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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3] xen: Work around Clang generating .data.rel.ro section for init-only files
>>> On 23.02.16 at 19:36, <andrew.cooper3@xxxxxxxxxx> wrote:
> Clang-3.8 generates several .data.rel.ro sections when compiling Xen. As
> these contain no global symbols, they should be .data.rel.ro.local. This
> breaks the SPECIAL_DATA_SECTIONS check when converting the transition units
> to
> being init-only.
>
> For alternatives.c, explicitly move the nops arrays into __initconst. For
> efi
> boot.c, manually create the optimisation performed by Clang by collapsing
> the
> switch statement into a lookup table. The double use of const is required
> to
> avoid breaking the ARM build by creating a section type conflict with
> fdt_guid.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> v2: Fix ARM build
> v3: Introduce and use __initconstrel
> ---
> xen/arch/arm/xen.lds.S | 1 +
> xen/arch/x86/alternative.c | 4 ++--
> xen/arch/x86/xen.lds.S | 1 +
> xen/common/efi/boot.c | 58
> +++++++++++++++-------------------------------
> xen/include/xen/init.h | 1 +
> 5 files changed, 24 insertions(+), 41 deletions(-)
>
> diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
> index f501a2f..9f7f915 100644
> --- a/xen/arch/arm/xen.lds.S
> +++ b/xen/arch/arm/xen.lds.S
> @@ -114,6 +114,7 @@ SECTIONS
> . = ALIGN(PAGE_SIZE);
> .init.data : {
> *(.init.rodata)
> + *(.init.rodata.rel)
> *(.init.rodata.str*)
> *(.init.data)
> *(.init.data.rel)
> diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c
> index 46ac0fd..9d54df1 100644
> --- a/xen/arch/x86/alternative.c
> +++ b/xen/arch/x86/alternative.c
> @@ -38,7 +38,7 @@ static const unsigned char k8nops[] __initconst = {
> K8_NOP7,
> K8_NOP8
> };
> -static const unsigned char * const k8_nops[ASM_NOP_MAX+1] = {
> +static const unsigned char * const k8_nops[ASM_NOP_MAX+1] __initconstrel =
> {
> NULL,
> k8nops,
> k8nops + 1,
> @@ -62,7 +62,7 @@ static const unsigned char p6nops[] __initconst = {
> P6_NOP7,
> P6_NOP8
> };
> -static const unsigned char * const p6_nops[ASM_NOP_MAX+1] = {
> +static const unsigned char * const p6_nops[ASM_NOP_MAX+1] __initconstrel =
> {
> NULL,
> p6nops,
> p6nops + 1,
> diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
> index 9fde1db..b3eb207 100644
> --- a/xen/arch/x86/xen.lds.S
> +++ b/xen/arch/x86/xen.lds.S
> @@ -119,6 +119,7 @@ SECTIONS
> } :text
> .init.data : {
> *(.init.rodata)
> + *(.init.rodata.rel)
> *(.init.rodata.str*)
> *(.init.data)
> *(.init.data.rel)
> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> index 53c7452..125c9ce 100644
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -241,53 +241,33 @@ static void __init noreturn blexit(const CHAR16 *str)
> /* generic routine for printing error messages */
> static void __init PrintErrMesg(const CHAR16 *mesg, EFI_STATUS ErrCode)
> {
> + static const CHAR16* const ErrCodeToStr[] __initconstrel = {
> + [~EFI_ERROR_MASK & EFI_NOT_FOUND] = L"Not found",
> + [~EFI_ERROR_MASK & EFI_NO_MEDIA] = L"The device has no
> media",
> + [~EFI_ERROR_MASK & EFI_MEDIA_CHANGED] = L"Media changed",
> + [~EFI_ERROR_MASK & EFI_DEVICE_ERROR] = L"Device error",
> + [~EFI_ERROR_MASK & EFI_VOLUME_CORRUPTED] = L"Volume corrupted",
> + [~EFI_ERROR_MASK & EFI_ACCESS_DENIED] = L"Access denied",
> + [~EFI_ERROR_MASK & EFI_OUT_OF_RESOURCES] = L"Out of resources",
> + [~EFI_ERROR_MASK & EFI_VOLUME_FULL] = L"Volume is full",
> + [~EFI_ERROR_MASK & EFI_SECURITY_VIOLATION] = L"Security violation",
> + [~EFI_ERROR_MASK & EFI_CRC_ERROR] = L"CRC error",
> + [~EFI_ERROR_MASK & EFI_COMPROMISED_DATA] = L"Compromised data",
> + [~EFI_ERROR_MASK & EFI_BUFFER_TOO_SMALL] = L"Buffer too small",
> + };
> + EFI_STATUS ErrIdx = ErrCode & ~EFI_ERROR_MASK;
> +
> StdOut = StdErr;
> PrintErr((CHAR16 *)mesg);
> PrintErr(L": ");
>
> - switch (ErrCode)
> + if( (ErrIdx < ARRAY_SIZE(ErrCodeToStr)) && ErrCodeToStr[ErrIdx] )
> + mesg = ErrCodeToStr[ErrIdx];
> + else
> {
> - case EFI_NOT_FOUND:
> - mesg = L"Not found";
> - break;
> - case EFI_NO_MEDIA:
> - mesg = L"The device has no media";
> - break;
> - case EFI_MEDIA_CHANGED:
> - mesg = L"Media changed";
> - break;
> - case EFI_DEVICE_ERROR:
> - mesg = L"Device error";
> - break;
> - case EFI_VOLUME_CORRUPTED:
> - mesg = L"Volume corrupted";
> - break;
> - case EFI_ACCESS_DENIED:
> - mesg = L"Access denied";
> - break;
> - case EFI_OUT_OF_RESOURCES:
> - mesg = L"Out of resources";
> - break;
> - case EFI_VOLUME_FULL:
> - mesg = L"Volume is full";
> - break;
> - case EFI_SECURITY_VIOLATION:
> - mesg = L"Security violation";
> - break;
> - case EFI_CRC_ERROR:
> - mesg = L"CRC error";
> - break;
> - case EFI_COMPROMISED_DATA:
> - mesg = L"Compromised data";
> - break;
> - case EFI_BUFFER_TOO_SMALL:
> - mesg = L"Buffer too small";
> - break;
> - default:
> PrintErr(L"ErrCode: ");
> DisplayUint(ErrCode, 0);
> mesg = NULL;
> - break;
> }
> blexit(mesg);
> }
> diff --git a/xen/include/xen/init.h b/xen/include/xen/init.h
> index fd8b614..671ac81 100644
> --- a/xen/include/xen/init.h
> +++ b/xen/include/xen/init.h
> @@ -11,6 +11,7 @@
> #define __exit __text_section(".exit.text")
> #define __initdata __section(".init.data")
> #define __initconst __section(".init.rodata")
> +#define __initconstrel __section(".init.rodata.rel")
> #define __exitdata __used_section(".exit.data")
> #define __initsetup __used_section(".init.setup")
> #define __init_call(lvl) __used_section(".initcall" lvl ".init")
> --
> 2.1.4
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