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Enable creation of static userspace probes in incremental builds.

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To define USDT probes, dtrace -G makes use of relocations for undefined
symbols: the target address is overwritten with NOPs and the location is
recorded in the DOF section of the output object file.  To avoid link
errors, the original relocation is destroyed.  However, this means that
the same input object file cannot be processed multiple times, as
happens during incremental rebuilds.  Instead, only set the relocation
type to NONE, so that all information required to reconstruct USDT
probes is preserved.

Reported by:	bdrewery
MFC after:	3 weeks
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Mark Johnston 2020-08-20 19:28:19 +00:00
parent 0e15d9fbeb
commit d2d16e5663
4 changed files with 89 additions and 69 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

146
cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c
View File

@ -773,6 +773,7 @@ dt_symtab_lookup(Elf_Data *data_sym, int start, int end, uintptr_t addr,
#define DT_OP_RET 0xd65f03c0
#define DT_OP_CALL26 0x94000000
#define DT_OP_JUMP26 0x14000000
#define DT_REL_NONE R_AACH64_NONE
static int
dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
@ -831,7 +832,8 @@ dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
return (0);
}
#elif defined(__arm__)
/* XXX */
#define DT_REL_NONE R_ARM_NONE
static int
dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
uint32_t *off)
@ -841,7 +843,8 @@ dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
return (-1);
}
#elif defined(__mips__)
/* XXX */
#define DT_REL_NONE R_MIPS_NONE
static int
dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
uint32_t *off)
@ -861,7 +864,8 @@ dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
#define DT_IS_BRANCH(inst) ((inst & 0xfc000000) == 0x48000000)
#define DT_IS_BL(inst) (DT_IS_BRANCH(inst) && (inst & 0x01))
/* XXX */
#define DT_REL_NONE R_PPC_NONE
static int
dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
uint32_t *off)
@ -878,7 +882,8 @@ dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
* We only know about some specific relocation types.
*/
if (GELF_R_TYPE(rela->r_info) != R_PPC_REL24 &&
GELF_R_TYPE(rela->r_info) != R_PPC_PLTREL24)
GELF_R_TYPE(rela->r_info) != R_PPC_PLTREL24 &&
GELF_R_TYPE(rela->r_info) != R_PPC_NONE)
return (-1);
/*
@ -932,7 +937,7 @@ dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
return (0);
}
#elif defined(__riscv)
/* XXX */
#define DT_REL_NONE R_RISCV_NONE
static int
dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
uint32_t *off)
@ -952,6 +957,8 @@ dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
#define DT_OP_XOR_EAX_0 0x33
#define DT_OP_XOR_EAX_1 0xc0
#define DT_REL_NONE R_386_NONE
static int
dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
uint32_t *off)
@ -974,7 +981,8 @@ dt_modtext(dtrace_hdl_t *dtp, char *p, int isenabled, GElf_Rela *rela,
* x86 architectures.
*/
if (GELF_R_TYPE(rela->r_info) != R_386_PC32 &&
GELF_R_TYPE(rela->r_info) != R_386_PLT32)
GELF_R_TYPE(rela->r_info) != R_386_PLT32 &&
GELF_R_TYPE(rela->r_info) != R_386_NONE)
return (-1);
/*
@ -1273,6 +1281,11 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
* We take a first pass through all the relocations to
* populate our string table and count the number of extra
* symbols we'll require.
*
* We also handle the case where the object has already been
* processed, to support incremental rebuilds. Relocations
* of interest are converted to type NONE, but all information
* needed to reconstruct the output DOF is retained.
*/
strtab = dt_strtab_create(1);
nsym = 0;
@ -1280,7 +1293,6 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
istr = data_str->d_size;
for (i = 0; i < shdr_rel.sh_size / shdr_rel.sh_entsize; i++) {
if (shdr_rel.sh_type == SHT_RELA) {
if (gelf_getrela(data_rel, i, &rela) == NULL)
continue;
@ -1345,7 +1357,12 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
objkey, s);
if (dt_strtab_index(strtab, p) == -1) {
nsym++;
/*
* Do not add new symbols if this object file
* has already been processed.
*/
if (GELF_R_TYPE(rela.r_info) != DT_REL_NONE)
nsym++;
(void) dt_strtab_insert(strtab, p);
}
@ -1353,13 +1370,14 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
}
/*
* If any probes were found, allocate the additional space for
* the symbol table and string table, copying the old data into
