After commit 846a136881b8f73c1f74250bf6acfaa309cab1f2 ("ARM: vfp: fix
saving d16-d31 vfp registers on v6+ kernels"), the OMAP 2430SDP board
started crashing during boot with omap2plus_defconfig:
[ 3.875122] mmcblk0: mmc0:e624 SD04G 3.69 GiB
[ 3.915954] mmcblk0: p1
[ 4.086639] Internal error: Oops - undefined instruction: 0 [#1] SMP ARM
[ 4.093719] Modules linked in:
[ 4.096954] CPU: 0 Not tainted (3.6.0-02232-g759e00b #570)
[ 4.103149] PC is at vfp_reload_hw+0x1c/0x44
[ 4.107666] LR is at __und_usr_fault_32+0x0/0x8
It turns out that the context save/restore fix unmasked a latent bug in
commit 5aaf254409f8d58229107b59507a8235b715a960 ("ARM: 6203/1: Make VFPv3
usable on ARMv6"). When CONFIG_VFPv3 is set, but the kernel is booted on
a pre-VFPv3 core, the code attempts to save and restore the d16-d31 VFP
registers. These are only present on non-D16 VFPv3+, so the kernel dies
with an undefined instruction exception. The kernel didn't crash before
commit 846a136 because the save and restore code only touched d0-d15,
present on all VFP.
Fix to save and restore the d16-d31 registers only if they are
present.
Signed-off-by: Paul Walmsley <paul@xxxxxxxxx>
Cc: Tony Lindgren <tony@xxxxxxxxxxx>
Cc: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Dave Martin <dave.martin@xxxxxxxxxx>
---
arch/arm/include/asm/vfp.h | 6 ++++++
arch/arm/include/asm/vfpmacros.h | 8 ++++----
arch/arm/vfp/vfpmodule.c | 10 ++++++++++
3 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/arch/arm/include/asm/vfp.h b/arch/arm/include/asm/vfp.h
index f4ab34f..5689798 100644
--- a/arch/arm/include/asm/vfp.h
+++ b/arch/arm/include/asm/vfp.h
@@ -82,3 +82,9 @@
#define VFPOPDESC_UNUSED_BIT (24)
#define VFPOPDESC_UNUSED_MASK (0xFF << VFPOPDESC_UNUSED_BIT)
#define VFPOPDESC_OPDESC_MASK (~(VFPOPDESC_LENGTH_MASK | VFPOPDESC_UNUSED_MASK))
+
+#ifndef __ASSEMBLER__
+#include <linux/types.h>
+
+extern u32 vfp_has_d16_d31;
+#endif
diff --git a/arch/arm/include/asm/vfpmacros.h b/arch/arm/include/asm/vfpmacros.h
index 6a6f1e4..11496a9 100644
--- a/arch/arm/include/asm/vfpmacros.h
+++ b/arch/arm/include/asm/vfpmacros.h
@@ -25,9 +25,9 @@
#endif
#ifdef CONFIG_VFPv3
#if __LINUX_ARM_ARCH__ <= 6
- ldr \tmp, =elf_hwcap @ may not have MVFR regs
+ ldr \tmp, =vfp_has_d16_d31 @ have VFP regs d16-d31?
ldr \tmp, [\tmp, #0]
- tst \tmp, #HWCAP_VFPv3D16
+ cmp \tmp, #1
ldceql p11, cr0, [\base],#32*4 @ FLDMIAD \base!, {d16-d31}
addne \base, \base, #32*4 @ step over unused register space
#else
@@ -49,9 +49,9 @@
#endif
#ifdef CONFIG_VFPv3
#if __LINUX_ARM_ARCH__ <= 6
- ldr \tmp, =elf_hwcap @ may not have MVFR regs
+ ldr \tmp, =vfp_has_d16_d31 @ have VFP regs d16-d31?
ldr \tmp, [\tmp, #0]
- tst \tmp, #HWCAP_VFPv3D16
+ cmp \tmp, #1
stceql p11, cr0, [\base],#32*4 @ FSTMIAD \base!, {d16-d31}
addne \base, \base, #32*4 @ step over unused register space
#else
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index c834b32..929b53b 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -58,6 +58,12 @@ unsigned int VFP_arch;
union vfp_state *vfp_current_hw_state[NR_CPUS];
/*
+ * If the VFP on this ARM core has registers d16-d31, vfp_has_d16_d31 will
+ * be set to 1; otherwise, 0. Only valid after startup.
+ */
+u32 vfp_has_d16_d31;
+
+/*
* Is 'thread's most up to date state stored in this CPUs hardware?
* Must be called from non-preemptible context.
*/
@@ -691,6 +697,8 @@ static int __init vfp_init(void)
thread_register_notifier(&vfp_notifier_block);
vfp_pm_init();
+ vfp_has_d16_d31 = 0;
+
/*
* We detected VFP, and the support code is
* in place; report VFP support to userspace.
@@ -706,6 +714,8 @@ static int __init vfp_init(void)
*/
if (((fmrx(MVFR0) & MVFR0_A_SIMD_MASK)) == 1)
elf_hwcap |= HWCAP_VFPv3D16;
+ else
+ vfp_has_d16_d31 = 1;
}
#endif
/*
--
1.7.10.4
--
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