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From: Richard Henderson <richard.henderson@linaro.org>
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Date: Thu, 19 Jul 2018 04:13:18 -0700
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Subject: Re: [Qemu-devel] [PATCH] linux-user/ppc: Implement swapcontext
 syscall
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To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= <f4bug@amsat.org>, qemu-devel@nongnu.org
Cc: qemu-ppc@nongnu.org, alex.bennee@linaro.org, laurent@vivier.eu, david@gibson.dropbear.id.au

On 07/18/2018 03:56 PM, Philippe Mathieu-Daudé wrote:
>> +
>> +/* This syscall implements {get,set,swap}context for userland.  */
> 
> This comment confuses me because do_setcontext() is available at line 625.

But that's not wired up as a syscall.

>> +    /* For ppc32, ctx_size is "reserved for future use".
>> +     * For ppc64, we do not yet support the VSX extension.
>> +     */
>> +    if (ctx_size < sizeof(struct target_ucontext)) {
>> +        return -TARGET_EINVAL;
> 
> Shouldn't this be -TARGET_ENOMEM?
> 
> swapcontext(3):
> ERRORS
>        ENOMEM Insufficient stack space left.

No.  Please compare against the syscall, not the libc interface.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/kernel/signal_32.c#n1045


r~