On 12/05/20 11:44, Thomas Huth wrote:
> When compiling umip.c with -O2 instead of -O1, there are currently
> two problems. First, the compiler complains:
>
> x86/umip.c: In function ‘do_ring3’:
> x86/umip.c:162:37: error: array subscript 4096 is above array bounds of
> ‘unsigned char[4096]’ [-Werror=array-bounds]
> [user_stack_top]"m"(user_stack[sizeof user_stack]),
> ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
>
> This can be fixed by initializing the stack to point to one of the last
> bytes of the array instead.
>
> The second problem is that some tests are failing - and this is due
> to the fact that the GP_ASM macro uses inline asm without the "volatile"
> keyword - so that the compiler reorders this code in certain cases
> where it should not. Fix it by adding "volatile" here.
>
> Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
> ---
> v3: Use "sizeof(long)" instead of "2"
>
> x86/umip.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/x86/umip.c b/x86/umip.c
> index 7eee294..37f1ab8 100644
> --- a/x86/umip.c
> +++ b/x86/umip.c
> @@ -22,7 +22,8 @@ static void gp_handler(struct ex_regs *regs)
>
>
> #define GP_ASM(stmt, in, clobber) \
> - asm ("mov" W " $1f, %[expected_rip]\n\t" \
> + asm volatile ( \
> + "mov" W " $1f, %[expected_rip]\n\t" \
> "movl $2f-1f, %[skip_count]\n\t" \
> "1: " stmt "\n\t" \
> "2: " \
> @@ -159,7 +160,8 @@ static int do_ring3(void (*fn)(const char *), const char *arg)
> : [ret] "=&a" (ret)
> : [user_ds] "i" (USER_DS),
> [user_cs] "i" (USER_CS),
> - [user_stack_top]"m"(user_stack[sizeof user_stack]),
> + [user_stack_top]"m"(user_stack[sizeof(user_stack) -
> + sizeof(long)]),
> [fn]"r"(fn),
> [arg]"D"(arg),
> [kernel_ds]"i"(KERNEL_DS),
>
Pushed, thanks.
Paolo
