[PATCH] powerpc/uprobes: Implement arch_uretprobe_is_alive()

classic Classic list List threaded Threaded
3 messages Options
Reply | Threaded
Open this post in threaded view
|

[PATCH] powerpc/uprobes: Implement arch_uretprobe_is_alive()

Naveen N. Rao
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&m=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 <[hidden email]>
Reported-by: [hidden email]
Signed-off-by: Naveen N. Rao <[hidden email]>
---
 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

Reply | Threaded
Open this post in threaded view
|

Re: [PATCH] powerpc/uprobes: Implement arch_uretprobe_is_alive()

Srikar Dronamraju
Adding Oleg and Pratyush to the cc.

> 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&m=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 <[hidden email]>
> Reported-by: [hidden email]
> Signed-off-by: Naveen N. Rao <[hidden email]>

Looks good to me.

Acked-by: Srikar Dronamraju <[hidden email]>

Reply | Threaded
Open this post in threaded view
|

Re: powerpc/uprobes: Implement arch_uretprobe_is_alive()

Michael Ellerman-3
In reply to this post by Naveen N. Rao
On Wed, 2017-06-14 at 15:44:00 UTC, "Naveen N. Rao" wrote:

> 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&m=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 <[hidden email]>
> Reported-by: [hidden email]
> Signed-off-by: Naveen N. Rao <[hidden email]>
> Acked-by: Srikar Dronamraju <[hidden email]>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/2dea1d9c38e481051fa0e62807e518

cheers