On Wed, Feb 17, 2016 at 01:04:25PM +1100, David Gibson wrote:
> On Mon, Feb 15, 2016 at 02:49:20PM +0100, Andrew Jones wrote:
> > Add broken sc1 detection and patching and an hcall for putchar,
> > to use in puts. That, along with a couple more lines in start to
> > prepare for C code, and a branch to main(), gets us "hello world".
> > Run with
> >
> > qemu-system-ppc64 -M pseries \
> > -bios powerpc/boot_rom.bin \
> > -display none -serial stdio \
> > -kernel powerpc/selftest.elf
> >
> > (We're still not relocating yet, that comes in a later patch. Thus,
> > testing hello-world at this point requires a hacked QEMU and linking
> > the unit test at QEMU's kernel load address.)
> >
> > Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> > Tested-by: Laurent Vivier <lvivier@xxxxxxxxxx>
> > ---
> > lib/powerpc/asm/hcall.h | 46 ++++++++++++++++++++++++++++
> > lib/powerpc/hcall.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++
> > lib/powerpc/io.c | 15 ++++++++--
> > lib/ppc64/asm/hcall.h | 1 +
> > powerpc/Makefile.common | 2 ++
> > powerpc/cstart64.S | 21 +++++++++++++
> > 6 files changed, 162 insertions(+), 2 deletions(-)
> > create mode 100644 lib/powerpc/asm/hcall.h
> > create mode 100644 lib/powerpc/hcall.c
> > create mode 100644 lib/ppc64/asm/hcall.h
> >
> > diff --git a/lib/powerpc/asm/hcall.h b/lib/powerpc/asm/hcall.h
> > new file mode 100644
> > index 0000000000000..f861287ac2083
> > --- /dev/null
> > +++ b/lib/powerpc/asm/hcall.h
> > @@ -0,0 +1,46 @@
> > +#ifndef _ASMPOWERPC_HCALL_H_
> > +#define _ASMPOWERPC_HCALL_H_
> > +/*
> > + * Copyright (C) 2016, Red Hat Inc, Andrew Jones <drjones@xxxxxxxxxx>
> > + *
> > + * This work is licensed under the terms of the GNU LGPL, version 2.
> > + */
> > +
> > +#define SC1 0x44000022
> > +#define SC1_REPLACEMENT 0x7c000268
> > +
> > +#define H_SUCCESS 0
> > +#define H_HARDWARE -1
> > +#define H_FUNCTION -2
> > +#define H_PRIVILEGE -3
> > +#define H_PARAMETER -4
> > +
> > +#define H_SET_DABR 0x28
> > +#define H_PUT_TERM_CHAR 0x58
> > +
> > +#ifndef __ASSEMBLY__
> > +#include <libcflat.h>
> > +
> > +/*
> > + * hcall_have_broken_sc1 checks if we're on a host with a broken sc1.
> > + * Returns true if we are.
> > + */
> > +extern bool hcall_have_broken_sc1(void);
> > +
> > +/*
> > + * hcall_patch_broken_sc1 patches hcall's sc1 instruction, if needed,
> > + * allowing all hypercalls built on it to work.
> > + */
> > +extern void hcall_patch_broken_sc1(void);
> > +
> > +/*
> > + * hcall is the hypercall wrapper function. unittests may do what
> > + * they like, but the framework should make all hypercalls through
> > + * here to ensure they use a working sc1 instruction, and properly
> > + * handle clobbered registers. @nr is the hypercall number.
> > + */
> > +extern unsigned long
> > +hcall(unsigned long nr, unsigned long *in, unsigned long *out);
> > +
> > +#endif /* !__ASSEMBLY__ */
> > +#endif /* _ASMPOWERPC_HCALL_H_ */
> > diff --git a/lib/powerpc/hcall.c b/lib/powerpc/hcall.c
> > new file mode 100644
> > index 0000000000000..db99949352133
> > --- /dev/null
> > +++ b/lib/powerpc/hcall.c
> > @@ -0,0 +1,79 @@
> > +/*
> > + * Hypercall helpers
> > + *
> > + * broken_sc1 probing/patching inspired by SLOF, see
> > + * SLOF:lib/libhvcall/brokensc1.c
> > + *
> > + * hcall() implementation inspired by Linux's epapr_hypercall, see
> > + * arch/powerpc/include/asm/epapr_hcalls.h
> > + *
> > + * Copyright (C) 2016, Red Hat Inc, Andrew Jones <drjones@xxxxxxxxxx>
> > + *
> > + * This work is licensed under the terms of the GNU LGPL, version 2.
> > + */
> > +#include <libcflat.h>
> > +#include <asm/hcall.h>
> > +
> > +static u32 sc1[];
> > +
> > +bool hcall_have_broken_sc1(void)
> > +{
> > + register unsigned long r3 asm("r3") = H_SET_DABR;
> > + register unsigned long r4 asm("r4") = 0;
> > +
> > + asm volatile("sc 1"
> > + : "=r" (r3)
> > + : "r" (r3), "r" (r4)
> > + : "r5", "r6", "r7", "r8", "r9", "r10", "r11", "r12");
> > + return r3 == (unsigned long)H_PRIVILEGE;
> > +}
> > +
> > +void hcall_patch_broken_sc1(void)
> > +{
> > + if (!hcall_have_broken_sc1())
> > + return;
> > + sc1[0] = SC1_REPLACEMENT;
> > +}
> > +
> > +unsigned long hcall(unsigned long nr, unsigned long *in, unsigned long *out)
> > +{
> > + register unsigned long r3 asm("r3") = nr;
> > + register unsigned long r4 asm("r4") = in[0];
> > + register unsigned long r5 asm("r5") = in[1];
> > + register unsigned long r6 asm("r6") = in[2];
> > + register unsigned long r7 asm("r7") = in[3];
> > + register unsigned long r8 asm("r8") = in[4];
> > + register unsigned long r9 asm("r9") = in[5];
> > + register unsigned long r10 asm("r10") = in[6];
> > + register unsigned long r11 asm("r11") = in[7];
> > +
> > + asm volatile("bl sc1"
> > + : "=r"(r3), "=r"(r4), "=r"(r5), "=r"(r6), "=r"(r7),
> > + "=r"(r8), "=r"(r9), "=r"(r10), "=r"(r11)
> > + : "r"(r3), "r"(r4), "r"(r5), "r"(r6), "r"(r7),
> > + "r"(r8), "r"(r9), "r"(r10), "r"(r11)
> > + : "r12", "memory", "lr");
> > +
> > + out[0] = r4;
> > + out[1] = r5;
> > + out[2] = r6;
> > + out[3] = r7;
> > + out[4] = r8;
> > + out[5] = r9;
> > + out[6] = r10;
> > + out[7] = r11;
> > +
> > + return r3;
>
> I'm not sure there's much advantage to having this in C, rather than
> folding this and the sc1 symbol into a single asm implemented hcall
> function.
