+++ /dev/null
-From ccb24bbd6d60771bac1510a86cd783c2c299093a Mon Sep 17 00:00:00 2001
-From: Sasha Levin <sashal@kernel.org>
-Date: Wed, 12 Apr 2023 09:50:20 +0100
-Subject: ARM: 9294/2: vfp: Fix broken softirq handling with instrumentation
- enabled
-
-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();
---
-2.39.2
-
projects / thirdparty / kernel / stable-queue.git / commitdiff
