Hi Sean,
On Thu, Sep 22, 2022 at 10:35 PM Sean Anderson sean.anderson@seco.com wrote:
On 9/19/22 7:49 AM, Kautuk Consul wrote:
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 | 11 +++++++++++ arch/riscv/lib/semihosting.c | 24 ++++++++++++++++++++++++ lib/Kconfig | 6 +++--- 5 files changed, 41 insertions(+), 3 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 06020fcc2a..64e29804c1 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..bd7cd772b8 100644 --- a/arch/riscv/lib/interrupts.c +++ b/arch/riscv/lib/interrupts.c @@ -17,6 +17,7 @@ #include <asm/ptrace.h> #include <asm/system.h> #include <asm/encoding.h> +#include <semihosting.h>
DECLARE_GLOBAL_DATA_PTR;
@@ -149,6 +150,16 @@ 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)) {Hm, shouldn't we check to see if this is actually a semihosting breakpoint? This involves reading the prior and posterior instructions, which might be a bit too much. Alternatively, we could only take this trap if semihosting_enabled(), which would limit any suppression of spurious breakpoints to one instruction.
Agreed. Will read the prior and posterior instructions in v5 and send this out. Thanks.
/* For semihosting fallback we simply skip the ebreak* instruction.*/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 97920e7552..eed3a231d9 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -85,7 +85,7 @@ 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@@ -108,8 +108,8 @@ config SPL_SEMIHOSTING
config SPL_SEMIHOSTING_FALLBACK bool "Recover gracefully when semihosting fails in SPL"
depends on SPL_SEMIHOSTING && ARM64select 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 isThe rest looks fine.
--Sean