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authorWang YanQing <udknight@gmail.com>2018-01-24 15:48:26 +0800
committerDaniel Borkmann <daniel@iogearbox.net>2018-01-24 16:43:11 +0100
commite9dcd80b9d77a92bfae6ce42a451f5c5fd318832 (patch)
tree1d3e153507734dfd36e70028b631583a175c1db8
parentMerge branch 'bpf-samples-sockmap-improvements' (diff)
downloadlinux-dev-e9dcd80b9d77a92bfae6ce42a451f5c5fd318832.tar.xz
linux-dev-e9dcd80b9d77a92bfae6ce42a451f5c5fd318832.zip
bpf, doc: Correct one wrong value in "Register value tracking"
If we then OR this with 0x40, then the value of 6th bit (0th is first bit) become known, so the right mask is 0xbf instead of 0xcf. Signed-off-by: Wang YanQing <udknight@gmail.com> Acked-by: Edward Cree <ecree@solarflare.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
-rw-r--r--Documentation/networking/filter.txt2
1 files changed, 1 insertions, 1 deletions
diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt
index 87814859cfc2..a4508ec1816b 100644
--- a/Documentation/networking/filter.txt
+++ b/Documentation/networking/filter.txt
@@ -1134,7 +1134,7 @@ The verifier's knowledge about the variable offset consists of:
mask and value; no bit should ever be 1 in both. For example, if a byte is read
into a register from memory, the register's top 56 bits are known zero, while
the low 8 are unknown - which is represented as the tnum (0x0; 0xff). If we
-then OR this with 0x40, we get (0x40; 0xcf), then if we add 1 we get (0x0;
+then OR this with 0x40, we get (0x40; 0xbf), then if we add 1 we get (0x0;
0x1ff), because of potential carries.
Besides arithmetic, the register state can also be updated by conditional
branches. For instance, if a SCALAR_VALUE is compared > 8, in the 'true' branch