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e39828d2c1
The "P" asm operand modifier is a x86 target-specific modifier. When used for a constant, it drops all syntax-specific prefixes and issues the bare constant. This modifier is not correct for address handling, in this case a generic "a" operand modifier should be used. The "a" asm operand modifier substitutes a memory reference, with the actual operand treated as address. For x86_64, when a symbol is provided, the "a" modifier emits "sym(%rip)" instead of "sym", enabling shorter %rip-relative addressing. Clang allows only "i" and "r" operand constraints with an "a" modifier, so the patch normalizes the modifier/constraint pair to "a"/"i" which is consistent between both compilers. The patch reduces code size of a test build by 4072 bytes: text data bss dec hex filename 25523268 4388300 808452 30720020 1d4c014 vmlinux-old.o 25519196 4388300 808452 30715948 1d4b02c vmlinux-new.o [ mingo: Changelog clarity. ] Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Uros Bizjak <ubizjak@gmail.com> Cc: Sean Christopherson <seanjc@google.com> Link: https://lore.kernel.org/r/20231016200755.287403-1-ubizjak@gmail.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.