[edk2-devel] [PATCH v3 1/2] ArmPkg/AsmMacroIoLibV8: Introduce ASM_FUNC_ALIGN()

[Marvin Häuser]

With the current ASM_FUNC() macro, there is no good way to declare an
alignment constraint for a function. As ASM_FUNC() switches sections,
declaring the constraint before the macro invocation applies it to the
current location in the previous section. Declaring the constraint after
the macro invocation lets the function label point to the location prior
to alignment. Depending on toolchain behaviour, this may cause the label
to point to alignment padding preceding the actual function definition.

To address these issues, introduce the ASM_FUNC_ALIGN() macro, which
declares the alignment constraint right before the function label.

Signed-off-by: Marvin Häuser <mhaeuser at posteo.de>
Cc: Leif Lindholm <quic_llindhol at quicinc.com>
Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
Cc: Sami Mujawar <sami.mujawar at arm.com>
Cc: Vitaly Cheptsov <vit9696 at protonmail.com>
---
 ArmPkg/Include/AsmMacroIoLibV8.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/ArmPkg/Include/AsmMacroIoLibV8.h b/ArmPkg/Include/AsmMacroIoLibV8.h
index 135aaeca5d0b..81164ea9c9e7 100644
--- a/ArmPkg/Include/AsmMacroIoLibV8.h
+++ b/ArmPkg/Include/AsmMacroIoLibV8.h
@@ -41,8 +41,19 @@
   Name:                           ; \
   AARCH64_BTI(c)
 
+#define _ASM_FUNC_ALIGN(Name, Section, Align)       \
+  .global   Name                                  ; \
+  .section  #Section, "ax"                        ; \
+  .type     Name, %function                       ; \
+  .balign   Align                                 ; \
+  Name:                                           ; \
+  AARCH64_BTI(c)
+
 #define ASM_FUNC(Name)  _ASM_FUNC(ASM_PFX(Name), .text. ## Name)
 
+#define ASM_FUNC_ALIGN(Name, Align)  \
+  _ASM_FUNC_ALIGN(ASM_PFX(Name), .text. ## Name, Align)
+
 #define MOV32(Reg, Val)                   \
   movz      Reg, (Val) >> 16, lsl #16   ; \
   movk      Reg, (Val) & 0xffff
-- 
2.40.0



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