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Allow multiple FBT probes to share a tracepoint.

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With GNU ifuncs, multiple FBT probes may correspond to the same
instruction.  fbt_invop() assumed that this could not happen and
would return after the first probe found in the global FBT hash
table, which might not be the one that's enabled.  Fix the problem
on x86 by linking probes that share a tracepoint and having each
linked probe fire when the tracepoint is hit.

PR:		230846
Approved by:	re (gjb)
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D16921
This commit is contained in:
Mark Johnston 2018-08-28 20:21:36 +00:00
parent 4ec2e460b5
commit c208cb9923
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=338359
8 changed files with 97 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
sys/cddl/dev/fbt/aarch64/fbt_isa.c
View File

@ -152,7 +152,7 @@ fbt_provide_module_function(linker_file_t lf, int symindx,
fbt->fbtp_id = dtrace_probe_create(fbt_id, modname,
name, FBT_RETURN, 3, fbt);
} else {
retfbt->fbtp_next = fbt;
retfbt->fbtp_probenext = fbt;
fbt->fbtp_id = retfbt->fbtp_id;
}
retfbt = fbt;

2
sys/cddl/dev/fbt/arm/fbt_isa.c
View File

@ -165,7 +165,7 @@ fbt_provide_module_function(linker_file_t lf, int symindx,
fbt->fbtp_id = dtrace_probe_create(fbt_id, modname,
name, FBT_RETURN, 2, fbt);
} else {
retfbt->fbtp_next = fbt;
retfbt->fbtp_probenext = fbt;
fbt->fbtp_id = retfbt->fbtp_id;
}
retfbt = fbt;

92
sys/cddl/dev/fbt/fbt.c
View File

@ -156,7 +156,7 @@ fbt_doubletrap(void)
for (i = 0; i < fbt_probetab_size; i++) {
fbt = fbt_probetab[i];
for (; fbt != NULL; fbt = fbt->fbtp_next)
for (; fbt != NULL; fbt = fbt->fbtp_probenext)
fbt_patch_tracepoint(fbt, fbt->fbtp_savedval);
}
}
@ -204,40 +204,53 @@ fbt_provide_module(void *arg, modctl_t *lf)
(void) linker_file_function_listall(lf, fbt_provide_module_function, modname);
}
static void
fbt_destroy_one(fbt_probe_t *fbt)
{
fbt_probe_t *hash, *hashprev, *next;
int ndx;
ndx = FBT_ADDR2NDX(fbt->fbtp_patchpoint);
for (hash = fbt_probetab[ndx], hashprev = NULL; hash != NULL;
hash = hash->fbtp_hashnext, hashprev = hash) {
if (hash == fbt) {
if ((next = fbt->fbtp_tracenext) != NULL)
next->fbtp_hashnext = hash->fbtp_hashnext;
else
next = hash->fbtp_hashnext;
if (hashprev != NULL)
hashprev->fbtp_hashnext = next;
else
fbt_probetab[ndx] = next;
goto free;
} else if (hash->fbtp_patchpoint == fbt->fbtp_patchpoint) {
for (next = hash; next->fbtp_tracenext != NULL;
next = next->fbtp_tracenext) {
if (fbt == next->fbtp_tracenext) {
next->fbtp_tracenext =
fbt->fbtp_tracenext;
goto free;
}
}
}
}
panic("probe %p not found in hash table", fbt);
free:
free(fbt, M_FBT);
}
static void
fbt_destroy(void *arg, dtrace_id_t id, void *parg)
{
fbt_probe_t *fbt = parg, *next, *hash, *last;
fbt_probe_t *fbt = parg, *next;
modctl_t *ctl;
int ndx;
do {
ctl = fbt->fbtp_ctl;
ctl->fbt_nentries--;
/*
* Now we need to remove this probe from the fbt_probetab.
*/
ndx = FBT_ADDR2NDX(fbt->fbtp_patchpoint);
last = NULL;
hash = fbt_probetab[ndx];
while (hash != fbt) {
ASSERT(hash != NULL);
last = hash;
hash = hash->fbtp_hashnext;
}
if (last != NULL) {
last->fbtp_hashnext = fbt->fbtp_hashnext;
} else {
fbt_probetab[ndx] = fbt->fbtp_hashnext;
}
next = fbt->fbtp_next;
free(fbt, M_FBT);
next = fbt->fbtp_probenext;
fbt_destroy_one(fbt);
fbt = next;
} while (fbt != NULL);
}
@ -265,14 +278,16 @@ fbt_enable(void *arg, dtrace_id_t id, void *parg)
return;
}
for (; fbt != NULL; fbt = fbt->fbtp_next)
for (; fbt != NULL; fbt = fbt->fbtp_probenext) {
fbt_patch_tracepoint(fbt, fbt->fbtp_patchval);
fbt->fbtp_enabled++;
}
}
static void
fbt_disable(void *arg, dtrace_id_t id, void *parg)
{
fbt_probe_t *fbt = parg;
fbt_probe_t *fbt = parg, *hash;
modctl_t *ctl = fbt->fbtp_ctl;
ASSERT(ctl->nenabled > 0);
@ -281,8 +296,21 @@ fbt_disable(void *arg, dtrace_id_t id, void *parg)
if ((ctl->loadcnt != fbt->fbtp_loadcnt))
return;
for (; fbt != NULL; fbt = fbt->fbtp_next)
fbt_patch_tracepoint(fbt, fbt->fbtp_savedval);
for (; fbt != NULL; fbt = fbt->fbtp_probenext) {
fbt->fbtp_enabled--;
for (hash = fbt_probetab[FBT_ADDR2NDX(fbt->fbtp_patchpoint)];
hash != NULL; hash = hash->fbtp_hashnext) {
if (hash->fbtp_patchpoint == fbt->fbtp_patchpoint) {
for (; hash != NULL; hash = hash->fbtp_tracenext)
if (hash->fbtp_enabled > 0)
break;
break;
}
}
if (hash == NULL)
fbt_patch_tracepoint(fbt, fbt->fbtp_savedval);
}
}
static void
@ -296,7 +324,7 @@ fbt_suspend(void *arg, dtrace_id_t id, void *parg)
if ((ctl->loadcnt != fbt->fbtp_loadcnt))
return;
for (; fbt != NULL; fbt = fbt->fbtp_next)
for (; fbt != NULL; fbt = fbt->fbtp_probenext)
fbt_patch_tracepoint(fbt, fbt->fbtp_savedval);
}
@ -311,7 +339,7 @@ fbt_resume(void *arg, dtrace_id_t id, void *parg)
if ((ctl->loadcnt != fbt->fbtp_loadcnt))
return;
for (; fbt != NULL; fbt = fbt->fbtp_next)
for (; fbt != NULL; fbt = fbt->fbtp_probenext)
fbt_patch_tracepoint(fbt, fbt->fbtp_patchval);
}

