In order to be able to produce meaningful diagnostic output when taking
synchronous exceptions that have been caused by corruption of the stack
pointer, prepare the EL0 stack pointer and switch to it when handling the
'Sync exception using SPx' exception class. Other exception classes (of
which we really only care about IrqSPx) are left functionally intact.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
Note that some code has been moved around so that the macro doesn't grow too
big to fit in a 128 byte slot, while keeping the code logically consistent.
ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c | 17 +++-
ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S | 86 ++++++++++++--------
ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf | 5 +-
3 files changed, 70 insertions(+), 38 deletions(-)
diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
index 3d6eb4974d74..bd307628af87 100644
--- a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
+++ b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
@@ -16,7 +16,7 @@
#include <Uefi.h>
#include <Chipset/AArch64.h>
-
+#include <Library/MemoryAllocationLib.h>
#include <Protocol/DebugSupport.h> // for MAX_AARCH64_EXCEPTION
UINTN gMaxExceptionNumber = MAX_AARCH64_EXCEPTION;
@@ -25,11 +25,26 @@ EFI_EXCEPTION_CALLBACK gDebuggerExceptionHandlers[MAX_AARCH64_EXCEPTION + 1] =
PHYSICAL_ADDRESS gExceptionVectorAlignmentMask = ARM_VECTOR_TABLE_ALIGNMENT;
UINTN gDebuggerNoHandlerValue = 0; // todo: define for AArch64
+#define EL0_STACK_PAGES 2
+
+VOID
+RegisterEl0Stack (
+ IN VOID *Stack
+ );
+
RETURN_STATUS ArchVectorConfig(
IN UINTN VectorBaseAddress
)
{
UINTN HcrReg;
+ UINT8 *Stack;
+
+ Stack = AllocatePages (EL0_STACK_PAGES);
+ if (Stack == NULL) {
+ return RETURN_OUT_OF_RESOURCES;
+ }
+
+ RegisterEl0Stack ((UINT8 *)Stack + EFI_PAGES_TO_SIZE (EL0_STACK_PAGES));
if (ArmReadCurrentEL() == AARCH64_EL2) {
HcrReg = ArmReadHcr();
diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
index ff1f5fc81316..ac426d72a150 100644
--- a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
+++ b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
@@ -100,6 +100,7 @@
GCC_ASM_EXPORT(ExceptionHandlersEnd)
GCC_ASM_EXPORT(CommonCExceptionHandler)
+GCC_ASM_EXPORT(RegisterEl0Stack)
.text
@@ -122,35 +123,41 @@ ASM_PFX(ExceptionHandlersStart):
VECTOR_BASE(ExceptionHandlersStart)
#endif
- .macro ExceptionEntry, val
+ .macro ExceptionEntry, val, sp=SPx
+ .ifnc \sp, SPx
+ msr SPsel, xzr
+ .endif
+
// Move the stackpointer so we can reach our structure with the str instruction.
sub sp, sp, #(FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE)
- // Push some GP registers so we can record the exception context
+ // Push the GP registers so we can record the exception context
stp x0, x1, [sp, #-GP_CONTEXT_SIZE]!
stp x2, x3, [sp, #0x10]
stp x4, x5, [sp, #0x20]
stp x6, x7, [sp, #0x30]
+ stp x8, x9, [sp, #0x40]
+ stp x10, x11, [sp, #0x50]
+ stp x12, x13, [sp, #0x60]
+ stp x14, x15, [sp, #0x70]
+ stp x16, x17, [sp, #0x80]
+ stp x18, x19, [sp, #0x90]
+ stp x20, x21, [sp, #0xa0]
+ stp x22, x23, [sp, #0xb0]
+ stp x24, x25, [sp, #0xc0]
+ stp x26, x27, [sp, #0xd0]
+ stp x28, x29, [sp, #0xe0]
+ add x28, sp, #(GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE)
- EL1_OR_EL2_OR_EL3(x1)
-1:mrs x2, elr_el1 // Exception Link Register
- mrs x3, spsr_el1 // Saved Processor Status Register 32bit
- mrs x5, esr_el1 // EL1 Exception syndrome register 32bit
- mrs x6, far_el1 // EL1 Fault Address Register
- b 4f
-
-2:mrs x2, elr_el2 // Exception Link Register
- mrs x3, spsr_el2 // Saved Processor Status Register 32bit
- mrs x5, esr_el2 // EL2 Exception syndrome register 32bit
- mrs x6, far_el2 // EL2 Fault Address Register
- b 4f
-
-3:mrs x2, elr_el3 // Exception Link Register
- mrs x3, spsr_el3 // Saved Processor Status Register 32bit
- mrs x5, esr_el3 // EL3 Exception syndrome register 32bit
- mrs x6, far_el3 // EL3 Fault Address Register
+ .ifnc \sp, SPx
+ msr SPsel, #1 // Switch back to read the SP value upon entry
+ mov x7, sp
+ msr SPsel, xzr
+ .else
+ mov x7, x28 // x28 contains the SP value upon entry
+ .endif
-4:mrs x4, fpsr // Floating point Status Register 32bit
+ stp x30, x7, [sp, #0xf0]
// Record the type of exception that occurred.
