Re: [Qemu-devel] [PULL 18/76] optionrom: add new PVH option rom

[Paolo Bonzini]

It's likely that the compiler will online it. But indeed it's better to add -minline-all-stringops to the compiler command line.

Paolo

Il ven 19 mar 2021, 18:35 Stefano Garzarella <sgarzare@redhat.com> ha scritto:

On Fri, Mar 19, 2021 at 06:03:59PM +0100, Paolo Bonzini wrote:
>On 19/03/21 15:06, Philippe Mathieu-Daudé wrote:
>>>+
>>>+/* Search RSDP signature. */
>>>+static uintptr_t search_rsdp(uint32_t start_addr, uint32_t end_addr)
>>>+{
>>>+    uint64_t *rsdp_p;
>>>+
>>>+    /* RSDP signature is always on a 16 byte boundary */
>>>+    for (rsdp_p = (uint64_t *)start_addr; rsdp_p < (uint64_t *)end_addr;
>>>+         rsdp_p += 2) {
>>>+        if (*rsdp_p == RSDP_SIGNATURE) {
>>>+            return (uintptr_t)rsdp_p;
>>>+        }
>>>+    }
>>>+
>>>+    return 0;
>>>+}
>>gcc 10.2.1 "cc (Alpine 10.2.1_pre2) 10.2.1 20210313" reports:
>>
>>pc-bios/optionrom/pvh_main.c: In function 'search_rsdp':
>>pc-bios/optionrom/pvh_main.c:61:21: warning: comparison is always false
>>due to limited range of data type [-Wtype-limits]
>>    61 |         if (*rsdp_p == RSDP_SIGNATURE) {
>>       |                     ^~
>
>This is probably a different bug, but I'll also add that uint64_t is
>supposed to be aligned to 64 bits, so you need either
>__attribute__((packed)), or use char* and memcmp.  If you go for the
>latter, it would fix the issue that Philippe is reporting.

Yes, memcmp maybe is also more readable, but being baremetal, I have to
implement it right?

Thanks,
Stefano