| Message ID | 1354804718-1662-2-git-send-email-nschichan@freebox.fr (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Am 06.12.2012 15:38, schrieb Nicolas Schichan: > The offset must be multiplied by 4 to be sure to access the correct > 32bit word in the stack scratch space. > > For instance, a store at scratch memory cell #1 was generating the > following: > > st r4, [sp, #1] > > While the correct code for this is: > > st r4, [sp, #4] > > To reproduce the bug (assuming your system has a NIC with the mac > address 52:54:00:12:34:56): > > echo 0 > /proc/sys/net/core/bpf_jit_enable > tcpdump -ni eth0 "ether[1] + ether[2] - ether[3] * ether[4] - ether[5] \ > == -0x3AA" # this will capture packets as expected > > echo 1 > /proc/sys/net/core/bpf_jit_enable > tcpdump -ni eth0 "ether[1] + ether[2] - ether[3] * ether[4] - ether[5] \ > == -0x3AA" # this will not. > > This bug was present since the original inclusion of bpf_jit for ARM > (ddecdfce: ARM: 7259/3: net: JIT compiler for packet filters). > > Signed-off-by: Nicolas Schichan <nschichan@freebox.fr> > --- > arch/arm/net/bpf_jit_32.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c > index a64d349..b6f305e 100644 > --- a/arch/arm/net/bpf_jit_32.c > +++ b/arch/arm/net/bpf_jit_32.c > @@ -42,7 +42,7 @@ > #define r_skb_hl ARM_R8 > > #define SCRATCH_SP_OFFSET 0 > -#define SCRATCH_OFF(k) (SCRATCH_SP_OFFSET + (k)) > +#define SCRATCH_OFF(k) (SCRATCH_SP_OFFSET + 4 * (k)) > > #define SEEN_MEM ((1 << BPF_MEMWORDS) - 1) > #define SEEN_MEM_WORD(k) (1 << (k)) Acked-by: Mircea Gherzan <mgherzan@gmail.com>
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index a64d349..b6f305e 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -42,7 +42,7 @@ #define r_skb_hl ARM_R8 #define SCRATCH_SP_OFFSET 0 -#define SCRATCH_OFF(k) (SCRATCH_SP_OFFSET + (k)) +#define SCRATCH_OFF(k) (SCRATCH_SP_OFFSET + 4 * (k)) #define SEEN_MEM ((1 << BPF_MEMWORDS) - 1) #define SEEN_MEM_WORD(k) (1 << (k))
The offset must be multiplied by 4 to be sure to access the correct 32bit word in the stack scratch space. For instance, a store at scratch memory cell #1 was generating the following: st r4, [sp, #1] While the correct code for this is: st r4, [sp, #4] To reproduce the bug (assuming your system has a NIC with the mac address 52:54:00:12:34:56): echo 0 > /proc/sys/net/core/bpf_jit_enable tcpdump -ni eth0 "ether[1] + ether[2] - ether[3] * ether[4] - ether[5] \ == -0x3AA" # this will capture packets as expected echo 1 > /proc/sys/net/core/bpf_jit_enable tcpdump -ni eth0 "ether[1] + ether[2] - ether[3] * ether[4] - ether[5] \ == -0x3AA" # this will not. This bug was present since the original inclusion of bpf_jit for ARM (ddecdfce: ARM: 7259/3: net: JIT compiler for packet filters). Signed-off-by: Nicolas Schichan <nschichan@freebox.fr> --- arch/arm/net/bpf_jit_32.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)