mov x0, #\val
@@ -189,7 +196,7 @@ ASM_PFX(SErrorSP0):
//
VECTOR_ENTRY(ExceptionHandlersStart, ARM_VECTOR_CUR_SPx_SYNC)
ASM_PFX(SynchronousExceptionSPx):
- ExceptionEntry EXCEPT_AARCH64_SYNCHRONOUS_EXCEPTIONS
+ ExceptionEntry EXCEPT_AARCH64_SYNCHRONOUS_EXCEPTIONS, SP0
VECTOR_ENTRY(ExceptionHandlersStart, ARM_VECTOR_CUR_SPx_IRQ)
ASM_PFX(IrqSPx):
@@ -248,20 +255,25 @@ ASM_PFX(ExceptionHandlersEnd):
ASM_PFX(CommonExceptionEntry):
- // Stack the remaining GP registers
- stp x8, x9, [sp, #0x40]
- stp x10, x11, [sp, #0x50]
- stp x12, x13, [sp, #0x60]
- stp x14, x15, [sp, #0x70]
- stp x16, x17, [sp, #0x80]
- stp x18, x19, [sp, #0x90]
- stp x20, x21, [sp, #0xa0]
- stp x22, x23, [sp, #0xb0]
- stp x24, x25, [sp, #0xc0]
- stp x26, x27, [sp, #0xd0]
- stp x28, x29, [sp, #0xe0]
- add x28, sp, #GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
- stp x30, x28, [sp, #0xf0]
+ EL1_OR_EL2_OR_EL3(x1)
+1:mrs x2, elr_el1 // Exception Link Register
+ mrs x3, spsr_el1 // Saved Processor Status Register 32bit
+ mrs x5, esr_el1 // EL1 Exception syndrome register 32bit
+ mrs x6, far_el1 // EL1 Fault Address Register
+ b 4f
+
+2:mrs x2, elr_el2 // Exception Link Register
+ mrs x3, spsr_el2 // Saved Processor Status Register 32bit
+ mrs x5, esr_el2 // EL2 Exception syndrome register 32bit
+ mrs x6, far_el2 // EL2 Fault Address Register
+ b 4f
+
+3:mrs x2, elr_el3 // Exception Link Register
+ mrs x3, spsr_el3 // Saved Processor Status Register 32bit
+ mrs x5, esr_el3 // EL3 Exception syndrome register 32bit
+ mrs x6, far_el3 // EL3 Fault Address Register
+
+4:mrs x4, fpsr // Floating point Status Register 32bit
// Save the SYS regs
stp x2, x3, [x28, #-SYS_CONTEXT_SIZE]!
@@ -368,3 +380,7 @@ ASM_PFX(CommonExceptionEntry):
add sp, sp, #FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
eret
+
+ASM_PFX(RegisterEl0Stack):
+ msr sp_el0, x0
+ ret
diff --git a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
index 10d9ae0f4afc..cd9149cf76c6 100644
--- a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
+++ b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
@@ -53,10 +53,11 @@ [Packages]
[LibraryClasses]
ArmLib
- DebugLib
- DefaultExceptionHandlerLib
BaseMemoryLib
CacheMaintenanceLib
+ DebugLib
+ DefaultExceptionHandlerLib
+ MemoryAllocationLib
[Pcd]
gArmTokenSpaceGuid.PcdDebuggerExceptionSupport
--
2.7.4
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On Mon, Mar 20, 2017 at 08:53:01PM +0000, Ard Biesheuvel wrote:
> In order to be able to produce meaningful diagnostic output when taking
> synchronous exceptions that have been caused by corruption of the stack
> pointer, prepare the EL0 stack pointer and switch to it when handling the
> 'Sync exception using SPx' exception class. Other exception classes (of
> which we really only care about IrqSPx) are left functionally intact.
>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>
> Note that some code has been moved around so that the macro doesn't grow too
> big to fit in a 128 byte slot, while keeping the code logically consistent.
>
> ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c | 17 +++-
> ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S | 86 ++++++++++++--------
> ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf | 5 +-
> 3 files changed, 70 insertions(+), 38 deletions(-)
>
> diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
> index 3d6eb4974d74..bd307628af87 100644
> --- a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
> +++ b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
> @@ -16,7 +16,7 @@
> #include <Uefi.h>
>
> #include <Chipset/AArch64.h>
> -
> +#include <Library/MemoryAllocationLib.h>
> #include <Protocol/DebugSupport.h> // for MAX_AARCH64_EXCEPTION
>
> UINTN gMaxExceptionNumber = MAX_AARCH64_EXCEPTION;
> @@ -25,11 +25,26 @@ EFI_EXCEPTION_CALLBACK gDebuggerExceptionHandlers[MAX_AARCH64_EXCEPTION + 1] =
> PHYSICAL_ADDRESS gExceptionVectorAlignmentMask = ARM_VECTOR_TABLE_ALIGNMENT;
> UINTN gDebuggerNoHandlerValue = 0; // todo: define for AArch64
>
> +#define EL0_STACK_PAGES 2
> +
> +VOID
> +RegisterEl0Stack (
> + IN VOID *Stack
> + );
> +
> RETURN_STATUS ArchVectorConfig(
> IN UINTN VectorBaseAddress
> )
> {
> UINTN HcrReg;
> + UINT8 *Stack;
> +
> + Stack = AllocatePages (EL0_STACK_PAGES);
> + if (Stack == NULL) {
> + return RETURN_OUT_OF_RESOURCES;
> + }
> +
> + RegisterEl0Stack ((UINT8 *)Stack + EFI_PAGES_TO_SIZE (EL0_STACK_PAGES));
>
> if (ArmReadCurrentEL() == AARCH64_EL2) {
> HcrReg = ArmReadHcr();
> diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
> index ff1f5fc81316..ac426d72a150 100644
> --- a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
> +++ b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
> @@ -100,6 +100,7 @@
>
> GCC_ASM_EXPORT(ExceptionHandlersEnd)
> GCC_ASM_EXPORT(CommonCExceptionHandler)
> +GCC_ASM_EXPORT(RegisterEl0Stack)
>
> .text
>
> @@ -122,35 +123,41 @@ ASM_PFX(ExceptionHandlersStart):
> VECTOR_BASE(ExceptionHandlersStart)
> #endif
>
> - .macro ExceptionEntry, val
> + .macro ExceptionEntry, val, sp=SPx
> + .ifnc \sp, SPx
> + msr SPsel, xzr
> + .endif
Is this esoteric enough to motivate a comment?
> +
> // Move the stackpointer so we can reach our structure with the str instruction.
> sub sp, sp, #(FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE)
>
> - // Push some GP registers so we can record the exception context
> + // Push the GP registers so we can record the exception context
> stp x0, x1, [sp, #-GP_CONTEXT_SIZE]!
