[PATCH v2 7/9] lib/vsprintf: Replace space with '_' before crng is ready

Andy Shevchenko
2018-02-16T21:07:53Z

From: Shunyong Yang <shunyong.yang@hxt-semitech.com>

Before crng is ready, output of "%p" composes of "(ptrval)" and
left padding spaces for alignment as no random address can be
generated. This seems a little strange when default string width
is larger than strlen("(ptrval)").

For example, when irq domain names are built with "%p", the nodes
under /sys/kernel/debug/irq/domains like this on AArch64 system,

[root@y irq]# ls domains/
default irqchip@ (ptrval)-2
irqchip@ (ptrval)-4 \_SB_.TCS0.QIC1 \_SB_.TCS0.QIC3
irqchip@ (ptrval) irqchip@ (ptrval)-3
\_SB_.TCS0.QIC0 \_SB_.TCS0.QIC2

The name "irqchip@ (ptrval)-2" is not so readable in console
output.

This patch replaces space with readable "_" when output needs padding.
Following is the output after applying the patch,

[root@y domains]# ls
default irqchip@(____ptrval____)-2
irqchip@(____ptrval____)-4 \_SB_.TCS0.QIC1 \_SB_.TCS0.QIC3
irqchip@(____ptrval____) irqchip@(____ptrval____)-3 \_SB_.TCS0.QIC0
\_SB_.TCS0.QIC2

There is same problem in some subsystem's dmesg output. Moreover,
someone may call "%p" in a similar case. In addition, the timing of
crng initialization done may vary on different system. So, the change
is made in vsprintf.c.

Cc: Joey Zheng <yu.zheng@hxt-semitech.com>
Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Shunyong Yang <shunyong.yang@hxt-semitech.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
lib/vsprintf.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 9004bbb3d84d..97be2d07297a 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1681,12 +1681,13 @@ early_initcall(initialize_ptr_random);
/* Maps a pointer to a 32 bit unique identifier. */
static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec spec)
{
+ const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
unsigned long hashval;

if (unlikely(!have_filled_random_ptr_key)) {
spec.field_width = 2 * sizeof(ptr);
/* string length must be less than default_width */
- return string(buf, end, "(ptrval)", spec);
+ return string(buf, end, str, spec);
}

#ifdef CONFIG_64BIT
--
2.15.1