Commit af8bc682 authored by Nathan Lynch's avatar Nathan Lynch Committed by Michael Ellerman
Browse files

powerpc/rtas: lockdep annotations 



Add lockdep annotations for the following properties that must hold:

* Any error log retrieval must be atomically coupled with the prior
  RTAS call, without a window for another RTAS call to occur before the
  error log can be retrieved.

* All users of the core rtas_args parameter block must hold rtas_lock.

Move the definitions of rtas_lock and rtas_args up in the file so that
__do_enter_rtas_trace() can refer to them.

Signed-off-by: default avatarNathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: default avatarAndrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230220-rtas-queue-for-6-4-v1-6-010e4416f13f@linux.ibm.com
parent 32740fce

arch/powerpc/kernel/rtas.c

+23 −10
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/init.h>

#include <linux/kconfig.h>

#include <linux/kernel.h>

#include <linux/lockdep.h>

#include <linux/memblock.h>

#include <linux/of.h>

#include <linux/of_fdt.h>
@@ -453,6 +454,16 @@ static struct rtas_function rtas_function_table[] __ro_after_init = { 
	},

};



/*

 * Nearly all RTAS calls need to be serialized. All uses of the

 * default rtas_args block must hold rtas_lock.

 *

 * Exceptions to the RTAS serialization requirement (e.g. stop-self)

 * must use a separate rtas_args structure.

 */

static DEFINE_RAW_SPINLOCK(rtas_lock);

static struct rtas_args rtas_args;



/**

 * rtas_function_token() - RTAS function token lookup.

 * @handle: Function handle, e.g. RTAS_FN_EVENT_SCAN.
@@ -560,6 +571,9 @@ static void __do_enter_rtas(struct rtas_args *args) 
static void __do_enter_rtas_trace(struct rtas_args *args)

{

	const char *name = NULL;



	if (args == &rtas_args)

		lockdep_assert_held(&rtas_lock);

	/*

	 * If the tracepoints that consume the function name aren't

	 * active, avoid the lookup.
@@ -619,16 +633,6 @@ static void do_enter_rtas(struct rtas_args *args) 


struct rtas_t rtas;



/*

 * Nearly all RTAS calls need to be serialized. All uses of the

 * default rtas_args block must hold rtas_lock.

 *

 * Exceptions to the RTAS serialization requirement (e.g. stop-self)

 * must use a separate rtas_args structure.

 */

static DEFINE_RAW_SPINLOCK(rtas_lock);

static struct rtas_args rtas_args;



DEFINE_SPINLOCK(rtas_data_buf_lock);

EXPORT_SYMBOL_GPL(rtas_data_buf_lock);
@@ -951,6 +955,8 @@ static char *__fetch_rtas_last_error(char *altbuf) 
	u32 bufsz;

	char *buf = NULL;



	lockdep_assert_held(&rtas_lock);



	if (token == -1)

		return NULL;
@@ -1108,6 +1114,7 @@ static bool token_is_restricted_errinjct(s32 token) 
 */

int rtas_call(int token, int nargs, int nret, int *outputs, ...)

{

	struct pin_cookie cookie;

	va_list list;

	int i;

	unsigned long flags;
@@ -1134,6 +1141,8 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...) 
	}



	raw_spin_lock_irqsave(&rtas_lock, flags);

	cookie = lockdep_pin_lock(&rtas_lock);



	/* We use the global rtas args buffer */

	args = &rtas_args;
@@ -1151,6 +1160,7 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...) 
			outputs[i] = be32_to_cpu(args->rets[i + 1]);

	ret = (nret > 0) ? be32_to_cpu(args->rets[0]) : 0;



	lockdep_unpin_lock(&rtas_lock, cookie);

	raw_spin_unlock_irqrestore(&rtas_lock, flags);



	if (buff_copy) {
@@ -1782,6 +1792,7 @@ static bool block_rtas_call(int token, int nargs, 
/* We assume to be passed big endian arguments */

SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)

{

	struct pin_cookie cookie;

	struct rtas_args args;

	unsigned long flags;

	char *buff_copy, *errbuf = NULL;
@@ -1850,6 +1861,7 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs) 
	buff_copy = get_errorlog_buffer();



	raw_spin_lock_irqsave(&rtas_lock, flags);

	cookie = lockdep_pin_lock(&rtas_lock);



	rtas_args = args;

	do_enter_rtas(&rtas_args);
@@ -1860,6 +1872,7 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs) 
	if (be32_to_cpu(args.rets[0]) == -1)

		errbuf = __fetch_rtas_last_error(buff_copy);



	lockdep_unpin_lock(&rtas_lock, cookie);

	raw_spin_unlock_irqrestore(&rtas_lock, flags);



	if (buff_copy) {