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drgn/libdrgn/linux_kernel_helpers.c
Omar Sandoval 761da83ddd libdrgn: add {min,max}_iconst() and rewrite min() and max() 
min() and max() from the Linux kernel go through the trouble of
resulting in a constant expression if the arguments are constant
expressions, but they can't be used outside of a function due to their
use of ({ }). This means that they can't be used for, e.g., enumerators
or global arrays. Let's simplify min() and max() and instead add
explicit min_iconst() and max_iconst() macros that can be used
everywhere that an integer constant expression is required. We can then
use it in hash_table.h. While we're here, let's split these into their
own header file and document them better.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2020-10-10 23:48:03 -07:00

513 lines
14 KiB
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// Copyright (c) Facebook, Inc. and its affiliates.
// SPDX-License-Identifier: GPL-3.0+
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include "drgn.h"
#include "minmax.h"
#include "platform.h"
#include "program.h"
struct drgn_error *linux_helper_read_vm(struct drgn_program *prog,
uint64_t pgtable, uint64_t virt_addr,
void *buf, size_t count)
{
struct drgn_error *err;
struct pgtable_iterator *it;
pgtable_iterator_next_fn *next;
uint64_t read_addr = 0;
size_t read_size = 0;
if (!(prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL)) {
return drgn_error_create(DRGN_ERROR_INVALID_ARGUMENT,
"virtual address translation is only available for the Linux kernel");
}
if (!prog->has_platform) {
return drgn_error_create(DRGN_ERROR_INVALID_ARGUMENT,
"cannot do virtual address translation without platform");
}
if (!prog->platform.arch->linux_kernel_pgtable_iterator_next) {
return drgn_error_format(DRGN_ERROR_INVALID_ARGUMENT,
"virtual address translation is not implemented for %s architecture",
prog->platform.arch->name);
}
if (!count)
return NULL;
if (prog->pgtable_it_in_use) {
return drgn_error_create_fault("recursive address translation; "
"page table may be missing from core dump",
virt_addr);
}
if (prog->pgtable_it) {
it = prog->pgtable_it;
} else {
it = malloc(sizeof(*it) +
prog->platform.arch->pgtable_iterator_arch_size);
if (!it)
return &drgn_enomem;
prog->pgtable_it = it;
it->prog = prog;
}
it->pgtable = pgtable;
it->virt_addr = virt_addr;
prog->pgtable_it_in_use = true;
prog->platform.arch->pgtable_iterator_arch_init(it->arch);
next = prog->platform.arch->linux_kernel_pgtable_iterator_next;
do {
uint64_t virt_addr, start_virt_addr, end_virt_addr;
uint64_t start_phys_addr, end_phys_addr;
size_t n;
virt_addr = it->virt_addr;
err = next(it, &start_virt_addr, &start_phys_addr);
if (err)
break;
if (start_phys_addr == UINT64_MAX) {
err = drgn_error_create_fault("address is not mapped",
virt_addr);
break;
}
end_virt_addr = it->virt_addr;
end_phys_addr = start_phys_addr + (end_virt_addr - start_virt_addr);
n = min(end_virt_addr - virt_addr, (uint64_t)count);
if (read_size && end_phys_addr == read_addr + read_size) {
read_size += n;
} else {
if (read_size) {
err = drgn_program_read_memory(prog, buf,
read_addr,
read_size, true);
if (err)
break;
buf = (char *)buf + read_size;
}
read_addr = start_phys_addr + (virt_addr - start_virt_addr);
read_size = n;
}
count -= n;
} while (count);
if (!err) {
err = drgn_program_read_memory(prog, buf, read_addr, read_size,
true);
}
prog->pgtable_it_in_use = false;
return err;
}
struct drgn_error *
linux_helper_radix_tree_lookup(struct drgn_object *res,
const struct drgn_object *root, uint64_t index)
{
