Re: [PATCH v1 1/8] tools/nolibc: add support for powerpc

Hi Willy,

On Tue, Jul 25, 2023 at 07:02:55PM +0800, Zhangjin Wu wrote:

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With this new syscall.h, to support my_syscall<N>, the arch-<ARCH>.h will only require to add ~10 lines to define their own syscall instructions, registers and clobberlist, which looks like this (for powerpc):

#define _NOLIBC_SYSCALL_CALL "sc; bns+ 1f; neg  %0, %0; 1:"

/* PowerPC doesn't always restore r3-r12 for us */
#define _NOLIBC_SYSCALL_CLOBBERLIST 
	"memory", "cr0", "r12", "r11", "r10", "r9", "r8", "r7", "r6", "r5", "r4"

/* PowerPC write GPRS in kernel side but not restore them */
#define _NOLIBC_GPRS_AS_OUTPUT_OPERANDS

#define _NOLIBC_REG_NUM "r0" #define _NOLIBC_REG_RET "r3" #define _NOLIBC_REG_arg1 "r3" #define _NOLIBC_REG_arg2 "r4" #define _NOLIBC_REG_arg3 "r5" #define _NOLIBC_REG_arg4 "r6" #define _NOLIBC_REG_arg5 "r7" #define _NOLIBC_REG_arg6 "r8"

Before:

$ ls tools/include/nolibc/arch-*.h | while read f; do git show dfef4fc45d5713eb23d87f0863aff9c33bd4bfaf:$f 2>/dev/null | wc -l | tr -d '\n'; echo " $f"; done
157 tools/include/nolibc/arch-aarch64.h
199 tools/include/nolibc/arch-arm.h
178 tools/include/nolibc/arch-i386.h
164 tools/include/nolibc/arch-loongarch.h
195 tools/include/nolibc/arch-mips.h
0 tools/include/nolibc/arch-powerpc.h
160 tools/include/nolibc/arch-riscv.h
186 tools/include/nolibc/arch-s390.h
176 tools/include/nolibc/arch-x86_64.h

After:

$ wc -l tools/include/nolibc/arch-*.h
   54 tools/include/nolibc/arch-aarch64.h
   84 tools/include/nolibc/arch-arm.h
   90 tools/include/nolibc/arch-i386.h                        /* the last one use stack to pass arguments, reserve as-is */
   59 tools/include/nolibc/arch-loongarch.h
  120 tools/include/nolibc/arch-mips.h                        /* the last two use stack to pass arguments, reserve as-is */
   73 tools/include/nolibc/arch-powerpc.h
   58 tools/include/nolibc/arch-riscv.h
   87 tools/include/nolibc/arch-s390.h
   67 tools/include/nolibc/arch-x86_64.h

syscall.h itself:

$ wc -l tools/include/nolibc/syscall.h
112 tools/include/nolibc/syscall.h 

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Hoping this clarifies my position on this.

Willy, Thanks very much for your detailed reply, based on your reply, I plan to renew the powerpc patchset itself at first since both you and Thomas have already reviewed it carefully.

After that, I will come back to read your reply again and discuss more about our new syscall.h, I still think it is something valuable to take a look at, although something about it still need more attention, perhaps a RFC patchset is better for more discuss, it may show us the profile easily.

Best regards, Zhangjin

Thanks, Willy