On 3/20/23 18:13, Ilias Apalodimas wrote:
Tom reports that compiling with LTO & EFI breaks armv7 and arm11*
builds. The reason is that LTO (maybe a binutils bug?) replaces the
asm version of allow_unaligned() with the __weak definition of the
function. As a result EFI code ends up running with unaligned accesses
disabled and eventually crashes.
allow_unaligned() hardware specific variants are usually defined in .S
files. Switching those to inline assembly fixes the problem and the
linker keeps the correct version in the final binary
Reported-by: Tom Rini <[email protected]>
Signed-off-by: Ilias Apalodimas <[email protected]>
---
This is an alternative approach to
https://lore.kernel.org/u-boot/ZBRy1oSZ5iVFqrdV@hera/
since enabling unaligned accesses by default has been rejected in the past
arch/arm/cpu/arm11/Makefile | 4 ----
arch/arm/cpu/arm11/cpu.c | 13 +++++++++++++
arch/arm/cpu/arm11/sctlr.S | 25 -------------------------
arch/arm/cpu/armv7/Makefile | 1 -
arch/arm/cpu/armv7/cpu.c | 11 +++++++++++
arch/arm/cpu/armv7/sctlr.S | 22 ----------------------
6 files changed, 24 insertions(+), 52 deletions(-)
delete mode 100644 arch/arm/cpu/arm11/sctlr.S
delete mode 100644 arch/arm/cpu/armv7/sctlr.S
diff --git a/arch/arm/cpu/arm11/Makefile b/arch/arm/cpu/arm11/Makefile
index 5dfa01ae8d05..5d721fce12b5 100644
--- a/arch/arm/cpu/arm11/Makefile
+++ b/arch/arm/cpu/arm11/Makefile
@@ -4,7 +4,3 @@
# Wolfgang Denk, DENX Software Engineering, [email protected].
obj-y = cpu.o
-
-ifneq ($(CONFIG_SPL_BUILD),y)
-obj-$(CONFIG_EFI_LOADER) += sctlr.o
-endif
diff --git a/arch/arm/cpu/arm11/cpu.c b/arch/arm/cpu/arm11/cpu.c
index ffe35111d589..b19c4fc4a6c2 100644
--- a/arch/arm/cpu/arm11/cpu.c
+++ b/arch/arm/cpu/arm11/cpu.c
@@ -111,3 +111,16 @@ void enable_caches(void)
#endif
}
#endif
+
+#if !IS_ENABLED(CONFIG_SPL_BUILD)
+void allow_unaligned(void)
+{
+ asm volatile(
+ "mrc p15, 0, r0, c1, c0, 0\n" //load system control register
+ "orr r0, r0, #1 << 22\n" //set unaligned data support flag
+ "bic r0, r0, #2\n" //clear aligned flag
+ "mcr p15, 0, r0, c1, c0, 0\n" // write system control register
+ "bx lr\n" //return
+ );
+}
+#endif
diff --git a/arch/arm/cpu/arm11/sctlr.S b/arch/arm/cpu/arm11/sctlr.S
deleted file mode 100644
index 74a7fc4a25b6..000000000000
--- a/arch/arm/cpu/arm11/sctlr.S
+++ /dev/null
@@ -1,25 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0+ */
-/*
- * Routines to access the system control register
- *
- * Copyright (c) 2019 Heinrich Schuchardt
- */
-
-#include <linux/linkage.h>
-
-/*
- * void allow_unaligned(void) - allow unaligned access
- *
- * This routine sets the enable unaligned data support flag and clears the
- * aligned flag in the system control register.
- * After calling this routine unaligned access does no longer leads to a
- * data abort or undefined behavior but is handled by the CPU.
- * For details see the "ARM Architecture Reference Manual" for ARMv6.
- */
-ENTRY(allow_unaligned)
- mrc p15, 0, r0, c1, c0, 0 @ load system control register
- orr r0, r0, #1 << 22 @ set unaligned data support flag
- bic r0, r0, #2 @ clear aligned flag
- mcr p15, 0, r0, c1, c0, 0 @ write system control register
- bx lr @ return
-ENDPROC(allow_unaligned)
diff --git a/arch/arm/cpu/armv7/Makefile b/arch/arm/cpu/armv7/Makefile
index 653eef8ad79e..ca50f6e93e10 100644
--- a/arch/arm/cpu/armv7/Makefile
+++ b/arch/arm/cpu/armv7/Makefile
@@ -13,7 +13,6 @@ obj-y += syslib.o
obj-$(CONFIG_SYS_ARM_MPU) += mpu_v7r.o
ifneq ($(CONFIG_SPL_BUILD),y)
-obj-$(CONFIG_EFI_LOADER) += sctlr.o
obj-$(CONFIG_ARMV7_NONSEC) += exception_level.o
endif
diff --git a/arch/arm/cpu/armv7/cpu.c b/arch/arm/cpu/armv7/cpu.c
index 68807d209978..9742fa65e3cf 100644
--- a/arch/arm/cpu/armv7/cpu.c
+++ b/arch/arm/cpu/armv7/cpu.c
@@ -83,3 +83,14 @@ int cleanup_before_linux(void)
{
return cleanup_before_linux_select(CBL_ALL);
}
+
+#if !IS_ENABLED(CONFIG_SPL_BUILD)
Why do we need this #if? The linker should eliminate unused functions.
Best regards
Heinrich
+void allow_unaligned(void)
+{
+ asm volatile(
+ "mrc p15, 0, r0, c1, c0, 0\n" //load system control register
+ "bic r0, r0, #2\n" //clear aligned flag
+ "mcr p15, 0, r0, c1, c0, 0\n" //write system control register
+ );
+}
+#endif
diff --git a/arch/arm/cpu/armv7/sctlr.S b/arch/arm/cpu/armv7/sctlr.S
deleted file mode 100644
index bd56e41afe18..000000000000
--- a/arch/arm/cpu/armv7/sctlr.S
+++ /dev/null
@@ -1,22 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0+ */
-/*
- * Routines to access the system control register
- *
- * Copyright (c) 2018 Heinrich Schuchardt
- */
-
-#include <linux/linkage.h>
-
-/*
- * void allow_unaligned(void) - allow unaligned access
- *
- * This routine clears the aligned flag in the system control register.
- * After calling this routine unaligned access does no longer lead to a
- * data abort but is handled by the CPU.
- */
-ENTRY(allow_unaligned)
- mrc p15, 0, r0, c1, c0, 0 @ load system control register
- bic r0, r0, #2 @ clear aligned flag
- mcr p15, 0, r0, c1, c0, 0 @ write system control register
- bx lr @ return
-ENDPROC(allow_unaligned)
--
2.39.2
