Il mer 26 ago 2026, 16:31 Zhao Liu <[email protected]> ha scritto:
> On Tue, Aug 25, 2026 at 02:29:11PM +0200, Paolo Bonzini wrote:
> > Date: Tue, 25 Aug 2026 14:29:11 +0200
> > From: Paolo Bonzini <[email protected]>
> > Subject: [PATCH 10/20] target/i386/tcg: implement JMPABS instruction
> > X-Mailer: git-send-email 2.55.0
> >
> > This is the same as an indirect jump, just with immediate operand.
> > The requirement of W=0 and 0x67 are already available in the decoder.
> >
> > Signed-off-by: Paolo Bonzini <[email protected]>
> > ---
> > target/i386/tcg/decode-new.h | 3 +++
> > target/i386/tcg/decode-new.c.inc | 4 ++++
> > 2 files changed, 7 insertions(+)
> >
> > diff --git a/target/i386/tcg/decode-new.h b/target/i386/tcg/decode-new.h
> > index c974ca9d7c5..4998712e86d 100644
> > --- a/target/i386/tcg/decode-new.h
> > +++ b/target/i386/tcg/decode-new.h
> > @@ -184,6 +184,9 @@ typedef enum X86InsnCheck {
> >
> > /* No REX2 prefix allowed */
> > X86_CHECK_no_rex2 = 8192,
> > +
> > + /* No 0x67 prefix allowed */
> > + X86_CHECK_no_adr = 16384,
> > } X86InsnCheck;
> >
> > typedef enum X86InsnSpecial {
> > diff --git a/target/i386/tcg/decode-new.c.inc
> b/target/i386/tcg/decode-new.c.inc
> > index 1f59fd665f7..d215d28cec5 100644
> > --- a/target/i386/tcg/decode-new.c.inc
> > +++ b/target/i386/tcg/decode-new.c.inc
> > @@ -1991,6 +1991,7 @@ static const X86OpEntry opcodes_root[256] = {
> >
> > #ifdef TARGET_X86_64
> > static const X86OpEntry opcodes_rex2_map0_A0toAF[16] = {
> > + [1] = X86_OP_ENTRY1(JMP_m, I,q, p_00 chk2(W0, no_adr)),
> > };
>
> Maybe it should use X86_OP_ENTRYr? since JMPABS doesn't need to write
> back.
>
Absolutely, thanks Zhao!
Paolo
> Just a simple test:
>
> #include <stdio.h>
>
> int main(void)
> {
> __asm__ volatile (
> /* JMPABS: REX2(M0=0,W=0) = D5 00, opcode A1, then imm64 target */
> ".byte 0xd5, 0x00, 0xa1\n\t"
> ".quad 1f\n\t"
> "ud2\n\t" /* this should be skipped */
> "1:\n\t");
> puts("JMPABS -- OK");
> return 0;
> }
>
> And this hits an abort():
>
> $ ./build/qemu-x86_64 /tmp/jmpabs
> **
> ERROR:../target/i386/tcg/emit.c.inc:380:gen_writeback: code should not be
> reached
> Bail out! ERROR:../target/i386/tcg/emit.c.inc:380:gen_writeback: code
> should not be reached
> Aborted (core dumped)
>
> more GDB backtrace:
>
> Thread 1 "qemu-x86_64" received signal SIGABRT, Aborted.
> __pthread_kill_implementation (no_tid=0, signo=6,
> threadid=140737352460800) at ./nptl/pthread_kill.c:44
> 44 ./nptl/pthread_kill.c: No such file or directory.
> #0 __pthread_kill_implementation (no_tid=0, signo=6,
> threadid=140737352460800) at ./nptl/pthread_kill.c:44
> #1 __pthread_kill_internal (signo=6, threadid=140737352460800) at
> ./nptl/pthread_kill.c:78
> #2 __GI___pthread_kill (threadid=140737352460800, signo=signo@entry=6)
> at ./nptl/pthread_kill.c:89
> #3 0x00007ffff7242476 in __GI_raise (sig=sig@entry=6) at
> ../sysdeps/posix/raise.c:26
> #4 0x00007ffff72287f3 in __GI_abort () at ./stdlib/abort.c:79
> #5 0x00007ffff76e3b57 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
> #6 0x00007ffff773d70f in g_assertion_message_expr () from
> /lib/x86_64-linux-gnu/libglib-2.0.so.0
> #7 0x0000555555664f37 in gen_writeback (s=s@entry=0x7fffffffd240,
> decode=decode@entry=0x7fffffffd0b0, opn=opn@entry=0, v=<optimized out>)
> at ../target/i386/tcg/emit.c.inc:380
> #8 0x0000555555677778 in disas_insn (cpu=0x55555593e780,
> s=0x7fffffffd240) at ../target/i386/tcg/decode-new.c.inc:3682
> #9 i386_tr_translate_insn (dcbase=0x7fffffffd240, cpu=0x55555593e780) at
> ../target/i386/tcg/translate.c:3608
> #10 0x00005555555d7962 in translator_loop (cpu=0x55555593e780,
> tb=0x7fffe80d0700 <code_gen_buffer+853715>, max_insns=0x7fffffffd4cc,
> pc=<optimized out>, host_pc=<optimized out>, ops=ops@entry=0x5555557dc5a0
> <i386_tr_ops>, db=0x7fffffffd240, addr_type=TCG_TYPE_I64) at
> ../accel/tcg/translator.c:178
> #11 0x000055555567b212 in x86_translate_code (cpu=<optimized out>,
> tb=<optimized out>, max_insns=<optimized out>, pc=<optimized out>,
> host_pc=<optimized out>) at ../target/i386/tcg/translate.c:3699
> #12 0x00005555555d6644 in setjmp_gen_code (env=env@entry=0x5555559427f0,
> tb=tb@entry=0x7fffe80d0700 <code_gen_buffer+853715>, pc=pc@entry=4198710,
> host_pc=0x401136, max_insns=max_insns@entry=0x7fffffffd4cc, ti=<optimized
> out>) at ../accel/tcg/translate-all.c:251
> #13 0x00005555555d6b0e in tb_gen_code (cpu=cpu@entry=0x55555593e780,
> s=...) at ../accel/tcg/translate-all.c:324
> #14 0x00005555555cec1a in cpu_exec_loop (cpu=cpu@entry=0x55555593e780,
> sc=<optimized out>) at ../accel/tcg/cpu-exec.c:973
> #15 0x00005555555ced99 in cpu_exec_setjmp (cpu=cpu@entry=0x55555593e780,
> sc=<optimized out>) at ../accel/tcg/cpu-exec.c:1019
> #16 0x00005555555cf381 in cpu_exec (cpu=cpu@entry=0x55555593e780) at
> ../accel/tcg/cpu-exec.c:1045
> #17 0x0000555555622c80 in cpu_loop (env=env@entry=0x5555559427f0) at
> ../linux-user/x86_64/../i386/cpu_loop.c:217
> #18 0x00005555555a1d17 in main (argc=<optimized out>, argv=<optimized
> out>, envp=<optimized out>) at ../linux-user/main.c:1010
>
> Regards,
> Zhao
>
>