> stp x2, x3, [sp, #0x10]
> stp x4, x5, [sp, #0x20]
> stp x6, x7, [sp, #0x30]
> + stp x8, x9, [sp, #0x40]
> + stp x10, x11, [sp, #0x50]
> + stp x12, x13, [sp, #0x60]
> + stp x14, x15, [sp, #0x70]
> + stp x16, x17, [sp, #0x80]
> + stp x18, x19, [sp, #0x90]
> + stp x20, x21, [sp, #0xa0]
> + stp x22, x23, [sp, #0xb0]
> + stp x24, x25, [sp, #0xc0]
> + stp x26, x27, [sp, #0xd0]
> + stp x28, x29, [sp, #0xe0]
> + add x28, sp, #(GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE)
>
> - EL1_OR_EL2_OR_EL3(x1)
> -1:mrs x2, elr_el1 // Exception Link Register
> - mrs x3, spsr_el1 // Saved Processor Status Register 32bit
> - mrs x5, esr_el1 // EL1 Exception syndrome register 32bit
> - mrs x6, far_el1 // EL1 Fault Address Register
> - b 4f
> -
> -2:mrs x2, elr_el2 // Exception Link Register
> - mrs x3, spsr_el2 // Saved Processor Status Register 32bit
> - mrs x5, esr_el2 // EL2 Exception syndrome register 32bit
> - mrs x6, far_el2 // EL2 Fault Address Register
> - b 4f
> -
> -3:mrs x2, elr_el3 // Exception Link Register
> - mrs x3, spsr_el3 // Saved Processor Status Register 32bit
> - mrs x5, esr_el3 // EL3 Exception syndrome register 32bit
> - mrs x6, far_el3 // EL3 Fault Address Register
> + .ifnc \sp, SPx
> + msr SPsel, #1 // Switch back to read the SP value upon entry
> + mov x7, sp
> + msr SPsel, xzr
> + .else
> + mov x7, x28 // x28 contains the SP value upon entry
> + .endif
>
> -4:mrs x4, fpsr // Floating point Status Register 32bit
> + stp x30, x7, [sp, #0xf0]
>
> // Record the type of exception that occurred.
> mov x0, #\val
> @@ -189,7 +196,7 @@ ASM_PFX(SErrorSP0):
> //
> VECTOR_ENTRY(ExceptionHandlersStart, ARM_VECTOR_CUR_SPx_SYNC)
> ASM_PFX(SynchronousExceptionSPx):
> - ExceptionEntry EXCEPT_AARCH64_SYNCHRONOUS_EXCEPTIONS
> + ExceptionEntry EXCEPT_AARCH64_SYNCHRONOUS_EXCEPTIONS, SP0
>
> VECTOR_ENTRY(ExceptionHandlersStart, ARM_VECTOR_CUR_SPx_IRQ)
> ASM_PFX(IrqSPx):
> @@ -248,20 +255,25 @@ ASM_PFX(ExceptionHandlersEnd):
>
> ASM_PFX(CommonExceptionEntry):
>
> - // Stack the remaining GP registers
> - stp x8, x9, [sp, #0x40]
> - stp x10, x11, [sp, #0x50]
> - stp x12, x13, [sp, #0x60]
> - stp x14, x15, [sp, #0x70]
> - stp x16, x17, [sp, #0x80]
> - stp x18, x19, [sp, #0x90]
> - stp x20, x21, [sp, #0xa0]
> - stp x22, x23, [sp, #0xb0]
> - stp x24, x25, [sp, #0xc0]
> - stp x26, x27, [sp, #0xd0]
> - stp x28, x29, [sp, #0xe0]
> - add x28, sp, #GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
> - stp x30, x28, [sp, #0xf0]
> + EL1_OR_EL2_OR_EL3(x1)
> +1:mrs x2, elr_el1 // Exception Link Register
> + mrs x3, spsr_el1 // Saved Processor Status Register 32bit
> + mrs x5, esr_el1 // EL1 Exception syndrome register 32bit
> + mrs x6, far_el1 // EL1 Fault Address Register
> + b 4f
> +
> +2:mrs x2, elr_el2 // Exception Link Register
> + mrs x3, spsr_el2 // Saved Processor Status Register 32bit
> + mrs x5, esr_el2 // EL2 Exception syndrome register 32bit
> + mrs x6, far_el2 // EL2 Fault Address Register
> + b 4f
> +
> +3:mrs x2, elr_el3 // Exception Link Register
> + mrs x3, spsr_el3 // Saved Processor Status Register 32bit
> + mrs x5, esr_el3 // EL3 Exception syndrome register 32bit
> + mrs x6, far_el3 // EL3 Fault Address Register
> +
> +4:mrs x4, fpsr // Floating point Status Register 32bit
>
> // Save the SYS regs
> stp x2, x3, [x28, #-SYS_CONTEXT_SIZE]!
> @@ -368,3 +380,7 @@ ASM_PFX(CommonExceptionEntry):
> add sp, sp, #FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
>
> eret
> +
> +ASM_PFX(RegisterEl0Stack):
> + msr sp_el0, x0
> + ret
> diff --git a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
> index 10d9ae0f4afc..cd9149cf76c6 100644
> --- a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
> +++ b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
> @@ -53,10 +53,11 @@ [Packages]
>
> [LibraryClasses]
> ArmLib
> - DebugLib
> - DefaultExceptionHandlerLib
> BaseMemoryLib
> CacheMaintenanceLib
> + DebugLib
> + DefaultExceptionHandlerLib
> + MemoryAllocationLib
>
> [Pcd]
> gArmTokenSpaceGuid.PcdDebuggerExceptionSupport
> --
> 2.7.4
>
Not tested, but it looks quite plausible, so if Eugene agrees:
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
_______________________________________________
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On 22 March 2017 at 13:18, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> On Mon, Mar 20, 2017 at 08:53:01PM +0000, Ard Biesheuvel wrote:
>> In order to be able to produce meaningful diagnostic output when taking
>> synchronous exceptions that have been caused by corruption of the stack
>> pointer, prepare the EL0 stack pointer and switch to it when handling the
>> 'Sync exception using SPx' exception class. Other exception classes (of
>> which we really only care about IrqSPx) are left functionally intact.
>>
>> Contributed-under: TianoCore Contribution Agreement 1.0
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>>
>> Note that some code has been moved around so that the macro doesn't grow too
>> big to fit in a 128 byte slot, while keeping the code logically consistent.
