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| author | Kimplul <kimi.h.kuparinen@gmail.com> | 2022-09-15 19:21:14 +0300 |
|---|---|---|
| committer | Kimplul <kimi.h.kuparinen@gmail.com> | 2022-09-15 19:46:07 +0300 |
| commit | a717296a2036cede5fccfff544513043a984d614 (patch) | |
| tree | 68f75a23adc298628fb9cab41fd47402a99dd19d /arch/riscv64/kernel/entry.S | |
| parent | 619725a5f2f5272f9cbb547ed95c87312c2765a9 (diff) | |
| download | kmi-a717296a2036cede5fccfff544513043a984d614.tar.gz kmi-a717296a2036cede5fccfff544513043a984d614.zip | |
change syscalls to take 5 params and return 6
+ In total, a syscall is built up of 6 values, with the first being the
syscall number. Symmetrically, the first value is now a status and the
following five values return "values". This allows us to cram in more
info into the ipc_* functions. The performance difference is
absolutely minimal, at least from my testing in qemu.
Diffstat (limited to 'arch/riscv64/kernel/entry.S')
| -rw-r--r-- | arch/riscv64/kernel/entry.S | 35 |
1 files changed, 24 insertions, 11 deletions
diff --git a/arch/riscv64/kernel/entry.S b/arch/riscv64/kernel/entry.S index 1bd6046..8ff642a 100644 --- a/arch/riscv64/kernel/entry.S +++ b/arch/riscv64/kernel/entry.S @@ -86,25 +86,42 @@ handle_syscall: /* add 4 (size of ecall) to EPC to avoid running the same instruction * twice */ csrr s0, CSR_SEPC - addi s0, s0, 4 + addi s0, s0, 4 csrw CSR_SEPC, s0 + /* allocate space for sys_ret structure on stack and shift argument + * registers down one to make room for the pointer to this structure */ + addi sp, sp, -sizeof_sys_ret + mv a6, a5 + mv a5, a4 + mv a4, a3 + mv a3, a2 + mv a2, a1 + mv a1, a0 + mv a0, sp jal syscall_dispatch + /* move structure from stack into registers. */ + lr a0, offsetof_s(sp) + lr a1, offsetof_ar0(sp) + lr a2, offsetof_ar1(sp) + lr a3, offsetof_ar2(sp) + lr a4, offsetof_ar3(sp) + lr a5, offsetof_ar4(sp) + addi sp, sp, sizeof_sys_ret /* if we had a thread switch, load kernel stack of current thread and * restore its context */ - /* TODO: is a whole function call necessary? */ - mv s0, a0 - mv s1, a1 /* get associated kernel stack */ mv sp, tp addi sp, sp, -sizeof_registers /* restore system call result */ - mv a0, s0 - mv a1, s1 j restore_noreturn restore_all: lr a0, offsetof_a0(sp) lr a1, offsetof_a1(sp) + lr a2, offsetof_a2(sp) + lr a3, offsetof_a3(sp) + lr a4, offsetof_a4(sp) + lr a5, offsetof_a5(sp) restore_noreturn: /* restore registers besides possible return value, assume instruction @@ -117,11 +134,7 @@ restore_noreturn: lr t0, offsetof_t0(sp) lr t1, offsetof_t1(sp) lr t2, offsetof_t2(sp) - /* a0 and a1 should not be restored when coming from a syscall */ - lr a2, offsetof_a2(sp) - lr a3, offsetof_a3(sp) - lr a4, offsetof_a4(sp) - lr a5, offsetof_a5(sp) + /* a0 - a5 should not be restored when coming from a syscall */ lr a6, offsetof_a6(sp) lr s0, offsetof_s0(sp) lr s1, offsetof_s1(sp) |