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xous-core/kernel/src/asm.S

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initial commit This pulls together many disparate repositories into one xous-core repository. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-10 04:04:17 +00:00
#if __riscv_xlen == 64
# define STORE sd
# define LOAD ld
# define LOG_REGBYTES 3
#else
# define STORE sw
# define LOAD lw
# define LOG_REGBYTES 2
#endif
#define REGBYTES (1 << LOG_REGBYTES)
/*
Entry point of all programs (_start).
It initializes DWARF call frame information, the stack pointer, the
frame pointer (needed for closures to work in start_rust) and the global
pointer. Then it calls _start_rust.
*/
.section .text.init, "ax"
.global _start
_start:
// Set trap handler, which will be called
// on interrupts and cpu faults
la t0, _start_trap
csrw stvec, t0
// Jump to a program to initialize global variables.
// Note that at this point, the .data section should
// have already been set up by the loader.
jal x1, init
kernel: move to allow hosted init This prepares for new calls to init SystemServices and the MemoryManager so that they can be initialized with something other than a KernelArguments struct. Signed-off-by: Sean Cross <sean@xobs.io>
2020-06-03 10:28:22 +00:00
// Call the kmain function. This function diverges, so
initial commit This pulls together many disparate repositories into one xous-core repository. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-10 04:04:17 +00:00
// shouldn't ever return.
kernel: move to allow hosted init This prepares for new calls to init SystemServices and the MemoryManager so that they can be initialized with something other than a KernelArguments struct. Signed-off-by: Sean Cross <sean@xobs.io>
2020-06-03 10:28:22 +00:00
j kmain
initial commit This pulls together many disparate repositories into one xous-core repository. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-10 04:04:17 +00:00
/*
Trap entry point (_start_trap)
Saves all process context into a structure that is
mapped to each thread at 0xff801000. Return happens
elsewhere.
*/
.section .trap, "ax"
.global _start_trap
_start_trap:
csrw sscratch, sp
li sp, 0xff801000
kernel: fix isr context handling We were loading both the context and the banked context, which resulted in an invalid context being selected. This caused a cascading failure. Load only the lower halfword in order to correctly enter the interrupt context. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-24 07:24:19 +00:00
STORE x1, 0*REGBYTES(sp) // Store x1 in the scratch field
kernel: make contexts first-class Due to an initial misunderstanding of how the RISC-V is architected, contexts were going to be an emergent property of the kernel. However, after further consideration, contexts must now be baked into the kernel. Switching between contexts can be handled by the scheduler, but the kernel must keep track of processor registers. Keep track of context IDs and ensure they are sane. With this patch, interrupts work, as does basic context switching. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-27 04:30:29 +00:00
LOAD x1, 1*REGBYTES(sp) // Load current context number
kernel: fix isr context handling We were loading both the context and the banked context, which resulted in an invalid context being selected. This caused a cascading failure. Load only the lower halfword in order to correctly enter the interrupt context. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-24 07:24:19 +00:00
slli x1, x1, 7 // Multiply current context number by 32
add sp, sp, x1 // Set $sp to 0xff801000 + (current_context * 32)
initial commit This pulls together many disparate repositories into one xous-core repository. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-10 04:04:17 +00:00
STORE x1, 0*REGBYTES(sp)
// Skip SP for now
STORE x3, 2*REGBYTES(sp)
STORE x4, 3*REGBYTES(sp)
STORE x5, 4*REGBYTES(sp)
STORE x6, 5*REGBYTES(sp)
STORE x7, 6*REGBYTES(sp)
STORE x8, 7*REGBYTES(sp)
STORE x9, 8*REGBYTES(sp)
STORE x10, 9*REGBYTES(sp)
STORE x11, 10*REGBYTES(sp)
STORE x12, 11*REGBYTES(sp)
STORE x13, 12*REGBYTES(sp)
STORE x14, 13*REGBYTES(sp)
STORE x15, 14*REGBYTES(sp)
STORE x16, 15*REGBYTES(sp)
STORE x17, 16*REGBYTES(sp)
STORE x18, 17*REGBYTES(sp)
STORE x19, 18*REGBYTES(sp)
STORE x20, 19*REGBYTES(sp)
STORE x21, 20*REGBYTES(sp)
STORE x22, 21*REGBYTES(sp)
STORE x23, 22*REGBYTES(sp)
STORE x24, 23*REGBYTES(sp)
STORE x25, 24*REGBYTES(sp)
STORE x26, 25*REGBYTES(sp)
STORE x27, 26*REGBYTES(sp)
STORE x28, 27*REGBYTES(sp)
STORE x29, 28*REGBYTES(sp)
STORE x30, 29*REGBYTES(sp)
STORE x31, 30*REGBYTES(sp)
// Save SEPC
csrr t0, sepc
STORE t0, 31*REGBYTES(sp)
kernel: refactor processes to support banking We now have a concept of context banking. When an interrupt fires, the process context is banked. As part of this, process-level data is now stored in the page within the process itself. This reduces memory consumption and allows us to have features such as a hash within each process itself. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-16 10:22:59 +00:00
// Save x1, which was used to calculate the offset. Prior to
// calculating, it was stashed at 0xff801000.
li t0, 0xff801000
LOAD t1, 0*REGBYTES(t0)
STORE t1, 0*REGBYTES(sp)
initial commit This pulls together many disparate repositories into one xous-core repository. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-10 04:04:17 +00:00
// Finally, save SP
csrr t0, sscratch
STORE t0, 1*REGBYTES(sp)
// Restore a default stack pointer
li sp, 0xfffefffc
// Note that registers $a0-$a7 still contain the arguments
j _start_trap_rust
/*
Resume a context (_xous_resume_context)
kernel: get scalar message passing working again This gets basic scalar message passing working again. With this, the following operations may be performed: * Starting a server * Connecting to a server * Sending a scalar message Care must be taken to not overflow a server's queue, particularly if writers are faster than readers. Signed-off-by: Sean Cross <sean@xobs.io>
2020-06-16 08:34:49 +00:00
Restores all registers from a Context passed in $a0.
initial commit This pulls together many disparate repositories into one xous-core repository. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-10 04:04:17 +00:00
Note that the SEPC and SSTATUS should be set already.
