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BaseLib:Fix RISC-V Supervisor mode (S-Mode) trap handler reentry issue. 

While RISC-V hart is trapped into S-Mode, the S-Mode interrupt
CSR (SIE) is disabled by RISC-V hart. However the (SIE) is enabled
again by RestoreTPL, this causes the second S-Mode trap is triggered
by the machine mode (M-Mode)timer interrupt redirection. The SRET
instruction clear Supervisor Previous Privilege (SPP) to zero
(User mode) in the second S-Mode interrupt according to the RISC-V
spec. Above brings hart to the user mode (U-Mode) when execute
SRET in the nested S-Mode interrupt handler because SPP is set to
User Mode in the second interrupt. Afterward, system runs in U-Mode
and any accesses to S-Mode CSR causes the invalid instruction exception.

Signed-off-by: Abner Chang <abner.chang@hpe.com>

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Daniel Schaefer <daniel.schaefer@hpe.com>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Signed-off-by: Abner Chang <abner.chang@hpe.com>
Acked-by: Liming Gao <liming.gao@intel.com>
This commit is contained in:
Abner Chang 2020-07-16 12:35:32 +08:00 committed by mergify[bot]
parent a3741780fe
commit e6042aec1b
1 changed files with 38 additions and 7 deletions
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41
MdePkg/Library/BaseLib/RiscV64/RiscVInterrupt.S
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@ -12,21 +12,52 @@ ASM_GLOBAL ASM_PFX(RiscVDisableSupervisorModeInterrupts)
ASM_GLOBAL ASM_PFX(RiscVEnableSupervisorModeInterrupt)
ASM_GLOBAL ASM_PFX(RiscVGetSupervisorModeInterrupts)
# define MSTATUS_SIE 0x00000002
# define CSR_SSTATUS 0x100
#define SSTATUS_SIE 0x00000002
#define CSR_SSTATUS 0x100
#define SSTATUS_SPP_BIT_POSITION 8
//
// This routine disables supervisor mode interrupt
//
ASM_PFX(RiscVDisableSupervisorModeInterrupts):
li a1, MSTATUS_SIE
add sp, sp, -(__SIZEOF_POINTER__)
sd a1, (sp)
li a1, SSTATUS_SIE
csrc CSR_SSTATUS, a1
ld a1, (sp)
add sp, sp, (__SIZEOF_POINTER__)
ret
//
// This routine enables supervisor mode interrupt
//
ASM_PFX(RiscVEnableSupervisorModeInterrupt):
li a1, MSTATUS_SIE
add sp, sp, -2*(__SIZEOF_POINTER__)
sd a0, (0*__SIZEOF_POINTER__)(sp)
sd a1, (1*__SIZEOF_POINTER__)(sp)
csrr a0, CSR_SSTATUS
and a0, a0, (1 << SSTATUS_SPP_BIT_POSITION)
bnez a0, InTrap // We are in supervisor mode (SMode)
// trap handler.
// Skip enabling SIE becasue SIE
// is set to disabled by RISC-V hart
// when the trap takes hart to SMode.
li a1, SSTATUS_SIE
csrs CSR_SSTATUS, a1
InTrap:
ld a0, (0*__SIZEOF_POINTER__)(sp)
ld a1, (1*__SIZEOF_POINTER__)(sp)
add sp, sp, 2*(__SIZEOF_POINTER__)
ret
//
// This routine returns supervisor mode interrupt
// status.
//
ASM_PFX(RiscVGetSupervisorModeInterrupts):
csrr a0, CSR_SSTATUS
andi a0, a0, MSTATUS_SIE
andi a0, a0, SSTATUS_SIE
ret