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.
Message-Id: <20200122160944.29750-1-thuth@xxxxxxxxxx>
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
---
x86/umip.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/x86/umip.c b/x86/umip.c
index afb373d..c5700b3 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),
--
2.18.1
