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| author | Max Filippov <jcmvbkbc@gmail.com> | 2015-01-12 09:44:44 +0300 |
|---|---|---|
| committer | Max Filippov <jcmvbkbc@gmail.com> | 2019-09-01 23:11:57 +0300 |
| commit | 09f8a6db20e6ed8eab1b2b23d09d2458f6e15062 (patch) | |
| tree | 1c3b6baee5c51968f10d2af9c97e35208542ed53 /arch/xtensa/kernel/entry.S | |
| parent | 9e1e41c44782741c727688a19e5624d039b0de7e (diff) | |
| download | linux-09f8a6db20e6ed8eab1b2b23d09d2458f6e15062.tar.xz | |
xtensa: add support for call0 ABI in userspace
Provide a Kconfig choice to select whether only the default ABI, only
call0 ABI or both are supported. The default for XEA2 is windowed, but
it may change for XEA3. Call0 only runs userspace with PS.WOE disabled.
Supporting both windowed and call0 ABIs is tricky, as there's no
indication in the ELF binaries which ABI they use. So it is done by
probing: each process is started with PS.WOE disabled, but the handler
of an illegal instruction exception taken with PS.WOE retries faulting
instruction after enabling PS.WOE. It must happen before any signal is
delivered to the process, otherwise it may be delivered incorrectly.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Diffstat (limited to 'arch/xtensa/kernel/entry.S')
| -rw-r--r-- | arch/xtensa/kernel/entry.S | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S index 9afe8f612f23..9e3676879168 100644 --- a/arch/xtensa/kernel/entry.S +++ b/arch/xtensa/kernel/entry.S @@ -1003,7 +1003,41 @@ ENTRY(fast_alloca) 4: j _WindowUnderflow4 ENDPROC(fast_alloca) +#ifdef CONFIG_USER_ABI_CALL0_PROBE /* + * fast illegal instruction handler. + * + * This is used to fix up user PS.WOE on the exception caused + * by the first opcode related to register window. If PS.WOE is + * already set it goes directly to the common user exception handler. + * + * Entry condition: + * + * a0: trashed, original value saved on stack (PT_AREG0) + * a1: a1 + * a2: new stack pointer, original in DEPC + * a3: a3 + * depc: a2, original value saved on stack (PT_DEPC) + * excsave_1: dispatch table + */ + +ENTRY(fast_illegal_instruction_user) + + rsr a0, ps + bbsi.l a0, PS_WOE_BIT, user_exception + s32i a3, a2, PT_AREG3 + movi a3, PS_WOE_MASK + or a0, a0, a3 + wsr a0, ps + l32i a3, a2, PT_AREG3 + l32i a0, a2, PT_AREG0 + rsr a2, depc + rfe + +ENDPROC(fast_illegal_instruction_user) +#endif + + /* * fast system calls. * * WARNING: The kernel doesn't save the entire user context before |