>
> Doing it that way might more easily allow you to avoid packing the
> arguments into an array, before unpacking them into registers again,
> which seems a bit perverse.
Once I'd moved putchar to C, I decided to minimize the assembly,
but I agree that hcall might as well just be assembly.
>
> > +}
> > +
> > +void putchar(int c)
> > +{
> > + unsigned long in[8], out[8];
> > +
> > + in[0] = 0; /* default vty */
> > + in[1] = 1; /* just 1 byte */
> > + in[2] = (unsigned long)c << 56;
> > +
> > + hcall(H_PUT_TERM_CHAR, in, out);
> > +}
> > diff --git a/lib/powerpc/io.c b/lib/powerpc/io.c
> > index 0af45742fc900..5e1fa8dd96ab6 100644
> > --- a/lib/powerpc/io.c
> > +++ b/lib/powerpc/io.c
> > @@ -6,15 +6,26 @@
> > * This work is licensed under the terms of the GNU LGPL, version 2.
> > */
> > #include <libcflat.h>
> > +#include <asm/spinlock.h>
> > +
> > +extern void halt(int code);
> > +extern void putchar(int c);
> > +
> > +static struct spinlock uart_lock;
> >
> > void io_init(void)
> > {
> > }
> >
> > -void puts(const char *s __unused)
> > +void puts(const char *s)
> > {
> > + spin_lock(&uart_lock);
>
> The name uart_lock isn't really accurate, since it's a hypervisor
> console rather than serial.
Will rename.
>
> > + while (*s)
> > + putchar(*s++);
> > + spin_unlock(&uart_lock);
> > }
> >
> > -void exit(int code __unused)
> > +void exit(int code)
> > {
> > + halt(code);
> > }
> > diff --git a/lib/ppc64/asm/hcall.h b/lib/ppc64/asm/hcall.h
> > new file mode 100644
> > index 0000000000000..daabaca510cd4
> > --- /dev/null
> > +++ b/lib/ppc64/asm/hcall.h
> > @@ -0,0 +1 @@
> > +#include "../../powerpc/asm/hcall.h"
> > diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
> > index 0c3eaba0d3aab..89610b525f0c1 100644
> > --- a/powerpc/Makefile.common
> > +++ b/powerpc/Makefile.common
> > @@ -21,6 +21,7 @@ CFLAGS += -ffreestanding
> > CFLAGS += -Wextra
> > CFLAGS += -O2
> > CFLAGS += -I lib -I lib/libfdt
> > +CFLAGS += -Wa,-mregnames
> >
> > asm-offsets = lib/$(ARCH)/asm-offsets.h
> > include scripts/asm-offsets.mak
> > @@ -29,6 +30,7 @@ cflatobjs += lib/util.o
> > cflatobjs += lib/alloc.o
> > cflatobjs += lib/devicetree.o
> > cflatobjs += lib/powerpc/io.o
> > +cflatobjs += lib/powerpc/hcall.o
> >
> > libgcc := $(shell $(CC) $(machine) --print-libgcc-file-name)
> > start_addr := $(shell printf "%x\n" $$(( $(phys_base) + $(kernel_offset) )))
> > diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
> > index f90828dee1c19..623fd693b02d1 100644
> > --- a/powerpc/cstart64.S
> > +++ b/powerpc/cstart64.S
> > @@ -7,13 +7,34 @@
> > */
> > #define __ASSEMBLY__
> >
> > +#define LOAD_REG_IMMEDIATE(reg,expr) \
> > + lis reg,(expr)@highest; \
> > + ori reg,reg,(expr)@higher; \
> > + rldicr reg,reg,32,31; \
> > + oris reg,reg,(expr)@h; \
> > + ori reg,reg,(expr)@l;
> > +
> > +#define LOAD_REG_ADDR(reg,name) \
> > + ld reg,name@got(r2)
> > +
> > .section .init
> >
> > .globl start
> > start:
> > + LOAD_REG_IMMEDIATE(r1, stackptr)
> > + LOAD_REG_IMMEDIATE(r2, tocptr)
> > + bl hcall_patch_broken_sc1
>
> Come to that, is there any point putting hcall_patch_broken_sc1 in C,
> rather than just doing it inline here.
Hmm, actually no. I'll change that too.
Thanks,
drew
>
> > + bl main
> > + bl exit
> > b halt
> >
> > .text
> > +.align 3
> > +
> > +.globl sc1
> > +sc1:
> > + sc 1
> > + blr
> >
> > .globl halt
> > halt:
>
> --
> David Gibson | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
> | _way_ _around_!
> http://www.ozlabs.org/~dgibson
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