JakeHillion/drgn
1
0
Fork 0
mirror of https://github.com/JakeHillion/drgn.git synced 2024-12-22 17:23:06 +00:00
Code Issues Packages Projects Releases Wiki Activity

libdrgn: add an environment variable to disable use of /proc/modules and /sys/module

Browse Source 
We use /proc/modules and /sys/module to find loaded kernel modules for
the running kernel instead of walking the module list in the core dump
as an optimization. To make it easier to test the core dump path, add an
environment variable to disable the optimization.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
This commit is contained in:
Omar Sandoval 2020-10-13 11:24:39 -07:00
parent 661a5c56c3
commit 2b325b9262
2 changed files with 26 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
docs/advanced_usage.rst
View File

@ -95,3 +95,9 @@ Some of drgn's behavior can be modified through environment variables:
``DRGN_USE_LIBKDUMPFILE_FOR_ELF``
Whether drgn should use libkdumpfile for ELF vmcores (0 or 1). The default
is 0. This functionality will be removed in the future.
``DRGN_USE_PROC_AND_SYS_MODULES``
Whether drgn should use ``/proc/modules`` and ``/sys/module`` to find
loaded kernel modules for the running kernel instead of getting them from
the core dump (0 or 1). The default is 1. This environment variable is
mainly intended for testing and may be ignored in the future.

28
libdrgn/linux_kernel.c
View File

@ -429,12 +429,12 @@ static void kernel_module_iterator_deinit(struct kernel_module_iterator *it)
static struct drgn_error *
kernel_module_iterator_init(struct kernel_module_iterator *it,
struct drgn_program *prog)
struct drgn_program *prog, bool use_proc_and_sys)
{
struct drgn_error *err;
it->name = NULL;
if (prog->flags & DRGN_PROGRAM_IS_LIVE) {
if (use_proc_and_sys) {
it->modules_file = fopen("/proc/modules", "r");
if (!it->modules_file) {
return drgn_error_create_os("fopen", errno,
@ -1236,13 +1236,14 @@ report_default_kernel_module(struct drgn_debug_info_load_state *load,
static struct drgn_error *
report_loaded_kernel_modules(struct drgn_debug_info_load_state *load,
struct kernel_module_table *kmod_table,
struct depmod_index *depmod)
struct depmod_index *depmod,
bool use_proc_and_sys)
{
struct drgn_program *prog = load->dbinfo->prog;
struct drgn_error *err;
struct kernel_module_iterator kmod_it;
err = kernel_module_iterator_init(&kmod_it, prog);
err = kernel_module_iterator_init(&kmod_it, prog, use_proc_and_sys);
if (err) {
kernel_module_iterator_error:
return drgn_debug_info_report_error(load, "kernel modules",
@ -1313,14 +1314,24 @@ report_kernel_modules(struct drgn_debug_info_load_state *load,
return NULL;
/*
* If we're not debugging the running kernel, then we need to index
* vmlinux now so that we can walk the list of modules in the kernel.
* If we're debugging the running kernel, we can get the loaded kernel
* modules from /proc and /sys instead of from the core dump. This fast
* path can be disabled via an environment variable for testing.
*/
bool use_proc_and_sys = false;
if (prog->flags & DRGN_PROGRAM_IS_LIVE) {
char *env = getenv("DRGN_USE_PROC_AND_SYS_MODULES");
use_proc_and_sys = !env || atoi(env);
}
/*
* If we're not using /proc and /sys, then we need to index vmlinux now
* so that we can walk the list of modules in the kernel.
*
* If we need the definition of struct module to get the name of any
* kernel modules, then we also need to index vmlinux now.
*/
if (vmlinux_is_pending &&
(!(prog->flags & DRGN_PROGRAM_IS_LIVE) || need_module_definition)) {
(!use_proc_and_sys || need_module_definition)) {
err = drgn_debug_info_report_flush(load);
if (err)
return err;
@ -1393,7 +1404,8 @@ report_kernel_modules(struct drgn_debug_info_load_state *load,
err = report_loaded_kernel_modules(load,
num_kmods ? &kmod_table : NULL,
load->load_default ? &depmod : NULL);
load->load_default ? &depmod : NULL,
use_proc_and_sys);
if (err)
goto out;