update
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@197 c046a42c-6fe2-441c-8c8c-71466251a162
This commit is contained in:
bellard
parent
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@ -14,7 +14,11 @@ version 0.2:
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- SHL instruction C flag fix.
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- mmap emulation for host page size > 4KB
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- self-modifying code support
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- better VM86 support (dosemu begins to work)
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- better VM86 support (dosemu works on non trivial programs)
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- precise exception support (EIP is computed correctly in most cases)
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- more precise LDT/GDT/IDT emulation
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- faster segment load in vm86 mode
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- direct chaining of basic blocks (faster emulation)
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version 0.1.6:
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31
TODO
31
TODO
@ -1,15 +1,22 @@
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- fix gcc 2.96 compile bug
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- fix thread locks
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- optimize translated cache chaining (DLL PLT-like system)
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- fix iret/lret/fpush not before mem load restarting
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- fix all remaining thread lock issues (must put TBs in a specific invalid
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state, find a solution for tb_flush()).
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- handle fp87 state in signals
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- add gcc 2.96 test configure (some gcc3 flags are needed)
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- optimize FPU operations (evaluate x87 stack pointer statically)
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- add IPC syscalls
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- submit a patch to fix DOSEMU coopthreads
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lower priority:
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--------------
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- handle rare page fault cases (in particular if page fault in heplers or
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in syscall emulation code).
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- fix thread stack freeing (use kernel 2.5.x CLONE_CHILD_CLEARTID)
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- fix x86 stack allocation
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- fix iret/lret restarting
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- more syscalls (in particular all 64 bit ones, IPCs, fix 64 bit
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issues, fix 16 bit uid issues)
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- finish signal handing (fp87 state, more siginfo conversions)
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- fix FPU exceptions (in particular: gen_op_fpush not before mem load)
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- handle self-modifying code (track mmap and mark all pages containing
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translated code as readonly. use a custom signal handler to flush
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parts of the translation cache if write access to a readonly page
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containing translated code).
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- use gcc to compile to static code
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- use page_unprotect_range in every suitable syscall to handle all
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cases of self modifying code.
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- use gcc as a backend to generate better code (easy to do by using
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op-i386.c operations as local inline functions).
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- add SSE2/MMX operations
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136
qemu-doc.texi
136
qemu-doc.texi
@ -10,11 +10,11 @@
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@chapter Introduction
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QEMU is an x86 processor emulator. Its purpose is to run x86 Linux
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processes on non-x86 Linux architectures such as PowerPC or ARM. By
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using dynamic translation it achieves a reasonnable speed while being
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easy to port on new host CPUs. Its main goal is to be able to launch the
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@code{Wine} Windows API emulator (@url{http://www.winehq.org}) on
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non-x86 CPUs.
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processes on non-x86 Linux architectures such as PowerPC. By using
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dynamic translation it achieves a reasonnable speed while being easy to
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port on new host CPUs. Its main goal is to be able to launch the
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@code{Wine} Windows API emulator (@url{http://www.winehq.org}) or
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@code{DOSEMU} (@url{http://www.dosemu.org}) on non-x86 CPUs.
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QEMU features:
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@ -22,21 +22,26 @@ QEMU features:
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@item User space only x86 emulator.
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@item Currently ported on i386, PowerPC and S390.
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@item Currently ported on i386, PowerPC. Work in progress for S390, Alpha and Sparc.
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@item Using dynamic translation to native code for reasonnable speed.
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@item The virtual x86 CPU supports 16 bit and 32 bit addressing with segmentation.
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User space LDT and GDT are emulated. VM86 mode is also supported
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(experimental).
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User space LDT and GDT are emulated. VM86 mode is also supported.
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@item Generic Linux system call converter, including most ioctls.
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@item clone() emulation using native CPU clone() to use Linux scheduler for threads.
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@item Accurate signal handling by remapping host signals to virtual x86 signals.
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@item Accurate signal handling by remapping host signals to virtual x86 signals.
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@item QEMU can emulate itself on x86 (experimental).
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@item Precise user space x86 exceptions.
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@item Self-modifying code support.
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@item Support of host page sizes bigger than 4KB.
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@item QEMU can emulate itself on x86.
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@item The virtual x86 CPU is a library (@code{libqemu}) which can be used
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in other projects.
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@ -46,19 +51,15 @@ It can be used to test other x86 virtual CPUs.
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@end itemize
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Current QEMU Limitations:
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Current QEMU limitations:
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@itemize
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@item Not all x86 exceptions are precise (yet). [Very few programs need that].
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@item No support for self-modifying code (yet). [Very few programs need that, a notable exception is QEMU itself !].
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@item No SSE/MMX support (yet).
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@item No x86-64 support.
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@item Some Linux syscalls are missing.
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@item IPC syscalls are missing.
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@item The x86 segment limits and access rights are not tested at every
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memory access (and will never be to have good performances).
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@ -119,7 +120,7 @@ qemu /usr/local/qemu-i386/bin/qemu-i386 /usr/local/qemu-i386/bin/ls-i386
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@end itemize
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@section Wine launch (Currently only tested when emulating x86 on x86)
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@section Wine launch
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@itemize
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@ -152,17 +153,24 @@ qemu /usr/local/qemu-i386/wine/bin/wine /usr/local/qemu-i386/wine/c/Program\ Fil
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usage: qemu [-h] [-d] [-L path] [-s size] program [arguments...]
