Date: Sun, 6 Oct 2013 16:54:04 GMT From: Robert Watson <rwatson@FreeBSD.org> To: Perforce Change Reviews <perforce@FreeBSD.org> Subject: PERFORCE change 983497 for review Message-ID: <201310061654.r96Gs4xR007445@skunkworks.freebsd.org>
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http://p4web.freebsd.org/@@983497?ac=10 Change 983497 by rwatson@rwatson_zenith_cl_cam_ac_uk on 2013/10/06 16:53:28 As the trusted stack has three 64-bit fields free after the PC due to alignment requirements, use one of those fields to hold a copy of $sp, which is restored on CReturn. In a stronger capability world, we might want to also save a stack capability. The stack pointer is useful in pointing to the per-thread preserved state of the code invoking CCall, allowing it to be properly restored after CReturn. While here: be more clear about "stack pointer" vs "trusted stack pointer"; also remove a bit of unneeded padding in the CHERI stack structure, causing it to shrink 32 bytes. Affected files ... .. //depot/projects/ctsrd/cheribsd/src/sys/mips/cheri/ccall.S#10 edit .. //depot/projects/ctsrd/cheribsd/src/sys/mips/cheri/cheri_stack.c#3 edit .. //depot/projects/ctsrd/cheribsd/src/sys/mips/include/cheri.h#27 edit .. //depot/projects/ctsrd/cheribsd/src/sys/mips/mips/genassym.c#8 edit Differences ... ==== //depot/projects/ctsrd/cheribsd/src/sys/mips/cheri/ccall.S#10 (text+ko) ==== @@ -177,19 +177,19 @@ PTR_L k1, PC_CURPCB(k1) /* Retrieve current trusted stack pointer. */ - PTR_L k0, U_PCB_CHERISTACK_SP(k1) + PTR_L k0, U_PCB_CHERISTACK_TSP(k1) /* If at bottom (byte offset 0), then overflow. */ beqz k0, CCall_stack_overflow nop - /* Decrement stack pointer. */ + /* Decrement trusted stack pointer. */ PTR_SUBIU k0, k0, CHERI_FRAME_SIZE - /* Write back stack pointer. */ - PTR_S k0, U_PCB_CHERISTACK_SP(k1) + /* Write back trusted stack pointer. */ + PTR_S k0, U_PCB_CHERISTACK_TSP(k1) - /* Convert stack-relative offset to global pointer. */ + /* Convert trusted stack-relative offset to global pointer. */ PTR_ADDU k0, k1, k0 /* Add PCB pointer. */ PTR_ADDIU k0, k0, U_PCB_CHERISTACK_FRAMES /* Add PCB offset. */ @@ -199,6 +199,15 @@ /* Push PCC. */ csc CHERI_REG_EPCC, k0, CHERI_STACKFRAME_PCC(CHERI_REG_KDC) + /* + * Push SP; zero register afterwards since the caller is unable to do + * that before CCall. + * + * XXXRW: Not called for by CHERI spec. + */ + csd sp, k0, CHERI_STACKFRAME_SP(CHERI_REG_KDC) + move sp, zero + /* Push PC + 4; k1 is overwritten, so no longer PCB pointer. */ MFC0 k1, MIPS_COP_0_EXC_PC PTR_ADDU k1, k1, 4 @@ -280,15 +289,15 @@ * The only currently defined check in CReturn is stack underflow; * perform that check. */ - PTR_L k0, U_PCB_CHERISTACK_SP(k1) + PTR_L k0, U_PCB_CHERISTACK_TSP(k1) sltiu k0, CHERI_STACK_SIZE beqz k0, CReturn_stack_underflow nop - /* Reload stack pointer. */ - PTR_L k0, U_PCB_CHERISTACK_SP(k1) + /* Reload