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Re: [MIPS PATCH RFA] allow hardware hooks for exit, hazardavoidance.
- From: "J. Johnston" <jjohnstn at redhat dot com>
- To: cgd at broadcom dot com
- Cc: newlib at sources dot redhat dot com
- Date: Fri, 12 Jul 2002 11:51:06 -0400
- Subject: Re: [MIPS PATCH RFA] allow hardware hooks for exit, hazardavoidance.
- Organization: Red Hat Inc.
- References: <yov5sn2q227j.fsf@broadcom.com>
cgd@broadcom.com wrote:
>
> In porting MIPS libgloss to a new firmware environment (our "CFE"
> firmware, patches for that port to be submitted tomorrow, if I find
> the time) on our SB-1 MIPS CPU core, I encountered the need for a
> couple more hardware-related hooks in libgloss.
>
> The exit hook allows code to call back into the firmware to exit
> gracefully.
>
> The hazard hook allows machine-specific or hardware specific code to
> be used for CP0 hazard avoidance. MIPS64 specifically makes CP0
> hazard handling implementation specific, and some MIPS64
> implementations have ... interesting hazard avoidance procedures after
> certain operations. Specifically, on the SB-1, after changing CU1 the
> instruction fetch queue has to be flushed. (Instruction fetch and
> decode occur asychronously w.r.t. execution, and instructions may have
> been fetched and decoded w/ the previous CU1 value if the hazard has
> not been properly cleared. If those instructions are executed they
> will cause CP1 unusable exceptions.) The hazard hook is meant to
> provide a conservative, not-necessarily-best-performance mechanism to
> clear all sorts of execution hazards.
>
> Tested by cross-compiling targets mips-elf, mipsel-elf, mips64-elf,
> mipsisa32-elf, mipsisa64-elf from host x86-linux, and verifying no new
> regressions attributable to this patch for check-gcc, etc. (There
> were a couple of regressions, since I updated my gcc code base and it
> looks like some of the MIPS unordered handling changed... But, that
> was like one or two per target, out of ... Many tests run. 8-)
>
Patch checked in.
-- Jeff J.
> ===================================================================
> 2002-07-10 Chris Demetriou <cgd@broadcom.com>
>
> * mips/array.ld (hardware_exit_hook, hardware_hazard_hook): New
> symbols for optionally-provided functions.
> * mips/ddb-kseg0.ld: Likewise.
> * mips/ddb.ld: Likewise.
> * mips/dve.ld: Likewise.
> * mips/idt.ld: Likewise.
> * mips/idt32.ld: Likewise.
> * mips/idt64.ld: Likewise.
> * mips/idtecoff.ld: Likewise.
> * mips/jmr3904app-java.ld: Likewise.
> * mips/jmr3904app.ld: Likewise.
> * mips/jmr3904dram-java.ld: Likewise.
> * mips/jmr3904dram.ld: Likewise.
> * mips/lsi.ld: Likewise.
> * mips/nullmon.ld: Likewise.
> * mips/pmon.ld: Likewise.
> * mips/crt0.S: Invoke hardware_exit_hook and hardware_hazard_hook
> functions if they are provided.
> (_exit): Handle __embedded_pic properly.
>
> Index: array.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/array.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 array.ld
> --- array.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ array.ld 11 Jul 2002 06:23:08 -0000
> @@ -74,6 +74,8 @@ PROVIDE (__stack = 1M - 8);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: crt0.S
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/crt0.S,v
> retrieving revision 1.3
> diff -u -p -r1.3 crt0.S
> --- crt0.S 11 Sep 2001 14:24:35 -0000 1.3
> +++ crt0.S 11 Jul 2002 06:23:08 -0000
> @@ -54,11 +54,13 @@
> */
> nop
>
> + .globl hardware_hazard_hook .text
> .globl _start
> .ent _start
> _start:
> .set noreorder
> #ifdef __mips_embedded_pic
> +#define PICBASE start_PICBASE
> PICBASE = .+8
> bal PICBASE
> nop
> @@ -75,6 +77,14 @@ _start:
> mtc0 zero, C0_CAUSE
> nop
>
> + /* Avoid hazard from FPU enable and other SR changes. */
> + LA (t0, hardware_hazard_hook)
> + beq t0,zero,1f
> + nop
> + jal t0
> + nop
> +1:
> +
> /* Check for FPU presence. Don't check if we know that soft_float is
> being used. (This also avoids illegal instruction exceptions.) */
>
> @@ -97,6 +107,12 @@ _start:
> li v0, (STATUS_MASK-(STATUS_MASK & SR_CU1))
> mtc0 v0, C0_SR
> nop
> + /* Avoid hazard from FPU disable. */
> + LA (t0, hardware_hazard_hook)
> + beq t0,zero,2f
> + nop
> + jal t0
> + nop
> 2:
>
>
> @@ -205,6 +221,11 @@ init:
> # destructors
> move a0,v0 # pass through the exit code
> .end init
> +
> +/* Assume the PICBASE set up above is no longer valid below here. */
> +#ifdef __mips_embedded_pic
> +#undef PICBASE
> +#endif
>
> /*
> * _exit -- Exit from the application. Normally we cause a user trap
> @@ -214,19 +235,42 @@ init:
> * executables that contain a complete world to be linked with
> * just the crt0.o object.