* the new buffers, and marking the buffers as dirty. We inject
* those newly allocated buffers into the libelf data
* If any new probes were found, allocate the additional space
* for the symbol table and string table, copying the old data
* into the new buffers, and marking the buffers as dirty. We
* inject those newly allocated buffers into the libelf data
* structures, but are still responsible for freeing them once
* we're done with the elf handle.
*/
osym = isym;
if (nsym > 0) {
/*
* The first byte of the string table is reserved for
@ -1411,9 +1429,8 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
shdr_sym.sh_size += nsym * symsize;
(void) gelf_update_shdr(scn_sym, &shdr_sym);
osym = isym;
nsym += isym;
} else {
} else if (dt_strtab_empty(strtab)) {
dt_strtab_destroy(strtab);
continue;
}
@ -1423,7 +1440,6 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
* modifications described above.
*/
for (i = 0; i < shdr_rel.sh_size / shdr_rel.sh_entsize; i++) {
if (shdr_rel.sh_type == SHT_RELA) {
if (gelf_getrela(data_rel, i, &rela) == NULL)
continue;
@ -1490,32 +1506,51 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
bind = GELF_ST_BIND(fsym.st_info) == STB_WEAK ?
STB_WEAK : STB_GLOBAL;
/*
* Emit an alias for the symbol. It needs to be
* non-preemptible so that .SUNW_dof relocations
* may be resolved at static link time. Aliases
* of weak symbols are given a non-unique name
* so that they may be merged by the linker.
*/
dsym = fsym;
dsym.st_name = istr;
dsym.st_info = GELF_ST_INFO(bind, STT_FUNC);
dsym.st_other = GELF_ST_VISIBILITY(STV_HIDDEN);
(void) gelf_update_sym(data_sym, isym, &dsym);
r = (char *) data_str->d_buf + istr;
s = (char *) data_str->d_buf + fsym.st_name;
if (bind == STB_WEAK)
istr += sprintf(r, dt_weaksymfmt,
dt_symprefix, s);
else
istr += sprintf(r, dt_symfmt,
dt_symprefix, objkey, s);
istr++;
isym++;
assert(isym <= nsym);
} else
if (GELF_R_TYPE(rela.r_info) != DT_REL_NONE) {
/*
* Emit an alias for the symbol. It
* needs to be non-preemptible so that
* .SUNW_dof relocations may be resolved
* at static link time. Aliases of weak
* symbols are given a non-unique name
* so that they may be merged by the
* linker.
*/
dsym = fsym;
dsym.st_name = istr;
dsym.st_info = GELF_ST_INFO(bind,
STT_FUNC);
dsym.st_other =
GELF_ST_VISIBILITY(STV_HIDDEN);
(void) gelf_update_sym(data_sym, isym,
&dsym);
isym++;
assert(isym <= nsym);
r = (char *) data_str->d_buf + istr;
if (bind == STB_WEAK) {
istr += sprintf(r,
dt_weaksymfmt, dt_symprefix,
s);
} else {
istr += sprintf(r, dt_symfmt,
dt_symprefix, objkey, s);
}
istr++;
} else {
if (bind == STB_WEAK) {
(void) asprintf(&r,
dt_weaksymfmt, dt_symprefix,
s);
} else {
(void) asprintf(&r, dt_symfmt,
dt_symprefix, objkey, s);
}
}
} else {
goto err;
}
if ((pvp = dt_provider_lookup(dtp, pname)) == NULL) {
return (dt_link_error(dtp, elf, fd, bufs,
@ -1544,24 +1579,18 @@ process_obj(dtrace_hdl_t *dtp, const char *obj, int *eprobesp)
}
/*
* Our linker doesn't understand the SUNW_IGNORE ndx and
* will try to use this relocation when we build the
* final executable. Since we are done processing this
* relocation, mark it as inexistant and let libelf
* remove it from the file.
* If this wasn't done, we would have garbage added to
* the executable file as the symbol is going to be
* change from UND to ABS.
* We are done with this relocation, but it must be
* preserved in order to support incremental rebuilds.
*/
if (shdr_rel.sh_type == SHT_RELA) {
rela.r_offset = 0;
rela.r_info = 0;
rela.r_addend = 0;
rela.r_info =
GELF_R_INFO(GELF_R_SYM(rela.r_info), 0);
(void) gelf_update_rela(data_rel, i, &rela);
} else {
GElf_Rel rel;
rel.r_offset = 0;
rel.r_info = 0;
rel.r_offset = rela.r_offset;
rela.r_info =
GELF_R_INFO(GELF_R_SYM(rela.r_info), 0);
(void) gelf_update_rel(data_rel, i, &rel);
}
@ -1614,19 +1643,6 @@ dtrace_program_link(dtrace_hdl_t *dtp, dtrace_prog_t *pgp, uint_t dflags,
size_t len;
int eprobes = 0, ret = 0;
if (access(file, R_OK) == 0) {
fprintf(stderr, "dtrace: target object (%s) already exists. "
"Please remove the target\ndtrace: object and rebuild all "
"the source objects if you wish to run the DTrace\n"
"dtrace: linking process again\n", file);
/*
* Several build infrastructures run DTrace twice (e.g.
* postgres) and we don't want the build to fail. Return
* 0 here since this isn't really a fatal error.
*/
return (0);
}
/*
* A NULL program indicates a special use in which we just link
* together a bunch of object files specified in objv and then

