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Message-ID: <20231004151405.521596-3-cleger@rivosinc.com>
Date: Wed, 4 Oct 2023 17:13:59 +0200
From: Clément Léger <cleger@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>
Cc: Clément Léger <cleger@...osinc.com>,
Atish Patra <atishp@...osinc.com>,
Andrew Jones <ajones@...tanamicro.com>,
Evan Green <evan@...osinc.com>,
Björn Topel <bjorn@...osinc.com>,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
Ron Minnich <rminnich@...il.com>,
Daniel Maslowski <cyrevolt@...glemail.com>,
Conor Dooley <conor@...nel.org>
Subject: [PATCH v2 2/8] riscv: add support for misaligned trap handling in S-mode
Misalignment trap handling is only supported for M-mode and uses direct
accesses to user memory. In S-mode, when handling usermode fault, this
requires to use the get_user()/put_user() accessors. Implement
load_u8(), store_u8() and get_insn() using these accessors for
userspace and direct text access for kernel.
Signed-off-by: Clément Léger <cleger@...osinc.com>
---
arch/riscv/Kconfig | 8 ++
arch/riscv/include/asm/entry-common.h | 14 +++
arch/riscv/kernel/Makefile | 2 +-
arch/riscv/kernel/traps.c | 9 --
arch/riscv/kernel/traps_misaligned.c | 119 +++++++++++++++++++++++---
5 files changed, 129 insertions(+), 23 deletions(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index d607ab0f7c6d..6e167358a897 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -636,6 +636,14 @@ config THREAD_SIZE_ORDER
Specify the Pages of thread stack size (from 4KB to 64KB), which also
affects irq stack size, which is equal to thread stack size.
+config RISCV_MISALIGNED
+ bool "Support misaligned load/store traps for kernel and userspace"
+ default y
+ help
+ Say Y here if you want the kernel to embed support for misaligned
+ load/store for both kernel and userspace. When disable, misaligned
+ accesses will generate SIGBUS in userspace and panic in kernel.
+
endmenu # "Platform type"
menu "Kernel features"
diff --git a/arch/riscv/include/asm/entry-common.h b/arch/riscv/include/asm/entry-common.h
index 6e4dee49d84b..7ab5e34318c8 100644
--- a/arch/riscv/include/asm/entry-common.h
+++ b/arch/riscv/include/asm/entry-common.h
@@ -8,4 +8,18 @@
void handle_page_fault(struct pt_regs *regs);
void handle_break(struct pt_regs *regs);
+#ifdef CONFIG_RISCV_MISALIGNED
+int handle_misaligned_load(struct pt_regs *regs);
+int handle_misaligned_store(struct pt_regs *regs);
+#else
+static inline int handle_misaligned_load(struct pt_regs *regs)
+{
+ return -1;
+}
+static inline int handle_misaligned_store(struct pt_regs *regs)
+{
+ return -1;
+}
+#endif
+
#endif /* _ASM_RISCV_ENTRY_COMMON_H */
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 95cf25d48405..0d874fb24b51 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -59,7 +59,7 @@ obj-y += patch.o
obj-y += probes/
obj-$(CONFIG_MMU) += vdso.o vdso/
-obj-$(CONFIG_RISCV_M_MODE) += traps_misaligned.o
+obj-$(CONFIG_RISCV_MISALIGNED) += traps_misaligned.o
obj-$(CONFIG_FPU) += fpu.o
obj-$(CONFIG_RISCV_ISA_V) += vector.o
obj-$(CONFIG_SMP) += smpboot.o
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 19807c4d3805..d69779e4b967 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -179,14 +179,6 @@ asmlinkage __visible __trap_section void do_trap_insn_illegal(struct pt_regs *re
DO_ERROR_INFO(do_trap_load_fault,
SIGSEGV, SEGV_ACCERR, "load access fault");
-#ifndef CONFIG_RISCV_M_MODE
-DO_ERROR_INFO(do_trap_load_misaligned,
- SIGBUS, BUS_ADRALN, "Oops - load address misaligned");
-DO_ERROR_INFO(do_trap_store_misaligned,
- SIGBUS, BUS_ADRALN, "Oops - store (or AMO) address misaligned");
-#else
-int handle_misaligned_load(struct pt_regs *regs);
-int handle_misaligned_store(struct pt_regs *regs);
asmlinkage __visible __trap_section void do_trap_load_misaligned(struct pt_regs *regs)
{
@@ -229,7 +221,6 @@ asmlinkage __visible __trap_section void do_trap_store_misaligned(struct pt_regs
irqentry_nmi_exit(regs, state);
}
}
-#endif
DO_ERROR_INFO(do_trap_store_fault,
SIGSEGV, SEGV_ACCERR, "store (or AMO) access fault");
DO_ERROR_INFO(do_trap_ecall_s,
diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index e7bfb33089c1..9daed7d756ae 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -12,6 +12,7 @@
