Re: [RFC PATCH v2 3/3] selftests/x86: Augment SGX selftest to test new __vdso_sgx_enter_enclave() and its callback interface

["Xing, Cedric" <cedric.xing@intel.com>]

On 7/11/2019 8:25 PM, Jarkko Sakkinen wrote:
> On Tue, Apr 23, 2019 at 11:26:23PM -0700, Cedric Xing wrote:
>> This patch augments SGX selftest with two new tests.
>>
>> The first test exercises the newly added callback interface, by marking the
>> whole enclave range as PROT_READ, then calling mprotect() upon #PFs to add
>> necessary PTE permissions per PFEC (#PF Error Code) until the enclave finishes.
>> This test also serves as an example to demonstrate the callback interface.
>>
>> The second test single-steps through __vdso_sgx_enter_enclave() to make sure
>> the call stack can be unwound at every instruction within that vDSO API. Its
>> purpose is to validate the hand-crafted CFI directives in the assembly.
>>
>> Signed-off-by: Cedric Xing <cedric.xing@intel.com>
>> ---
>>   tools/testing/selftests/x86/sgx/Makefile   |   6 +-
>>   tools/testing/selftests/x86/sgx/main.c     | 323 ++++++++++++++++++---
>>   tools/testing/selftests/x86/sgx/sgx_call.S |  40 ++-
>>   3 files changed, 322 insertions(+), 47 deletions(-)
>>
>> diff --git a/tools/testing/selftests/x86/sgx/Makefile b/tools/testing/selftests/x86/sgx/Makefile
>> index 3af15d7c8644..31f937e220c4 100644
>> --- a/tools/testing/selftests/x86/sgx/Makefile
>> +++ b/tools/testing/selftests/x86/sgx/Makefile
>> @@ -14,16 +14,16 @@ TEST_CUSTOM_PROGS := $(OUTPUT)/test_sgx
>>   all_64: $(TEST_CUSTOM_PROGS)
>>   
>>   $(TEST_CUSTOM_PROGS): main.c sgx_call.S $(OUTPUT)/encl_piggy.o
>> -	$(CC) $(HOST_CFLAGS) -o $@ $^
>> +	$(CC) $(HOST_CFLAGS) -o $@ $^ -lunwind -ldl -Wl,--defsym,__image_base=0 -pie
>>   
>>   $(OUTPUT)/encl_piggy.o: encl_piggy.S $(OUTPUT)/encl.bin $(OUTPUT)/encl.ss
>>   	$(CC) $(HOST_CFLAGS) -I$(OUTPUT) -c $< -o $@
>>   
>>   $(OUTPUT)/encl.bin: $(OUTPUT)/encl.elf
>> -	objcopy --remove-section=.got.plt -O binary $< $@
>> +	objcopy -O binary $< $@
>>   
>>   $(OUTPUT)/encl.elf: encl.lds encl.c encl_bootstrap.S
>> -	$(CC) $(ENCL_CFLAGS) -T $^ -o $@
>> +	$(CC) $(ENCL_CFLAGS) -T $^ -o $@ -Wl,--build-id=none
>>   
>>   $(OUTPUT)/encl.ss: $(OUTPUT)/sgxsign signing_key.pem $(OUTPUT)/encl.bin
>>   	$^ $@
>> diff --git a/tools/testing/selftests/x86/sgx/main.c b/tools/testing/selftests/x86/sgx/main.c
>> index e2265f841fb0..d3e53c71306d 100644
>> --- a/tools/testing/selftests/x86/sgx/main.c
>> +++ b/tools/testing/selftests/x86/sgx/main.c
>> @@ -1,6 +1,7 @@
>>   // SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
>>   // Copyright(c) 2016-18 Intel Corporation.
>>   
>> +#define _GNU_SOURCE
>>   #include <elf.h>
>>   #include <fcntl.h>
>>   #include <stdbool.h>
>> @@ -9,16 +10,31 @@
>>   #include <stdlib.h>
>>   #include <string.h>
>>   #include <unistd.h>
>> +#include <errno.h>
>>   #include <sys/ioctl.h>
>>   #include <sys/mman.h>
>>   #include <sys/stat.h>
>> -#include <sys/time.h>
>> +#include <sys/auxv.h>
>> +#include <signal.h>
>> +#include <sys/ucontext.h>
>> +
>> +#define UNW_LOCAL_ONLY
>> +#include <libunwind.h>
>> +
>>   #include "encl_piggy.h"
>>   #include "defines.h"
>>   #include "../../../../../arch/x86/kernel/cpu/sgx/arch.h"
>>   #include "../../../../../arch/x86/include/uapi/asm/sgx.h"
>>   
>> -static const uint64_t MAGIC = 0x1122334455667788ULL;
>> +#define _Q(x)	__Q(x)
>> +#define __Q(x)	#x
>> +#define ERRLN	"Line " _Q(__LINE__)
>> +
>> +#define X86_EFLAGS_TF	(1ul << 8)
>> +
>> +extern char __image_base[];
>> +size_t eenter;
>> +static size_t vdso_base;
>>   
>>   struct vdso_symtab {
>>   	Elf64_Sym *elf_symtab;
