On Thu, Sep 05, 2024 at 07:03:34PM +0200, Jason A. Donenfeld wrote:
> On Thu, Sep 05, 2024 at 06:55:27PM +0200, Christophe Leroy wrote:
> >
> >
> > Le 05/09/2024 à 18:13, Jason A. Donenfeld a écrit :
> > >> +/*
> > >> + * The macro sets two stack frames, one for the caller and one for the callee
> > >> + * because there are no requirement for the caller to set a stack frame when
> > >> + * calling VDSO so it may have omitted to set one, especially on PPC64
> > >> + */
> > >> +
> > >> +.macro cvdso_call funct
> > >> + .cfi_startproc
> > >> + PPC_STLU r1, -PPC_MIN_STKFRM(r1)
> > >> + .cfi_adjust_cfa_offset PPC_MIN_STKFRM
> > >> + mflr r0
> > >> + PPC_STLU r1, -PPC_MIN_STKFRM(r1)
> > >> + .cfi_adjust_cfa_offset PPC_MIN_STKFRM
> > >> + PPC_STL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
> > >> + .cfi_rel_offset lr, PPC_MIN_STKFRM + PPC_LR_STKOFF
> > >> + get_datapage r8
> > >> + addi r8, r8, VDSO_RNG_DATA_OFFSET
> > >> + bl CFUNC(DOTSYM(\funct))
> > >> + PPC_LL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
> > >> + cmpwi r3, 0
> > >> + mtlr r0
> > >> + addi r1, r1, 2 * PPC_MIN_STKFRM
> > >> + .cfi_restore lr
> > >> + .cfi_def_cfa_offset 0
> > >> + crclr so
> > >> + bgelr+
> > >> + crset so
> > >> + neg r3, r3
> > >> + blr
> > >> + .cfi_endproc
> > >> +.endm
> > >
> > > You wrote in an earlier email that this worked with time namespaces, but
> > > in my testing that doesn't seem to be the case.
> >
> > Did I write that ? I can't remember and neither can I remember testing
> > it with time namespaces.
>
> It's possible I confused you with someone else? Hum. Anyway...
>
> > > From my test harness [1]:
> > >
> > > Normal single thread
> > > vdso: 25000000 times in 12.494133131 seconds
> > > libc: 25000000 times in 69.594625188 seconds
> > > syscall: 25000000 times in 67.349243972 seconds
> > > Time namespace single thread
> > > vdso: 25000000 times in 71.673057436 seconds
> > > libc: 25000000 times in 71.712774121 seconds
> > > syscall: 25000000 times in 66.902318080 seconds
> > >
> > > I'm seeing this on ppc, ppc64, and ppc64le.
> >
> > What is the command to use to test with time namespace ?
>
> Look at the C in the commit I linked.
The below also seems to work well for testing on x86. I'll clean that up
and send a patch to the list.
diff --git a/tools/testing/selftests/vDSO/vdso_test_getrandom.c b/tools/testing/selftests/vDSO/vdso_test_getrandom.c
index 8866b65a4605..4df80f769aa7 100644
--- a/tools/testing/selftests/vDSO/vdso_test_getrandom.c
+++ b/tools/testing/selftests/vDSO/vdso_test_getrandom.c
@@ -16,8 +16,11 @@
#include <sys/mman.h>
#include <sys/random.h>
#include <sys/syscall.h>
+#include <sys/ptrace.h>
+#include <sys/wait.h>
#include <sys/types.h>
#include <linux/random.h>
+#include <linux/ptrace.h>
#include "../kselftest.h"
#include "parse_vdso.h"
@@ -239,9 +242,10 @@ static void fill(void)
static void kselftest(void)
{
uint8_t weird_size[1263];
+ pid_t child;
ksft_print_header();
- ksft_set_plan(1);
+ ksft_set_plan(2);
for (size_t i = 0; i < 1000; ++i) {
ssize_t ret = vgetrandom(weird_size, sizeof(weird_size), 0);
@@ -250,6 +254,39 @@ static void kselftest(void)
}
ksft_test_result_pass("getrandom: PASS\n");
+
+ assert(unshare(CLONE_NEWTIME) == 0);
+ child = fork();
+ assert(child >= 0);
+
+ if (!child) {
+ vgetrandom_init();
+ child = getpid();
+ assert(ptrace(PTRACE_TRACEME, 0, NULL, NULL) == 0);
+ assert(kill(child, SIGSTOP) == 0);
+ assert(vgetrandom(weird_size, sizeof(weird_size), 0) == sizeof(weird_size));
+ _exit(0);
+ }
+ for (;;) {
+ struct ptrace_syscall_info info = { 0 };
+ int status, ret;
+ assert(waitpid(child, &status, 0) >= 0);
+ if (WIFEXITED(status))
+ break;
+ assert(WIFSTOPPED(status));
+ if (WSTOPSIG(status) == SIGSTOP)
+ assert(ptrace(PTRACE_SETOPTIONS, child, 0, PTRACE_O_TRACESYSGOOD) == 0);
+ else if (WSTOPSIG(status) == SIGTRAP | 0x80) {
+ assert(ptrace(PTRACE_GET_SYSCALL_INFO, child, sizeof(info), &info) > 0);
+ if (info.entry.nr == __NR_getrandom &&
+ ((void *)info.entry.args[0] == &weird_size && info.entry.args[1] == sizeof(weird_size)))
+ exit(KSFT_FAIL);
+ }
+ assert(ptrace(PTRACE_SYSCALL, child, 0, 0) == 0);
+ }
+
+ ksft_test_result_pass("getrandom timens: PASS\n");
+
exit(KSFT_PASS);
}