14
sys/cddl/dev/fbt/fbt.h
View File

@ -34,9 +34,18 @@
#include "fbt_isa.h"
/*
* fbt_probe is a bit of a misnomer. One of these structures is created for
* each trace point of an FBT probe. A probe might have multiple trace points
* (e.g., a function with multiple return instructions), and different probes
* might have a trace point at the same address (e.g., GNU ifuncs).
*/
typedef struct fbt_probe {
struct fbt_probe *fbtp_hashnext;
fbt_patchval_t *fbtp_patchpoint;
struct fbt_probe *fbtp_hashnext; /* global hash table linkage */
struct fbt_probe *fbtp_tracenext; /* next probe for tracepoint */
struct fbt_probe *fbtp_probenext; /* next tracepoint for probe */
int fbtp_enabled;
fbt_patchval_t *fbtp_patchpoint;
int8_t fbtp_rval;
fbt_patchval_t fbtp_patchval;
fbt_patchval_t fbtp_savedval;
@ -46,7 +55,6 @@ typedef struct fbt_probe {
modctl_t *fbtp_ctl;
int fbtp_loadcnt;
int fbtp_symindx;
struct fbt_probe *fbtp_next;
} fbt_probe_t;
struct linker_file;

2
sys/cddl/dev/fbt/mips/fbt_isa.c
View File

@ -142,7 +142,7 @@ fbt_provide_module_function(linker_file_t lf, int symindx,
fbt->fbtp_id = dtrace_probe_create(fbt_id, modname,
name, FBT_RETURN, 3, fbt);
} else {
retfbt->fbtp_next = fbt;
retfbt->fbtp_probenext = fbt;
fbt->fbtp_id = retfbt->fbtp_id;
}
retfbt = fbt;

