16, [%g3 + %g1] ASI_BLK_P
-       membar          #Sync
-       ba,pt           %xcc, 4f
-        nop
-
-       .align          32
-4:     and             %o5, FPRS_DU, %o5
-       jmpl            %g7 + %g0, %g0
-        wr             %o5, FPRS_FEF, %fprs

diff --git a/arch/sparc/lib/ksyms.c b/arch/sparc/lib/ksyms.c
index 1d649a95660c8cad57fbe90feadb7c43b9e8263f..8069ce12f20b13d514160cec8db0c0d88b64b27e 100644 (file)
--- a/arch/sparc/lib/ksyms.c
+++ b/arch/sparc/lib/ksyms.c
@@ -135,10 +135,6 @@ EXPORT_SYMBOL(copy_user_page);
 void VISenter(void);
 EXPORT_SYMBOL(VISenter);
 
-/* CRYPTO code needs this */
-void VISenterhalf(void);
-EXPORT_SYMBOL(VISenterhalf);
-
 extern void xor_vis_2(unsigned long, unsigned long *, unsigned long *);
 extern void xor_vis_3(unsigned long, unsigned long *, unsigned long *,
                unsigned long *);