Re: [Minios-devel] [UNIKRAFT PATCH 6/6] lib/syscall_shim: Binary system call handler

[Gaulthier Gain <Gaulthier.Gain@xxxxxxxxx>]

Reviewed-by: Gaulthier Gain <gaulthier.gain@xxxxxxxxx>

> On 11 Dec 2019, at 15:19, Simon Kuenzer <simon.kuenzer@xxxxxxxxx> wrote:
> 
> Provide the option to handle binary system call requests with
> libsyscall_shim. Linux-style ABI is implemented. System calls are
> handled with the raw variant `uk_syscall_r()`.
> 
> Signed-off-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
> ---
> lib/syscall_shim/Config.uk             | 15 ++++++++-
> lib/syscall_shim/Makefile.uk           |  2 ++
> lib/syscall_shim/regmap_linuxabi.h     | 46 ++++++++++++++++++++++++++
> lib/syscall_shim/uk_syscall_r.c.in_end | 18 ++++++++++
> 4 files changed, 80 insertions(+), 1 deletion(-)
> create mode 100644 lib/syscall_shim/regmap_linuxabi.h
> 
> diff --git a/lib/syscall_shim/Config.uk b/lib/syscall_shim/Config.uk
> index 7bf4ca8c..20962590 100644
> --- a/lib/syscall_shim/Config.uk
> +++ b/lib/syscall_shim/Config.uk
> @@ -1,3 +1,16 @@
> -config LIBSYSCALL_SHIM
> +menuconfig LIBSYSCALL_SHIM
>       bool "syscall_shim: Syscall shim layer"
>       default n
> +
> +if LIBSYSCALL_SHIM
> +     config LIBSYSCALL_SHIM_HANDLER
> +             bool "Binary system call handler (Linux ABI)"
> +             default n
> +             depends on ARCH_X86_64
> +             select HAVE_SYSCALL
> +             help
> +                     Enables a system call handler for binary system call
> +                     requests (e.g., sysenter/sysexit). The handler maps
> +                     register values accordingly to the Linux ABI standard
> +                     (see: man syscalls[2]).
> +endif
> diff --git a/lib/syscall_shim/Makefile.uk b/lib/syscall_shim/Makefile.uk
> index 7afa2014..17de49cd 100644
> --- a/lib/syscall_shim/Makefile.uk
> +++ b/lib/syscall_shim/Makefile.uk
> @@ -74,6 +74,8 @@ CXXINCLUDES-$(CONFIG_LIBSYSCALL_SHIM) += 
> -I$(LIBSYSCALL_SHIM_BUILD)/include
> CINCLUDES-y   += -I$(LIBSYSCALL_SHIM_BASE)/include
> CXXINCLUDES-y += -I$(LIBSYSCALL_SHIM_BASE)/include
> 
> +LIBSYSCALL_SHIM_CINCLUDES += -I$(LIBSYSCALL_SHIM_BASE)
> +
> LIBSYSCALL_SHIM_SRCS-y += $(LIBSYSCALL_SHIM_BUILD)/uk_syscall.c
> LIBSYSCALL_SHIM_SRCS-y += $(LIBSYSCALL_SHIM_BUILD)/uk_syscall_r.c
> LIBSYSCALL_SHIM_SRCS-y += $(LIBSYSCALL_SHIM_BUILD)/uk_syscall_name.c
> diff --git a/lib/syscall_shim/regmap_linuxabi.h 
> b/lib/syscall_shim/regmap_linuxabi.h
> new file mode 100644
> index 00000000..1bface67
> --- /dev/null
> +++ b/lib/syscall_shim/regmap_linuxabi.h
> @@ -0,0 +1,46 @@
> +#ifndef _REGMAP_LINUXABI_H_
> +
> +#include <uk/arch/lcpu.h>
> +
> +/*
> + * Mappings of `struct __reg` register fields
> + * according to Linux ABI definition for system calls
> + * (see: man syscall(2))
> + *  rip      - Instruction pointer
> + *  rsyscall - Syscall number
> + *  rargX    - Arguments 0..5
> + *  rretX    - System call return values 0..1
> + */
> +
> +#if (defined __X86_64__)
> +#define rip          rcx
> +#define rsyscall     orig_rax
> +#define rarg0                rdi
> +#define rarg1                rsi
> +#define rarg2                rdx
> +#define rarg3                r10
> +#define rarg4                r8
> +#define rarg5                r9
> +
> +#define rret0                rax
> +#define rret1                rdx
> +
> +#elif (defined __ARM64__)
> +#define rip          x[15] /* TODO: Is this correct? */
> +#define rsyscall     x[8]
> +#define rarg0                x[0]
> +#define rarg1                x[1]
> +#define rarg2                x[2]
> +#define rarg3                x[3]
> +#define rarg4                x[4]
> +#define rarg5                x[5]
> +
> +#define rret0                x[0]
> +#define rret1                x[1]
> +
> +#else
> +#error "Missing register mappings for selected target architecture"
> +
> +#endif
> +
> +#endif /* _REGMAP_LINUXABI_H_ */
> diff --git a/lib/syscall_shim/uk_syscall_r.c.in_end 
> b/lib/syscall_shim/uk_syscall_r.c.in_end
> index f2b9fc8e..ee8a5689 100644
> --- a/lib/syscall_shim/uk_syscall_r.c.in_end
> +++ b/lib/syscall_shim/uk_syscall_r.c.in_end
> @@ -13,3 +13,21 @@ long uk_syscall_r(long n, ...)
>       va_end(ap);
>       return __uk_syscall_r(n,a,b,c,d,e,f);
> }
> +
> +#if CONFIG_LIBSYSCALL_SHIM_HANDLER
> +#include <uk/plat/syscall.h>
> +#include <uk/assert.h>
> +#include <regmap_linuxabi.h>
> +
> +void ukplat_syscall_handler(struct __regs *r)
> +{
> +     UK_ASSERT(r);
> +
> +     uk_pr_debug("Binary system call request \"%s\" (%lu) at ip:%p 
> (arg0=0x%lx, arg1=0x%lx, ...)\n",
> +                 uk_syscall_name(r->rsyscall), r->rsyscall,
> +                 (void *) r->rip, r->rarg0, r->rarg1);
> +     r->rret0 = __uk_syscall_r(r->rsyscall,
> +                               r->rarg0, r->rarg1, r->rarg2,
> +                               r->rarg3, r->rarg4, r->rarg5);
> +}
> +#endif /* CONFIG_LIBSYSCALL_SHIM_HANDLER */
> -- 
> 2.20.1
> 


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