>>
>> ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c | 17 +++-
>> ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S | 86 ++++++++++++--------
>> ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf | 5 +-
>> 3 files changed, 70 insertions(+), 38 deletions(-)
>>
>> diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
>> index 3d6eb4974d74..bd307628af87 100644
>> --- a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
>> +++ b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
>> @@ -16,7 +16,7 @@
>> #include <Uefi.h>
>>
>> #include <Chipset/AArch64.h>
>> -
>> +#include <Library/MemoryAllocationLib.h>
>> #include <Protocol/DebugSupport.h> // for MAX_AARCH64_EXCEPTION
>>
>> UINTN gMaxExceptionNumber = MAX_AARCH64_EXCEPTION;
>> @@ -25,11 +25,26 @@ EFI_EXCEPTION_CALLBACK gDebuggerExceptionHandlers[MAX_AARCH64_EXCEPTION + 1] =
>> PHYSICAL_ADDRESS gExceptionVectorAlignmentMask = ARM_VECTOR_TABLE_ALIGNMENT;
>> UINTN gDebuggerNoHandlerValue = 0; // todo: define for AArch64
>>
>> +#define EL0_STACK_PAGES 2
>> +
>> +VOID
>> +RegisterEl0Stack (
>> + IN VOID *Stack
>> + );
>> +
>> RETURN_STATUS ArchVectorConfig(
>> IN UINTN VectorBaseAddress
>> )
>> {
>> UINTN HcrReg;
>> + UINT8 *Stack;
>> +
>> + Stack = AllocatePages (EL0_STACK_PAGES);
>> + if (Stack == NULL) {
>> + return RETURN_OUT_OF_RESOURCES;
>> + }
>> +
>> + RegisterEl0Stack ((UINT8 *)Stack + EFI_PAGES_TO_SIZE (EL0_STACK_PAGES));
>>
>> if (ArmReadCurrentEL() == AARCH64_EL2) {
>> HcrReg = ArmReadHcr();
>> diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
>> index ff1f5fc81316..ac426d72a150 100644
>> --- a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
>> +++ b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
>> @@ -100,6 +100,7 @@
>>
>> GCC_ASM_EXPORT(ExceptionHandlersEnd)
>> GCC_ASM_EXPORT(CommonCExceptionHandler)
>> +GCC_ASM_EXPORT(RegisterEl0Stack)
>>
>> .text
>>
>> @@ -122,35 +123,41 @@ ASM_PFX(ExceptionHandlersStart):
>> VECTOR_BASE(ExceptionHandlersStart)
>> #endif
>>
>> - .macro ExceptionEntry, val
>> + .macro ExceptionEntry, val, sp=SPx
>> + .ifnc \sp, SPx
>> + msr SPsel, xzr
>> + .endif
>
> Is this esoteric enough to motivate a comment?
>
Yeah, good point. This looks like a suitable spot to dedicate some
space to explain what's going on
>> +
>> // Move the stackpointer so we can reach our structure with the str instruction.
>> sub sp, sp, #(FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE)
>>
>> - // Push some GP registers so we can record the exception context
>> + // Push the GP registers so we can record the exception context
>> stp x0, x1, [sp, #-GP_CONTEXT_SIZE]!
>> stp x2, x3, [sp, #0x10]
>> stp x4, x5, [sp, #0x20]
>> stp x6, x7, [sp, #0x30]
>> + stp x8, x9, [sp, #0x40]
>> + stp x10, x11, [sp, #0x50]
>> + stp x12, x13, [sp, #0x60]
>> + stp x14, x15, [sp, #0x70]
>> + stp x16, x17, [sp, #0x80]
>> + stp x18, x19, [sp, #0x90]
>> + stp x20, x21, [sp, #0xa0]
>> + stp x22, x23, [sp, #0xb0]
>> + stp x24, x25, [sp, #0xc0]
>> + stp x26, x27, [sp, #0xd0]
>> + stp x28, x29, [sp, #0xe0]
>> + add x28, sp, #(GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE)
>>
>> - EL1_OR_EL2_OR_EL3(x1)
>> -1:mrs x2, elr_el1 // Exception Link Register
>> - mrs x3, spsr_el1 // Saved Processor Status Register 32bit
>> - mrs x5, esr_el1 // EL1 Exception syndrome register 32bit
>> - mrs x6, far_el1 // EL1 Fault Address Register
>> - b 4f
>> -
>> -2:mrs x2, elr_el2 // Exception Link Register
>> - mrs x3, spsr_el2 // Saved Processor Status Register 32bit
>> - mrs x5, esr_el2 // EL2 Exception syndrome register 32bit
>> - mrs x6, far_el2 // EL2 Fault Address Register
>> - b 4f
>> -
>> -3:mrs x2, elr_el3 // Exception Link Register
>> - mrs x3, spsr_el3 // Saved Processor Status Register 32bit
>> - mrs x5, esr_el3 // EL3 Exception syndrome register 32bit
>> - mrs x6, far_el3 // EL3 Fault Address Register
>> + .ifnc \sp, SPx
>> + msr SPsel, #1 // Switch back to read the SP value upon entry
>> + mov x7, sp
>> + msr SPsel, xzr
>> + .else
>> + mov x7, x28 // x28 contains the SP value upon entry
>> + .endif
>>
>> -4:mrs x4, fpsr // Floating point Status Register 32bit
>> + stp x30, x7, [sp, #0xf0]
>>
>> // Record the type of exception that occurred.
