[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen master] x86emul: rework wrapping of libc functions in test and fuzzing harnesses
commit 6fba45ca3be1c5d46cddb1eaf371d9e69550b244 Author: Jan Beulich <jbeulich@xxxxxxxx> AuthorDate: Fri Aug 18 15:04:28 2023 +0200 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Fri Aug 18 15:04:28 2023 +0200 x86emul: rework wrapping of libc functions in test and fuzzing harnesses Our present approach is working fully behind the compiler's back. This was found to not work with LTO. Employ ld's --wrap= option instead. Note that while this makes the build work at least with new enough gcc (it doesn't with gcc7, for example, due to tool chain side issues afaict), according to my testing things still won't work when building the fuzzing harness with afl-cc: While with the gcc7 tool chain I see afl-as getting invoked, this does not happen with gcc13. Yet without using that assembler wrapper the resulting binary will look uninstrumented to afl-fuzz. While checking the resulting binaries I noticed that we've gained uses of snprintf() and strstr(), which only just so happen to not cause any problems. Add a wrappers for them as well. Since we don't have any actual uses of v{,sn}printf(), no definitions of their wrappers appear (just yet). But I think we want __wrap_{,sn}printf() to properly use __real_v{,sn}printf() right away, which means we need delarations of the latter. Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> Tested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> --- tools/fuzz/x86_instruction_emulator/Makefile | 6 ++- tools/tests/x86_emulator/Makefile | 4 +- tools/tests/x86_emulator/wrappers.c | 55 ++++++++++++++++++++-------- tools/tests/x86_emulator/x86-emulate.h | 14 +++---- 4 files changed, 53 insertions(+), 26 deletions(-) diff --git a/tools/fuzz/x86_instruction_emulator/Makefile b/tools/fuzz/x86_instruction_emulator/Makefile index 0100cfc8ac..1e4c6b37f5 100644 --- a/tools/fuzz/x86_instruction_emulator/Makefile +++ b/tools/fuzz/x86_instruction_emulator/Makefile @@ -35,6 +35,8 @@ OBJS := fuzz-emul.o x86-emulate.o OBJS += x86_emulate/0f01.o x86_emulate/0fae.o x86_emulate/0fc7.o OBJS += x86_emulate/decode.o x86_emulate/fpu.o +WRAPPED = $(shell sed -n 's,^ *WRAP(\([[:alnum:]_]*\));,\1,p' x86-emulate.h) + private.h := x86-emulate.h x86_emulate/x86_emulate.h x86_emulate/private.h x86-emulate.h: x86_emulate/x86_emulate.h @@ -51,10 +53,10 @@ x86-insn-fuzzer.a: $(OBJS) cpuid.o $(AR) rc $@ $^ afl-harness: afl-harness.o $(OBJS) cpuid.o wrappers.o - $(CC) $(CFLAGS) $^ -o $@ + $(CC) $(CFLAGS) $(addprefix -Wl$(comma)--wrap=,$(WRAPPED)) $^ -o $@ afl-harness-cov: afl-harness-cov.o $(patsubst %.o,%-cov.o,$(OBJS)) cpuid.o wrappers.o - $(CC) $(CFLAGS) $(GCOV_FLAGS) $^ -o $@ + $(CC) $(CFLAGS) $(GCOV_FLAGS) $(addprefix -Wl$(comma)--wrap=,$(WRAPPED)) $^ -o $@ # Common targets .PHONY: all diff --git a/tools/tests/x86_emulator/Makefile b/tools/tests/x86_emulator/Makefile index 4079412d2e..affabc0277 100644 --- a/tools/tests/x86_emulator/Makefile +++ b/tools/tests/x86_emulator/Makefile @@ -259,8 +259,10 @@ OBJS := x86-emulate.o cpuid.o test_x86_emulator.o evex-disp8.o predicates.o wrap OBJS += x86_emulate/0f01.o x86_emulate/0fae.o x86_emulate/0fc7.o OBJS += x86_emulate/blk.o x86_emulate/decode.o x86_emulate/fpu.o x86_emulate/util.o +WRAPPED := $(shell sed -n 's,^ *WRAP(\([[:alnum:]_]*\));,\1,p' x86-emulate.h) + $(TARGET): $(OBJS) - $(HOSTCC) $(HOSTCFLAGS) -o $@ $^ + $(HOSTCC) $(HOSTCFLAGS) $(addprefix -Wl$(comma)--wrap=,$(WRAPPED)) -o $@ $^ .PHONY: clean clean: diff --git a/tools/tests/x86_emulator/wrappers.c b/tools/tests/x86_emulator/wrappers.c index eba7cc93c5..3829a6f416 100644 --- a/tools/tests/x86_emulator/wrappers.c +++ b/tools/tests/x86_emulator/wrappers.c @@ -1,78 +1,103 @@ #include <stdarg.h> -#define WRAP(x) typeof(x) emul_##x +#define WRAP(x) typeof(x) __wrap_ ## x, __real_ ## x #include "x86-emulate.h" -size_t emul_fwrite(const void *src, size_t sz, size_t n, FILE *f) +size_t __wrap_fwrite(const void *src, size_t sz, size_t n, FILE *f) { emul_save_fpu_state(); - sz = fwrite(src, sz, n, f); + sz = __real_fwrite(src, sz, n, f); emul_restore_fpu_state(); return sz; } -int emul_memcmp(const void *p1, const void *p2, size_t sz) +int __wrap_memcmp(const void *p1, const void *p2, size_t sz) { int rc; emul_save_fpu_state(); - rc = memcmp(p1, p2, sz); + rc = __real_memcmp(p1, p2, sz); emul_restore_fpu_state(); return rc; } -void *emul_memcpy(void *dst, const void *src, size_t sz) +void *__wrap_memcpy(void *dst, const void *src, size_t sz) { emul_save_fpu_state(); - memcpy(dst, src, sz); + __real_memcpy(dst, src, sz); emul_restore_fpu_state(); return dst; } -void *emul_memset(void *dst, int c, size_t sz) +void *__wrap_memset(void *dst, int c, size_t sz) { emul_save_fpu_state(); - memset(dst, c, sz); + __real_memset(dst, c, sz); emul_restore_fpu_state(); return dst; } -int emul_printf(const char *fmt, ...) +int __wrap_printf(const char *fmt, ...) { va_list varg; int rc; emul_save_fpu_state(); va_start(varg, fmt); - rc = vprintf(fmt, varg); + rc = __real_vprintf(fmt, varg); va_end(varg); emul_restore_fpu_state(); return rc; } -int emul_putchar(int c) +int __wrap_putchar(int c) { int rc; emul_save_fpu_state(); - rc = putchar(c); + rc = __real_putchar(c); emul_restore_fpu_state(); return rc; } -int emul_puts(const char *str) +int __wrap_puts(const char *str) { int rc; emul_save_fpu_state(); - rc = puts(str); + rc = __real_puts(str); emul_restore_fpu_state(); return rc; } + +int __wrap_snprintf(char *buf, size_t n, const char *fmt, ...) +{ + va_list varg; + int rc; + + emul_save_fpu_state(); + va_start(varg, fmt); + rc = __real_vsnprintf(buf, n, fmt, varg); + va_end(varg); + emul_restore_fpu_state(); + + return rc; +} + +char *__wrap_strstr(const char *s1, const char *s2) +{ + char *s; + + emul_save_fpu_state(); + s = __real_strstr(s1, s2); + emul_restore_fpu_state(); + + return s; +} diff --git a/tools/tests/x86_emulator/x86-emulate.h b/tools/tests/x86_emulator/x86-emulate.h index 350d1a0abf..34f0855114 100644 --- a/tools/tests/x86_emulator/x86-emulate.h +++ b/tools/tests/x86_emulator/x86-emulate.h @@ -32,9 +32,7 @@ #ifdef EOF # error "Must not include <stdio.h> before x86-emulate.h" #endif -#ifdef WRAP -# include <stdio.h> -#endif +#include <stdio.h> #include <xen/xen.h> @@ -88,11 +86,7 @@ struct x86_fxsr *get_fpu_save_area(void); * around the actual function. */ #ifndef WRAP -# if 0 /* This only works for explicit calls, not for compiler generated ones. */ -# define WRAP(x) typeof(x) x asm("emul_" #x) -# else -# define WRAP(x) asm(".equ " #x ", emul_" #x) -# endif +# define WRAP(x) typeof(x) __wrap_ ## x #endif WRAP(fwrite); @@ -102,6 +96,10 @@ WRAP(memset); WRAP(printf); WRAP(putchar); WRAP(puts); +WRAP(snprintf); +WRAP(strstr); +WRAP(vprintf); +WRAP(vsnprintf); #undef WRAP -- generated by git-patchbot for /home/xen/git/xen.git#master
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