From: Ard Biesheuvel ardb@kernel.org
[ Upstream commit c76c6c4ecbec0deb56a4f9e932b26866024a508f ]
Commit 62b95a7b44d1 ("ARM: 9282/1: vfp: Manipulate task VFP state with softirqs disabled") replaced the en/disable preemption calls inside the VFP state handling code with en/disabling of soft IRQs, which is necessary to allow kernel use of the VFP/SIMD unit when handling a soft IRQ.
Unfortunately, when lockdep is enabled (or other instrumentation that enables TRACE_IRQFLAGS), the disable path implemented in asm fails to perform the lockdep and RCU related bookkeeping, resulting in spurious warnings and other badness.
Set let's rework the VFP entry code a little bit so we can make the local_bh_disable() call from C, with all the instrumentations that happen to have been configured. Calling local_bh_enable() can be done from asm, as it is a simple wrapper around __local_bh_enable_ip(), which is always a callable function.
Link: https://lore.kernel.org/all/ZBBYCSZUJOWBg1s8@localhost.localdomain/
Fixes: 62b95a7b44d1 ("ARM: 9282/1: vfp: Manipulate task VFP state with softirqs disabled") Signed-off-by: Ard Biesheuvel ardb@kernel.org Reviewed-by: Linus Walleij linus.walleij@linaro.org Tested-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Russell King (Oracle) rmk+kernel@armlinux.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm/include/asm/assembler.h | 13 ------------- arch/arm/vfp/entry.S | 11 +---------- arch/arm/vfp/vfphw.S | 12 ++++++------ arch/arm/vfp/vfpmodule.c | 27 ++++++++++++++++++++++----- 4 files changed, 29 insertions(+), 34 deletions(-)
diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h index 06b48ce23e1ca..505a306e0271a 100644 --- a/arch/arm/include/asm/assembler.h +++ b/arch/arm/include/asm/assembler.h @@ -244,19 +244,6 @@ THUMB( fpreg .req r7 ) .endm #endif
- .macro local_bh_disable, ti, tmp - ldr \tmp, [\ti, #TI_PREEMPT] - add \tmp, \tmp, #SOFTIRQ_DISABLE_OFFSET - str \tmp, [\ti, #TI_PREEMPT] - .endm - - .macro local_bh_enable_ti, ti, tmp - get_thread_info \ti - ldr \tmp, [\ti, #TI_PREEMPT] - sub \tmp, \tmp, #SOFTIRQ_DISABLE_OFFSET - str \tmp, [\ti, #TI_PREEMPT] - .endm - #define USERL(l, x...) \ 9999: x; \ .pushsection __ex_table,"a"; \ diff --git a/arch/arm/vfp/entry.S b/arch/arm/vfp/entry.S index 6dabb47617781..7483ef8bccda3 100644 --- a/arch/arm/vfp/entry.S +++ b/arch/arm/vfp/entry.S @@ -24,14 +24,5 @@ ENTRY(do_vfp) mov r1, r10 mov r3, r9 - ldr r4, .LCvfp - ldr pc, [r4] @ call VFP entry point + b vfp_entry ENDPROC(do_vfp) - -ENTRY(vfp_null_entry) - ret lr -ENDPROC(vfp_null_entry) - - .align 2 -.LCvfp: - .word vfp_vector diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S index 60acd42e05786..4d8478264d82b 100644 --- a/arch/arm/vfp/vfphw.S +++ b/arch/arm/vfp/vfphw.S @@ -75,8 +75,6 @@ @ lr = unrecognised instruction return address @ IRQs enabled. ENTRY(vfp_support_entry) - local_bh_disable r1, r4 - ldr r11, [r1, #TI_CPU] @ CPU number add r10, r1, #TI_VFPSTATE @ r10 = workspace
@@ -179,9 +177,12 @@ vfp_hw_state_valid: @ else it's one 32-bit instruction, so @ always subtract 4 from the following @ instruction address. - local_bh_enable_ti r10, r4 - ret r3 @ we think we have handled things
+ mov lr, r3 @ we think we have handled things +local_bh_enable_and_ret: + adr r0, . + mov r1, #SOFTIRQ_DISABLE_OFFSET + b __local_bh_enable_ip @ tail call
look_for_VFP_exceptions: @ Check for synchronous or asynchronous exception @@ -204,8 +205,7 @@ skip: @ not recognised by VFP
DBGSTR "not VFP" - local_bh_enable_ti r10, r4 - ret lr + b local_bh_enable_and_ret
process_exception: DBGSTR "bounce" diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c index 01bc48d738478..349dcb944a937 100644 --- a/arch/arm/vfp/vfpmodule.c +++ b/arch/arm/vfp/vfpmodule.c @@ -32,10 +32,9 @@ /* * Our undef handlers (in entry.S) */ -asmlinkage void vfp_support_entry(void); -asmlinkage void vfp_null_entry(void); +asmlinkage void vfp_support_entry(u32, void *, u32, u32);
-asmlinkage void (*vfp_vector)(void) = vfp_null_entry; +static bool have_vfp __ro_after_init;
/* * Dual-use variable. @@ -645,6 +644,25 @@ static int vfp_starting_cpu(unsigned int unused) return 0; }
+/* + * Entered with: + * + * r0 = instruction opcode (32-bit ARM or two 16-bit Thumb) + * r1 = thread_info pointer + * r2 = PC value to resume execution after successful emulation + * r3 = normal "successful" return address + * lr = unrecognised instruction return address + */ +asmlinkage void vfp_entry(u32 trigger, struct thread_info *ti, u32 resume_pc, + u32 resume_return_address) +{ + if (unlikely(!have_vfp)) + return; + + local_bh_disable(); + vfp_support_entry(trigger, ti, resume_pc, resume_return_address); +} + #ifdef CONFIG_KERNEL_MODE_NEON
static int vfp_kmode_exception(struct pt_regs *regs, unsigned int instr) @@ -798,7 +816,6 @@ static int __init vfp_init(void) vfpsid = fmrx(FPSID); barrier(); unregister_undef_hook(&vfp_detect_hook); - vfp_vector = vfp_null_entry;
pr_info("VFP support v0.3: "); if (VFP_arch) { @@ -883,7 +900,7 @@ static int __init vfp_init(void) "arm/vfp:starting", vfp_starting_cpu, vfp_dying_cpu);
- vfp_vector = vfp_support_entry; + have_vfp = true;
thread_register_notifier(&vfp_notifier_block); vfp_pm_init();