> */
> + .globl hardware_exit_hook .text
> .globl _exit
> .ent _exit
> _exit:
> 7:
> +#ifdef __mips_embedded_pic
> + /* Need to reinit PICBASE, since we might be called via exit()
> + rather than via a return path which would restore old s0. */
> +#define PICBASE exit_PICBASE
> + PICBASE = .+8
> + bal PICBASE
> + nop
> + move s0,$31
> +#endif
> #ifdef GCRT0
> - jal _mcleanup
> + LA (t0, _mcleanup)
> + jal t0
> nop
> #endif
> + LA (t0, hardware_exit_hook)
> + beq t0,zero,1f
> + nop
> + jal t0
> + nop
> +1:
> +
> # break instruction can cope with 0xfffff, but GAS limits the range:
> break 1023
> nop
> b 7b # but loop back just in-case
> nop
> .end _exit
> +
> +/* Assume the PICBASE set up above is no longer valid below here. */
> +#ifdef __mips_embedded_pic
> +#undef PICBASE
> +#endif
>
> /* EOF crt0.S */
> Index: ddb-kseg0.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/ddb-kseg0.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 ddb-kseg0.ld
> --- ddb-kseg0.ld 18 Oct 2001 02:24:30 -0000 1.1
> +++ ddb-kseg0.ld 11 Jul 2002 06:23:08 -0000
> @@ -22,6 +22,8 @@ PROVIDE (__stack = 0);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: ddb.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/ddb.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 ddb.ld
> --- ddb.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ ddb.ld 11 Jul 2002 06:23:08 -0000
> @@ -22,6 +22,8 @@ PROVIDE (__stack = 0);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: dve.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/dve.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 dve.ld
> --- dve.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ dve.ld 11 Jul 2002 06:23:08 -0000
> @@ -22,6 +22,8 @@ PROVIDE (__stack = 0);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: idt.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/idt.ld,v
> retrieving revision 1.2
> diff -u -p -r1.2 idt.ld
> --- idt.ld 31 Aug 2001 19:22:51 -0000 1.2
> +++ idt.ld 11 Jul 2002 06:23:08 -0000
> @@ -23,6 +23,8 @@ PROVIDE (__stack = 0);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: idt32.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/idt32.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 idt32.ld
> --- idt32.ld 14 Sep 2001 18:40:47 -0000 1.1
> +++ idt32.ld 11 Jul 2002 06:23:08 -0000
> @@ -25,6 +25,8 @@ PROVIDE (__stack = 0);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: idt64.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/idt64.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 idt64.ld
> --- idt64.ld 14 Sep 2001 18:40:47 -0000 1.1
> +++ idt64.ld 11 Jul 2002 06:23:08 -0000
> @@ -25,6 +25,8 @@ PROVIDE (__stack = 0);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: idtecoff.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/idtecoff.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 idtecoff.ld
> --- idtecoff.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ idtecoff.ld 11 Jul 2002 06:23:08 -0000
> @@ -25,6 +25,8 @@ PROVIDE (__stack = 0);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: jmr3904app-java.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/jmr3904app-java.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 jmr3904app-java.ld
> --- jmr3904app-java.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ jmr3904app-java.ld 11 Jul 2002 06:23:08 -0000
> @@ -22,6 +22,8 @@ PROVIDE (_Jv_QthreadsStackSize = 0x10000
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: jmr3904app.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/jmr3904app.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 jmr3904app.ld
> --- jmr3904app.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ jmr3904app.ld 11 Jul 2002 06:23:08 -0000
> @@ -19,6 +19,8 @@ PROVIDE (_mem_size = 0x100000); /* JMR39
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: jmr3904dram-java.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/jmr3904dram-java.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 jmr3904dram-java.ld
> --- jmr3904dram-java.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ jmr3904dram-java.ld 11 Jul 2002 06:23:08 -0000
> @@ -23,6 +23,8 @@ PROVIDE (_Jv_QthreadsStackSize = 0x10000
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: jmr3904dram.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/jmr3904dram.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 jmr3904dram.ld
> --- jmr3904dram.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ jmr3904dram.ld 11 Jul 2002 06:23:08 -0000
> @@ -20,6 +20,8 @@ PROVIDE (_mem_size = 0x100000); /* JMR39
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: lsi.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/lsi.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 lsi.ld
> --- lsi.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ lsi.ld 11 Jul 2002 06:23:08 -0000
> @@ -23,6 +23,8 @@ PROVIDE (__stack = 0);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: nullmon.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/nullmon.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 nullmon.ld
> --- nullmon.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ nullmon.ld 11 Jul 2002 06:23:08 -0000
> @@ -23,6 +23,8 @@ PROVIDE (__stack = 0);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>
> Index: pmon.ld
> ===================================================================
> RCS file: /cvs/src/src/libgloss/mips/pmon.ld,v
> retrieving revision 1.1
> diff -u -p -r1.1 pmon.ld
> --- pmon.ld 17 Mar 2000 22:48:51 -0000 1.1
> +++ pmon.ld 11 Jul 2002 06:23:08 -0000
> @@ -23,6 +23,8 @@ PROVIDE (__stack = 0);
> * We have to initalize them twice, so we multiple object file
> * formats, as some prepend an underscore.
> */
> +PROVIDE (hardware_exit_hook = 0);
> +PROVIDE (hardware_hazard_hook = 0);
> PROVIDE (hardware_init_hook = 0);
> PROVIDE (software_init_hook = 0);
>