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@end example
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@table @samp
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@table @option
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@item -h
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Print the help
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@item -d
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Activate log (logfile=/tmp/qemu.log)
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@item -L path
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Set the x86 elf interpreter prefix (default=/usr/local/qemu-i386)
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@item -s size
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Set the x86 stack size in bytes (default=524288)
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@end table
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Debug options:
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@table @option
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@item -d
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Activate log (logfile=/tmp/qemu.log)
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@item -p pagesize
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Act as if the host page size was 'pagesize' bytes
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@end table
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@chapter QEMU Internals
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@section QEMU compared to other emulators
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@ -265,17 +273,59 @@ contains just a single basic block (a block of x86 instructions
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terminated by a jump or by a virtual CPU state change which the
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translator cannot deduce statically).
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[Currently, the translated code is not patched if it jumps to another
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translated code].
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@section Direct block chaining
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After each translated basic block is executed, QEMU uses the simulated
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Program Counter (PC) and other cpu state informations (such as the CS
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segment base value) to find the next basic block.
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In order to accelerate the most common cases where the new simulated PC
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is known, QEMU can patch a basic block so that it jumps directly to the
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next one.
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The most portable code uses an indirect jump. An indirect jump makes it
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easier to make the jump target modification atomic. On some
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architectures (such as PowerPC), the @code{JUMP} opcode is directly
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patched so that the block chaining has no overhead.
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@section Self-modifying code and translated code invalidation
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Self-modifying code is a special challenge in x86 emulation because no
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instruction cache invalidation is signaled by the application when code
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is modified.
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When translated code is generated for a basic block, the corresponding
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host page is write protected if it is not already read-only (with the
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system call @code{mprotect()}). Then, if a write access is done to the
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page, Linux raises a SEGV signal. QEMU then invalidates all the
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translated code in the page and enables write accesses to the page.
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Correct translated code invalidation is done efficiently by maintaining
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a linked list of every translated block contained in a given page. Other
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linked lists are also maintained to undo direct block chaining.
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Althought the overhead of doing @code{mprotect()} calls is important,
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most MSDOS programs can be emulated at reasonnable speed with QEMU and
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DOSEMU.
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Note that QEMU also invalidates pages of translated code when it detects
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that memory mappings are modified with @code{mmap()} or @code{munmap()}.
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@section Exception support
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longjmp() is used when an exception such as division by zero is
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encountered. The host SIGSEGV and SIGBUS signal handlers are used to get
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invalid memory accesses.
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encountered.
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[Currently, the virtual CPU cannot retrieve the exact CPU state in some
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exceptions, although it could except for the @code{EFLAGS} register].
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The host SIGSEGV and SIGBUS signal handlers are used to get invalid
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memory accesses. The exact CPU state can be retrieved because all the
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x86 registers are stored in fixed host registers. The simulated program
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counter is found by retranslating the corresponding basic block and by
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looking where the host program counter was at the exception point.
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The virtual CPU cannot retrieve the exact @code{EFLAGS} register because
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in some cases it is not computed because of condition code
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optimisations. It is not a big concern because the emulated code can
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still be restarted in any cases.
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@section Linux system call translation
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@ -284,6 +334,11 @@ the parameters of the system calls can be converted to fix the
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endianness and 32/64 bit issues. The IOCTLs are converted with a generic
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type description system (see @file{ioctls.h} and @file{thunk.c}).
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QEMU supports host CPUs which have pages bigger than 4KB. It records all
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the mappings the process does and try to emulated the @code{mmap()}
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system calls in cases where the host @code{mmap()} call would fail
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because of bad page alignment.
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@section Linux signals
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Normal and real-time signals are queued along with their information
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@ -312,6 +367,10 @@ thread.
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The virtual x86 CPU atomic operations are emulated with a global lock so
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that their semantic is preserved.
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Note that currently there are still some locking issues in QEMU. In
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particular, the translated cache flush is not protected yet against
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reentrancy.
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@section Self-virtualization
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QEMU was conceived so that ultimately it can emulate itself. Althought
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@ -323,10 +382,6 @@ space conflicts. QEMU solves this problem by being an executable ELF
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shared object as the ld-linux.so ELF interpreter. That way, it can be
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relocated at load time.
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Since self-modifying code is not supported yet, QEMU cannot emulate
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itself in case of translation cache flush. This limitation will be
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suppressed soon.
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@section Bibliography
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@table @asis
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@ -379,19 +434,10 @@ program and a @code{diff} on the generated output.
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The Linux system call @code{modify_ldt()} is used to create x86 selectors
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to test some 16 bit addressing and 32 bit with segmentation cases.
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@section @file{testsig}
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The Linux system call @code{vm86()} is used to test vm86 emulation.
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This program tests various signal cases, including SIGFPE, SIGSEGV and
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SIGILL.
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@section @file{testclone}
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Tests the @code{clone()} system call (basic test).
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@section @file{testthread}
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Tests the glibc threads (more complicated than @code{clone()} because signals
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are also used).
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Various exceptions are raised to test most of the x86 user space
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exception reporting.
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@section @file{sha1}
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@ -399,9 +445,3 @@ It is a simple benchmark. Care must be taken to interpret the results
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because it mostly tests the ability of the virtual CPU to optimize the
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@code{rol} x86 instruction and the condition code computations.
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@section @file{runcom}
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A very simple MSDOS emulator to test the Linux vm86() system call
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emulation. The excellent 54 byte @file{pi_10.com} PI number calculator
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can be launched with it. @file{pi_10.com} was written by Bertram
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Felgenhauer (more information at @url{http://www.boo.net/~jasonp/pipage.html}).
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