trusted stack pointer. */ + PTR_L k0, U_PCB_CHERISTACK_TSP(k1) - /* Convert stack-relative offset to global pointer. */ + /* Convert trusted stack-relative offset to global pointer. */ PTR_ADDU k0, k1, k0 /* Add PCB pointer. */ PTR_ADDIU k0, k0, U_PCB_CHERISTACK_FRAMES /* Add PCB offset. */ @@ -298,15 +307,22 @@ /* Pop PCC. */ clc CHERI_REG_EPCC, k0, CHERI_STACKFRAME_PCC(CHERI_REG_KDC) + /* + * Pop SP. + * + * XXXRW: Not called for by CHERI spec. + */ + cld sp, k0, CHERI_STACKFRAME_SP(CHERI_REG_KDC) + /* Pop PC + padding; +4 already done; toasts k0; k1 still PCB. */ cld k0, k0, CHERI_STACKFRAME_PC(CHERI_REG_KDC) MTC0 k0, MIPS_COP_0_EXC_PC COP0_SYNC - /* Update stack pointer. */ - PTR_L k0, U_PCB_CHERISTACK_SP(k1) + /* Update trusted stack pointer. */ + PTR_L k0, U_PCB_CHERISTACK_TSP(k1) PTR_ADDIU k0, CHERI_FRAME_SIZE - PTR_S k0, U_PCB_CHERISTACK_SP(k1) + PTR_S k0, U_PCB_CHERISTACK_TSP(k1) CHERI_EXCEPTION_RETURN(k0) eret ==== //depot/projects/ctsrd/cheribsd/src/sys/mips/cheri/cheri_stack.c#3 (text+ko) ==== @@ -82,7 +82,7 @@ { bzero(&pcb->pcb_cheristack, sizeof(pcb->pcb_cheristack)); - pcb->pcb_cheristack.cs_sp = CHERI_STACK_SIZE; + pcb->pcb_cheristack.cs_tsp = CHERI_STACK_SIZE; } /* ==== //depot/projects/ctsrd/cheribsd/src/sys/mips/include/cheri.h#27 (text+ko) ==== @@ -110,21 +110,20 @@ * will want to manage the idea of a "trusted stack". */ struct cheri_stack_frame { - register_t csf_pc; + register_t csf_pc; /* MIPS program counter. */ + register_t csf_sp; /* MIPS stack pointer. */ register_t _csf_pad0; register_t _csf_pad1; - register_t _csf_pad2; struct chericap csf_pcc; struct chericap csf_idc; }; #define CHERI_STACK_DEPTH 2 /* XXXRW: 2 is a nice round number. */ struct cheri_stack { - register_t cs_sp; /* Byte offset, not frame index. */ + register_t cs_tsp; /* Byte offset, not frame index. */ register_t _cs_pad0; register_t _cs_pad1; register_t _cs_pad2; - register_t _cs_pad3; struct cheri_stack_frame cs_frames[CHERI_STACK_DEPTH]; } __aligned(CHERICAP_SIZE); ==== //depot/projects/ctsrd/cheribsd/src/sys/mips/mips/genassym.c#8 (text+ko) ==== @@ -109,9 +109,10 @@ ASSYM(CHERI_FRAME_SIZE, sizeof(struct cheri_stack_frame) * CHERI_STACK_DEPTH); ASSYM(CHERI_STACK_SIZE, sizeof(struct cheri_stack_frame)); ASSYM(U_PCB_CHERIFRAME, offsetof(struct pcb, pcb_cheriframe)); -ASSYM(U_PCB_CHERISTACK_SP, offsetof(struct pcb, pcb_cheristack.cs_sp)); +ASSYM(U_PCB_CHERISTACK_TSP, offsetof(struct pcb, pcb_cheristack.cs_tsp)); ASSYM(U_PCB_CHERISTACK_FRAMES, offsetof(struct pcb, pcb_cheristack.cs_frames)); ASSYM(CHERI_STACKFRAME_PC, offsetof(struct cheri_stack_frame, csf_pc)); +ASSYM(CHERI_STACKFRAME_SP, offsetof(struct cheri_stack_frame, csf_sp)); ASSYM(CHERI_STACKFRAME_PCC, offsetof(struct cheri_stack_frame, csf_pcc)); ASSYM(CHERI_STACKFRAME_IDC, offsetof(struct cheri_stack_frame, csf_idc)); #endif
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