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    Subject[PATCH 4.15 161/163] media: r820t: fix r820t_write_reg for KASAN
    Date
    4.15-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Arnd Bergmann <arnd@arndb.de>

    commit 16c3ada89cff9a8c2a0eea34ffa1aa20af3f6008 upstream.

    With CONFIG_KASAN, we get an overly long stack frame due to inlining
    the register access functions:

    drivers/media/tuners/r820t.c: In function 'generic_set_freq.isra.7':
    drivers/media/tuners/r820t.c:1334:1: error: the frame size of 2880 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]

    This is caused by a gcc bug that has now been fixed in gcc-8.
    To work around the problem, we can pass the register data
    through a local variable that older gcc versions can optimize
    out as well.

    Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715

    Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/media/tuners/r820t.c | 13 ++++++++-----
    1 file changed, 8 insertions(+), 5 deletions(-)

    --- a/drivers/media/tuners/r820t.c
    +++ b/drivers/media/tuners/r820t.c
    @@ -396,9 +396,11 @@ static int r820t_write(struct r820t_priv
    return 0;
    }

    -static int r820t_write_reg(struct r820t_priv *priv, u8 reg, u8 val)
    +static inline int r820t_write_reg(struct r820t_priv *priv, u8 reg, u8 val)
    {
    - return r820t_write(priv, reg, &val, 1);
    + u8 tmp = val; /* work around GCC PR81715 with asan-stack=1 */
    +
    + return r820t_write(priv, reg, &tmp, 1);
    }

    static int r820t_read_cache_reg(struct r820t_priv *priv, int reg)
    @@ -411,17 +413,18 @@ static int r820t_read_cache_reg(struct r
    return -EINVAL;
    }

    -static int r820t_write_reg_mask(struct r820t_priv *priv, u8 reg, u8 val,
    +static inline int r820t_write_reg_mask(struct r820t_priv *priv, u8 reg, u8 val,
    u8 bit_mask)
    {
    + u8 tmp = val;
    int rc = r820t_read_cache_reg(priv, reg);

    if (rc < 0)
    return rc;

    - val = (rc & ~bit_mask) | (val & bit_mask);
    + tmp = (rc & ~bit_mask) | (tmp & bit_mask);

    - return r820t_write(priv, reg, &val, 1);
    + return r820t_write(priv, reg, &tmp, 1);
    }

    static int r820t_read(struct r820t_priv *priv, u8 reg, u8 *val, int len)

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