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truss: improved support for decoding compat32 arguments

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Currently running `truss -a -e` does not decode any
argument values for freebsd32_* syscalls (open/readlink/etc.)

This change checks whether a syscall starts with freebsd{32,64}_ and if
so strips that prefix when looking up the syscall information. To ensure
that the truss logs include the real syscall name we create a copy of
the syscall information struct with the updated.

The other problem is that when reading string array values, truss
naively iterates over an array of char* and fetches the pointer value.
This will result in arguments not being loaded if the pointer is not
aligned to sizeof(void*), which can happens in the compat32 case. If it
happens to be aligned, we would end up printing every other value.
To fix this problem, this changes adds a pointer_size member to the
procabi struct and uses that to correctly read indirect arguments
as 64/32 bit addresses in the the compat32 case (and also compat64 on
CheriBSD).

The motivating use-case for this change is using truss for 64-bit
programs on a CHERI system, but most of the diff also applies to 32-bit
compat on a 64-bit system, so I'm upstreaming this instead of keeping it
as a local CheriBSD patch.

Output of `truss -aef ldd32 /usr/bin/ldd32` before:
39113: freebsd32_mmap(0x0,0x1000,0x3,0x1002,0xffffffff,0x0,0x0) = 543440896 (0x20644000)
39113: freebsd32_ioctl(0x1,0x402c7413,0xffffd2a0) = 0 (0x0)
/usr/bin/ldd32:
39113: write(1,"/usr/bin/ldd32:\n",16)		 = 16 (0x10)
39113: fork()					 = 39114 (0x98ca)
39114: <new process>
39114: freebsd32_execve(0xffffd97e,0xffffd680,0x20634000) EJUSTRETURN
39114: freebsd32_mmap(0x0,0x20000,0x3,0x1002,0xffffffff,0x0,0x0) = 541237248 (0x2042a000)
39114: freebsd32_mprotect(0x20427000,0x1000,0x1) = 0 (0x0)
39114: issetugid()				 = 0 (0x0)
39114: openat(AT_FDCWD,"/etc/libmap32.conf",O_RDONLY|O_CLOEXEC,00) ERR#2 'No such file or directory'
39114: openat(AT_FDCWD,"/var/run/ld-elf32.so.hints",O_RDONLY|O_CLOEXEC,00) = 3 (0x3)
39114: read(3,"Ehnt\^A\0\0\0\M^@\0\0\0#\0\0\0\0"...,128) = 128 (0x80)
39114: freebsd32_fstat(0x3,0xffffbd98)		 = 0 (0x0)
39114: freebsd32_pread(0x3,0x2042f000,0x23,0x80,0x0) = 35 (0x23)
39114: close(3)					 = 0 (0x0)
39114: openat(AT_FDCWD,"/usr/lib32/libc.so.7",O_RDONLY|O_CLOEXEC|O_VERIFY,00) = 3 (0x3)
39114: freebsd32_fstat(0x3,0xffffc7d0)		 = 0 (0x0)
39114: freebsd32_mmap(0x0,0x1000,0x1,0x40002,0x3,0x0,0x0) = 541368320 (0x2044a000)

After:
  783: freebsd32_mmap(0x0,4096,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANON|MAP_ALIGNED(12),-1,0x0) = 543543296 (0x2065d000)
  783: freebsd32_ioctl(1,TIOCGETA,0xffffd7b0)    = 0 (0x0)
/usr/bin/ldd32:
  783: write(1,"/usr/bin/ldd32:\n",16)           = 16 (0x10)
  784: <new process>
  783: fork()                                    = 784 (0x310)
  784: freebsd32_execve("/usr/bin/ldd32",[ "(null)" ],[ "LD_32_TRACE_LOADED_OBJECTS_PROGNAME=/usr/bin/ldd32", "LD_TRACE_LOADED_OBJECTS_PROGNAME=/usr/bin/ldd32", "LD_32_TRACE_LOADED_OBJECTS=yes", "LD_TRACE_LOADED_OBJECTS=yes", "USER=root", "LOGNAME=root", "HOME=/root", "SHELL=/bin/csh", "BLOCKSIZE=K", "MAIL=/var/mail/root", "MM_CHARSET=UTF-8", "LANG=C.UTF-8", "PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:/root/bin", "TERM=vt100", "HOSTTYPE=FreeBSD", "VENDOR=amd", "OSTYPE=FreeBSD", "MACHTYPE=x86_64", "SHLVL=1", "PWD=/root", "GROUP=wheel", "HOST=freebsd-amd64", "EDITOR=vi", "PAGER=less" ]) EJUSTRETURN
  784: freebsd32_mmap(0x0,135168,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANON,-1,0x0) = 541212672 (0x20424000)
  784: freebsd32_mprotect(0x20421000,4096,PROT_READ) = 0 (0x0)
  784: issetugid()                               = 0 (0x0)
  784: sigfastblock(0x1,0x204234fc)              = 0 (0x0)
  784: open("/etc/libmap32.conf",O_RDONLY|O_CLOEXEC,00) ERR#2 'No such file or directory'
  784: open("/var/run/ld-elf32.so.hints",O_RDONLY|O_CLOEXEC,00) = 3 (0x3)
  784: read(3,"Ehnt\^A\0\0\0\M^@\0\0\0\v\0\0\0"...,128) = 128 (0x80)
  784: freebsd32_fstat(3,{ mode=-r--r--r-- ,inode=18680,size=32768,blksize=0 }) = 0 (0x0)
  784: freebsd32_pread(3,"/usr/lib32\0",11,0x80) = 11 (0xb)

