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commit 2cf8ac2f637ddfe9c6cc618eff4573ed0fc9f95c Author: Ville Juven <[email protected]> AuthorDate: Wed Jul 31 13:32:57 2024 +0300 risc-v/riscv_swint.c: Simplify implementation of dispatch_syscall Simplifies the implementation of dispatch_syscall, making it easier to understand and maintain. Let the C-compiler do most of the work, instead of doing everything as inline assembly. --- arch/risc-v/src/common/riscv_swint.c | 112 +++++++++++++++++++++++------------ 1 file changed, 75 insertions(+), 37 deletions(-) diff --git a/arch/risc-v/src/common/riscv_swint.c b/arch/risc-v/src/common/riscv_swint.c index 43654b5f33..3cae985f96 100644 --- a/arch/risc-v/src/common/riscv_swint.c +++ b/arch/risc-v/src/common/riscv_swint.c @@ -48,16 +48,74 @@ * Pre-processor Definitions ****************************************************************************/ -#ifdef CONFIG_LIB_SYSCALL -# define TCB_FLAGS_OFFSET offsetof(struct tcb_s, flags) -#endif - /**************************************************************************** * Private Functions ****************************************************************************/ #ifdef CONFIG_LIB_SYSCALL +/**************************************************************************** + * Name: do_syscall + * + * Description: + * Call the stub function corresponding to the system call. NOTE the non- + * standard parameter passing: + * + * A0 = SYS_ call number + * A1 = parm0 + * A2 = parm1 + * A3 = parm2 + * A4 = parm3 + * A5 = parm4 + * A6 = parm5 + * + * Note: + * Do not allow the compiler to inline this function, as it does a jump to + * another procedure which can clobber any register and the compiler will + * not understand it happens. + * + ****************************************************************************/ + +static uintptr_t do_syscall(unsigned int nbr, uintptr_t parm1, + uintptr_t parm2, uintptr_t parm3, + uintptr_t parm4, uintptr_t parm5, + uintptr_t parm6) noinline_function; +static uintptr_t do_syscall(unsigned int nbr, uintptr_t parm1, + uintptr_t parm2, uintptr_t parm3, + uintptr_t parm4, uintptr_t parm5, + uintptr_t parm6) +{ + register long a0 asm("a0") = (long)(nbr); + register long a1 asm("a1") = (long)(parm1); + register long a2 asm("a2") = (long)(parm2); + register long a3 asm("a3") = (long)(parm3); + register long a4 asm("a4") = (long)(parm4); + register long a5 asm("a5") = (long)(parm5); + register long a6 asm("a6") = (long)(parm6); + + asm volatile + ( + "la t0, g_stublookup\n" /* t0=The base of the stub lookup table */ +#ifdef CONFIG_ARCH_RV32 + "slli a0, a0, 2\n" /* a0=Offset for the stub lookup table */ +#else + "slli a0, a0, 3\n" /* a0=Offset for the stub lookup table */ +#endif + "add t0, t0, a0\n" /* t0=The address in the table */ + REGLOAD " t0, 0(t0)\n" /* t0=The address of the stub for this syscall */ + "jalr ra, t0\n" /* Call the stub (modifies ra) */ + : "+r"(a0) + : "r"(a1), "r"(a2), "r"(a3), "r"(a4), "r"(a5), "r"(a6) + : "t0", "ra", "memory" + ); + + return a0; +} + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + /**************************************************************************** * Name: dispatch_syscall * @@ -87,7 +145,7 @@ uintptr_t dispatch_syscall(unsigned int nbr, uintptr_t parm1, register long a4 asm("a4") = (long)(parm4); register long a5 asm("a5") = (long)(parm5); register long a6 asm("a6") = (long)(parm6); - + register struct tcb_s *rtcb asm("tp"); uintptr_t ret; /* Valid system call ? */ @@ -99,37 +157,21 @@ uintptr_t dispatch_syscall(unsigned int nbr, uintptr_t parm1, return -ENOSYS; } - /* ra gets clobbered below, but it does not matter */ + /* Indicate that we are in a syscall handler */ - asm volatile - ( - REGLOAD " t0, %1(tp)\n" /* Load tcb->flags */ - "ori t0, t0, %2\n" /* tcb->flags |= TCB_FLAG_SYSCALL */ - REGSTORE " t0, %1(tp)\n" - "addi a0, a0, -%3\n" /* Offset a0 to account for the reserved syscalls */ - "la t0, g_stublookup\n" /* t0=The base of the stub lookup table */ -#ifdef CONFIG_ARCH_RV32 - "slli a0, a0, 2\n" /* a0=Offset for the stub lookup table */ -#else - "slli a0, a0, 3\n" /* a0=Offset for the stub lookup table */ -#endif - "add t0, t0, a0\n" /* t0=The address in the table */ - REGLOAD " t0, 0(t0)\n" /* t0=The address of the stub for this syscall */ - "jalr ra, t0\n" /* Call the stub (modifies ra) */ - REGLOAD " t0, %1(tp)\n" /* Load tcb->flags */ - "andi t0, t0, ~%2\n" /* tcb->flags &= ~TCB_FLAG_SYSCALL */ - REGSTORE " t0, %1(tp)\n" - : "+r"(a0) - : "i"(TCB_FLAGS_OFFSET), - "i"(TCB_FLAG_SYSCALL), - "i"(CONFIG_SYS_RESERVED), - "r"(a1), "r"(a2), "r"(a3), "r"(a4), "r"(a5), "r"(a6) - : "t0", "memory" - ); + rtcb->flags |= TCB_FLAG_SYSCALL; + + /* Offset a0 to account for the reserved syscalls */ - /* a0 gets clobbered below, save it locally here */ + a0 -= CONFIG_SYS_RESERVED; - ret = a0; + /* Run the system call, save return value locally */ + + ret = do_syscall(a0, a1, a2, a3, a4, a5, a6); + + /* System call is now done */ + + rtcb->flags &= ~TCB_FLAG_SYSCALL; /* Unmask any pending signals now */ @@ -139,10 +181,6 @@ uintptr_t dispatch_syscall(unsigned int nbr, uintptr_t parm1, } #endif -/**************************************************************************** - * Public Functions - ****************************************************************************/ - /**************************************************************************** * Name: riscv_swint *
