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Message-ID: <20230920083907.30479-1-mark-pk.tsai@mediatek.com>
Date: Wed, 20 Sep 2023 16:39:00 +0800
From: Mark-PK Tsai <mark-pk.tsai@...iatek.com>
To: Russell King <linux@...linux.org.uk>,
Matthias Brugger <matthias.bgg@...il.com>,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com>
CC: <yj.chiang@...iatek.com>, Mark-PK Tsai <mark-pk.tsai@...iatek.com>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>,
<linux-mediatek@...ts.infradead.org>
Subject: [PATCH] ARM: vfp: Add vudot opcode to VFP undef hook
Add vudot opcode to the VFP undef hook to fix the
potentially undefined instruction error when the
user space executes vudot instruction.
Before this commit, kernel didn't handle the undef exception
caused by vudot and didn't enable VFP in lazy VFP context
switch code like other NEON instructions.
This led to the occurrence of the undefined instruction
error as following:
[ 250.741238 ] 0904 (26902): undefined instruction: pc=004014ec
...
[ 250.741287 ] PC is at 0x4014ec
[ 250.741298 ] LR is at 0xb677874f
[ 250.741303 ] pc : [<004014ec>] lr : [<b677874f>] psr: 80070010
[ 250.741309 ] sp : beffedb0 ip : b67d7864 fp : beffee58
[ 250.741314 ] r10: 00000000 r9 : 00000000 r8 : 00000000
[ 250.741319 ] r7 : 00000001 r6 : 00000001 r5 : beffee90 r4 : 00401470
[ 250.741324 ] r3 : beffee20 r2 : beffee30 r1 : beffee40 r0 : 004003a8
[ 250.741331 ] Flags: Nzcv IRQs on FIQs on Mode USER_32 ISA ARM Segment user
[ 250.741339 ] Control: 10c5383d Table: 32d0406a DAC: 00000055
[ 250.741348 ] Code: f4434aef f4610aef f4622aef f4634aef (fc620df4)
Below is the assembly of the user program:
0x4014dc <+108>: vst1.64 {d20, d21}, [r3:128]
0x4014e0 <+112>: vld1.64 {d16, d17}, [r1:128]
0x4014e4 <+116>: vld1.64 {d18, d19}, [r2:128]
0x4014e8 <+120>: vld1.64 {d20, d21}, [r3:128] --> switch out
0x4014ec <+124>: vudot.u8 q8, q9, q10 <-- switch in, and FPEXC.EN = 0
SIGILL(illegal instruction)
Link: https://services.arm.com/support/s/case/5004L00000XsOjP
Signed-off-by: Mark-PK Tsai <mark-pk.tsai@...iatek.com>
---
arch/arm/vfp/vfpmodule.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 7e8773a2d99d..7eab8d1019d2 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -788,6 +788,12 @@ static struct undef_hook neon_support_hook[] = {{
.cpsr_mask = PSR_T_BIT,
.cpsr_val = 0,
.fn = vfp_support_entry,
+}, {
+ .instr_mask = 0xffb00000,
+ .instr_val = 0xfc200000,
+ .cpsr_mask = PSR_T_BIT,
+ .cpsr_val = 0,
+ .fn = vfp_support_entry,
}, {
.instr_mask = 0xef000000,
.instr_val = 0xef000000,
@@ -800,6 +806,12 @@ static struct undef_hook neon_support_hook[] = {{
.cpsr_mask = PSR_T_BIT,
.cpsr_val = PSR_T_BIT,
.fn = vfp_support_entry,
+}, {
+ .instr_mask = 0xffb00000,
+ .instr_val = 0xfc200000,
+ .cpsr_mask = PSR_T_BIT,
+ .cpsr_val = PSR_T_BIT,
+ .fn = vfp_support_entry,
}};
static struct undef_hook vfp_support_hook = {
--
2.18.0
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