Reviewed By:	jhb
Differential Revision: https://reviews.freebsd.org/D27625
This commit is contained in:
Alex Richardson 2021-03-25 11:12:17 +00:00
parent 29dd5e7a87
commit 7daca4e204
3 changed files with 87 additions and 45 deletions
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71
usr.bin/truss/setup.c
View File

@ -74,59 +74,72 @@ static void new_proc(struct trussinfo *, pid_t, lwpid_t);
static struct procabi cloudabi32 = { static struct procabi cloudabi32 = {
"CloudABI32", .type = "CloudABI32",
SYSDECODE_ABI_CLOUDABI32, .abi = SYSDECODE_ABI_CLOUDABI32,
STAILQ_HEAD_INITIALIZER(cloudabi32.extra_syscalls), .pointer_size = sizeof(uint32_t),
{ NULL } .extra_syscalls = STAILQ_HEAD_INITIALIZER(cloudabi32.extra_syscalls),
.syscalls = { NULL }
}; };
static struct procabi cloudabi64 = { static struct procabi cloudabi64 = {
"CloudABI64", .type = "CloudABI64",
SYSDECODE_ABI_CLOUDABI64, .abi = SYSDECODE_ABI_CLOUDABI64,
STAILQ_HEAD_INITIALIZER(cloudabi64.extra_syscalls), .pointer_size = sizeof(uint64_t),
{ NULL } .extra_syscalls = STAILQ_HEAD_INITIALIZER(cloudabi64.extra_syscalls),
.syscalls = { NULL }
}; };
static struct procabi freebsd = { static struct procabi freebsd = {
"FreeBSD", .type = "FreeBSD",
SYSDECODE_ABI_FREEBSD, .abi = SYSDECODE_ABI_FREEBSD,
STAILQ_HEAD_INITIALIZER(freebsd.extra_syscalls), .pointer_size = sizeof(void *),
{ NULL } .extra_syscalls = STAILQ_HEAD_INITIALIZER(freebsd.extra_syscalls),
.syscalls = { NULL }
}; };
#ifdef __LP64__ #if !defined(__SIZEOF_POINTER__)
#error "Use a modern compiler."
#endif
#if __SIZEOF_POINTER__ > 4
static struct procabi freebsd32 = { static struct procabi freebsd32 = {
"FreeBSD32", .type = "FreeBSD32",
SYSDECODE_ABI_FREEBSD32, .abi = SYSDECODE_ABI_FREEBSD32,
STAILQ_HEAD_INITIALIZER(freebsd32.extra_syscalls), .pointer_size = sizeof(uint32_t),
{ NULL } .compat_prefix = "freebsd32",
.extra_syscalls = STAILQ_HEAD_INITIALIZER(freebsd32.extra_syscalls),
.syscalls = { NULL }
}; };
#endif #endif
static struct procabi linux = { static struct procabi linux = {
"Linux", .type = "Linux",
SYSDECODE_ABI_LINUX, .abi = SYSDECODE_ABI_LINUX,
STAILQ_HEAD_INITIALIZER(linux.extra_syscalls), .pointer_size = sizeof(void *),
{ NULL } .extra_syscalls = STAILQ_HEAD_INITIALIZER(linux.extra_syscalls),
.syscalls = { NULL }
}; };
#ifdef __LP64__ #if __SIZEOF_POINTER__ > 4
static struct procabi linux32 = { static struct procabi linux32 = {
"Linux32", .type = "Linux32",
SYSDECODE_ABI_LINUX32, .abi = SYSDECODE_ABI_LINUX32,
STAILQ_HEAD_INITIALIZER(linux32.extra_syscalls), .pointer_size = sizeof(uint32_t),
{ NULL } .extra_syscalls = STAILQ_HEAD_INITIALIZER(linux32.extra_syscalls),
.syscalls = { NULL }
}; };
#endif #endif
static struct procabi_table abis[] = { static struct procabi_table abis[] = {
{ "CloudABI ELF32", &cloudabi32 }, { "CloudABI ELF32", &cloudabi32 },
{ "CloudABI ELF64", &cloudabi64 }, { "CloudABI ELF64", &cloudabi64 },
#ifdef __LP64__ #if __SIZEOF_POINTER__ == 4
{ "FreeBSD ELF32", &freebsd },
#elif __SIZEOF_POINTER__ == 8
{ "FreeBSD ELF64", &freebsd }, { "FreeBSD ELF64", &freebsd },
{ "FreeBSD ELF32", &freebsd32 }, { "FreeBSD ELF32", &freebsd32 },
#else #else
{ "FreeBSD ELF32", &freebsd }, #error "Unsupported pointer size"
#endif #endif
#if defined(__powerpc64__) #if defined(__powerpc64__)
{ "FreeBSD ELF64 V2", &freebsd }, { "FreeBSD ELF64 V2", &freebsd },
@ -137,7 +150,7 @@ static struct procabi_table abis[] = {
#if defined(__i386__) #if defined(__i386__)
{ "FreeBSD a.out", &freebsd }, { "FreeBSD a.out", &freebsd },
#endif #endif
#ifdef __LP64__ #if __SIZEOF_POINTER__ >= 8
{ "Linux ELF64", &linux }, { "Linux ELF64", &linux },
{ "Linux ELF32", &linux32 }, { "Linux ELF32", &linux32 },
#else #else

