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xtensa: fix fast_syscall_spill_registers_fixup

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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>
This commit is contained in:
Max Filippov
2013-10-15 02:22:42 +04:00
committed by Chris Zankel
parent 61e6cfa80d
commit 244066f4be
1 changed files with 30 additions and 19 deletions
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49
arch/xtensa/kernel/entry.S
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@@ -1122,7 +1122,7 @@ ENDPROC(fast_syscall_spill_registers)
* a3: exctable, original value in excsave1 * 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) rsr a2, windowbase # get current windowbase (a2 is saved)
xsr a0, depc # restore depc and a0 xsr a0, depc # restore depc and a0
@@ -1134,22 +1134,26 @@ fast_syscall_spill_registers_fixup:
*/ */
xsr a3, excsave1 # get spill-mask 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 slli a2, a3, 32-WSBITS
src a2, a2, a3 # a1 = xxwww1yyxxxwww1yy...... src a2, a3, a2 # a2 = xxwww1yyxxxwww1yy......
wsr a2, windowstart # set corrected windowstart wsr a2, windowstart # set corrected windowstart
rsr a3, excsave1 srli a3, a3, 1
l32i a2, a3, EXC_TABLE_DOUBLE_SAVE # restore a2 rsr a2, excsave1
l32i a3, a3, EXC_TABLE_PARAM # original WB (in user task) 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. /* Return to the original (user task) WINDOWBASE.
* We leave the following frame behind: * We leave the following frame behind:
* a0, a1, a2 same * 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) * depc: depc (we have to return to that address)
* excsave_1: a3 * excsave_1: exctable
*/ */
wsr a3, windowbase wsr a3, windowbase
@@ -1159,9 +1163,9 @@ fast_syscall_spill_registers_fixup:
* a0: return address * a0: return address
* a1: used, stack pointer * a1: used, stack pointer
* a2: kernel stack pointer * a2: kernel stack pointer
* a3: available, saved in EXCSAVE_1 * a3: available
* depc: exception address * depc: exception address
* excsave: a3 * excsave: exctable
* Note: This frame might be the same as above. * Note: This frame might be the same as above.
*/ */
@@ -1181,9 +1185,12 @@ fast_syscall_spill_registers_fixup:
rsr a0, exccause rsr a0, exccause
addx4 a0, a0, a3 # find entry in table addx4 a0, a0, a3 # find entry in table
l32i a0, a0, EXC_TABLE_FAST_USER # load handler l32i a0, a0, EXC_TABLE_FAST_USER # load handler
l32i a3, a3, EXC_TABLE_DOUBLE_SAVE
jx a0 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) */ /* When we return here, all registers have been restored (a2: DEPC) */
@@ -1191,13 +1198,13 @@ fast_syscall_spill_registers_fixup_return:
/* Restore fixup handler. */ /* Restore fixup handler. */
xsr a3, excsave1 rsr a2, excsave1
movi a2, fast_syscall_spill_registers_fixup s32i a3, a2, EXC_TABLE_DOUBLE_SAVE
s32i a2, a3, EXC_TABLE_FIXUP movi a3, fast_syscall_spill_registers_fixup
s32i a0, a3, EXC_TABLE_DOUBLE_SAVE s32i a3, a2, EXC_TABLE_FIXUP
rsr a2, windowbase rsr a3, windowbase
s32i a2, a3, EXC_TABLE_PARAM s32i a3, a2, EXC_TABLE_PARAM
l32i a2, a3, EXC_TABLE_KSTK l32i a2, a2, EXC_TABLE_KSTK
/* Load WB at the time the exception occurred. */ /* Load WB at the time the exception occurred. */
@@ -1206,8 +1213,12 @@ fast_syscall_spill_registers_fixup_return:
wsr a3, windowbase wsr a3, windowbase
rsync rsync
rsr a3, excsave1
l32i a3, a3, EXC_TABLE_DOUBLE_SAVE
rfde rfde
ENDPROC(fast_syscall_spill_registers_fixup_return)
/* /*
* spill all registers. * spill all registers.