>> mov x0, #\val
>> @@ -189,7 +196,7 @@ ASM_PFX(SErrorSP0):
>> //
>> VECTOR_ENTRY(ExceptionHandlersStart, ARM_VECTOR_CUR_SPx_SYNC)
>> ASM_PFX(SynchronousExceptionSPx):
>> - ExceptionEntry EXCEPT_AARCH64_SYNCHRONOUS_EXCEPTIONS
>> + ExceptionEntry EXCEPT_AARCH64_SYNCHRONOUS_EXCEPTIONS, SP0
>>
>> VECTOR_ENTRY(ExceptionHandlersStart, ARM_VECTOR_CUR_SPx_IRQ)
>> ASM_PFX(IrqSPx):
>> @@ -248,20 +255,25 @@ ASM_PFX(ExceptionHandlersEnd):
>>
>> ASM_PFX(CommonExceptionEntry):
>>
>> - // Stack the remaining GP registers
>> - stp x8, x9, [sp, #0x40]
>> - stp x10, x11, [sp, #0x50]
>> - stp x12, x13, [sp, #0x60]
>> - stp x14, x15, [sp, #0x70]
>> - stp x16, x17, [sp, #0x80]
>> - stp x18, x19, [sp, #0x90]
>> - stp x20, x21, [sp, #0xa0]
>> - stp x22, x23, [sp, #0xb0]
>> - stp x24, x25, [sp, #0xc0]
>> - stp x26, x27, [sp, #0xd0]
>> - stp x28, x29, [sp, #0xe0]
>> - add x28, sp, #GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
>> - stp x30, x28, [sp, #0xf0]
>> + EL1_OR_EL2_OR_EL3(x1)
>> +1:mrs x2, elr_el1 // Exception Link Register
>> + mrs x3, spsr_el1 // Saved Processor Status Register 32bit
>> + mrs x5, esr_el1 // EL1 Exception syndrome register 32bit
>> + mrs x6, far_el1 // EL1 Fault Address Register
>> + b 4f
>> +
>> +2:mrs x2, elr_el2 // Exception Link Register
>> + mrs x3, spsr_el2 // Saved Processor Status Register 32bit
>> + mrs x5, esr_el2 // EL2 Exception syndrome register 32bit
>> + mrs x6, far_el2 // EL2 Fault Address Register
>> + b 4f
>> +
>> +3:mrs x2, elr_el3 // Exception Link Register
>> + mrs x3, spsr_el3 // Saved Processor Status Register 32bit
>> + mrs x5, esr_el3 // EL3 Exception syndrome register 32bit
>> + mrs x6, far_el3 // EL3 Fault Address Register
>> +
>> +4:mrs x4, fpsr // Floating point Status Register 32bit
>>
>> // Save the SYS regs
>> stp x2, x3, [x28, #-SYS_CONTEXT_SIZE]!
>> @@ -368,3 +380,7 @@ ASM_PFX(CommonExceptionEntry):
>> add sp, sp, #FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
>>
>> eret
>> +
>> +ASM_PFX(RegisterEl0Stack):
>> + msr sp_el0, x0
>> + ret
>> diff --git a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
>> index 10d9ae0f4afc..cd9149cf76c6 100644
>> --- a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
>> +++ b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
>> @@ -53,10 +53,11 @@ [Packages]
>>
>> [LibraryClasses]
>> ArmLib
>> - DebugLib
>> - DefaultExceptionHandlerLib
>> BaseMemoryLib
>> CacheMaintenanceLib
>> + DebugLib
>> + DefaultExceptionHandlerLib
>> + MemoryAllocationLib
>>
>> [Pcd]
>> gArmTokenSpaceGuid.PcdDebuggerExceptionSupport
>> --
>> 2.7.4
>>
>
> Not tested, but it looks quite plausible, so if Eugene agrees:
> Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
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On 22 March 2017 at 13:18, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> On Mon, Mar 20, 2017 at 08:53:01PM +0000, Ard Biesheuvel wrote:
>> In order to be able to produce meaningful diagnostic output when taking
>> synchronous exceptions that have been caused by corruption of the stack
>> pointer, prepare the EL0 stack pointer and switch to it when handling the
>> 'Sync exception using SPx' exception class. Other exception classes (of
>> which we really only care about IrqSPx) are left functionally intact.
>>
>> Contributed-under: TianoCore Contribution Agreement 1.0
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>>
>> Note that some code has been moved around so that the macro doesn't grow too
>> big to fit in a 128 byte slot, while keeping the code logically consistent.
>>
>> ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c | 17 +++-
>> ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S | 86 ++++++++++++--------
>> ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf | 5 +-
>> 3 files changed, 70 insertions(+), 38 deletions(-)
>>
>> diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
>> index 3d6eb4974d74..bd307628af87 100644
>> --- a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
>> +++ b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
>> @@ -16,7 +16,7 @@
>> #include <Uefi.h>
>>
>> #include <Chipset/AArch64.h>
>> -
>> +#include <Library/MemoryAllocationLib.h>
>> #include <Protocol/DebugSupport.h> // for MAX_AARCH64_EXCEPTION
>>
>> UINTN gMaxExceptionNumber = MAX_AARCH64_EXCEPTION;
>> @@ -25,11 +25,26 @@ EFI_EXCEPTION_CALLBACK gDebuggerExceptionHandlers[MAX_AARCH64_EXCEPTION + 1] =
>> PHYSICAL_ADDRESS gExceptionVectorAlignmentMask = ARM_VECTOR_TABLE_ALIGNMENT;
>> UINTN gDebuggerNoHandlerValue = 0; // todo: define for AArch64
>>
>> +#define EL0_STACK_PAGES 2
>> +
>> +VOID
>> +RegisterEl0Stack (
>> + IN VOID *Stack
>> + );
>> +
>> RETURN_STATUS ArchVectorConfig(
>> IN UINTN VectorBaseAddress
>> )
>> {
>> UINTN HcrReg;
>> + UINT8 *Stack;
>> +
>> + Stack = AllocatePages (EL0_STACK_PAGES);
>> + if (Stack == NULL) {
>> + return RETURN_OUT_OF_RESOURCES;
>> + }
>> +
>> + RegisterEl0Stack ((UINT8 *)Stack + EFI_PAGES_TO_SIZE (EL0_STACK_PAGES));
>>
>> if (ArmReadCurrentEL() == AARCH64_EL2) {
>> HcrReg = ArmReadHcr();
>> diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
>> index ff1f5fc81316..ac426d72a150 100644
>> --- a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
>> +++ b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
>> @@ -100,6 +100,7 @@
>>
>> GCC_ASM_EXPORT(ExceptionHandlersEnd)
>> GCC_ASM_EXPORT(CommonCExceptionHandler)
>> +GCC_ASM_EXPORT(RegisterEl0Stack)
>>
>> .text
>>
>> @@ -122,35 +123,41 @@ ASM_PFX(ExceptionHandlersStart):
>> VECTOR_BASE(ExceptionHandlersStart)
>> #endif
>>
>> - .macro ExceptionEntry, val
>> + .macro ExceptionEntry, val, sp=SPx
>> + .ifnc \sp, SPx
>> + msr SPsel, xzr
>> + .endif
>
> Is this esoteric enough to motivate a comment?