59
usr.bin/truss/syscalls.c
View File

@ -963,7 +963,6 @@ print_mask_arg32(bool (*decoder)(FILE *, uint32_t, uint32_t *), FILE *fp,
fprintf(fp, "|0x%x", rem); fprintf(fp, "|0x%x", rem);
} }
#ifndef __LP64__
/* /*
* Add argument padding to subsequent system calls after Quad * Add argument padding to subsequent system calls after Quad
* syscall arguments as needed. This used to be done by hand in the * syscall arguments as needed. This used to be done by hand in the
@ -1008,7 +1007,6 @@ quad_fixup(struct syscall_decode *sc)
} }
} }
} }
#endif
static struct syscall * static struct syscall *
find_syscall(struct procabi *abi, u_int number) find_syscall(struct procabi *abi, u_int number)
@ -1029,10 +1027,13 @@ add_syscall(struct procabi *abi, u_int number, struct syscall *sc)
{ {
struct extra_syscall *es; struct extra_syscall *es;
#ifndef __LP64__ /*
/* FIXME: should be based on syscall ABI not truss ABI */ * quad_fixup() is currently needed for all 32-bit ABIs.
quad_fixup(&sc->decode); * TODO: This should probably be a function pointer inside struct
#endif * procabi instead.
*/
if (abi->pointer_size == 4)
quad_fixup(&sc->decode);
if (number < nitems(abi->syscalls)) { if (number < nitems(abi->syscalls)) {
assert(abi->syscalls[number] == NULL); assert(abi->syscalls[number] == NULL);
@ -1055,16 +1056,19 @@ struct syscall *
get_syscall(struct threadinfo *t, u_int number, u_int nargs) get_syscall(struct threadinfo *t, u_int number, u_int nargs)
{ {
struct syscall *sc; struct syscall *sc;
struct procabi *procabi;
const char *sysdecode_name; const char *sysdecode_name;
const char *lookup_name;
const char *name; const char *name;
u_int i; u_int i;
sc = find_syscall(t->proc->abi, number); procabi = t->proc->abi;
sc = find_syscall(procabi, number);
if (sc != NULL) if (sc != NULL)
return (sc); return (sc);
/* Memory is not explicitly deallocated, it's released on exit(). */ /* Memory is not explicitly deallocated, it's released on exit(). */
sysdecode_name = sysdecode_syscallname(t->proc->abi->abi, number); sysdecode_name = sysdecode_syscallname(procabi->abi, number);
if (sysdecode_name == NULL) if (sysdecode_name == NULL)
asprintf(__DECONST(char **, &name), "#%d", number); asprintf(__DECONST(char **, &name), "#%d", number);
else else
@ -1073,8 +1077,14 @@ get_syscall(struct threadinfo *t, u_int number, u_int nargs)
sc = calloc(1, sizeof(*sc)); sc = calloc(1, sizeof(*sc));
sc->name = name; sc->name = name;
/* Also decode compat syscalls arguments by stripping the prefix. */
lookup_name = name;
if (procabi->compat_prefix != NULL && strncmp(procabi->compat_prefix,
name, strlen(procabi->compat_prefix)) == 0)
lookup_name += strlen(procabi->compat_prefix);
for (i = 0; i < nitems(decoded_syscalls); i++) { for (i = 0; i < nitems(decoded_syscalls); i++) {
