[Minios-devel] [UNIKRAFT PATCH 09/10] lib/syscall_shim: introduce uk_syscall_dynamic

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

The macro layer is efficient, but the exact syscall must be known at
the compilation stage. If a syscall number is kept in a variable macro
layer will not be able to resolve it to the syscall function.

For this case another file is generated - syscall_entry.c. Where
syscalls are 'dynamically' resolved into a destination functions.

Signed-off-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>
---
 lib/syscall_shim/Makefile.uk          |  9 +++++-
 lib/syscall_shim/entry.c.in_end       | 15 ++++++++++
 lib/syscall_shim/gen_entry.awk        | 40 +++++++++++++++++++++++++++
 lib/syscall_shim/include/uk/syscall.h |  2 ++
 4 files changed, 65 insertions(+), 1 deletion(-)
 create mode 100644 lib/syscall_shim/entry.c.in_end
 create mode 100644 lib/syscall_shim/gen_entry.awk

diff --git a/lib/syscall_shim/Makefile.uk b/lib/syscall_shim/Makefile.uk
index 67677fc6..5ea15963 100644
--- a/lib/syscall_shim/Makefile.uk
+++ b/lib/syscall_shim/Makefile.uk
@@ -7,7 +7,8 @@ __PHONY_GEN_SRC := $(addprefix $(__GEN_INCLUDES_PATH)/, 
$(__PHONY_GEN_SRC))
 __PHONY_GEN_SRC += $(LIBSYSCALL_SHIM_BUILD)/provided_syscalls.h.in
 __PHONY_GEN_SRC_NEW := $(addsuffix .new, $(__PHONY_GEN_SRC))
 
-__GEN_SRC := $(__GEN_INCLUDES_PATH)/provided_syscalls.h
+__GEN_SRC := $(__GEN_INCLUDES_PATH)/provided_syscalls.h \
+               $(LIBSYSCALL_SHIM_BUILD)/syscall_entry.c
 
 UK_PREPARE-$(CONFIG_LIBSYSCALL_SHIM) += $(__PHONY_GEN_SRC) $(__GEN_SRC)
 
@@ -43,6 +44,10 @@ $(__GEN_INCLUDES_PATH)/provided_syscalls.h: 
$(LIBSYSCALL_SHIM_BUILD)/provided_sy
         printf "\nUK_SYSCALL_PROTO(%s, %s);\n", $$2, $$1;}' \
        $^ > $@
 
+$(LIBSYSCALL_SHIM_BUILD)/syscall_entry.c: 
$(LIBSYSCALL_SHIM_BUILD)/provided_syscalls.h.in 
$(LIBSYSCALL_SHIM_BASE)/gen_entry.awk
+       $(Q) awk -F '-' -f $(LIBSYSCALL_SHIM_BASE)/gen_entry.awk $< > $@
+       $(Q) cat $(LIBSYSCALL_SHIM_BASE)/entry.c.in_end >> $@
+
 $(LIBSYSCALL_SHIM_BUILD)/provided_syscalls.h.in.new:
        $Q echo $(UK_PROVIDED_SYSCALLS-y) | tr ' ' '\n' > $@
 
@@ -55,4 +60,6 @@ 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_SRCS-y += $(LIBSYSCALL_SHIM_BUILD)/syscall_entry.c
+
 LIBSYSCALL_SHIM_CLEAN = $(__PHONY_GEN_SRC) $(__PHONY_GEN_SRC_NEW) $(__GEN_SRC)
diff --git a/lib/syscall_shim/entry.c.in_end b/lib/syscall_shim/entry.c.in_end
new file mode 100644
index 00000000..58145bbc
--- /dev/null
+++ b/lib/syscall_shim/entry.c.in_end
@@ -0,0 +1,15 @@
+
+long uk_syscall_dynamic(long n, ...)
+{
+       va_list ap;
+       syscall_arg_t a,b,c,d,e,f;
+       va_start(ap, n);
+       a=va_arg(ap, long);
+       b=va_arg(ap, long);
+       c=va_arg(ap, long);
+       d=va_arg(ap, long);
+       e=va_arg(ap, long);
+       f=va_arg(ap, long);
+       va_end(ap);
+       return __syscall_dynamic(n,a,b,c,d,e,f);
+}
diff --git a/lib/syscall_shim/gen_entry.awk b/lib/syscall_shim/gen_entry.awk
new file mode 100644
index 00000000..92457089
--- /dev/null
+++ b/lib/syscall_shim/gen_entry.awk
@@ -0,0 +1,40 @@
+BEGIN {
+       max_args = 6
+       print "/* Auto generated file. DO NOT EDIT */\n\n"
+
+       print "#include <uk/syscall.h>"
+       print "#include <uk/print.h>\n"
+
+       printf "static inline long __syscall_dynamic(long nr, "
+       for (i = 1; i < max_args; i++)
+               printf "long arg%d, ",i
+       printf "long arg%d)\n{\n", max_args
+
+       for (i = 1; i <= max_args; i++)
+               printf "\t(void) arg%d;\n", i
+
+       print "\n\tswitch (nr) {"
+}
+
+
+/[a-zA-Z0-9]+-[0-9]+/{
+       name = $1
+       sys_name = "SYS_" name
+       uk_name = "uk_syscall_" name
+       args_nr = $2 + 0
+       printf "\tcase %s:\n", sys_name;
+       printf "\t\treturn %s(", uk_name;
+       for (i = 1; i < args_nr; i++)
+               printf("arg%d, ", i)
+       if (args_nr > 0)
+               printf("arg%d", args_nr)
+       printf(");\n")
+}
+
+END {
+       printf "\tdefault:\n"
+       printf "\t\tuk_pr_debug(\"syscall nr %%ld is not implemented\", nr);\n"
+       printf "\t\terrno = -ENOSYS;\n"
+       printf "\t\treturn -1;\n"
+       printf "\t}\n}\n"
+}
diff --git a/lib/syscall_shim/include/uk/syscall.h 
b/lib/syscall_shim/include/uk/syscall.h
index 19161e5e..13913bab 100644
--- a/lib/syscall_shim/include/uk/syscall.h
+++ b/lib/syscall_shim/include/uk/syscall.h
@@ -93,6 +93,8 @@ typedef long syscall_arg_t;
 #include <uk/bits/provided_syscalls.h>
 #include <uk/bits/syscall_stubs.h>
 
+long uk_syscall_dynamic(long n, ...);
+
 #define syscall(...)                                                   \
        UK_CONCAT(__uk_syscall, __SYSCALL_NARGS(__VA_ARGS__))(__VA_ARGS__)
 #endif
-- 
2.19.2


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