From 4dcc29e1574d88f4465ba865ed82800032f76418 Mon Sep 17 00:00:00 2001 From: Tony Luck Date: Tue, 27 May 2008 13:23:16 -0700 Subject: [IA64] Workaround for RSE issue Problem: An application violating the architectural rules regarding operation dependencies and having specific Register Stack Engine (RSE) state at the time of the violation, may result in an illegal operation fault and invalid RSE state. Such faults may initiate a cascade of repeated illegal operation faults within OS interruption handlers. The specific behavior is OS dependent. Implication: An application causing an illegal operation fault with specific RSE state may result in a series of illegal operation faults and an eventual OS stack overflow condition. Workaround: OS interruption handlers that switch to kernel backing store implement a check for invalid RSE state to avoid the series of illegal operation faults. The core of the workaround is the RSE_WORKAROUND code sequence inserted into each invocation of the SAVE_MIN_WITH_COVER and SAVE_MIN_WITH_COVER_R19 macros. This sequence includes hard-coded constants that depend on the number of stacked physical registers being 96. The rest of this patch consists of code to disable this workaround should this not be the case (with the presumption that if a future Itanium processor increases the number of registers, it would also remove the need for this patch). Move the start of the RBS up to a mod32 boundary to avoid some corner cases. The dispatch_illegal_op_fault code outgrew the spot it was squatting in when built with this patch and CONFIG_VIRT_CPU_ACCOUNTING=y Move it out to the end of the ivt. Signed-off-by: Tony Luck --- arch/ia64/kernel/patch.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'arch/ia64/kernel/patch.c') diff --git a/arch/ia64/kernel/patch.c b/arch/ia64/kernel/patch.c index e0dca8743db..b83b2c51600 100644 --- a/arch/ia64/kernel/patch.c +++ b/arch/ia64/kernel/patch.c @@ -115,6 +115,29 @@ ia64_patch_vtop (unsigned long start, unsigned long end) ia64_srlz_i(); } +/* + * Disable the RSE workaround by turning the conditional branch + * that we tagged in each place the workaround was used into an + * unconditional branch. + */ +void __init +ia64_patch_rse (unsigned long start, unsigned long end) +{ + s32 *offp = (s32 *) start; + u64 ip, *b; + + while (offp < (s32 *) end) { + ip = (u64) offp + *offp; + + b = (u64 *)(ip & -16); + b[1] &= ~0xf800000L; + ia64_fc((void *) ip); + ++offp; + } + ia64_sync_i(); + ia64_srlz_i(); +} + void __init ia64_patch_mckinley_e9 (unsigned long start, unsigned long end) { -- cgit v1.2.3