diff options
| author | Russell King <rmk+kernel@armlinux.org.uk> | 2017-11-24 23:49:34 +0000 |
|---|---|---|
| committer | Russell King <rmk+kernel@armlinux.org.uk> | 2017-11-26 15:41:39 +0000 |
| commit | 8bafae202c82dc257f649ea3c275a0f35ee15113 (patch) | |
| tree | 1c2a7d64f216df552e4509dc746d8da3436e39ab /arch/arm/kernel/entry-header.S | |
| parent | 400eeffaffc7232c0ae1134fe04e14ae4fb48d8c (diff) | |
ARM: BUG if jumping to usermode address in kernel mode
Detect if we are returning to usermode via the normal kernel exit paths
but the saved PSR value indicates that we are in kernel mode. This
could occur due to corrupted stack state, which has been observed with
"ftracetest".
This ensures that we catch the problem case before we get to user code.
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/kernel/entry-header.S')
| -rw-r--r-- | arch/arm/kernel/entry-header.S | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S index 6391728c8f03..75f7a4e8541a 100644 --- a/arch/arm/kernel/entry-header.S +++ b/arch/arm/kernel/entry-header.S @@ -299,6 +299,8 @@ mov r2, sp ldr r1, [r2, #\offset + S_PSR] @ get calling cpsr ldr lr, [r2, #\offset + S_PC]! @ get pc + tst r1, #0xcf + bne 1f msr spsr_cxsf, r1 @ save in spsr_svc #if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_32v6K) @ We must avoid clrex due to Cortex-A15 erratum #830321 @@ -313,6 +315,7 @@ @ after ldm {}^ add sp, sp, #\offset + PT_REGS_SIZE movs pc, lr @ return & move spsr_svc into cpsr +1: bug "Returning to usermode but unexpected PSR bits set?", \@ #elif defined(CONFIG_CPU_V7M) @ V7M restore. @ Note that we don't need to do clrex here as clearing the local @@ -328,6 +331,8 @@ ldr r1, [sp, #\offset + S_PSR] @ get calling cpsr ldr lr, [sp, #\offset + S_PC] @ get pc add sp, sp, #\offset + S_SP + tst r1, #0xcf + bne 1f msr spsr_cxsf, r1 @ save in spsr_svc @ We must avoid clrex due to Cortex-A15 erratum #830321 @@ -340,6 +345,7 @@ .endif add sp, sp, #PT_REGS_SIZE - S_SP movs pc, lr @ return & move spsr_svc into cpsr +1: bug "Returning to usermode but unexpected PSR bits set?", \@ #endif /* !CONFIG_THUMB2_KERNEL */ .endm |