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ArmPkg/ArmExceptionLib: use EL0 stack for synchronous exceptions 

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.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
This commit is contained in:
Ard Biesheuvel 2017-03-15 16:26:41 +00:00
parent 0b36d8fa73
commit 2d12048958
3 changed files with 82 additions and 38 deletions
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17
ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
View File

@ -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();

98
ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
View File

@ -100,6 +100,7 @@
GCC_ASM_EXPORT(ExceptionHandlersEnd)
GCC_ASM_EXPORT(CommonCExceptionHandler)
GCC_ASM_EXPORT(RegisterEl0Stack)
.text
@ -122,35 +123,53 @@ ASM_PFX(ExceptionHandlersStart):
VECTOR_BASE(ExceptionHandlersStart)
#endif
.macro ExceptionEntry, val
.macro ExceptionEntry, val, sp=SPx
//
// 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.
//
.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
.ifnc \sp, SPx
msr SPsel, #1
mov x7, sp
msr SPsel, xzr
.else
mov x7, x28
.endif
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
stp x30, x7, [sp, #0xf0]
// Record the type of exception that occurred.
mov x0, #\val
@ -189,7 +208,7 @@ 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 +267,25 @@ 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 +392,7 @@ ASM_PFX(CommonExceptionEntry):
add sp, sp, #FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE
eret
ASM_PFX(RegisterEl0Stack):
msr sp_el0, x0
ret

5
ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.inf
View File

@ -53,10 +53,11 @@
[LibraryClasses]
ArmLib
DebugLib
DefaultExceptionHandlerLib
BaseMemoryLib
CacheMaintenanceLib
DebugLib
DefaultExceptionHandlerLib
MemoryAllocationLib
[Pcd]
gArmTokenSpaceGuid.PcdDebuggerExceptionSupport