>
>> +
>> // Move the stackpointer so we can reach our structure with the str instruction.
>> sub sp, sp, #(FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE)
>>
>> - // Push some GP registers so we can record the exception context
>> + // Push the GP registers so we can record the exception context
>> stp x0, x1, [sp, #-GP_CONTEXT_SIZE]!
>> stp x2, x3, [sp, #0x10]
>> stp x4, x5, [sp, #0x20]
>> stp x6, x7, [sp, #0x30]
>> + stp x8, x9, [sp, #0x40]
>> + stp x10, x11, [sp, #0x50]
>> + stp x12, x13, [sp, #0x60]
>> + stp x14, x15, [sp, #0x70]
>> + stp x16, x17, [sp, #0x80]
>> + stp x18, x19, [sp, #0x90]
>> + stp x20, x21, [sp, #0xa0]
>> + stp x22, x23, [sp, #0xb0]
>> + stp x24, x25, [sp, #0xc0]
>> + stp x26, x27, [sp, #0xd0]
>> + stp x28, x29, [sp, #0xe0]
>> + add x28, sp, #(GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE)
>>
>> - EL1_OR_EL2_OR_EL3(x1)
>> -1:mrs x2, elr_el1 // Exception Link Register
>> - mrs x3, spsr_el1 // Saved Processor Status Register 32bit
>> - mrs x5, esr_el1 // EL1 Exception syndrome register 32bit
>> - mrs x6, far_el1 // EL1 Fault Address Register
>> - b 4f
>> -
>> -2:mrs x2, elr_el2 // Exception Link Register
>> - mrs x3, spsr_el2 // Saved Processor Status Register 32bit
>> - mrs x5, esr_el2 // EL2 Exception syndrome register 32bit
>> - mrs x6, far_el2 // EL2 Fault Address Register
>> - b 4f
>> -
>> -3:mrs x2, elr_el3 // Exception Link Register
>> - mrs x3, spsr_el3 // Saved Processor Status Register 32bit
>> - mrs x5, esr_el3 // EL3 Exception syndrome register 32bit
>> - mrs x6, far_el3 // EL3 Fault Address Register
>> + .ifnc \sp, SPx
>> + msr SPsel, #1 // Switch back to read the SP value upon entry
>> + mov x7, sp
>> + msr SPsel, xzr
>> + .else
>> + mov x7, x28 // x28 contains the SP value upon entry
>> + .endif
>>
>> -4:mrs x4, fpsr // Floating point Status Register 32bit
>> + stp x30, x7, [sp, #0xf0]
>>
>> // Record the type of exception that occurred.
>> mov x0, #\val
>> @@ -189,7 +196,7 @@ ASM_PFX(SErrorSP0):
>> //
>> VECTOR_ENTRY(ExceptionHandlersStart, ARM_VECTOR_CUR_SPx_SYNC)
>> ASM_PFX(SynchronousExceptionSPx):
>> - ExceptionEntry EXCEPT_AARCH64_SYNCHRONOUS_EXCEPTIONS
>> + ExceptionEntry EXCEPT_AARCH64_SYNCHRONOUS_EXCEPTIONS, SP0
>>
>> VECTOR_ENTRY(ExceptionHandlersStart, ARM_VECTOR_CUR_SPx_IRQ)
>> ASM_PFX(IrqSPx):
>> @@ -248,20 +255,25 @@ ASM_PFX(ExceptionHandlersEnd):
>>
>> ASM_PFX(CommonExceptionEntry):
>>
>> - // Stack the remaining GP registers
>> - stp x8, x9, [sp, #0x40]
>> - stp x10, x11, [sp, #0x50]
>> - stp x12, x13, [sp, #0x60]
>> - stp x14, x15, [sp, #0x70]
>> - stp x16, x17, [sp, #0x80]
>> - stp x18, x19, [sp, #0x90]
>> - stp x20, x21, [sp, #0xa0]
>> - stp x22, x23, [sp, #0xb0]
>> - stp x24, x25, [sp, #0xc0]
>> - stp x26, x27, [sp, #0xd0]
>> - stp x28, x29, [sp, #0xe0]
>> - add x28, sp, #GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
>> - stp x30, x28, [sp, #0xf0]
>> + EL1_OR_EL2_OR_EL3(x1)
>> +1:mrs x2, elr_el1 // Exception Link Register
>> + mrs x3, spsr_el1 // Saved Processor Status Register 32bit
>> + mrs x5, esr_el1 // EL1 Exception syndrome register 32bit
>> + mrs x6, far_el1 // EL1 Fault Address Register
>> + b 4f
>> +
>> +2:mrs x2, elr_el2 // Exception Link Register
>> + mrs x3, spsr_el2 // Saved Processor Status Register 32bit
>> + mrs x5, esr_el2 // EL2 Exception syndrome register 32bit
>> + mrs x6, far_el2 // EL2 Fault Address Register
>> + b 4f
>> +
>> +3:mrs x2, elr_el3 // Exception Link Register
>> + mrs x3, spsr_el3 // Saved Processor Status Register 32bit
>> + mrs x5, esr_el3 // EL3 Exception syndrome register 32bit
>> + mrs x6, far_el3 // EL3 Fault Address Register
>> +
>> +4:mrs x4, fpsr // Floating point Status Register 32bit
>>
>> // Save the SYS regs
>> stp x2, x3, [x28, #-SYS_CONTEXT_SIZE]!
>> @@ -368,3 +380,7 @@ ASM_PFX(CommonExceptionEntry):
>> add sp, sp, #FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
>>
>> eret
>> +
>> +ASM_PFX(RegisterEl0Stack):
>> + msr sp_el0, x0
>> + ret
>> diff --git a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
>> index 10d9ae0f4afc..cd9149cf76c6 100644
>> --- a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
>> +++ b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
>> @@ -53,10 +53,11 @@ [Packages]
>>
>> [LibraryClasses]
>> ArmLib
>> - DebugLib
>> - DefaultExceptionHandlerLib
>> BaseMemoryLib
>> CacheMaintenanceLib
>> + DebugLib
>> + DefaultExceptionHandlerLib
>> + MemoryAllocationLib
>>
>> [Pcd]
>> gArmTokenSpaceGuid.PcdDebuggerExceptionSupport
>> --
>> 2.7.4
>>
>
> Not tested, but it looks quite plausible, so if Eugene agrees:
> Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
No word back from Eugene, so I am going to assume that he is on board with this.