struct drgn_error *err;
static const uint64_t RADIX_TREE_ENTRY_MASK = 3;
uint64_t RADIX_TREE_INTERNAL_NODE;
uint64_t RADIX_TREE_MAP_MASK;
struct drgn_object node, tmp;
struct drgn_member_info member;
struct drgn_qualified_type node_type;
drgn_object_init(&node, drgn_object_program(res));
drgn_object_init(&tmp, drgn_object_program(res));
/* node = root->xa_head */
err = drgn_object_member_dereference(&node, root, "xa_head");
if (!err) {
err = drgn_program_find_type(drgn_object_program(res),
"struct xa_node *", NULL,
&node_type);
if (err)
goto out;
RADIX_TREE_INTERNAL_NODE = 2;
} else if (err->code == DRGN_ERROR_LOOKUP) {
drgn_error_destroy(err);
/* node = (void *)root.rnode */
err = drgn_object_member_dereference(&node, root, "rnode");
if (err)
goto out;
err = drgn_program_find_type(drgn_object_program(res), "void *",
NULL, &node_type);
if (err)
goto out;
err = drgn_object_cast(&node, node_type, &node);
if (err)
goto out;
err = drgn_program_find_type(drgn_object_program(res),
"struct radix_tree_node *", NULL,
&node_type);
if (err)
goto out;
RADIX_TREE_INTERNAL_NODE = 1;
} else {
goto out;
}
err = drgn_program_member_info(drgn_object_program(res),
drgn_type_type(node_type.type).type,
"slots", &member);
if (err)
goto out;
if (drgn_type_kind(member.qualified_type.type) != DRGN_TYPE_ARRAY) {
err = drgn_error_create(DRGN_ERROR_TYPE,
"struct radix_tree_node slots member is not an array");
goto out;
}
RADIX_TREE_MAP_MASK = drgn_type_length(member.qualified_type.type) - 1;
for (;;) {
uint64_t value;
union drgn_value shift;
uint64_t offset;
err = drgn_object_read(&node, &node);
if (err)
goto out;
err = drgn_object_read_unsigned(&node, &value);
if (err)
goto out;
if ((value & RADIX_TREE_ENTRY_MASK) != RADIX_TREE_INTERNAL_NODE)
break;
err = drgn_object_set_unsigned(&node, node_type,
value & ~RADIX_TREE_INTERNAL_NODE,
0);
if (err)
goto out;
err = drgn_object_member_dereference(&tmp, &node, "shift");
if (err)
goto out;
err = drgn_object_read_integer(&tmp, &shift);
if (err)
goto out;
if (shift.uvalue >= 64)
offset = 0;
else
offset = (index >> shift.uvalue) & RADIX_TREE_MAP_MASK;
err = drgn_object_member_dereference(&tmp, &node, "slots");
if (err)
goto out;
err = drgn_object_subscript(&node, &tmp, offset);
if (err)
goto out;
}
err = drgn_object_copy(res, &node);
out:
drgn_object_deinit(&tmp);
drgn_object_deinit(&node);
return err;
}
struct drgn_error *linux_helper_idr_find(struct drgn_object *res,
const struct drgn_object *idr,
uint64_t id)
{
struct drgn_error *err;
struct drgn_object tmp;
drgn_object_init(&tmp, drgn_object_program(res));
/* id -= idr->idr_base */
err = drgn_object_member_dereference(&tmp, idr, "idr_base");
if (!err) {
union drgn_value idr_base;
err = drgn_object_read_integer(&tmp, &idr_base);
if (err)
goto out;
id -= idr_base.uvalue;
} else if (err->code == DRGN_ERROR_LOOKUP) {
/* idr_base was added in v4.16. */
drgn_error_destroy(err);
} else {
goto out;
}
/* radix_tree_lookup(&idr->idr_rt, id) */
err = drgn_object_member_dereference(&tmp, idr, "idr_rt");
if (err)
goto out;
err = drgn_object_address_of(&tmp, &tmp);
if (err)
goto out;
err = linux_helper_radix_tree_lookup(res, &tmp, id);
out:
drgn_object_deinit(&tmp);
return err;
}
/*
* Before Linux kernel commit 95846ecf9dac ("pid: replace pid bitmap
* implementation with IDR API") (in v4.15), (struct pid_namespace).idr does not
* exist, so we have to search pid_hash. We could implement pid_hashfn() and
* only search that bucket, but it's different for 32-bit and 64-bit systems,
* and it has changed at least once, in v4.7. Searching the whole hash table is
* slower but foolproof.
