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xtensa: improve call0 ABI probing

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When call0 userspace ABI support by probing is enabled instructions that
cause illegal instruction exception when PS.WOE is clear are retried
with PS.WOE set before calling c-level exception handler. Record user pc
at which PS.WOE was set in the fast exception handler and clear PS.WOE
in the c-level exception handler if we get there from the same address.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
This commit is contained in:
Max Filippov 2022-05-13 08:11:14 -07:00
parent d74862007e
commit 5cc5f19f88
4 changed files with 24 additions and 0 deletions
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4
arch/xtensa/include/asm/thread_info.h
View File

@ -56,6 +56,10 @@ struct thread_info {
/* result of the most recent exclusive store */
unsigned long atomctl8;
#endif
#ifdef CONFIG_USER_ABI_CALL0_PROBE
/* Address where PS.WOE was enabled by the ABI probing code */
unsigned long ps_woe_fix_addr;
#endif
/*
* If i-th bit is set then coprocessor state is loaded into the

3
arch/xtensa/kernel/asm-offsets.c
View File

@ -88,6 +88,9 @@ int main(void)
OFFSET(TI_STSTUS, thread_info, status);
OFFSET(TI_CPU, thread_info, cpu);
OFFSET(TI_PRE_COUNT, thread_info, preempt_count);
#ifdef CONFIG_USER_ABI_CALL0_PROBE
OFFSET(TI_PS_WOE_FIX_ADDR, thread_info, ps_woe_fix_addr);
#endif
/* struct thread_info (offset from start_struct) */
DEFINE(THREAD_RA, offsetof (struct task_struct, thread.ra));

5
arch/xtensa/kernel/entry.S
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@ -1056,6 +1056,11 @@ ENTRY(fast_illegal_instruction_user)
movi a3, PS_WOE_MASK
or a0, a0, a3
wsr a0, ps
#ifdef CONFIG_USER_ABI_CALL0_PROBE
GET_THREAD_INFO(a3, a2)
rsr a0, epc1
s32i a0, a3, TI_PS_WOE_FIX_ADDR
#endif
l32i a3, a2, PT_AREG3
l32i a0, a2, PT_AREG0
rsr a2, depc

12
arch/xtensa/kernel/traps.c
View File

@ -317,6 +317,18 @@ static bool check_div0(struct pt_regs *regs)
static void do_illegal_instruction(struct pt_regs *regs)
{
#ifdef CONFIG_USER_ABI_CALL0_PROBE
/*
* When call0 application encounters an illegal instruction fast
* exception handler will attempt to set PS.WOE and retry failing
* instruction.
* If we get here we know that that instruction is also illegal
* with PS.WOE set, so it's not related to the windowed option
* hence PS.WOE may be cleared.
*/
if (regs->pc == current_thread_info()->ps_woe_fix_addr)
regs->ps &= ~PS_WOE_MASK;
#endif
if (check_div0(regs)) {
do_div0(regs);
return;