Hi Juergen,
thank you for the patches.
On 2023/03/13 22:01, Juergen Gross wrote:
> Since many years now the stack address of each percpu stack is
> available via the stack_base[] array now. Use that instead of the
> indirect method via the percpu variables tss_init or tss_page,
> especially as the layout of tss_page has changed in Xen 4.16,
> resulting in the stack no longer to be found.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
> xen_hyper.c | 50 ++++++++++++++++++++++++++++++--------------------
> 1 file changed, 30 insertions(+), 20 deletions(-)
>
> diff --git a/xen_hyper.c b/xen_hyper.c
> index 1030c0a..72720e2 100644
> --- a/xen_hyper.c
> +++ b/xen_hyper.c
> @@ -324,7 +324,7 @@ void
> xen_hyper_x86_pcpu_init(void)
> {
> ulong cpu_info;
> - ulong init_tss_base, init_tss;
> + ulong init_tss_base, init_tss, stack_base;
> ulong sp;
> struct xen_hyper_pcpu_context *pcc;
> char *buf, *bp;
> @@ -340,34 +340,44 @@ xen_hyper_x86_pcpu_init(void)
> }
> /* get physical cpu context */
> xen_hyper_alloc_pcpu_context_space(XEN_HYPER_MAX_CPUS());
> - if (symbol_exists("per_cpu__init_tss")) {
> + if (symbol_exists("stack_base")) {
> + stack_base = symbol_value("stack_base");
> + flag = 0;
> + } else if (symbol_exists("per_cpu__init_tss")) {
> init_tss_base = symbol_value("per_cpu__init_tss");
> - flag = TRUE;
> + flag = 1;
> } else if (symbol_exists("per_cpu__tss_page")) {
> init_tss_base = symbol_value("per_cpu__tss_page");
> - flag = TRUE;
> + flag = 1;
> } else {
> init_tss_base = symbol_value("init_tss");
> - flag = FALSE;
> + flag = 2;
> }
> buf = GETBUF(XEN_HYPER_SIZE(tss));
> for_cpu_indexes(i, cpuid)
> {
> - if (flag)
> - init_tss = xen_hyper_per_cpu(init_tss_base, cpuid);
> - else
> - init_tss = init_tss_base +
> - XEN_HYPER_SIZE(tss) * cpuid;
> - if (!readmem(init_tss, KVADDR, buf,
> - XEN_HYPER_SIZE(tss), "init_tss", RETURN_ON_ERROR)) {
> - error(FATAL, "cannot read init_tss.\n");
> - }
> - if (machine_type("X86")) {
> - sp = ULONG(buf + XEN_HYPER_OFFSET(tss_esp0));
> - } else if (machine_type("X86_64")) {
> - sp = ULONG(buf + XEN_HYPER_OFFSET(tss_rsp0));
> - } else
> - sp = 0;
> + if (flag) {
> + if (flag == 1)
> + init_tss = xen_hyper_per_cpu(init_tss_base, cpuid);
> + else
> + init_tss = init_tss_base +
> + XEN_HYPER_SIZE(tss) * cpuid;
> + if (!readmem(init_tss, KVADDR, buf,
> + XEN_HYPER_SIZE(tss), "init_tss", RETURN_ON_ERROR)) {
> + error(FATAL, "cannot read init_tss.\n");
> + }
> + if (machine_type("X86")) {
> + sp = ULONG(buf + XEN_HYPER_OFFSET(tss_esp0));
> + } else if (machine_type("X86_64")) {
> + sp = ULONG(buf + XEN_HYPER_OFFSET(tss_rsp0));
> + } else
> + sp = 0;
> + } else {
> + if (!readmem(stack_base + sizeof(ulong) * cpuid, KVADDR, &sp,
> + sizeof(ulong), "stack_base", RETURN_ON_ERROR)) {
> + error(FATAL, "cannot read stack_base.\n");
> + }
> + }
> cpu_info = XEN_HYPER_GET_CPU_INFO(sp);
> if (CRASHDEBUG(1)) {
> fprintf(fp, "sp=%lx, cpu_info=%lx\n", sp, cpu_info);
The following warning is emitted with the patch:
$ make clean ; make warn
...
cc -c -g -DX86_64 -DLZO -DSNAPPY -DZSTD -DGDB_10_2 xen_hyper.c -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector -Wformat-security
xen_hyper.c: In function ‘xen_hyper_x86_pcpu_init’:
xen_hyper.c:390:3: warning: ‘init_tss’ may be used uninitialized in this function [-Wmaybe-uninitialized]
xen_hyper_store_pcpu_context_tss(pcc, init_tss, buf);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Assuming we have init_tss = 0 first, the buf also may be used as it is
(filled by zero), then xen_hyper_store_pcpu_context_tss() looks
meaningless. What about not calling it?
if (init_tss)
xen_hyper_store_pcpu_context_tss(pcc, init_tss, buf);
Thanks,
Kazu
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