Re: [PATCH 02/12] tcg: Fix error reporting on mprotect() failure in tcg_region_init()

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Aug 08, 2025 at 10:08:13AM +0200, 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 <richard.henderson@linaro.org>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>  tcg/region.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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