Ziyang Zhang <[email protected]> writes:
> The syscall return value passed back through the syscall filter
> callback is semantically signed: negative values encode errno codes.
> Declaring the sysret pointer as uint64_t * is therefore misleading and
> forces callers to launder the value through an unsigned temporary.
>
> Change the sysret pointer to int64_t * across the public plugin API
> typedef (qemu_plugin_vcpu_syscall_filter_cb_t), the internal
> qemu_plugin_vcpu_syscall_filter() prototypes and stub, its
> implementation in plugins/core.c, the linux-user caller, and the
> in-tree example plugins.
>
> Signed-off-by: Ziyang Zhang <[email protected]>
> ---
> include/plugins/qemu-plugin.h | 2 +-
> include/qemu/plugin.h | 4 ++--
> linux-user/syscall.c | 2 +-
> plugins/core.c | 2 +-
> tests/tcg/plugins/setpc.c | 2 +-
> tests/tcg/plugins/syscall.c | 2 +-
> 6 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/include/plugins/qemu-plugin.h b/include/plugins/qemu-plugin.h
> index 4eb1d2cd85..8eb10b1f48 100644
> --- a/include/plugins/qemu-plugin.h
> +++ b/include/plugins/qemu-plugin.h
> @@ -870,7 +870,7 @@ typedef bool
> int64_t num, uint64_t a1, uint64_t
> a2,
> uint64_t a3, uint64_t a4, uint64_t
> a5,
> uint64_t a6, uint64_t a7, uint64_t
> a8,
> - uint64_t *sysret);
> + int64_t *sysret);
>
> /**
> * typedef qemu_plugin_vcpu_syscall_ret_cb_t - vCPU syscall return callback
> diff --git a/include/qemu/plugin.h b/include/qemu/plugin.h
> index ddd77bd82c..1ce4b281c1 100644
> --- a/include/qemu/plugin.h
> +++ b/include/qemu/plugin.h
> @@ -174,7 +174,7 @@ bool
> qemu_plugin_vcpu_syscall_filter(CPUState *cpu, int64_t num, uint64_t a1,
> uint64_t a2, uint64_t a3, uint64_t a4,
> uint64_t a5, uint64_t a6, uint64_t a7,
> - uint64_t a8, uint64_t *sysret);
> + uint64_t a8, int64_t *sysret);
>
> void qemu_plugin_vcpu_mem_cb(CPUState *cpu, uint64_t vaddr,
> uint64_t value_low,
> @@ -290,7 +290,7 @@ static inline bool
> qemu_plugin_vcpu_syscall_filter(CPUState *cpu, int64_t num, uint64_t a1,
> uint64_t a2, uint64_t a3, uint64_t a4,
> uint64_t a5, uint64_t a6, uint64_t a7,
> - uint64_t a8, uint64_t *sysret)
> + uint64_t a8, int64_t *sysret)
> {
> return false;
> }
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index f4b74ad350..63c0a5f8f3 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -14378,7 +14378,7 @@ static bool send_through_syscall_filters(CPUState
> *cpu, int num,
> abi_long arg7, abi_long arg8,
> abi_long *sysret)
> {
> - uint64_t sysret64 = 0;
> + int64_t sysret64 = 0;
> bool filtered = qemu_plugin_vcpu_syscall_filter(cpu, num, arg1, arg2,
> arg3, arg4, arg5, arg6,
> arg7, arg8,
> &sysret64);
All of the arguments here are abi_long which go to int32_t or
target_long->int64_t so perhaps we should be using that for all args to
ensure signedness is correct?
> diff --git a/plugins/core.c b/plugins/core.c
> index 2324bbffa3..58f293462a 100644
> --- a/plugins/core.c
> +++ b/plugins/core.c
> @@ -596,7 +596,7 @@ bool
> qemu_plugin_vcpu_syscall_filter(CPUState *cpu, int64_t num, uint64_t a1,
> uint64_t a2, uint64_t a3, uint64_t a4,
> uint64_t a5, uint64_t a6, uint64_t a7,
> - uint64_t a8, uint64_t *sysret)
> + uint64_t a8, int64_t *sysret)
> {
> struct qemu_plugin_cb *cb, *next;
> enum qemu_plugin_event ev = QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER;
> diff --git a/tests/tcg/plugins/setpc.c b/tests/tcg/plugins/setpc.c
> index 8f2d025e24..23862eaaf0 100644
> --- a/tests/tcg/plugins/setpc.c
> +++ b/tests/tcg/plugins/setpc.c
> @@ -27,7 +27,7 @@ static bool vcpu_syscall_filter(qemu_plugin_id_t id,
> unsigned int vcpu_index,
> int64_t num, uint64_t a1, uint64_t a2,
> uint64_t a3, uint64_t a4, uint64_t a5,
> uint64_t a6, uint64_t a7, uint64_t a8,
> - uint64_t *sysret)
> + int64_t *sysret)
> {
> if (num == MAGIC_SYSCALL) {
> if (a1 == SETPC) {
> diff --git a/tests/tcg/plugins/syscall.c b/tests/tcg/plugins/syscall.c
> index 5658f83087..76d52b98aa 100644
> --- a/tests/tcg/plugins/syscall.c
> +++ b/tests/tcg/plugins/syscall.c
> @@ -174,7 +174,7 @@ static bool vcpu_syscall_filter(qemu_plugin_id_t id,
> unsigned int vcpu_index,
> int64_t num, uint64_t a1, uint64_t a2,
> uint64_t a3, uint64_t a4, uint64_t a5,
> uint64_t a6, uint64_t a7, uint64_t a8,
> - uint64_t *sysret)
> + int64_t *sysret)
> {
> /* Special syscall to test the filter functionality. */
> if (num == 4096 && a1 == 0x66CCFF) {
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
