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Re: [PATCH v4] Avoid crash calling PrintErrMesg from efi_multiboot2
On Mon, Aug 19, 2024 at 3:30 PM Frediano Ziglio
<frediano.ziglio@xxxxxxxxx> wrote:
>
> Although code is compiled with -fpic option data is not position
> independent. This causes data pointer to become invalid if
> code is not relocated properly which is what happens for
> efi_multiboot2 which is called by multiboot entry code.
>
> Code tested adding
> PrintErrMesg(L"Test message", EFI_BUFFER_TOO_SMALL);
> in efi_multiboot2 before calling efi_arch_edd (this function
> can potentially call PrintErrMesg).
>
> Before the patch (XenServer installation on Qemu, xen replaced
> with vanilla xen.gz):
> Booting `XenServer (Serial)'Booting `XenServer (Serial)'
> Test message: !!!! X64 Exception Type - 0E(#PF - Page-Fault) CPU Apic ID - 00000000 !!!!
> ExceptionData - 0000000000000000 I:0 R:0 U:0 W:0 P:0 PK:0 SS:0 SGX:0
> RIP - 000000007DC29E46, CS - 0000000000000038, RFLAGS - 0000000000210246
> RAX - 0000000000000000, RCX - 0000000000000050, RDX - 0000000000000000
> RBX - 000000007DAB4558, RSP - 000000007EFA1200, RBP - 0000000000000000
> RSI - FFFF82D040467A88, RDI - 0000000000000000
> R8 - 000000007EFA1238, R9 - 000000007EFA1230, R10 - 0000000000000000
> R11 - 000000007CF42665, R12 - FFFF82D040467A88, R13 - 000000007EFA1228
> R14 - 000000007EFA1225, R15 - 000000007DAB45A8
> DS - 0000000000000030, ES - 0000000000000030, FS - 0000000000000030
> GS - 0000000000000030, SS - 0000000000000030
> CR0 - 0000000080010033, CR2 - FFFF82D040467A88, CR3 - 000000007EC01000
> CR4 - 0000000000000668, CR8 - 0000000000000000
> DR0 - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000
> DR3 - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400
> GDTR - 000000007E9E2000 0000000000000047, LDTR - 0000000000000000
> IDTR - 000000007E4E5018 0000000000000FFF, TR - 0000000000000000
> FXSAVE_STATE - 000000007EFA0E60
> !!!! Find image based on IP(0x7DC29E46) (No PDB) (ImageBase=000000007DC28000, EntryPoint=000000007DC2B917) !!!!
>
> After the patch:
> Booting `XenServer (Serial)'Booting `XenServer (Serial)'
> Test message: Buffer too small
> BdsDxe: loading Boot0000 "UiApp" from Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(462CAA21-7614-4503-836E-8AB6F4662331)
> BdsDxe: starting Boot0000 "UiApp" from Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(462CAA21-7614-4503-836E-8AB6F4662331)
>
> Fixes: 9180f5365524 ("x86: add multiboot2 protocol support for EFI platforms")
> Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>
> ---
> xen/common/efi/boot.c | 46 ++++++++++++++++++++++++++++++-------------
> 1 file changed, 32 insertions(+), 14 deletions(-)
> ---
> Changes since v1:
> - added "Fixes:" tag;
> - fixed cast style change.
>
> Changes since v2:
> - wrap long line.
>
> Changes since v3:
> - fixed "Fixes:" tag.
>
> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> index efbec00af9..fdbe75005c 100644
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -287,19 +287,36 @@ static bool __init match_guid(const EFI_GUID *guid1, const EFI_GUID *guid2)
> /* 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",
> +#define ERROR_MESSAGE_LIST \
> + ERROR_MESSAGE(EFI_NOT_FOUND, "Not found") \
> + ERROR_MESSAGE(EFI_NO_MEDIA, "The device has no media") \
> + ERROR_MESSAGE(EFI_MEDIA_CHANGED, "Media changed") \
> + ERROR_MESSAGE(EFI_DEVICE_ERROR, "Device error") \
> + ERROR_MESSAGE(EFI_VOLUME_CORRUPTED, "Volume corrupted") \
> + ERROR_MESSAGE(EFI_ACCESS_DENIED, "Access denied") \
> + ERROR_MESSAGE(EFI_OUT_OF_RESOURCES, "Out of resources") \
> + ERROR_MESSAGE(EFI_VOLUME_FULL, "Volume is full") \
> + ERROR_MESSAGE(EFI_SECURITY_VIOLATION, "Security violation") \
> + ERROR_MESSAGE(EFI_CRC_ERROR, "CRC error") \
> + ERROR_MESSAGE(EFI_COMPROMISED_DATA, "Compromised data") \
> + ERROR_MESSAGE(EFI_BUFFER_TOO_SMALL, "Buffer too small")
> +
> + static const struct ErrorStrings {
> + CHAR16 start;
> +#undef ERROR_MESSAGE
> +#define ERROR_MESSAGE(code, str) CHAR16 msg_ ## code[sizeof(str)];
> + ERROR_MESSAGE_LIST
> + } ErrorStrings __initconst = {
> + 0
> +#undef ERROR_MESSAGE
> +#define ERROR_MESSAGE(code, str) , L ## str
> + ERROR_MESSAGE_LIST
> + };
> + static const uint16_t ErrCodeToStr[] __initconst = {
> +#undef ERROR_MESSAGE
> +#define ERROR_MESSAGE(code, str) \
> + [~EFI_ERROR_MASK & code] = offsetof(struct ErrorStrings, msg_ ## code),
> + ERROR_MESSAGE_LIST
> };
> EFI_STATUS ErrIdx = ErrCode & ~EFI_ERROR_MASK;
>
> @@ -308,7 +325,8 @@ static void __init PrintErrMesg(const CHAR16 *mesg, EFI_STATUS ErrCode)
> PrintErr(L": ");
>
> if( (ErrIdx < ARRAY_SIZE(ErrCodeToStr)) && ErrCodeToStr[ErrIdx] )
> - mesg = ErrCodeToStr[ErrIdx];
> + mesg = (const CHAR16 *)((const void *)&ErrorStrings +
> + ErrCodeToStr[ErrIdx]);
> else
> {
> PrintErr(L"ErrCode: ");
Any update on this?
ping
The issue still apply, checked that I addressed all comments.
Frediano
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