arm64: define the KASAN_SHADOW_SCALE_SHIFT macro #2518
Conversation
viktormalik
requested review from
ajor,
danobi,
fbs and
BurntBrunch
as code owners
viktormalik
force-pushed
the
aarch-kasan-fix
branch
from
67cd416
to
eef400b
Compare
|
It seems like kconfig values are stored in BTF: https://github.com/libbpf/libbpf/blob/b5e9722ec268702b2ec62863222277148e4fe656/src/libbpf.c#L3773-L3798 Is it possible for us to get it from BTF instead? I think it'll be more likely to be the source of truth, as reading from |
| config.emplace(option.substr(0, split), option.substr(split + 1)); | ||
| } | ||
| } | ||
| gzclose(file); |
There was a problem hiding this comment.
Should there be a break after this? If both locations are available, probably best not to duplicate effort.
There was a problem hiding this comment.
Yes, of course, thanks.
| return; | ||
| config_locs = { | ||
| "/boot/config-" + std::string(utsname.release), | ||
| "/proc/config.gz", |
There was a problem hiding this comment.
Maybe order procfs option first. The /boot/.. configs can suffer from skew when installing new kernels.
I may be missing something, but IIUC, this is a libbpf CO-RE feature when it can pass values of kernel configs to a BPF program via external symbols. The values are loaded from kconfig files upon program load in the same way as I used here. |
viktormalik
force-pushed
the
aarch-kasan-fix
branch
from
eef400b
to
d865e96
Compare
Oh, ha. I did not dig that far. Please ignore me :) |
| TEST(utils, parse_kconfig) | ||
| { | ||
| char path[] = "/tmp/configXXXXXX"; | ||
| int fd = mkstemp(path); |
There was a problem hiding this comment.
Might be nice to unlink this after use
There was a problem hiding this comment.
Done and resolved the changelog conflict.
viktormalik
force-pushed
the
aarch-kasan-fix
branch
from
d865e96
to
718b891
Compare
In future, it may (and will) be useful to have access to the running kernel configuration, e.g. to add config-specific compilation options to ClangParser. This adds and fills a new map BPFtrace::kconfig that maps config options to their values. Both the option name and the value are strings. The configuration is parsed from one of two sources: - /proc/config.gz - /boot/config-$(uname -r) For testing purposes, the config filename may be passed through the BPFTRACE_KCONFIG_TEST env variable.
arm64 defines this macro from Makefile instead of defining it in a
header file as is the case for other architectures. Since we're not
running make, we need to define the macro manually via CFLAGS.
The value definition is taken from kernel's arch/arm64/Makefile and it
depends on the running kernel configuration.
This fixes the runqlat.bt tcpdrop.bt, and undump.bt tools on
aarch64+debug kernel which previously failed with:
# /usr/share/bpftrace/tools/runqlat.bt
[...]/source/arch/arm64/include/asm/memory.h:300:9: error: use of undeclared identifier 'KASAN_SHADOW_SCALE_SHIFT'
[...]
viktormalik
force-pushed
the
aarch-kasan-fix
branch
from
718b891
to
5cac578
Compare
arm64 defines the
KASAN_SHADOW_SCALE_SHIFTmacro from Makefile instead of defining it in a header file as is the case for other architectures. This causes ClangParser not to find it and fail on arm64 systems withCONFIG_KASAN=y.This resolves the issue by defining the macro manually via CFLAGS. The definition is taken from kernel's
arch/arm64/Makefileand it depends on the running kernel configuration. Therefore, the first commit adds support for parsing the kernel config.This fixes the
runqlat.bt,tcpdrop.bt, andundump.bttools onaarch64+debugkernel which previously failed with:Checklist
man/adoc/bpftrace.adocand if needed indocs/reference_guide.mdCHANGELOG.md