@@ -213,14 +213,32 @@ int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
/*
* VFP save/restore code.
+ *
+ * We have to be careful with endianness, since the fpsimd context-switch
+ * code operates on 128-bit (Q) register values whereas the compat ABI
+ * uses an array of 64-bit (D) registers. Consequently, we need to swap
+ * the two halves of each Q register when running on a big-endian CPU.
*/
+union __fpsimd_vreg {
+ __uint128_t raw;
+ struct {
+#ifdef __AARCH64EB__
+ u64 hi;
+ u64 lo;
+#else
+ u64 lo;
+ u64 hi;
+#endif
+ };
+};
+
static int compat_preserve_vfp_context(struct compat_vfp_sigframe __user *frame)
{
struct fpsimd_state *fpsimd = ¤t->thread.fpsimd_state;
compat_ulong_t magic = VFP_MAGIC;
compat_ulong_t size = VFP_STORAGE_SIZE;
compat_ulong_t fpscr, fpexc;
- int err = 0;
+ int i, err = 0;
/*
* Save the hardware registers to the fpsimd_state structure.
@@ -236,10 +254,15 @@ static int compat_preserve_vfp_context(struct compat_vfp_sigframe __user *frame)
/*
* Now copy the FP registers. Since the registers are packed,
* we can copy the prefix we want (V0-V15) as it is.
- * FIXME: Won't work if big endian.
*/
- err |= __copy_to_user(&frame->ufp.fpregs, fpsimd->vregs,
- sizeof(frame->ufp.fpregs));
+ for (i = 0; i < ARRAY_SIZE(frame->ufp.fpregs); i += 2) {
+ union __fpsimd_vreg vreg = {
+ .raw = fpsimd->vregs[i >> 1],
+ };
+
+ __put_user_error(vreg.lo, &frame->ufp.fpregs[i], err);
+ __put_user_error(vreg.hi, &frame->ufp.fpregs[i + 1], err);
+ }
/* Create an AArch32 fpscr from the fpsr and the fpcr. */
fpscr = (fpsimd->fpsr & VFP_FPSCR_STAT_MASK) |
@@ -264,7 +287,7 @@ static int compat_restore_vfp_context(struct compat_vfp_sigframe __user *frame)
compat_ulong_t magic = VFP_MAGIC;
compat_ulong_t size = VFP_STORAGE_SIZE;
compat_ulong_t fpscr;
- int err = 0;
+ int i, err = 0;
__get_user_error(magic, &frame->magic, err);
__get_user_error(size, &frame->size, err);
@@ -274,12 +297,14 @@ static int compat_restore_vfp_context(struct compat_vfp_sigframe __user *frame)
if (magic != VFP_MAGIC || size != VFP_STORAGE_SIZE)
return -EINVAL;
- /*
- * Copy the FP registers into the start of the fpsimd_state.
- * FIXME: Won't work if big endian.
- */
- err |= __copy_from_user(fpsimd.vregs, frame->ufp.fpregs,
- sizeof(frame->ufp.fpregs));
+ /* Copy the FP registers into the start of the fpsimd_state. */
+ for (i = 0; i < ARRAY_SIZE(frame->ufp.fpregs); i += 2) {
+ union __fpsimd_vreg vreg;
+
+ __get_user_error(vreg.lo, &frame->ufp.fpregs[i], err);
+ __get_user_error(vreg.hi, &frame->ufp.fpregs[i + 1], err);
+ fpsimd.vregs[i >> 1] = vreg.raw;
+ }
/* Extract the fpsr and the fpcr from the fpscr */
__get_user_error(fpscr, &frame->ufp.fpscr, err);
This is a note to let you know that I have just added a patch titled arm64: compat: fix vfp save/restore across signal handlers in big-endian to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue This patch is scheduled to be released in version 3.19.8-ckt9. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.16.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 67684b80952b869001e04285258c46460e5289b4 Mon Sep 17 00:00:00 2001 From: Will Deacon <will.deacon@arm.com> Date: Tue, 15 Sep 2015 12:07:06 +0100 Subject: arm64: compat: fix vfp save/restore across signal handlers in big-endian commit bdec97a855ef1e239f130f7a11584721c9a1bf04 upstream. When saving/restoring the VFP registers from a compat (AArch32) signal frame, we rely on the compat registers forming a prefix of the native register file and therefore make use of copy_{to,from}_user to transfer between the native fpsimd_state and the compat_vfp_sigframe. Unfortunately, this doesn't work so well in a big-endian environment. Our fpsimd save/restore code operates directly on 128-bit quantities (Q registers) whereas the compat_vfp_sigframe represents the registers as an array of 64-bit (D) registers. The architecture packs the compat D registers into the Q registers, with the least significant bytes holding the lower register. Consequently, we need to swap the 64-bit halves when converting between these two representations on a big-endian machine. This patch replaces the __copy_{to,from}_user invocations in our compat VFP signal handling code with explicit __put_user loops that operate on 64-bit values and swap them accordingly. Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/arm64/kernel/signal32.c | 47 +++++++++++++++++++++++++++++++++----------- 1 file changed, 36 insertions(+), 11 deletions(-) -- 1.9.1