2
sys/cddl/dev/fbt/powerpc/fbt_isa.c
View File

@ -208,7 +208,7 @@ fbt_provide_module_function(linker_file_t lf, int symindx,
fbt->fbtp_id = dtrace_probe_create(fbt_id, modname,
name, FBT_RETURN, FBT_AFRAMES, fbt);
} else {
retfbt->fbtp_next = fbt;
retfbt->fbtp_probenext = fbt;
fbt->fbtp_id = retfbt->fbtp_id;
}

2
sys/cddl/dev/fbt/riscv/fbt_isa.c
View File

@ -141,7 +141,7 @@ fbt_provide_module_function(linker_file_t lf, int symindx,
fbt->fbtp_id = dtrace_probe_create(fbt_id, modname,
name, FBT_RETURN, 3, fbt);
} else {
retfbt->fbtp_next = fbt;
retfbt->fbtp_probenext = fbt;
fbt->fbtp_id = retfbt->fbtp_id;
}
retfbt = fbt;

28
sys/cddl/dev/fbt/x86/fbt_isa.c
View File

@ -67,6 +67,7 @@ fbt_invop(uintptr_t addr, struct trapframe *frame, uintptr_t rval)
uintptr_t *stack;
uintptr_t arg0, arg1, arg2, arg3, arg4;
fbt_probe_t *fbt;
int8_t fbtrval;
#ifdef __amd64__
stack = (uintptr_t *)frame->tf_rsp;
@ -78,7 +79,11 @@ fbt_invop(uintptr_t addr, struct trapframe *frame, uintptr_t rval)
cpu = &solaris_cpu[curcpu];
fbt = fbt_probetab[FBT_ADDR2NDX(addr)];
for (; fbt != NULL; fbt = fbt->fbtp_hashnext) {
if ((uintptr_t)fbt->fbtp_patchpoint == addr) {
if ((uintptr_t)fbt->fbtp_patchpoint != addr)
continue;
fbtrval = fbt->fbtp_rval;
for (; fbt != NULL; fbt = fbt->fbtp_tracenext) {
ASSERT(fbt->fbtp_rval == fbtrval);
if (fbt->fbtp_roffset == 0) {
#ifdef __amd64__
/* fbt->fbtp_rval == DTRACE_INVOP_PUSHQ_RBP */
@ -135,9 +140,8 @@ fbt_invop(uintptr_t addr, struct trapframe *frame, uintptr_t rval)
rval, 0, 0, 0);
cpu->cpu_dtrace_caller = 0;
}
return (fbt->fbtp_rval);
}
return (fbtrval);
}
return (0);
@ -162,7 +166,7 @@ fbt_provide_module_function(linker_file_t lf, int symindx,
{
char *modname = opaque;
const char *name = symval->name;
fbt_probe_t *fbt, *retfbt;
fbt_probe_t *fbt, *hash, *retfbt;
int j;
int size;
uint8_t *instr, *limit;
@ -224,8 +228,18 @@ fbt_provide_module_function(linker_file_t lf, int symindx,
fbt->fbtp_patchval = FBT_PATCHVAL;
fbt->fbtp_symindx = symindx;
fbt->fbtp_hashnext = fbt_probetab[FBT_ADDR2NDX(instr)];
fbt_probetab[FBT_ADDR2NDX(instr)] = fbt;
for (hash = fbt_probetab[FBT_ADDR2NDX(instr)]; hash != NULL;
hash = hash->fbtp_hashnext) {
if (hash->fbtp_patchpoint == fbt->fbtp_patchpoint) {
fbt->fbtp_tracenext = hash->fbtp_tracenext;
hash->fbtp_tracenext = fbt;
break;
}
}
if (hash == NULL) {
fbt->fbtp_hashnext = fbt_probetab[FBT_ADDR2NDX(instr)];
fbt_probetab[FBT_ADDR2NDX(instr)] = fbt;
}
lf->fbt_nentries++;
@ -301,7 +315,7 @@ fbt_provide_module_function(linker_file_t lf, int symindx,
fbt->fbtp_id = dtrace_probe_create(fbt_id, modname,
name, FBT_RETURN, 3, fbt);
} else {
retfbt->fbtp_next = fbt;
retfbt->fbtp_probenext = fbt;
fbt->fbtp_id = retfbt->fbtp_id;
}