syscall_abi.hh

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/*
 * Copyright 2019 Google, Inc.
 *
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 * modification, are permitted provided that the following conditions are
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 * notice, this list of conditions and the following disclaimer;
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 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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#ifndef __SIM_SYSCALL_ABI_HH__
#define __SIM_SYSCALL_ABI_HH__
 
#include "base/types.hh"
#include "cpu/thread_context.hh"
#include "sim/guest_abi.hh"
#include "sim/syscall_return.hh"
 
class SyscallDesc;
 
namespace GuestABI
{
 
// Does this normally 64 bit data type shrink down to 32 bits for 32 bit ABIs?
template <typename T, typename Enabled=void>
struct IsConforming : public std::false_type {};
 
template <>
struct IsConforming<Addr> : public std::true_type {};
 
} // namespace GuestABI
 
struct GenericSyscallABI
{
    using State = int;
};
 
struct GenericSyscallABI64 : public GenericSyscallABI
{};
 
struct GenericSyscallABI32 : public GenericSyscallABI
{
    // Is this argument too big for a single register?
    template <typename T, typename Enabled=void>
    struct IsWide;
 
    template <typename T>
    struct IsWide<T, typename std::enable_if<
        std::is_integral<T>::value &&
        (sizeof(T) < sizeof(uint64_t) ||
         GuestABI::IsConforming<T>::value)>::type>
    {
        static const bool value = false;
    };
 
    template <typename T>
    struct IsWide<T, typename std::enable_if<
        std::is_integral<T>::value &&
        sizeof(T) == sizeof(uint64_t) &&
        !GuestABI::IsConforming<T>::value>::type>
    {
        static const bool value = true;
    };
 
    // Read two registers and merge them into one value.
    static uint64_t
    mergeRegs(ThreadContext *tc, RegIndex low_idx, RegIndex high_idx)
    {
        RegVal low = tc->readIntReg(low_idx);
        RegVal high = tc->readIntReg(high_idx);
        return insertBits(low, 63, 32, high);
    }
};
 
namespace GuestABI
{
 
// For 64 bit systems, return syscall args directly.
template <typename ABI, typename Arg>
struct Argument<ABI, Arg,
    typename std::enable_if<
        std::is_base_of<GenericSyscallABI64, ABI>::value &&
        std::is_integral<Arg>::value>::type>
{
    static Arg
    get(ThreadContext *tc, typename ABI::State &state)
    {
        panic_if(state >= ABI::ArgumentRegs.size(),
                "Ran out of syscall argument registers.");
        return tc->readIntReg(ABI::ArgumentRegs[state++]);
    }
};
 
// For 32 bit systems, return small enough syscall args directly. Large
// arguments aren't handled generically.
template <typename ABI, typename Arg>
struct Argument<ABI, Arg,
    typename std::enable_if<!ABI::template IsWide<Arg>::value>::type>
{
    static Arg
    get(ThreadContext *tc, typename ABI::State &state)
    {
        panic_if(state >= ABI::ArgumentRegs.size(),
                "Ran out of syscall argument registers.");
        return bits(tc->readIntReg(ABI::ArgumentRegs[state++]), 31, 0);
    }
};
 
} // namespace GuestABI
 
#endif // __SIM_SYSCALL_ABI_HH__