#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/csr.h>
+#include <asm/entry-common.h>
#define INSN_MATCH_LB 0x3
#define INSN_MASK_LB 0x707f
@@ -151,21 +152,25 @@
#define PRECISION_S 0
#define PRECISION_D 1
-static inline u8 load_u8(const u8 *addr)
+#ifdef CONFIG_RISCV_M_MODE
+static inline int load_u8(struct pt_regs *regs, const u8 *addr, u8 *r_val)
{
u8 val;
asm volatile("lbu %0, %1" : "=&r" (val) : "m" (*addr));
+ *r_val = val;
- return val;
+ return 0;
}
-static inline void store_u8(u8 *addr, u8 val)
+static inline int store_u8(struct pt_regs *regs, u8 *addr, u8 val)
{
asm volatile ("sb %0, %1\n" : : "r" (val), "m" (*addr));
+
+ return 0;
}
-static inline ulong get_insn(ulong mepc)
+static inline int get_insn(struct pt_regs *regs, ulong mepc, ulong *r_insn)
{
register ulong __mepc asm ("a2") = mepc;
ulong val, rvc_mask = 3, tmp;
@@ -194,9 +199,87 @@ static inline ulong get_insn(ulong mepc)
: [addr] "r" (__mepc), [rvc_mask] "r" (rvc_mask),
[xlen_minus_16] "i" (XLEN_MINUS_16));
- return val;
+ *r_insn = val;
+
+ return 0;
+}
+#else
+static inline int load_u8(struct pt_regs *regs, const u8 *addr, u8 *r_val)
+{
+ if (user_mode(regs)) {
+ return __get_user(*r_val, addr);
+ } else {
+ *r_val = *addr;
+ return 0;
+ }
}
+static inline int store_u8(struct pt_regs *regs, u8 *addr, u8 val)
+{
+ if (user_mode(regs)) {
+ return __put_user(val, addr);
+ } else {
+ *addr = val;
+ return 0;
+ }
+}
+
+#define __read_insn(regs, insn, insn_addr) \
+({ \
+ int __ret; \
+ \
+ if (user_mode(regs)) { \
+ __ret = __get_user(insn, insn_addr); \
+ } else { \
+ insn = *insn_addr; \
+ __ret = 0; \
+ } \
+ \
+ __ret; \
+})
+
+static inline int get_insn(struct pt_regs *regs, ulong epc, ulong *r_insn)
+{
+ ulong insn = 0;
+
+ if (epc & 0x2) {
+ ulong tmp = 0;
+ u16 __user *insn_addr = (u16 __user *)epc;
+
+ if (__read_insn(regs, insn, insn_addr))
+ return -EFAULT;
+ /* __get_user() uses regular "lw" which sign extend the loaded
+ * value make sure to clear higher order bits in case we "or" it
+ * below with the upper 16 bits half.
+ */
+ insn &= GENMASK(15, 0);
+ if ((insn & __INSN_LENGTH_MASK) != __INSN_LENGTH_32) {
+ *r_insn = insn;
+ return 0;
+ }
+ insn_addr++;
+ if (__read_insn(regs, tmp, insn_addr))
+ return -EFAULT;
+ *r_insn = (tmp << 16) | insn;
+
+ return 0;
+ } else {
+ u32 __user *insn_addr = (u32 __user *)epc;
+
+ if (__read_insn(regs, insn, insn_addr))
+ return -EFAULT;
+ if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32) {
+ *r_insn = insn;
+ return 0;
+ }
+ insn &= GENMASK(15, 0);
+ *r_insn = insn;
+
+ return 0;
+ }
+}
+#endif
+
union reg_data {
u8 data_bytes[8];
ulong data_ulong;
@@ -207,10 +290,13 @@ int handle_misaligned_load(struct pt_regs *regs)
{
union reg_data val;
unsigned long epc = regs->epc;
- unsigned long insn = get_insn(epc);
- unsigned long addr = csr_read(mtval);
+ unsigned long insn;
+ unsigned long addr = regs->badaddr;
int i, fp = 0, shift = 0, len = 0;
+ if (get_insn(regs, epc, &insn))
+ return -1;
+
regs->epc = 0;
if ((insn & INSN_MASK_LW) == INSN_MATCH_LW) {
@@ -274,8 +360,10 @@ int handle_misaligned_load(struct pt_regs *regs)
}
val.data_u64 = 0;
- for (i = 0; i < len; i++)
- val.data_bytes[i] = load_u8((void *)(addr + i));
+ for (i = 0; i < len; i++) {
+ if (load_u8(regs, (void *)(addr + i), &val.data_bytes[i]))
+ return -1;
+ }
if (fp)
return -1;
@@ -290,10 +378,13 @@ int handle_misaligned_store(struct pt_regs *regs)
{
union reg_data val;
unsigned long epc = regs->epc;
- unsigned long insn = get_insn(epc);
- unsigned long addr = csr_read(mtval);
+ unsigned long insn;
+ unsigned long addr = regs->badaddr;
int i, len = 0;
+ if (get_insn(regs, epc, &insn))
+ return -1;
+
regs->epc = 0;
val.data_ulong = GET_RS2(insn, regs);
@@ -327,8 +418,10 @@ int handle_misaligned_store(struct pt_regs *regs)
return -1;
}
- for (i = 0; i < len; i++)
- store_u8((void *)(addr + i), val.data_bytes[i]);
+ for (i = 0; i < len; i++) {
+ if (store_u8(regs, (void *)(addr + i), val.data_bytes[i]))
+ return -1;
+ }
regs->epc = epc + INSN_LEN(insn);
--
2.42.0
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