From f2e4b9d3c2f858f5ce7e317b2974d74353abb2a2 Mon Sep 17 00:00:00 2001 From: Heinrich Schuchardt Date: Thu, 21 Sep 2023 10:42:18 +0200 Subject: [PATCH] cmd/exception: support RISC-V compressed instruction Eliminating the C extension on application processors is under discussion. Support emitting a compressed instruction. This will lead to an illegal instruction exception if the C extension is not implemented. For testing build qemu-riscv64_defconfig with CONFIG_RISCV_ISA_C=n and run with qemu-system-riscv64 -M virt -bios u-boot -nographic -cpu rv64,c=false => exception compressed Unhandled exception: Illegal instruction EPC: 0000000087731708 RA: 000000008773fe44 TVAL: 0000000000004501 EPC: 000000008001b708 RA: 0000000080029e44 reloc adjusted Code: 0b93 0000 0493 0000 0993 0000 f06f ccdf (4501) Signed-off-by: Heinrich Schuchardt Reviewed-by: Leo Yu-Chi Liang --- cmd/riscv/exception.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/cmd/riscv/exception.c b/cmd/riscv/exception.c index 7a08061d12..db8d8af048 100644 --- a/cmd/riscv/exception.c +++ b/cmd/riscv/exception.c @@ -8,6 +8,15 @@ #include #include +static int do_compressed(struct cmd_tbl *cmdtp, int flag, int argc, + char *const argv[]) +{ + /* c.li a0, 0; c.li a0, 0 */ + asm volatile (".long 0x45014501\n"); + printf("The system supports compressed instructions.\n"); + return CMD_RET_SUCCESS; +} + static int do_ebreak(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[]) { @@ -35,6 +44,8 @@ static int do_undefined(struct cmd_tbl *cmdtp, int flag, int argc, } static struct cmd_tbl cmd_sub[] = { + U_BOOT_CMD_MKENT(compressed, CONFIG_SYS_MAXARGS, 1, do_compressed, + "", ""), U_BOOT_CMD_MKENT(ebreak, CONFIG_SYS_MAXARGS, 1, do_ebreak, "", ""), U_BOOT_CMD_MKENT(unaligned, CONFIG_SYS_MAXARGS, 1, do_unaligned, @@ -46,9 +57,10 @@ static struct cmd_tbl cmd_sub[] = { static char exception_help_text[] = "\n" " The following exceptions are available:\n" - " ebreak - breakpoint\n" - " undefined - illegal instruction\n" - " unaligned - load address misaligned\n" + " compressed - compressed instruction\n" + " ebreak - breakpoint\n" + " undefined - illegal instruction\n" + " unaligned - load address misaligned\n" ; #include -- 2.39.5