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    Subject[PATCH 4.9 114/223] um: Allow building and running on older hosts
    Date
    From: Florian Fainelli <f.fainelli@gmail.com>

    commit 0a987645672ebde7844a9c0732a5a25f3d4bb6c6 upstream.

    Commit a78ff1112263 ("um: add extended processor state save/restore
    support") and b6024b21fec8 ("um: extend fpstate to _xstate to support
    YMM registers") forced the use of the x86 FP _xstate and
    PTRACE_GETREGSET/SETREGSET. On older hosts, we would neither be able to
    build UML nor run it anymore with these two commits applied because we
    don't have definitions for struct _xstate nor these two ptrace requests.

    We can determine at build time which fp context structure to check
    against, just like we can keep using the old i387 fp save/restore if
    PTRACE_GETRESET/SETREGSET are not defined.

    Fixes: a78ff1112263 ("um: add extended processor state save/restore support")
    Fixes: b6024b21fec8 ("um: extend fpstate to _xstate to support YMM registers")
    Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
    Signed-off-by: Richard Weinberger <richard@nod.at>
    Signed-off-by: Alessio Balsini <balsini@android.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/um/os-Linux/registers.c | 12 ++++++++----
    arch/x86/um/user-offsets.c | 4 ++++
    2 files changed, 12 insertions(+), 4 deletions(-)

    --- a/arch/x86/um/os-Linux/registers.c
    +++ b/arch/x86/um/os-Linux/registers.c
    @@ -26,6 +26,7 @@ int save_i387_registers(int pid, unsigne

    int save_fp_registers(int pid, unsigned long *fp_regs)
    {
    +#ifdef PTRACE_GETREGSET
    struct iovec iov;

    if (have_xstate_support) {
    @@ -34,9 +35,9 @@ int save_fp_registers(int pid, unsigned
    if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
    return -errno;
    return 0;
    - } else {
    + } else
    +#endif
    return save_i387_registers(pid, fp_regs);
    - }
    }

    int restore_i387_registers(int pid, unsigned long *fp_regs)
    @@ -48,6 +49,7 @@ int restore_i387_registers(int pid, unsi

    int restore_fp_registers(int pid, unsigned long *fp_regs)
    {
    +#ifdef PTRACE_SETREGSET
    struct iovec iov;

    if (have_xstate_support) {
    @@ -56,9 +58,9 @@ int restore_fp_registers(int pid, unsign
    if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
    return -errno;
    return 0;
    - } else {
    + } else
    +#endif
    return restore_i387_registers(pid, fp_regs);
    - }
    }

    #ifdef __i386__
    @@ -122,6 +124,7 @@ int put_fp_registers(int pid, unsigned l

    void arch_init_registers(int pid)
    {
    +#ifdef PTRACE_GETREGSET
    struct _xstate fp_regs;
    struct iovec iov;

    @@ -129,6 +132,7 @@ void arch_init_registers(int pid)
    iov.iov_len = sizeof(struct _xstate);
    if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) == 0)
    have_xstate_support = 1;
    +#endif
    }
    #endif

    --- a/arch/x86/um/user-offsets.c
    +++ b/arch/x86/um/user-offsets.c
    @@ -50,7 +50,11 @@ void foo(void)
    DEFINE(HOST_GS, GS);
    DEFINE(HOST_ORIG_AX, ORIG_EAX);
    #else
    +#if defined(PTRACE_GETREGSET) && defined(PTRACE_SETREGSET)
    DEFINE(HOST_FP_SIZE, sizeof(struct _xstate) / sizeof(unsigned long));
    +#else
    + DEFINE(HOST_FP_SIZE, sizeof(struct _fpstate) / sizeof(unsigned long));
    +#endif
    DEFINE_LONGS(HOST_BX, RBX);
    DEFINE_LONGS(HOST_CX, RCX);
    DEFINE_LONGS(HOST_DI, RDI);

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