diff options
| author | Max Filippov <jcmvbkbc@gmail.com> | 2013-10-15 02:22:42 +0400 |
|---|---|---|
| committer | Chris Zankel <chris@zankel.net> | 2013-10-15 13:39:06 -0700 |
| commit | 244066f4be8ce2dc2d2d60f01bceeba55c71a783 (patch) | |
| tree | a1a266f7ae41b3418a1f858712c52ba3cf141100 /arch | |
| parent | 61e6cfa80de5760bbe406f4e815b7739205754d2 (diff) | |
xtensa: fix fast_syscall_spill_registers_fixup
fast_syscall_spill_registers_fixup was not correctly updated by the
'keep a3 and excsave1 on entry to exception handlers' patch: it doesn't
preserve a3 that it gets on entry, breaking _spill_registers in case of
page fault on stack during register spilling, leading to unhandled
exception in kernel mode.
Preserve a3 by saving it in the original _spill_registers stack frame's
a3 during exception handling and restoring it afterwards.
Also fix comments and function bounds annotations.
Reported-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Tested-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Chris Zankel <chris@zankel.net>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/xtensa/kernel/entry.S | 49 |
1 files changed, 30 insertions, 19 deletions
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S index de1dfa18d0a..21dbe6bdb8e 100644 --- a/arch/xtensa/kernel/entry.S +++ b/arch/xtensa/kernel/entry.S @@ -1122,7 +1122,7 @@ ENDPROC(fast_syscall_spill_registers) * a3: exctable, original value in excsave1 */ -fast_syscall_spill_registers_fixup: +ENTRY(fast_syscall_spill_registers_fixup) rsr a2, windowbase # get current windowbase (a2 is saved) xsr a0, depc # restore depc and a0 @@ -1134,22 +1134,26 @@ fast_syscall_spill_registers_fixup: */ xsr a3, excsave1 # get spill-mask - slli a2, a3, 1 # shift left by one + slli a3, a3, 1 # shift left by one - slli a3, a2, 32-WSBITS - src a2, a2, a3 # a1 = xxwww1yyxxxwww1yy...... + slli a2, a3, 32-WSBITS + src a2, a3, a2 # a2 = xxwww1yyxxxwww1yy...... wsr a2, windowstart # set corrected windowstart - rsr a3, excsave1 - l32i a2, a3, EXC_TABLE_DOUBLE_SAVE # restore a2 - l32i a3, a3, EXC_TABLE_PARAM # original WB (in user task) + srli a3, a3, 1 + rsr a2, excsave1 + l32i a2, a2, EXC_TABLE_DOUBLE_SAVE # restore a2 + xsr a2, excsave1 + s32i a3, a2, EXC_TABLE_DOUBLE_SAVE # save a3 + l32i a3, a2, EXC_TABLE_PARAM # original WB (in user task) + xsr a2, excsave1 /* Return to the original (user task) WINDOWBASE. * We leave the following frame behind: * a0, a1, a2 same - * a3: trashed (saved in excsave_1) + * a3: trashed (saved in EXC_TABLE_DOUBLE_SAVE) * depc: depc (we have to return to that address) - * excsave_1: a3 + * excsave_1: exctable */ wsr a3, windowbase @@ -1159,9 +1163,9 @@ fast_syscall_spill_registers_fixup: * a0: return address * a1: used, stack pointer * a2: kernel stack pointer - * a3: available, saved in EXCSAVE_1 + * a3: available * depc: exception address - * excsave: a3 + * excsave: exctable * Note: This frame might be the same as above. */ @@ -1181,9 +1185,12 @@ fast_syscall_spill_registers_fixup: rsr a0, exccause addx4 a0, a0, a3 # find entry in table l32i a0, a0, EXC_TABLE_FAST_USER # load handler + l32i a3, a3, EXC_TABLE_DOUBLE_SAVE jx a0 -fast_syscall_spill_registers_fixup_return: +ENDPROC(fast_syscall_spill_registers_fixup) + +ENTRY(fast_syscall_spill_registers_fixup_return) /* When we return here, all registers have been restored (a2: DEPC) */ @@ -1191,13 +1198,13 @@ fast_syscall_spill_registers_fixup_return: /* Restore fixup handler. */ - xsr a3, excsave1 - movi a2, fast_syscall_spill_registers_fixup - s32i a2, a3, EXC_TABLE_FIXUP - s32i a0, a3, EXC_TABLE_DOUBLE_SAVE - rsr a2, windowbase - s32i a2, a3, EXC_TABLE_PARAM - l32i a2, a3, EXC_TABLE_KSTK + rsr a2, excsave1 + s32i a3, a2, EXC_TABLE_DOUBLE_SAVE + movi a3, fast_syscall_spill_registers_fixup + s32i a3, a2, EXC_TABLE_FIXUP + rsr a3, windowbase + s32i a3, a2, EXC_TABLE_PARAM + l32i a2, a2, EXC_TABLE_KSTK /* Load WB at the time the exception occurred. */ @@ -1206,8 +1213,12 @@ fast_syscall_spill_registers_fixup_return: wsr a3, windowbase rsync + rsr a3, excsave1 + l32i a3, a3, EXC_TABLE_DOUBLE_SAVE + rfde +ENDPROC(fast_syscall_spill_registers_fixup_return) /* * spill all registers. |