i386: hvf: Don't miss 16-bit displacement

[Qemu-devel] [PATCH] i386: hvf: Don't miss 16-bit displacement

Roman Bolshakov posted 1 patch 6 years, 9 months ago

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git fetch https://github.com/patchew-project/qemu tags/patchew/20190125154743.14498-1-r.bolshakov@yadro.com

Maintainers: Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>, Eduardo Habkost <ehabkost@redhat.com>

target/i386/hvf/x86_decode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

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[Qemu-devel] [PATCH] i386: hvf: Don't miss 16-bit displacement

Posted by Roman Bolshakov 6 years, 9 months ago

In 16-bit addressing mode, when Mod = 0 and R/M = 6, decoded displacement
doesn't reach decode_linear_addr and gets lost. Instructions that
involve the combination of ModRM always get a pointer with zero offset
from the beginning of DS segment.

The change fixes drawing in F-BIRD from day 1 of '18 advent calendar.

Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 target/i386/hvf/x86_decode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/i386/hvf/x86_decode.c b/target/i386/hvf/x86_decode.c
index 5f513c5563..9ef7d7513f 100644
--- a/target/i386/hvf/x86_decode.c
+++ b/target/i386/hvf/x86_decode.c
@@ -1642,7 +1642,7 @@ void calc_modrm_operand16(CPUX86State *env, struct x86_decode *decode,
     X86Seg seg = R_DS;
 
     if (!decode->modrm.mod && 6 == decode->modrm.rm) {
-        op->ptr = (uint16_t)decode->displacement;
+        ptr = decode->displacement;
         goto calc_addr;
     }
 
-- 
2.20.1