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target/s390x: Fix translation exception on illegal instruction

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Hitting an uretprobe in a s390x TCG guest causes a SIGSEGV. What
happens is:

* uretprobe maps a userspace page containing an invalid instruction.
* uretprobe replaces the target function's return address with the
  address of that page.
* When tb_gen_code() is called on that page, tb->size ends up being 0
  (because the page starts with the invalid instruction), which causes
  virt_page2 to point to the previous page.
* The previous page is not mapped, so this causes a spurious
  translation exception.

tb->size must never be 0: even if there is an illegal instruction, the
instruction bytes that have been looked at must count towards tb->size.
So adjust s390x's translate_one() to act this way for both illegal
instructions and instructions that are known to generate exceptions.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210416154939.32404-2-iii@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
This commit is contained in:
Ilya Leoshkevich 2021-04-16 17:49:36 +02:00 committed by Cornelia Huck
parent fea2ad71c3
commit 86131c71b1
1 changed files with 11 additions and 5 deletions
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16
target/s390x/translate.c
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@ -6412,7 +6412,8 @@ static DisasJumpType translate_one(CPUS390XState *env, DisasContext *s)
qemu_log_mask(LOG_UNIMP, "unimplemented opcode 0x%02x%02x\n",
s->fields.op, s->fields.op2);
gen_illegal_opcode(s);
return DISAS_NORETURN;
ret = DISAS_NORETURN;
goto out;
}
#ifndef CONFIG_USER_ONLY
@ -6428,7 +6429,8 @@ static DisasJumpType translate_one(CPUS390XState *env, DisasContext *s)
/* privileged instruction */
if ((s->base.tb->flags & FLAG_MASK_PSTATE) && (insn->flags & IF_PRIV)) {
gen_program_exception(s, PGM_PRIVILEGED);
return DISAS_NORETURN;
ret = DISAS_NORETURN;
goto out;
}
/* if AFP is not enabled, instructions and registers are forbidden */
@ -6455,7 +6457,8 @@ static DisasJumpType translate_one(CPUS390XState *env, DisasContext *s)
}
if (dxc) {
gen_data_exception(dxc);
return DISAS_NORETURN;
ret = DISAS_NORETURN;
goto out;
}
}
@ -6463,7 +6466,8 @@ static DisasJumpType translate_one(CPUS390XState *env, DisasContext *s)
if (insn->flags & IF_VEC) {
if (!((s->base.tb->flags & FLAG_MASK_VECTOR))) {
gen_data_exception(0xfe);
return DISAS_NORETURN;
ret = DISAS_NORETURN;
goto out;
}
}
@ -6484,7 +6488,8 @@ static DisasJumpType translate_one(CPUS390XState *env, DisasContext *s)
(insn->spec & SPEC_r1_f128 && !is_fp_pair(get_field(s, r1))) ||
(insn->spec & SPEC_r2_f128 && !is_fp_pair(get_field(s, r2)))) {
gen_program_exception(s, PGM_SPECIFICATION);
return DISAS_NORETURN;
ret = DISAS_NORETURN;
goto out;
}
}
@ -6544,6 +6549,7 @@ static DisasJumpType translate_one(CPUS390XState *env, DisasContext *s)
}
#endif
out:
/* Advance to the next instruction. */
s->base.pc_next = s->pc_tmp;
return ret;