I have added the following comment
//
// Our backtrace and register dump code is written in C and so it requires
// a stack. This makes it difficult to produce meaningful diagnostics when
// the stack pointer has been corrupted. So in such cases (i.e., when taking
// synchronous exceptions), this macro is expanded with \sp set to SP0, in
// which case we switch to the SP_EL0 stack pointer, which has been
// initialized to point to a buffer that has been set aside for this purpose.
//
// Since 'sp' may no longer refer to the stack frame that was active when
// the exception was taken, we may have to switch back and forth between
// SP_EL0 and SP_ELx to record the correct value for SP in the context struct.
//
Pushed as 21dbcff5be3c
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On 27 March 2017 at 13:54, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> On 22 March 2017 at 13:18, Leif Lindholm <leif.lindholm@linaro.org> wrote:
>> On Mon, Mar 20, 2017 at 08:53:01PM +0000, Ard Biesheuvel wrote:
>>> In order to be able to produce meaningful diagnostic output when taking
>>> synchronous exceptions that have been caused by corruption of the stack
>>> pointer, prepare the EL0 stack pointer and switch to it when handling the
>>> 'Sync exception using SPx' exception class. Other exception classes (of
>>> which we really only care about IrqSPx) are left functionally intact.
>>>
>>> Contributed-under: TianoCore Contribution Agreement 1.0
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>> ---
>>>
>>> Note that some code has been moved around so that the macro doesn't grow too
>>> big to fit in a 128 byte slot, while keeping the code logically consistent.
>>>
>>> ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c | 17 +++-
>>> ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S | 86 ++++++++++++--------
>>> ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf | 5 +-
>>> 3 files changed, 70 insertions(+), 38 deletions(-)
>>>
>>> diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
>>> index 3d6eb4974d74..bd307628af87 100644
>>> --- a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
>>> +++ b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
>>> @@ -16,7 +16,7 @@
>>> #include <Uefi.h>
>>>
>>> #include <Chipset/AArch64.h>
>>> -
>>> +#include <Library/MemoryAllocationLib.h>
>>> #include <Protocol/DebugSupport.h> // for MAX_AARCH64_EXCEPTION
>>>
>>> UINTN gMaxExceptionNumber = MAX_AARCH64_EXCEPTION;
>>> @@ -25,11 +25,26 @@ EFI_EXCEPTION_CALLBACK gDebuggerExceptionHandlers[MAX_AARCH64_EXCEPTION + 1] =
>>> PHYSICAL_ADDRESS gExceptionVectorAlignmentMask = ARM_VECTOR_TABLE_ALIGNMENT;
>>> UINTN gDebuggerNoHandlerValue = 0; // todo: define for AArch64
>>>
>>> +#define EL0_STACK_PAGES 2
>>> +
>>> +VOID
>>> +RegisterEl0Stack (
>>> + IN VOID *Stack
>>> + );
>>> +
>>> RETURN_STATUS ArchVectorConfig(
>>> IN UINTN VectorBaseAddress
>>> )
>>> {
>>> UINTN HcrReg;
>>> + UINT8 *Stack;
>>> +
>>> + Stack = AllocatePages (EL0_STACK_PAGES);
>>> + if (Stack == NULL) {
>>> + return RETURN_OUT_OF_RESOURCES;
>>> + }
>>> +
>>> + RegisterEl0Stack ((UINT8 *)Stack + EFI_PAGES_TO_SIZE (EL0_STACK_PAGES));
>>>
>>> if (ArmReadCurrentEL() == AARCH64_EL2) {
>>> HcrReg = ArmReadHcr();
>>> diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
>>> index ff1f5fc81316..ac426d72a150 100644
>>> --- a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
>>> +++ b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
>>> @@ -100,6 +100,7 @@
>>>
>>> GCC_ASM_EXPORT(ExceptionHandlersEnd)
>>> GCC_ASM_EXPORT(CommonCExceptionHandler)
>>> +GCC_ASM_EXPORT(RegisterEl0Stack)
>>>
>>> .text
>>>
>>> @@ -122,35 +123,41 @@ ASM_PFX(ExceptionHandlersStart):
>>> VECTOR_BASE(ExceptionHandlersStart)
>>> #endif
>>>
>>> - .macro ExceptionEntry, val
>>> + .macro ExceptionEntry, val, sp=SPx
>>> + .ifnc \sp, SPx
>>> + msr SPsel, xzr
>>> + .endif
>>
>> Is this esoteric enough to motivate a comment?
>>
>>> +
>>> // Move the stackpointer so we can reach our structure with the str instruction.
>>> sub sp, sp, #(FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE)
>>>
>>> - // Push some GP registers so we can record the exception context
>>> + // Push the GP registers so we can record the exception context
>>> stp x0, x1, [sp, #-GP_CONTEXT_SIZE]!
