Philippe Mathieu-Daudé <[email protected]> writes:
> On 23/9/25 11:09, Markus Armbruster wrote:
>> tcg_region_init() calls one of qemu_mprotect_rwx(),
>> qemu_mprotect_rw(), and mprotect(), then reports failure with
>> error_setg_errno(&error_fatal, errno, ...).
>>
>> The use of &error_fatal is undesirable. qapi/error.h advises:
>>
>> * Please don't error_setg(&error_fatal, ...), use error_report() and
>> * exit(), because that's more obvious.
>>
>> The use of errno is wrong. qemu_mprotect_rwx() and qemu_mprotect_rw()
>> wrap around qemu_mprotect__osdep(). qemu_mprotect__osdep() calls
>> mprotect() on POSIX, VirtualProtect() on Windows, and reports failure
>> with error_report(). VirtualProtect() doesn't set errno. mprotect()
>> does, but error_report() may clobber it.
>>
>> Fix tcg_region_init() to report errors only when it calls mprotect(),
>> and rely on qemu_mprotect_rwx()'s and qemu_mprotect_rw()'s error
>> reporting otherwise. Use error_report(), not error_setg().
>>
>> Fixes: 22c6a9938f75 (tcg: Merge buffer protection and guard page protection)
>> Fixes: 6bc144237a85 (tcg: Use Error with alloc_code_gen_buffer)
>> Cc: Richard Henderson <[email protected]>
>> Signed-off-by: Markus Armbruster <[email protected]>
>> Reviewed-by: Daniel P. Berrangé <[email protected]>
>> Reviewed-by: Richard Henderson <[email protected]>
>> ---
>> tcg/region.c | 7 +++++--
>> 1 file changed, 5 insertions(+), 2 deletions(-)
>> diff --git a/tcg/region.c b/tcg/region.c
>> index 7ea0b37a84..2181267e48 100644
>> --- a/tcg/region.c
>> +++ b/tcg/region.c
>> @@ -832,13 +832,16 @@ void tcg_region_init(size_t tb_size, int splitwx,
>> unsigned max_threads)
>> } else {
>> #ifdef CONFIG_POSIX
>> rc = mprotect(start, end - start, need_prot);
>> + if (rc) {
>> + error_report("mprotect of jit buffer: %s",
>> + strerror(errno));
>
> I'm not keen on handling errors differently in the same function.
>
> qemu_mprotect_rwx() and qemu_mprotect_rw() already print the error.
Yes: they call qemu_mprotect__osdep(), which uses error_report().
> Why not add qemu_mprotect() as a simple qemu_mprotect__osdep() alias,
> then call it here, also covering the non-POSIX case?
> (Question for Richard, after looking at commits 22c6a9938f7 and more
> importantly 97a83753c9 -- wondering about WoA).
There is no commit 97a83753c9. Do you mean a97a83753c9?
I'd like to merge this commit as is. It's a minimal fix, and it's been
reviewed. We can always improve on top.
>> + }
>> #else
>> g_assert_not_reached();
>> #endif
>> }
>> if (rc) {
>> - error_setg_errno(&error_fatal, errno,
>> - "mprotect of jit buffer");
>> + exit(1);
>> }
>> }
>> if (have_prot != 0) {
