[PATCH] target/arm: Fix A64 LDRA immediate decode

[PATCH] target/arm: Fix A64 LDRA immediate decode

[Peter Maydell]

In commit be23a049 in the conversion to decodetree we broke the
decoding of the immediate value in the LDRA instruction.  This should
be a 10 bit signed value that is scaled by 8, but in the conversion
we incorrectly ended up scaling it only by 2.  Fix the scaling
factor.

Cc: qemu-stable@nongnu.org
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1970
Fixes: be23a049 ("target/arm: Convert load (pointer auth) insns to decodetree")
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/tcg/translate.h | 5 +++++
 target/arm/tcg/a64.decode  | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/target/arm/tcg/translate.h b/target/arm/tcg/translate.h
index 9efe00cf6ca..3c3bb3431ad 100644
--- a/target/arm/tcg/translate.h
+++ b/target/arm/tcg/translate.h
@@ -205,6 +205,11 @@ static inline int times_4(DisasContext *s, int x)
     return x * 4;
 }
 
+static inline int times_8(DisasContext *s, int x)
+{
+    return x * 8;
+}
+
 static inline int times_2_plus_1(DisasContext *s, int x)
 {
     return x * 2 + 1;
diff --git a/target/arm/tcg/a64.decode b/target/arm/tcg/a64.decode
index 0cf11470741..8a20dce3c8f 100644
--- a/target/arm/tcg/a64.decode
+++ b/target/arm/tcg/a64.decode
@@ -462,7 +462,7 @@ LDAPR           sz:2 111 0 00 1 0 1 11111 1100 00 rn:5 rt:5
 # Load/store register (pointer authentication)
 
 # LDRA immediate is 10 bits signed and scaled, but the bits aren't all contiguous
-%ldra_imm       22:s1 12:9 !function=times_2
+%ldra_imm       22:s1 12:9 !function=times_8
 
 LDRA            11 111 0 00 m:1 . 1 ......... w:1 1 rn:5 rt:5 imm=%ldra_imm
 
-- 
2.34.1

Re: [PATCH] target/arm: Fix A64 LDRA immediate decode

[Philippe Mathieu-Daudé]

On 6/11/23 12:34, Peter Maydell wrote:
> In commit be23a049 in the conversion to decodetree we broke the
> decoding of the immediate value in the LDRA instruction.  This should
> be a 10 bit signed value that is scaled by 8, but in the conversion
> we incorrectly ended up scaling it only by 2.  Fix the scaling
> factor.
> 
> Cc: qemu-stable@nongnu.org
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1970
> Fixes: be23a049 ("target/arm: Convert load (pointer auth) insns to decodetree")
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   target/arm/tcg/translate.h | 5 +++++
>   target/arm/tcg/a64.decode  | 2 +-
>   2 files changed, 6 insertions(+), 1 deletion(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>