*/
.global _xous_resume_context
_xous_resume_context:
move sp, a0
LOAD x1, 0*REGBYTES(sp)
// Skip SP for now
LOAD x3, 2*REGBYTES(sp)
LOAD x4, 3*REGBYTES(sp)
LOAD x5, 4*REGBYTES(sp)
LOAD x6, 5*REGBYTES(sp)
LOAD x7, 6*REGBYTES(sp)
LOAD x8, 7*REGBYTES(sp)
LOAD x9, 8*REGBYTES(sp)
LOAD x10, 9*REGBYTES(sp)
LOAD x11, 10*REGBYTES(sp)
LOAD x12, 11*REGBYTES(sp)
LOAD x13, 12*REGBYTES(sp)
LOAD x14, 13*REGBYTES(sp)
LOAD x15, 14*REGBYTES(sp)
LOAD x16, 15*REGBYTES(sp)
LOAD x17, 16*REGBYTES(sp)
LOAD x18, 17*REGBYTES(sp)
LOAD x19, 18*REGBYTES(sp)
LOAD x20, 19*REGBYTES(sp)
LOAD x21, 20*REGBYTES(sp)
LOAD x22, 21*REGBYTES(sp)
LOAD x23, 22*REGBYTES(sp)
LOAD x24, 23*REGBYTES(sp)
LOAD x25, 24*REGBYTES(sp)
LOAD x26, 25*REGBYTES(sp)
LOAD x27, 26*REGBYTES(sp)
LOAD x28, 27*REGBYTES(sp)
LOAD x29, 28*REGBYTES(sp)
LOAD x30, 29*REGBYTES(sp)
LOAD x31, 30*REGBYTES(sp)
// Restore SP
LOAD x2, 1*REGBYTES(sp)
sret
/*
Return from a syscall with arguments (_xous_syscall_return_result)
Xous passes arguments in $a0-$a7, however the RISC-V calling convention
states that only $a0 and $a1 are used. To work around this, we pass
a pointer to a 32-byte structure in $a0, and this function moves that
into the registers. It then restores the context from other registers.
*/
.global _xous_syscall_return_result
_xous_syscall_return_result:
kernel: refactor processes to support banking We now have a concept of context banking. When an interrupt fires, the process context is banked. As part of this, process-level data is now stored in the page within the process itself. This reduces memory consumption and allows us to have features such as a hash within each process itself. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-16 10:22:59 +00:00
move sp, a1
LOAD t0, 31*REGBYTES(sp)
csrw sepc, t0
initial commit This pulls together many disparate repositories into one xous-core repository. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-10 04:04:17 +00:00
LOAD x1, 0*REGBYTES(sp)
// Skip SP for now
LOAD x3, 2*REGBYTES(sp)
LOAD x4, 3*REGBYTES(sp)
LOAD x5, 4*REGBYTES(sp)
LOAD x6, 5*REGBYTES(sp)
LOAD x7, 6*REGBYTES(sp)
LOAD x8, 7*REGBYTES(sp)
LOAD x9, 8*REGBYTES(sp)
kernel: refactor processes to support banking We now have a concept of context banking. When an interrupt fires, the process context is banked. As part of this, process-level data is now stored in the page within the process itself. This reduces memory consumption and allows us to have features such as a hash within each process itself. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-16 10:22:59 +00:00
// Load argument registers from the value pointed
// to by $a0
LOAD a7, 7*REGBYTES(a0)
LOAD a6, 6*REGBYTES(a0)
LOAD a5, 5*REGBYTES(a0)
LOAD a4, 4*REGBYTES(a0)
LOAD a3, 3*REGBYTES(a0)
LOAD a2, 2*REGBYTES(a0)
LOAD a1, 1*REGBYTES(a0)
LOAD a0, 0*REGBYTES(a0)
initial commit This pulls together many disparate repositories into one xous-core repository. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-10 04:04:17 +00:00
LOAD x18, 17*REGBYTES(sp)
LOAD x19, 18*REGBYTES(sp)
LOAD x20, 19*REGBYTES(sp)
LOAD x21, 20*REGBYTES(sp)
LOAD x22, 21*REGBYTES(sp)
LOAD x23, 22*REGBYTES(sp)
LOAD x24, 23*REGBYTES(sp)
LOAD x25, 24*REGBYTES(sp)
LOAD x26, 25*REGBYTES(sp)
LOAD x27, 26*REGBYTES(sp)
LOAD x28, 27*REGBYTES(sp)
LOAD x29, 28*REGBYTES(sp)
LOAD x30, 29*REGBYTES(sp)
LOAD x31, 30*REGBYTES(sp)
kernel: refactor processes to support banking We now have a concept of context banking. When an interrupt fires, the process context is banked. As part of this, process-level data is now stored in the page within the process itself. This reduces memory consumption and allows us to have features such as a hash within each process itself. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-16 10:22:59 +00:00
// Restore SP
//csrr t0, sscratch
initial commit This pulls together many disparate repositories into one xous-core repository. Signed-off-by: Sean Cross <sean@xobs.io>
2020-03-10 04:04:17 +00:00
LOAD x2, 1*REGBYTES(sp)
sret
.global flush_mmu
flush_mmu:
sfence.vma
ret
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