Unverified Commit fdff9911 authored by Palmer Dabbelt's avatar Palmer Dabbelt
Browse files

RISC-V: Inline the assembly register save/restore macros 



These are only used once, and when reading the code I've always found them to
be more of a headache than a benefit.  While they were never worth removing
before, LLVM's integrated assembler doesn't support LOCAL so rather that trying
to figure out how to refactor the macros it seems saner to just inline them.

Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: default avatarPalmer Dabbelt <palmerdabbelt@google.com>
parent 52e7c52d

arch/riscv/kernel/entry.S

+61 −82
Original line number Diff line number Diff line
@@ -13,17 +13,11 @@ 
#include <asm/thread_info.h>

#include <asm/asm-offsets.h>



	.text

	.altmacro



/*

 * Prepares to enter a system call or exception by saving all registers to the

 * stack.

 */

	.macro SAVE_ALL

	LOCAL _restore_kernel_tpsp

	LOCAL _save_context

#if !IS_ENABLED(CONFIG_PREEMPTION)

.set resume_kernel, restore_all

#endif



ENTRY(handle_exception)

	/*

	 * If coming from userspace, preserve the user thread pointer and load

	 * the kernel thread pointer.  If we came from the kernel, the scratch
@@ -90,77 +84,6 @@ _save_context: 
	REG_S s3, PT_BADADDR(sp)

	REG_S s4, PT_CAUSE(sp)

	REG_S s5, PT_TP(sp)

	.endm



/*

 * Prepares to return from a system call or exception by restoring all

 * registers from the stack.

 */

	.macro RESTORE_ALL

	REG_L a0, PT_STATUS(sp)

	/*

	 * The current load reservation is effectively part of the processor's

	 * state, in the sense that load reservations cannot be shared between

	 * different hart contexts.  We can't actually save and restore a load

	 * reservation, so instead here we clear any existing reservation --

	 * it's always legal for implementations to clear load reservations at

	 * any point (as long as the forward progress guarantee is kept, but

	 * we'll ignore that here).

	 *

	 * Dangling load reservations can be the result of taking a trap in the

	 * middle of an LR/SC sequence, but can also be the result of a taken

	 * forward branch around an SC -- which is how we implement CAS.  As a

	 * result we need to clear reservations between the last CAS and the

	 * jump back to the new context.  While it is unlikely the store

	 * completes, implementations are allowed to expand reservations to be

	 * arbitrarily large.

	 */

	REG_L  a2, PT_EPC(sp)

	REG_SC x0, a2, PT_EPC(sp)



	csrw CSR_STATUS, a0

	csrw CSR_EPC, a2



	REG_L x1,  PT_RA(sp)

	REG_L x3,  PT_GP(sp)

	REG_L x4,  PT_TP(sp)

	REG_L x5,  PT_T0(sp)

	REG_L x6,  PT_T1(sp)

	REG_L x7,  PT_T2(sp)

	REG_L x8,  PT_S0(sp)

	REG_L x9,  PT_S1(sp)

	REG_L x10, PT_A0(sp)

	REG_L x11, PT_A1(sp)

	REG_L x12, PT_A2(sp)

	REG_L x13, PT_A3(sp)

	REG_L x14, PT_A4(sp)

	REG_L x15, PT_A5(sp)

	REG_L x16, PT_A6(sp)

	REG_L x17, PT_A7(sp)

	REG_L x18, PT_S2(sp)

	REG_L x19, PT_S3(sp)

	REG_L x20, PT_S4(sp)

	REG_L x21, PT_S5(sp)

	REG_L x22, PT_S6(sp)

	REG_L x23, PT_S7(sp)

	REG_L x24, PT_S8(sp)

	REG_L x25, PT_S9(sp)

	REG_L x26, PT_S10(sp)

	REG_L x27, PT_S11(sp)

	REG_L x28, PT_T3(sp)

	REG_L x29, PT_T4(sp)

	REG_L x30, PT_T5(sp)

	REG_L x31, PT_T6(sp)



	REG_L x2,  PT_SP(sp)

	.endm



#if !IS_ENABLED(CONFIG_PREEMPTION)

.set resume_kernel, restore_all

#endif



ENTRY(handle_exception)

	SAVE_ALL



	/*

	 * Set the scratch register to 0, so that if a recursive exception
@@ -298,7 +221,63 @@ resume_userspace: 
	csrw CSR_SCRATCH, tp



restore_all:

	RESTORE_ALL

	REG_L a0, PT_STATUS(sp)

	/*

	 * The current load reservation is effectively part of the processor's

	 * state, in the sense that load reservations cannot be shared between

	 * different hart contexts.  We can't actually save and restore a load

	 * reservation, so instead here we clear any existing reservation --

	 * it's always legal for implementations to clear load reservations at

	 * any point (as long as the forward progress guarantee is kept, but

	 * we'll ignore that here).

	 *

	 * Dangling load reservations can be the result of taking a trap in the

	 * middle of an LR/SC sequence, but can also be the result of a taken

	 * forward branch around an SC -- which is how we implement CAS.  As a

	 * result we need to clear reservations between the last CAS and the

	 * jump back to the new context.  While it is unlikely the store

	 * completes, implementations are allowed to expand reservations to be

	 * arbitrarily large.

	 */

	REG_L  a2, PT_EPC(sp)

	REG_SC x0, a2, PT_EPC(sp)



	csrw CSR_STATUS, a0

	csrw CSR_EPC, a2



	REG_L x1,  PT_RA(sp)

	REG_L x3,  PT_GP(sp)

	REG_L x4,  PT_TP(sp)

	REG_L x5,  PT_T0(sp)

	REG_L x6,  PT_T1(sp)

	REG_L x7,  PT_T2(sp)

	REG_L x8,  PT_S0(sp)

	REG_L x9,  PT_S1(sp)

	REG_L x10, PT_A0(sp)

	REG_L x11, PT_A1(sp)

	REG_L x12, PT_A2(sp)

	REG_L x13, PT_A3(sp)

	REG_L x14, PT_A4(sp)

	REG_L x15, PT_A5(sp)

	REG_L x16, PT_A6(sp)

	REG_L x17, PT_A7(sp)

	REG_L x18, PT_S2(sp)

	REG_L x19, PT_S3(sp)

	REG_L x20, PT_S4(sp)

	REG_L x21, PT_S5(sp)

	REG_L x22, PT_S6(sp)

	REG_L x23, PT_S7(sp)

	REG_L x24, PT_S8(sp)

	REG_L x25, PT_S9(sp)

	REG_L x26, PT_S10(sp)

	REG_L x27, PT_S11(sp)

	REG_L x28, PT_T3(sp)

	REG_L x29, PT_T4(sp)

	REG_L x30, PT_T5(sp)

	REG_L x31, PT_T6(sp)



	REG_L x2,  PT_SP(sp)



#ifdef CONFIG_RISCV_M_MODE

	mret

#else

CRA Git | Maintained and supported by SUSTech CRA and CCSE