*/
static struct drgn_error *
find_pid_in_pid_hash(struct drgn_object *res, const struct drgn_object *ns,
const struct drgn_object *pid_hash, uint64_t pid)
{
struct drgn_error *err;
struct drgn_qualified_type pidp_type, upid_type;
struct drgn_member_info pid_chain_member, nr_member, ns_member;
struct drgn_object node, tmp;
uint64_t ns_addr;
union drgn_value ns_level, pidhash_shift;
uint64_t i;
err = drgn_program_find_type(drgn_object_program(res), "struct pid *",
NULL, &pidp_type);
if (err)
return err;
err = drgn_program_find_type(drgn_object_program(res), "struct upid",
NULL, &upid_type);
if (err)
return err;
err = drgn_program_member_info(drgn_object_program(res), upid_type.type,
"pid_chain", &pid_chain_member);
if (err)
return err;
err = drgn_program_member_info(drgn_object_program(res), upid_type.type,
"nr", &nr_member);
if (err)
return err;
err = drgn_program_member_info(drgn_object_program(res), upid_type.type,
"ns", &ns_member);
if (err)
return err;
drgn_object_init(&node, drgn_object_program(res));
drgn_object_init(&tmp, drgn_object_program(res));
err = drgn_object_read(&tmp, ns);
if (err)
goto out;
err = drgn_object_read_unsigned(&tmp, &ns_addr);
if (err)
goto out;
err = drgn_object_member_dereference(&tmp, &tmp, "level");
if (err)
goto out;
err = drgn_object_read_integer(&tmp, &ns_level);
if (err)
goto out;
/* i = 1 << pidhash_shift */
err = drgn_program_find_object(drgn_object_program(res),
"pidhash_shift", NULL,
DRGN_FIND_OBJECT_ANY, &tmp);
if (err)
goto out;
err = drgn_object_read_integer(&tmp, &pidhash_shift);
if (err)
goto out;
if (pidhash_shift.uvalue >= 64)
i = 0;
else
i = UINT64_C(1) << pidhash_shift.uvalue;
while (i--) {
/* for (node = pid_hash[i].first; node; node = node->next) */
err = drgn_object_subscript(&node, pid_hash, i);
if (err)
goto out;
err = drgn_object_member(&node, &node, "first");
if (err)
goto out;
for (;;) {
uint64_t addr, tmp_addr;
union drgn_value node_nr;
uint64_t node_ns;
char member[64];
err = drgn_object_read(&node, &node);
if (err)
goto out;
err = drgn_object_read_unsigned(&node, &addr);
if (err)
goto out;
if (!addr)
break;
addr -= pid_chain_member.bit_offset / 8;
/* tmp = container_of(node, struct upid, pid_chain)->nr */
tmp_addr = addr + nr_member.bit_offset / 8;
err = drgn_object_set_reference(&tmp, nr_member.qualified_type,
tmp_addr, 0, 0,
DRGN_PROGRAM_ENDIAN);
if (err)
goto out;
err = drgn_object_read_integer(&tmp, &node_nr);
if (err)
goto out;
if (node_nr.uvalue != pid)
goto next;
/* tmp = container_of(node, struct upid, pid_chain)->ns */
tmp_addr = addr + ns_member.bit_offset / 8;
err = drgn_object_set_reference(&tmp, ns_member.qualified_type,
tmp_addr, 0, 0,
DRGN_PROGRAM_ENDIAN);
if (err)
goto out;
err = drgn_object_read_unsigned(&tmp, &node_ns);
if (err)
goto out;
if (node_ns != ns_addr)
goto next;
sprintf(member, "numbers[%" PRIu64 "].pid_chain",
ns_level.uvalue);
err = drgn_object_container_of(res, &node,
drgn_type_type(pidp_type.type),
member);
goto out;
next:
err = drgn_object_member_dereference(&node, &node, "next");
if (err)
goto out;
}
}
err = drgn_object_set_unsigned(res, pidp_type, 0, 0);
out:
drgn_object_deinit(&tmp);
drgn_object_deinit(&node);
return err;
}
struct drgn_error *linux_helper_find_pid(struct drgn_object *res,