>>> stp x2, x3, [sp, #0x10]
>>> stp x4, x5, [sp, #0x20]
>>> stp x6, x7, [sp, #0x30]
>>> + stp x8, x9, [sp, #0x40]
>>> + stp x10, x11, [sp, #0x50]
>>> + stp x12, x13, [sp, #0x60]
>>> + stp x14, x15, [sp, #0x70]
>>> + stp x16, x17, [sp, #0x80]
>>> + stp x18, x19, [sp, #0x90]
>>> + stp x20, x21, [sp, #0xa0]
>>> + stp x22, x23, [sp, #0xb0]
>>> + stp x24, x25, [sp, #0xc0]
>>> + stp x26, x27, [sp, #0xd0]
>>> + stp x28, x29, [sp, #0xe0]
>>> + add x28, sp, #(GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE)
>>>
>>> - EL1_OR_EL2_OR_EL3(x1)
>>> -1:mrs x2, elr_el1 // Exception Link Register
>>> - mrs x3, spsr_el1 // Saved Processor Status Register 32bit
>>> - mrs x5, esr_el1 // EL1 Exception syndrome register 32bit
>>> - mrs x6, far_el1 // EL1 Fault Address Register
>>> - b 4f
>>> -
>>> -2:mrs x2, elr_el2 // Exception Link Register
>>> - mrs x3, spsr_el2 // Saved Processor Status Register 32bit
>>> - mrs x5, esr_el2 // EL2 Exception syndrome register 32bit
>>> - mrs x6, far_el2 // EL2 Fault Address Register
>>> - b 4f
>>> -
>>> -3:mrs x2, elr_el3 // Exception Link Register
>>> - mrs x3, spsr_el3 // Saved Processor Status Register 32bit
>>> - mrs x5, esr_el3 // EL3 Exception syndrome register 32bit
>>> - mrs x6, far_el3 // EL3 Fault Address Register
>>> + .ifnc \sp, SPx
>>> + msr SPsel, #1 // Switch back to read the SP value upon entry
>>> + mov x7, sp
>>> + msr SPsel, xzr
>>> + .else
>>> + mov x7, x28 // x28 contains the SP value upon entry
>>> + .endif
>>>
>>> -4:mrs x4, fpsr // Floating point Status Register 32bit
>>> + stp x30, x7, [sp, #0xf0]
>>>
>>> // Record the type of exception that occurred.
>>> mov x0, #\val
>>> @@ -189,7 +196,7 @@ ASM_PFX(SErrorSP0):
>>> //
>>> VECTOR_ENTRY(ExceptionHandlersStart, ARM_VECTOR_CUR_SPx_SYNC)
>>> ASM_PFX(SynchronousExceptionSPx):
>>> - ExceptionEntry EXCEPT_AARCH64_SYNCHRONOUS_EXCEPTIONS
>>> + ExceptionEntry EXCEPT_AARCH64_SYNCHRONOUS_EXCEPTIONS, SP0
>>>
>>> VECTOR_ENTRY(ExceptionHandlersStart, ARM_VECTOR_CUR_SPx_IRQ)
>>> ASM_PFX(IrqSPx):
>>> @@ -248,20 +255,25 @@ ASM_PFX(ExceptionHandlersEnd):
>>>
>>> ASM_PFX(CommonExceptionEntry):
>>>
>>> - // Stack the remaining GP registers
>>> - stp x8, x9, [sp, #0x40]
>>> - stp x10, x11, [sp, #0x50]
>>> - stp x12, x13, [sp, #0x60]
>>> - stp x14, x15, [sp, #0x70]
>>> - stp x16, x17, [sp, #0x80]
>>> - stp x18, x19, [sp, #0x90]
>>> - stp x20, x21, [sp, #0xa0]
>>> - stp x22, x23, [sp, #0xb0]
>>> - stp x24, x25, [sp, #0xc0]
>>> - stp x26, x27, [sp, #0xd0]
>>> - stp x28, x29, [sp, #0xe0]
>>> - add x28, sp, #GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
>>> - stp x30, x28, [sp, #0xf0]
>>> + EL1_OR_EL2_OR_EL3(x1)
>>> +1:mrs x2, elr_el1 // Exception Link Register
>>> + mrs x3, spsr_el1 // Saved Processor Status Register 32bit
>>> + mrs x5, esr_el1 // EL1 Exception syndrome register 32bit
>>> + mrs x6, far_el1 // EL1 Fault Address Register
>>> + b 4f
>>> +
>>> +2:mrs x2, elr_el2 // Exception Link Register
>>> + mrs x3, spsr_el2 // Saved Processor Status Register 32bit
>>> + mrs x5, esr_el2 // EL2 Exception syndrome register 32bit
>>> + mrs x6, far_el2 // EL2 Fault Address Register
>>> + b 4f
>>> +
>>> +3:mrs x2, elr_el3 // Exception Link Register
>>> + mrs x3, spsr_el3 // Saved Processor Status Register 32bit
>>> + mrs x5, esr_el3 // EL3 Exception syndrome register 32bit
>>> + mrs x6, far_el3 // EL3 Fault Address Register
>>> +
>>> +4:mrs x4, fpsr // Floating point Status Register 32bit
>>>
>>> // Save the SYS regs
>>> stp x2, x3, [x28, #-SYS_CONTEXT_SIZE]!
>>> @@ -368,3 +380,7 @@ ASM_PFX(CommonExceptionEntry):
>>> add sp, sp, #FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
>>>
>>> eret
>>> +
>>> +ASM_PFX(RegisterEl0Stack):
>>> + msr sp_el0, x0
>>> + ret
>>> diff --git a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
>>> index 10d9ae0f4afc..cd9149cf76c6 100644
>>> --- a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
>>> +++ b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
>>> @@ -53,10 +53,11 @@ [Packages]
>>>
>>> [LibraryClasses]
>>> ArmLib
>>> - DebugLib
>>> - DefaultExceptionHandlerLib
>>> BaseMemoryLib
>>> CacheMaintenanceLib
>>> + DebugLib
>>> + DefaultExceptionHandlerLib
>>> + MemoryAllocationLib
>>>
>>> [Pcd]
>>> gArmTokenSpaceGuid.PcdDebuggerExceptionSupport
>>> --
>>> 2.7.4
>>>
>>
>> Not tested, but it looks quite plausible, so if Eugene agrees:
>> Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
>
> No word back from Eugene, so I am going to assume that he is on board with this.
>
> I have added the following comment
>
> //
> // Our backtrace and register dump code is written in C and so it requires
> // a stack. This makes it difficult to produce meaningful diagnostics when
> // the stack pointer has been corrupted. So in such cases (i.e., when taking
> // synchronous exceptions), this macro is expanded with \sp set to SP0, in
> // which case we switch to the SP_EL0 stack pointer, which has been
> // initialized to point to a buffer that has been set aside for this purpose.
> //
> // Since 'sp' may no longer refer to the stack frame that was active when
> // the exception was taken, we may have to switch back and forth between
> // SP_EL0 and SP_ELx to record the correct value for SP in the context struct.
> //
>
> Pushed as 21dbcff5be3c
.. or rather, 2d120489583a
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