7
cddl/contrib/opensolaris/lib/libdtrace/common/dt_strtab.c
View File

@ -206,6 +206,13 @@ dt_strtab_copyin(dt_strtab_t *sp, const char *str, size_t len)
return (-1);
}
boolean_t
dt_strtab_empty(dt_strtab_t *sp)
{
/* Always contains "\0". */
return (sp->str_nstrs == 1);
}
ssize_t
dt_strtab_index(dt_strtab_t *sp, const char *str)
{

1
cddl/contrib/opensolaris/lib/libdtrace/common/dt_strtab.h
View File

@ -58,6 +58,7 @@ typedef ssize_t dt_strtab_write_f(const char *, size_t, size_t, void *);
extern dt_strtab_t *dt_strtab_create(size_t);
extern void dt_strtab_destroy(dt_strtab_t *);
extern boolean_t dt_strtab_empty(dt_strtab_t *);
extern ssize_t dt_strtab_index(dt_strtab_t *, const char *);
extern ssize_t dt_strtab_insert(dt_strtab_t *, const char *);
extern size_t dt_strtab_size(const dt_strtab_t *);

4
cddl/usr.sbin/dtrace/tests/tools/exclude.sh
View File

@ -201,10 +201,6 @@ exclude EXFAIL common/usdt/tst.eliminate.ksh
# Generated headers include <sys/sdt.h>, so _DTRACE_VERSION is always defined.
exclude EXFAIL common/usdt/tst.nodtrace.ksh
# The second dtrace -G invocation returns an error with "no probes found," which
# makes sense to me. Not yet sure what the expected behaviour is here.
exclude EXFAIL common/usdt/tst.static2.ksh
# Uses the Solaris-specific ppriv(1).
exclude EXFAIL common/usdt/tst.user.ksh