[PATCH] efi_loader: define allow_unaligned as 'asm volatile'
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 trini@konsulko.com Signed-off-by: Ilias Apalodimas ilias.apalodimas@linaro.org --- 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, wd@denx.de.
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) +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
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 trini@konsulko.com Signed-off-by: Ilias Apalodimas ilias.apalodimas@linaro.org
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, wd@denx.de.
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
participants (2)
-
Heinrich Schuchardt -
Ilias Apalodimas