Hi Radim,
Radim Krčmář <rkrcmar@xxxxxxxxxx> writes:
...
> static __always_inline int __linearize(struct x86_emulate_ctxt *ctxt,
> @@ -704,7 +708,7 @@ static __always_inline int __linearize(struct x86_emulate_ctxt *ctxt,
> }
> break;
> }
> - if (insn_aligned(ctxt, size) && ((la & (size - 1)) != 0))
> + if (la & (insn_alignment(ctxt, size) - 1))
> return emulate_gp(ctxt, 0);
> return X86EMUL_CONTINUE;
> bad:
> @@ -3856,6 +3860,75 @@ static int em_movsxd(struct x86_emulate_ctxt *ctxt)
> return X86EMUL_CONTINUE;
> }
>
> +static int check_fxsr(struct x86_emulate_ctxt *ctxt)
> +{
> + u32 eax = 1, ebx, ecx = 0, edx;
> +
> + ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
> + if (!(edx & FFL(FXSR)))
> + return emulate_ud(ctxt);
> +
> + if (ctxt->ops->get_cr(ctxt, 0) & (X86_CR0_TS | X86_CR0_EM))
> + return emulate_nm(ctxt);
> +
> + return X86EMUL_CONTINUE;
> +}
> +
> +/*
> + * FXSAVE and FXRSTOR have 3 different formats depending on execution mode,
> + * 1) non-64-bit mode
> + * 2) 64-bit mode with REX.W prefix
> + * 3) 64-bit mode without REX.W prefix
> + *
> + * Emulation uses (3) for for (1) mode because only the number of XMM registers
> + * is different.
> + */
> +static int em_fxsave(struct x86_emulate_ctxt *ctxt)
> +{
> + char fx_state[512] __aligned(16);
> + int rc;
> +
> + rc = check_fxsr(ctxt);
> + if (rc != X86EMUL_CONTINUE)
> + return rc;
> +
> + ctxt->ops->get_fpu(ctxt);
> +#ifdef CONFIG_X86_64
> + if (ctxt->rex_prefix & (1 << 3))
> + asm volatile("fxsave64 %0" : "+m"(fx_state));
> + else
> +#endif
> + asm volatile("fxsave %0" : "+m"(fx_state));
> + ctxt->ops->put_fpu(ctxt);
> +
> + return segmented_write(ctxt, ctxt->memop.addr.mem, fx_state, 512);
> +}
> +
> +static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
> +{
> + char fx_state[512] __aligned(16);
> + int rc;
> +
> + rc = check_fxsr(ctxt);
Is this check enough here ? What I mean is that is it possible that the memory
image that is read from has data in an invalid format/corrupt or is that irrelevant ?
Bandan
> + if (rc != X86EMUL_CONTINUE)
> + return rc;
> +
> + rc = segmented_read(ctxt, ctxt->memop.addr.mem, fx_state, 512);
> + if (rc != X86EMUL_CONTINUE)
> + return rc;
> +
> + ctxt->ops->get_fpu(ctxt);
> +#ifdef CONFIG_X86_64
> + if (ctxt->rex_prefix & (1 << 3))
> + asm volatile("fxrstor64 %0" : "+m"(fx_state));
> + else
> +#endif
> + asm volatile("fxrstor %0" : "+m"(fx_state));
> + ctxt->ops->put_fpu(ctxt);
> +
> + return X86EMUL_CONTINUE;
> +}
> +
> static bool valid_cr(int nr)
> {
> switch (nr) {
> @@ -4208,7 +4281,9 @@ static const struct gprefix pfx_0f_ae_7 = {
> };
>
> static const struct group_dual group15 = { {
> - N, N, N, N, N, N, N, GP(0, &pfx_0f_ae_7),
> + I(ModRM | Aligned16, em_fxsave),
> + I(ModRM | Aligned16, em_fxrstor),
> + N, N, N, N, N, GP(0, &pfx_0f_ae_7),
> }, {
> N, N, N, N, N, N, N, N,
> } };
--
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