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    Subject[PATCH v2] KVM: emulator: Use linearize() when fetching instructions.
    Date
    Since segments need to be handled slightly differently when fetching
    instructions, we add a __linearize helper that accepts a new 'fetch' boolean.

    Signed-off-by: Nelson Elhage <nelhage@ksplice.com>
    ---
    arch/x86/include/asm/kvm_emulate.h | 1 -
    arch/x86/kvm/emulate.c | 26 ++++++++++++++++++--------
    2 files changed, 18 insertions(+), 9 deletions(-)

    diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
    index 0818448..9b760c8 100644
    --- a/arch/x86/include/asm/kvm_emulate.h
    +++ b/arch/x86/include/asm/kvm_emulate.h
    @@ -265,7 +265,6 @@ struct x86_emulate_ctxt {
    unsigned long eip; /* eip before instruction emulation */
    /* Emulated execution mode, represented by an X86EMUL_MODE value. */
    int mode;
    - u32 cs_base;

    /* interruptibility state, as a result of execution of STI or MOV SS */
    int interruptibility;
    diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
    index a5f63d4..427d78a 100644
    --- a/arch/x86/kvm/emulate.c
    +++ b/arch/x86/kvm/emulate.c
    @@ -540,9 +540,9 @@ static int emulate_nm(struct x86_emulate_ctxt *ctxt)
    return emulate_exception(ctxt, NM_VECTOR, 0, false);
    }

    -static int linearize(struct x86_emulate_ctxt *ctxt,
    +static int __linearize(struct x86_emulate_ctxt *ctxt,
    struct segmented_address addr,
    - unsigned size, bool write,
    + unsigned size, bool write, bool fetch,
    ulong *linear)
    {
    struct decode_cache *c = &ctxt->decode;
    @@ -569,7 +569,7 @@ static int linearize(struct x86_emulate_ctxt *ctxt,
    if (((desc.type & 8) || !(desc.type & 2)) && write)
    goto bad;
    /* unreadable code segment */
    - if ((desc.type & 8) && !(desc.type & 2))
    + if (!fetch && (desc.type & 8) && !(desc.type & 2))
    goto bad;
    lim = desc_limit_scaled(&desc);
    if ((desc.type & 8) || !(desc.type & 4)) {
    @@ -602,7 +602,7 @@ static int linearize(struct x86_emulate_ctxt *ctxt,
    }
    break;
    }
    - if (c->ad_bytes != 8)
    + if (fetch ? ctxt->mode != X86EMUL_MODE_PROT64 : c->ad_bytes != 8)
    la &= (u32)-1;
    *linear = la;
    return X86EMUL_CONTINUE;
    @@ -613,6 +613,15 @@ bad:
    return emulate_gp(ctxt, addr.seg);
    }

    +static int linearize(struct x86_emulate_ctxt *ctxt,
    + struct segmented_address addr,
    + unsigned size, bool write,
    + ulong *linear)
    +{
    + return __linearize(ctxt, addr, size, write, false, linear);
    +}
    +
    +
    static int segmented_read_std(struct x86_emulate_ctxt *ctxt,
    struct segmented_address addr,
    void *data,
    @@ -637,11 +646,13 @@ static int do_fetch_insn_byte(struct x86_emulate_ctxt *ctxt,
    int size, cur_size;

    if (eip == fc->end) {
    - unsigned long linear = eip + ctxt->cs_base;
    - if (ctxt->mode != X86EMUL_MODE_PROT64)
    - linear &= (u32)-1;
    + unsigned long linear;
    + struct segmented_address addr = {VCPU_SREG_CS, eip};
    cur_size = fc->end - fc->start;
    size = min(15UL - cur_size, PAGE_SIZE - offset_in_page(eip));
    + rc = __linearize(ctxt, addr, size, false, true, &linear);
    + if (rc != X86EMUL_CONTINUE)
    + return rc;
    rc = ops->fetch(linear, fc->data + cur_size,
    size, ctxt->vcpu, &ctxt->exception);
    if (rc != X86EMUL_CONTINUE)
    @@ -3154,7 +3165,6 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
    c->fetch.end = c->fetch.start + insn_len;
    if (insn_len > 0)
    memcpy(c->fetch.data, insn, insn_len);
    - ctxt->cs_base = seg_base(ctxt, ops, VCPU_SREG_CS);

    switch (mode) {
    case X86EMUL_MODE_REAL:
    --
    1.7.4.44.gf9e72


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