* [PATCH] loads-stores.rst: add footnote that clarifies GETPC usage
@ 2020-10-15 9:51 Emanuele Giuseppe Esposito
2020-10-20 13:18 ` Peter Maydell
0 siblings, 1 reply; 2+ messages in thread
From: Emanuele Giuseppe Esposito @ 2020-10-15 9:51 UTC (permalink / raw)
To: qemu-devel
Cc: Peter Maydell, Richard Henderson, Emanuele Giuseppe Esposito,
Paolo Bonzini
Current documentation is not too clear on the GETPC usage.
In particular, when used outside the top level helper function
it causes unexpected behavior.
Signed-off-by: Emanuele Giuseppe Esposito <e.emanuelegiuseppe@gmail.com>
---
docs/devel/loads-stores.rst | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/docs/devel/loads-stores.rst b/docs/devel/loads-stores.rst
index 9a944ef1af..59c1225391 100644
--- a/docs/devel/loads-stores.rst
+++ b/docs/devel/loads-stores.rst
@@ -93,7 +93,13 @@ guest CPU state in case of a guest CPU exception. This is passed
to ``cpu_restore_state()``. Therefore the value should either be 0,
to indicate that the guest CPU state is already synchronized, or
the result of ``GETPC()`` from the top level ``HELPER(foo)``
-function, which is a return address into the generated code.
+function, which is a return address into the generated code [#gpc]_.
+
+.. [#gpc] Note that ``GETPC()`` should be used with great care: calling
+ it in other functions that are *not* the top level
+ ``HELPER(foo)`` will cause unexpected behavior. Instead, the
+ value of ``GETPC()`` should be read from the helper and passed
+ if needed to the functions that the helper calls.
Function names follow the pattern:
--
2.17.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] loads-stores.rst: add footnote that clarifies GETPC usage
2020-10-15 9:51 [PATCH] loads-stores.rst: add footnote that clarifies GETPC usage Emanuele Giuseppe Esposito
@ 2020-10-20 13:18 ` Peter Maydell
0 siblings, 0 replies; 2+ messages in thread
From: Peter Maydell @ 2020-10-20 13:18 UTC (permalink / raw)
To: Emanuele Giuseppe Esposito
Cc: Paolo Bonzini, Richard Henderson, QEMU Developers
On Thu, 15 Oct 2020 at 10:51, Emanuele Giuseppe Esposito
<e.emanuelegiuseppe@gmail.com> wrote:
>
> Current documentation is not too clear on the GETPC usage.
> In particular, when used outside the top level helper function
> it causes unexpected behavior.
>
> Signed-off-by: Emanuele Giuseppe Esposito <e.emanuelegiuseppe@gmail.com>
Applied to target-arm.next, thanks.
-- PMM
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