const struct drgn_object *ns,
uint64_t pid)
{
struct drgn_error *err;
struct drgn_object tmp;
drgn_object_init(&tmp, drgn_object_program(res));
/* (struct pid *)idr_find(&ns->idr, pid) */
err = drgn_object_member_dereference(&tmp, ns, "idr");
if (!err) {
struct drgn_qualified_type qualified_type;
err = drgn_object_address_of(&tmp, &tmp);
if (err)
goto out;
err = linux_helper_idr_find(&tmp, &tmp, pid);
if (err)
goto out;
err = drgn_program_find_type(drgn_object_program(res),
"struct pid *", NULL,
&qualified_type);
if (err)
goto out;
err = drgn_object_cast(res, qualified_type, &tmp);
} else if (err->code == DRGN_ERROR_LOOKUP) {
drgn_error_destroy(err);
err = drgn_program_find_object(drgn_object_program(res),
"pid_hash", NULL,
DRGN_FIND_OBJECT_ANY, &tmp);
if (err)
goto out;
err = find_pid_in_pid_hash(res, ns, &tmp, pid);
}
out:
drgn_object_deinit(&tmp);
return err;
}
struct drgn_error *linux_helper_pid_task(struct drgn_object *res,
const struct drgn_object *pid,
uint64_t pid_type)
{
struct drgn_error *err;
struct drgn_qualified_type task_structp_type;
struct drgn_qualified_type task_struct_type;
bool truthy;
struct drgn_object first;
char member[64];
drgn_object_init(&first, drgn_object_program(res));
err = drgn_program_find_type(drgn_object_program(res),
"struct task_struct *", NULL,
&task_structp_type);
if (err)
goto out;
task_struct_type = drgn_type_type(task_structp_type.type);
err = drgn_object_bool(pid, &truthy);
if (!truthy)
goto null;
/* first = &pid->tasks[pid_type].first */
err = drgn_object_member_dereference(&first, pid, "tasks");
if (err)
goto out;
err = drgn_object_subscript(&first, &first, pid_type);
if (err)
goto out;
err = drgn_object_member(&first, &first, "first");
if (err)
goto out;
err = drgn_object_bool(&first, &truthy);
if (err)
goto out;
if (!truthy)
goto null;
/* container_of(first, struct task_struct, pid_links[pid_type]) */
sprintf(member, "pid_links[%" PRIu64 "]", pid_type);
err = drgn_object_container_of(res, &first, task_struct_type, member);
if (err && err->code == DRGN_ERROR_LOOKUP) {
drgn_error_destroy(err);
/* container_of(first, struct task_struct, pids[pid_type].node) */
sprintf(member, "pids[%" PRIu64 "].node", pid_type);
err = drgn_object_container_of(res, &first, task_struct_type,
member);
}
out:
drgn_object_deinit(&first);
return err;
null:
err = drgn_object_set_unsigned(res, task_structp_type, 0, 0);
goto out;
}
struct drgn_error *linux_helper_find_task(struct drgn_object *res,
const struct drgn_object *ns,
uint64_t pid)
{
struct drgn_error *err;
struct drgn_object pid_obj;
struct drgn_object pid_type_obj;
union drgn_value pid_type;
drgn_object_init(&pid_obj, drgn_object_program(res));
drgn_object_init(&pid_type_obj, drgn_object_program(res));
err = linux_helper_find_pid(&pid_obj, ns, pid);
if (err)
goto out;
err = drgn_program_find_object(drgn_object_program(res), "PIDTYPE_PID",
NULL, DRGN_FIND_OBJECT_CONSTANT,
&pid_type_obj);
if (err)
goto out;
err = drgn_object_read_integer(&pid_type_obj, &pid_type);
if (err)
goto out;
err = linux_helper_pid_task(res, &pid_obj, pid_type.uvalue);
out:
drgn_object_deinit(&pid_type_obj);
drgn_object_deinit(&pid_obj);
return err;
}
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