From a18f36453e0788d2d285a62b85c7c668ec119a64 Mon Sep 17 00:00:00 2001 From: Daniel Thompson Date: Fri, 9 Jan 2015 18:30:13 +0100 Subject: ARM: 8266/1: Remove early stack deallocation from restore_user_regs Currently restore_user_regs deallocates the SVC stack early in its execution and relies on no exception being taken between the deallocation and the registers being restored. The introduction of a default FIQ handler that also uses the SVC stack breaks this assumption and can result in corrupted register state. This patch works around the problem by removing the early stack deallocation and using r2 as a temporary instead. I have not found a way to do this without introducing an extra mov instruction to the macro. Signed-off-by: Daniel Thompson Signed-off-by: Russell King --- arch/arm/kernel/entry-header.S | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'arch/arm') diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S index 4176df721bf0..1a0045abead7 100644 --- a/arch/arm/kernel/entry-header.S +++ b/arch/arm/kernel/entry-header.S @@ -253,21 +253,22 @@ .endm .macro restore_user_regs, fast = 0, offset = 0 - ldr r1, [sp, #\offset + S_PSR] @ get calling cpsr - ldr lr, [sp, #\offset + S_PC]! @ get pc + mov r2, sp + ldr r1, [r2, #\offset + S_PSR] @ get calling cpsr + ldr lr, [r2, #\offset + S_PC]! @ get pc msr spsr_cxsf, r1 @ save in spsr_svc #if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_32v6K) @ We must avoid clrex due to Cortex-A15 erratum #830321 - strex r1, r2, [sp] @ clear the exclusive monitor + strex r1, r2, [r2] @ clear the exclusive monitor #endif .if \fast - ldmdb sp, {r1 - lr}^ @ get calling r1 - lr + ldmdb r2, {r1 - lr}^ @ get calling r1 - lr .else - ldmdb sp, {r0 - lr}^ @ get calling r0 - lr + ldmdb r2, {r0 - lr}^ @ get calling r0 - lr .endif mov r0, r0 @ ARMv5T and earlier require a nop @ after ldm {}^ - add sp, sp, #S_FRAME_SIZE - S_PC + add sp, sp, #\offset + S_FRAME_SIZE movs pc, lr @ return & move spsr_svc into cpsr .endm -- cgit v1.2.3 From 2d9ed7406fd24987b75f78fea8290202d8108f34 Mon Sep 17 00:00:00 2001 From: Daniel Thompson Date: Mon, 5 Jan 2015 15:58:54 +0100 Subject: ARM: 8255/1: perf: Prevent wraparound during overflow If the overflow threshold for a counter is set above or near the 0xffffffff boundary then the kernel may lose track of the overflow causing only events that occur *after* the overflow to be recorded. Specifically the problem occurs when the value of the performance counter overtakes its original programmed value due to wrap around. Typical solutions to this problem are either to avoid programming in values likely to be overtaken or to treat the overflow bit as the 33rd bit of the counter. Its somewhat fiddly to refactor the code to correctly handle the 33rd bit during irqsave sections (context switches for example) so instead we take the simpler approach of avoiding values likely to be overtaken. We set the limit to half of max_period because this matches the limit imposed in __hw_perf_event_init(). This causes a doubling of the interrupt rate for large threshold values, however even with a very fast counter ticking at 4GHz the interrupt rate would only be ~1Hz. Signed-off-by: Daniel Thompson Acked-by: Will Deacon Signed-off-by: Russell King --- arch/arm/kernel/perf_event.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'arch/arm') diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c index f7c65adaa428..557e128e4df0 100644 --- a/arch/arm/kernel/perf_event.c +++ b/arch/arm/kernel/perf_event.c @@ -116,8 +116,14 @@ int armpmu_event_set_period(struct perf_event *event) ret = 1; } - if (left > (s64)armpmu->max_period) - left = armpmu->max_period; + /* + * Limit the maximum period to prevent the counter value + * from overtaking the one we are about to program. In + * effect we are reducing max_period to account for + * interrupt latency (and we are being very conservative). + */ + if (left > (armpmu->max_period >> 1)) + left = armpmu->max_period >> 1; local64_set(&hwc->prev_count, (u64)-left); -- cgit v1.2.3 From 909ba297beb50981a9d12364688d3c5f3084c6eb Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Tue, 20 Jan 2015 04:38:25 +0100 Subject: ARM: 8292/1: mm: fix size rounding-down of arm_add_memory() function The current rounding of "size" is wrong: - If "start" is sufficiently near the next page boundary, "size" is decremented by more than enough and the last page is lost. - If "size" is sufficiently small, it is wrapped around and gets a bogus value. Signed-off-by: Masahiro Yamada Acked-by: Geert Uytterhoeven Acked-by: Ard Biesheuvel Signed-off-by: Russell King --- arch/arm/kernel/setup.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'arch/arm') diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c index f9c863911038..d13f185e7bd5 100644 --- a/arch/arm/kernel/setup.c +++ b/arch/arm/kernel/setup.c @@ -657,10 +657,13 @@ int __init arm_add_memory(u64 start, u64 size) /* * Ensure that start/size are aligned to a page boundary. - * Size is appropriately rounded down, start is rounded up. + * Size is rounded down, start is rounded up. */ - size -= start & ~PAGE_MASK; aligned_start = PAGE_ALIGN(start); + if (aligned_start > start + size) + size = 0; + else + size -= aligned_start - start; #ifndef CONFIG_ARCH_PHYS_ADDR_T_64BIT if (aligned_start > ULONG_MAX) { -- cgit v1.2.3