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    SubjectRe: [PATCH 0/6] Don't use BIT() macro in UAPI headers
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    On 20/05/21 12:43, Joe Richey wrote:
    > From: Joe Richey <joerichey@google.com>
    >
    > The BIT(n) macro is used in the kernel as an alias for (1 << n).
    > However, it is not defined in the UAPI headers, which means that any
    > UAPI header files must be careful not to use it, or else the user
    > will get a linker error. For example, compiling the following program:
    >
    > #include <sys/auxv.h>
    > #include <asm/hwcap2.h>
    >
    > // Detect if FSGSBASE instructions are enabled
    > int main() {
    > unsigned long val = getauxval(AT_HWCAP2);
    > return !(val & HWCAP2_FSGSBASE);
    > }
    >
    > Results in the following likner error:
    >
    > /usr/bin/ld: /tmp/cceFpAdR.o: in function `main':
    > gs.c:(.text+0x21): undefined reference to `BIT'
    >
    > This patch series changes all UAPI uses of BIT() to just be open-coded.
    > However, there really should be a check for this in checkpatch.pl
    > Currently, the script actually _encourages_ users to use the BIT macro
    > even if adding things to UAPI.
    >
    > Running `rg "BIT\(" **/uapi/**` shows no more usage of BIT() in any
    > UAPI headers. Tested by building a basic kernel. Changes are trivial.
    >
    > Joe Richey (6):
    > x86/elf: Don't use BIT() macro in UAPI headers
    > KVM: X86: Don't use BIT() macro in UAPI headers
    > drivers: firmware: psci: Don't use BIT() macro in UAPI headers
    > uacce: Don't use BIT() macro in UAPI headers
    > media: vicodec: Don't use BIT() macro in UAPI headers
    > tools headers UAPI: Sync pkt_sched.h with the kernel sources
    >
    > arch/x86/include/uapi/asm/hwcap2.h | 2 +-
    > include/uapi/linux/kvm.h | 4 +-
    > include/uapi/linux/psci.h | 2 +-
    > include/uapi/linux/v4l2-controls.h | 22 ++---
    > include/uapi/misc/uacce/uacce.h | 2 +-
    > tools/include/uapi/linux/kvm.h | 4 +-
    > tools/include/uapi/linux/pkt_sched.h | 122 ++++++++++++++++++++++++---
    > 7 files changed, 130 insertions(+), 28 deletions(-)
    >

    Will queue the KVM one, thanks!

    Paolo

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