>> @@ -26,20 +42,11 @@ struct vdso_symtab {
>>   	Elf64_Word *elf_hashtab;
>>   };
>>   
>> -static void *vdso_get_base_addr(char *envp[])
>> +static void vdso_init(void)
>>   {
>> -	Elf64_auxv_t *auxv;
>> -	int i;
>> -
>> -	for (i = 0; envp[i]; i++);
>> -	auxv = (Elf64_auxv_t *)&envp[i + 1];
>> -
>> -	for (i = 0; auxv[i].a_type != AT_NULL; i++) {
>> -		if (auxv[i].a_type == AT_SYSINFO_EHDR)
>> -			return (void *)auxv[i].a_un.a_val;
>> -	}
>> -
>> -	return NULL;
>> +	vdso_base = getauxval(AT_SYSINFO_EHDR);
>> +	if (!vdso_base)
>> +		exit(1);
>>   }
> 
> The clean up makes sense but should be a separate patch i.e. one
> logical change per patch. Right now the patch does other mods
> than the ones explcitly stated in the commit message.
> 
> I'd suggest open coding vdso_init() to the call site in that
> patch.
> 
> Please try to always minimize for diff's.
> 
>>   
>>   static Elf64_Dyn *vdso_get_dyntab(void *addr)
>> @@ -66,8 +73,9 @@ static void *vdso_get_dyn(void *addr, Elf64_Dyn *dyntab, Elf64_Sxword tag)
>>   	return NULL;
>>   }
>>   
>> -static bool vdso_get_symtab(void *addr, struct vdso_symtab *symtab)
>> +static bool vdso_get_symtab(struct vdso_symtab *symtab)
>>   {
>> +	void *addr = (void *)vdso_base;
>>   	Elf64_Dyn *dyntab = vdso_get_dyntab(addr);
>>   
>>   	symtab->elf_symtab = vdso_get_dyn(addr, dyntab, DT_SYMTAB);
>> @@ -138,7 +146,7 @@ static bool encl_create(int dev_fd, unsigned long bin_size,
>>   	base = mmap(NULL, secs->size, PROT_READ | PROT_WRITE | PROT_EXEC,
>>   		    MAP_SHARED, dev_fd, 0);
>>   	if (base == MAP_FAILED) {
>> -		perror("mmap");
>> +		perror(ERRLN);
>>   		return false;
>>   	}
>>   
>> @@ -224,35 +232,271 @@ static bool encl_load(struct sgx_secs *secs, unsigned long bin_size)
>>   	return false;
>>   }
>>   
>> -void sgx_call(void *rdi, void *rsi, void *tcs,
>> -	      struct sgx_enclave_exception *exception,
>> -	      void *eenter);
>> +int sgx_call(void *rdi, void *rsi, long rdx, void *rcx, void *r8, void *r9,
>> +	     void *tcs, struct sgx_enclave_exinfo *ei, void *cb);
>> +
>> +static void show_enclave_exinfo(const struct sgx_enclave_exinfo *exinfop,
>> +				const char *header)
>> +{
>> +	static const char * const enclu_leaves[] = {
>> +		"EREPORT",
>> +		"EGETKEY",
>> +		"EENTER",
>> +		"ERESUME",
>> +		"EEXIT"
>> +	};
>> +	static const char * const exception_names[] = {
>> +		"#DE",
>> +		"#DB",
>> +		"NMI",
>> +		"#BP",
>> +		"#OF",
>> +		"#BR",
>> +		"#UD",
>> +		"#NM",
>> +		"#DF",
>> +		"CSO",
>> +		"#TS",
>> +		"#NP",
>> +		"#SS",
>> +		"#GP",
>> +		"#PF",
>> +		"Unknown",
>> +		"#MF",
>> +		"#AC",
>> +		"#MC",
>> +		"#XM",
>> +		"#VE",
>> +		"Unknown",
>> +		"Unknown",
>> +		"Unknown",
>> +		"Unknown",
>> +		"Unknown",
>> +		"Unknown",
>> +		"Unknown",
>> +		"Unknown",
>> +		"Unknown",
>> +		"Unknown",
>> +		"Unknown"
>> +	};
>> +
>> +	printf("%s: leaf:%s(%d)", header,
>> +		enclu_leaves[exinfop->leaf], exinfop->leaf);
>> +	if (exinfop->leaf != 4)
>> +		printf(" trap:%s(%d) ec:%d addr:0x%llx\n",
>> +			exception_names[exinfop->trapnr], exinfop->trapnr,
>> +			exinfop->error_code, exinfop->address);
>> +	else
>> +		printf("\n");
>> +}
>> +
>> +static const uint64_t MAGIC = 0x1122334455667788ULL;
>>   
>> -int main(int argc, char *argv[], char *envp[])
>> +static void test1(struct sgx_secs *secs)
> 
> test1, test2 and test3 are not too descriptive names. Every patch should
> make the code base cleaner, not messier.

I don't think it that important, as there are many test## occurrences in 
existing selftests. Anyway, I've added comments to those test functions 
to brief what is done. Hope you'll find them helpful.

> /Jarkko
>