if (strcmp(name, decoded_syscalls[i].name) == 0) { if (strcmp(lookup_name, decoded_syscalls[i].name) == 0) {
sc->decode = decoded_syscalls[i]; sc->decode = decoded_syscalls[i];
add_syscall(t->proc->abi, number, sc); add_syscall(t->proc->abi, number, sc);
return (sc); return (sc);
@ -1817,12 +1827,15 @@ print_arg(struct syscall_arg *sc, unsigned long *args, register_t *retval,
case StringArray: { case StringArray: {
uintptr_t addr; uintptr_t addr;
union { union {
char *strarray[0]; int32_t strarray32[PAGE_SIZE / sizeof(int32_t)];
int64_t strarray64[PAGE_SIZE / sizeof(int64_t)];
char buf[PAGE_SIZE]; char buf[PAGE_SIZE];
} u; } u;
char *string; char *string;
size_t len; size_t len;
u_int first, i; u_int first, i;
size_t pointer_size =
trussinfo->curthread->proc->abi->pointer_size;
/* /*
* Only parse argv[] and environment arrays from exec calls * Only parse argv[] and environment arrays from exec calls
@ -1842,7 +1855,7 @@ print_arg(struct syscall_arg *sc, unsigned long *args, register_t *retval,
* a partial page. * a partial page.
*/ */
addr = args[sc->offset]; addr = args[sc->offset];
if (addr % sizeof(char *) != 0) { if (addr % pointer_size != 0) {
print_pointer(fp, args[sc->offset]); print_pointer(fp, args[sc->offset]);
break; break;
} }
@ -1852,22 +1865,36 @@ print_arg(struct syscall_arg *sc, unsigned long *args, register_t *retval,
print_pointer(fp, args[sc->offset]); print_pointer(fp, args[sc->offset]);
break; break;
} }
assert(len > 0);
fputc('[', fp); fputc('[', fp);
first = 1; first = 1;
i = 0; i = 0;
while (u.strarray[i] != NULL) { for (;;) {
string = get_string(pid, (uintptr_t)u.strarray[i], 0); uintptr_t straddr;
if (pointer_size == 4) {
if (u.strarray32[i] == 0)
break;
/* sign-extend 32-bit pointers */
straddr = (intptr_t)u.strarray32[i];
} else if (pointer_size == 8) {
if (u.strarray64[i] == 0)
break;
straddr = (intptr_t)u.strarray64[i];
} else {
errx(1, "Unsupported pointer size: %zu",
pointer_size);
}
string = get_string(pid, straddr, 0);
fprintf(fp, "%s \"%s\"", first ? "" : ",", string); fprintf(fp, "%s \"%s\"", first ? "" : ",", string);
free(string); free(string);
first = 0; first = 0;
i++; i++;
if (i == len / sizeof(char *)) { if (i == len / pointer_size) {
addr += len; addr += len;
len = PAGE_SIZE; len = PAGE_SIZE;
if (get_struct(pid, addr, u.buf, len) == if (get_struct(pid, addr, u.buf, len) == -1) {
-1) {
fprintf(fp, ", <inval>"); fprintf(fp, ", <inval>");
break; break;
} }

2
usr.bin/truss/truss.h
View File

@ -58,6 +58,8 @@ struct extra_syscall {
struct procabi { struct procabi {
const char *type; const char *type;
enum sysdecode_abi abi; enum sysdecode_abi abi;
size_t pointer_size;
const char *compat_prefix;
STAILQ_HEAD(, extra_syscall) extra_syscalls; STAILQ_HEAD(, extra_syscall) extra_syscalls;
struct syscall *syscalls[SYSCALL_NORMAL_COUNT]; struct syscall *syscalls[SYSCALL_NORMAL_COUNT];
}; };