We add RISC-V semihosting based serial console for JTAG based early debugging.
The RISC-V semihosting specification is available at: https://github.com/riscv/riscv-semihosting-spec/blob/main/riscv-semihosting-...
Signed-off-by: Anup Patel apatel@ventanamicro.com Signed-off-by: Kautuk Consul kconsul@ventanamicro.com --- arch/riscv/include/asm/spl.h | 1 + arch/riscv/lib/Makefile | 2 ++ arch/riscv/lib/interrupts.c | 25 +++++++++++++++++++++++++ arch/riscv/lib/semihosting.c | 24 ++++++++++++++++++++++++ lib/Kconfig | 10 +++++----- 5 files changed, 57 insertions(+), 5 deletions(-) create mode 100644 arch/riscv/lib/semihosting.c
diff --git a/arch/riscv/include/asm/spl.h b/arch/riscv/include/asm/spl.h index e8a94fcb1f..2898a770ee 100644 --- a/arch/riscv/include/asm/spl.h +++ b/arch/riscv/include/asm/spl.h @@ -25,6 +25,7 @@ enum { BOOT_DEVICE_DFU, BOOT_DEVICE_XIP, BOOT_DEVICE_BOOTROM, + BOOT_DEVICE_SMH, BOOT_DEVICE_NONE };
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile index d6a8ae9728..e5a81ba722 100644 --- a/arch/riscv/lib/Makefile +++ b/arch/riscv/lib/Makefile @@ -42,3 +42,5 @@ extra-$(CONFIG_EFI) += $(EFI_CRT0) $(EFI_RELOC) obj-$(CONFIG_$(SPL_TPL_)USE_ARCH_MEMSET) += memset.o obj-$(CONFIG_$(SPL_TPL_)USE_ARCH_MEMMOVE) += memmove.o obj-$(CONFIG_$(SPL_TPL_)USE_ARCH_MEMCPY) += memcpy.o + +obj-$(CONFIG_$(SPL_TPL_)SEMIHOSTING) += semihosting.o diff --git a/arch/riscv/lib/interrupts.c b/arch/riscv/lib/interrupts.c index 100be2e966..e966afa7e3 100644 --- a/arch/riscv/lib/interrupts.c +++ b/arch/riscv/lib/interrupts.c @@ -9,6 +9,7 @@ * Copyright (C) 2019 Sean Anderson seanga2@gmail.com */
+#include <linux/compat.h> #include <common.h> #include <efi_loader.h> #include <hang.h> @@ -17,6 +18,7 @@ #include <asm/ptrace.h> #include <asm/system.h> #include <asm/encoding.h> +#include <semihosting.h>
DECLARE_GLOBAL_DATA_PTR;
@@ -149,6 +151,29 @@ ulong handle_trap(ulong cause, ulong epc, ulong tval, struct pt_regs *regs) /* An UEFI application may have changed gd. Restore U-Boot's gd. */ efi_restore_gd();
+ if (cause == CAUSE_BREAKPOINT && + CONFIG_IS_ENABLED(SEMIHOSTING_FALLBACK)) { + ulong pre_addr = epc - 4, post_addr = epc + 4; + + /* Check for prior and post addresses to be in same page. */ + if ((pre_addr & ~(PAGE_SIZE - 1)) == + (post_addr & ~(PAGE_SIZE - 1))) { + u32 pre = *(u32 *)pre_addr; + u32 post = *(u32 *)post_addr; + + /* Check for semihosting, i.e.: + * slli zero,zero,0x1f + * ebreak + * srai zero,zero,0x7 + */ + if (pre == 0x01f01013 && post == 0x40705013) { + disable_semihosting(); + epc += 4; + return epc; + } + } + } + is_irq = (cause & MCAUSE_INT); irq = (cause & ~MCAUSE_INT);
diff --git a/arch/riscv/lib/semihosting.c b/arch/riscv/lib/semihosting.c new file mode 100644 index 0000000000..d6593b02a6 --- /dev/null +++ b/arch/riscv/lib/semihosting.c @@ -0,0 +1,24 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (C) 2022 Ventana Micro Systems Inc. + */ + +#include <common.h> + +long smh_trap(int sysnum, void *addr) +{ + register int ret asm ("a0") = sysnum; + register void *param0 asm ("a1") = addr; + + asm volatile (".align 4\n" + ".option push\n" + ".option norvc\n" + + "slli zero, zero, 0x1f\n" + "ebreak\n" + "srai zero, zero, 7\n" + ".option pop\n" + : "+r" (ret) : "r" (param0) : "memory"); + + return ret; +} diff --git a/lib/Kconfig b/lib/Kconfig index b8833e0183..3c5a4ab386 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -73,7 +73,7 @@ config LIB_UUID
config SEMIHOSTING bool "Support semihosting" - depends on ARM + depends on ARM || RISCV help Semihosting is a method for a target to communicate with a host debugger. It uses special instructions which the debugger will trap @@ -86,7 +86,7 @@ config SEMIHOSTING
config SEMIHOSTING_FALLBACK bool "Recover gracefully when semihosting fails" - depends on SEMIHOSTING && ARM64 + depends on SEMIHOSTING && (ARM64 || RISCV) default y help Normally, if U-Boot makes a semihosting call and no debugger is @@ -96,7 +96,7 @@ config SEMIHOSTING_FALLBACK
config SPL_SEMIHOSTING bool "Support semihosting in SPL" - depends on SPL && ARM + depends on SPL && (ARM || RISCV) help Semihosting is a method for a target to communicate with a host debugger. It uses special instructions which the debugger will trap @@ -109,8 +109,8 @@ config SPL_SEMIHOSTING
config SPL_SEMIHOSTING_FALLBACK bool "Recover gracefully when semihosting fails in SPL" - depends on SPL_SEMIHOSTING && ARM64 - select ARMV8_SPL_EXCEPTION_VECTORS + depends on SPL_SEMIHOSTING && (ARM64 || RISCV) + select ARMV8_SPL_EXCEPTION_VECTORS if ARM64 default y help Normally, if U-Boot makes a semihosting call and no debugger is