This helper is used to detect if a uprobe'd function has returned
through a setjmp/longjmp, rather than branching to the LR that was
updated previously by us. This fixes a SIGSEGV that gets generated when
programs use setjmp/longjmp with uretprobes.
We use the arm64 model (arch/arm64/kernel/probes/uprobes.c:
arch_uretprobe_is_alive()) for detecting when stack frames have been
removed from under us.
Reference:
https://marc.info/?l=linux-kernel=143748610330073
commit 7b868e4802a86 ("uprobes/x86: Reimplement arch_uretprobe_is_alive()")
commit db087ef69a2b1 ("uprobes/x86: Make arch_uretprobe_is_alive(RP_CHECK_CALL)
more
clever")
Tested with the test program from:
https://sourceware.org/git/gitweb.cgi?p=systemtap.git;a=blob;f=testsuite/systemtap.base/bz5274.c;hb=HEAD
And this script:
$ cat test.sh
#!/bin/bash
perf probe -x ./bz5274 -a bz5274_main_return=main%return
perf probe -x ./bz5274 -a bz5274_funca_return=funca%return
perf probe -x ./bz5274 -a bz5274_funcb_return=funcb%return
perf probe -x ./bz5274 -a bz5274_funcc_return=funcc%return
perf probe -x ./bz5274 -a bz5274_funcd_return=funcd%return
perf record -e 'probe_bz5274:*' -aR ./bz5274
Reported-by: Gustavo Luiz Duarte
Reported-by: z...@redhat.com
Signed-off-by: Naveen N. Rao
---
arch/powerpc/kernel/uprobes.c | 9 +
1 file changed, 9 insertions(+)
diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c
index 003b20964ea0..5d105b8eeece 100644
--- a/arch/powerpc/kernel/uprobes.c
+++ b/arch/powerpc/kernel/uprobes.c
@@ -205,3 +205,12 @@ arch_uretprobe_hijack_return_addr(unsigned long
trampoline_vaddr, struct pt_regs
return orig_ret_vaddr;
}
+
+bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
+ struct pt_regs *regs)
+{
+ if (ctx == RP_CHECK_CHAIN_CALL)
+ return regs->gpr[1] <= ret->stack;
+ else
+ return regs->gpr[1] < ret->stack;
+}
--
2.12.2
