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A single fix for objtool to generate proper unwind info for newer

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toolchains which do not generate section symbols anymore. And a cleanup
 ontop.
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Merge tag 'x86_entry_for_v5.11_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fix from Borislav Petkov:
 "A single fix for objtool to generate proper unwind info for newer
  toolchains which do not generate section symbols anymore. And a
  cleanup ontop.

  This was originally going to go during the next merge window but
  people can already trigger a build error with binutils-2.36 which
  doesn't emit section symbols - something which objtool relies on - so
  let's expedite it"

* tag 'x86_entry_for_v5.11_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/entry: Remove put_ret_addr_in_rdi THUNK macro argument
  x86/entry: Emit a symbol for register restoring thunk
This commit is contained in:
Linus Torvalds 2021-01-31 11:48:12 -08:00
commit f5a376edde
3 changed files with 15 additions and 10 deletions
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5
Documentation/asm-annotations.rst
View File

@ -100,6 +100,11 @@ Instruction Macros
~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~
This section covers ``SYM_FUNC_*`` and ``SYM_CODE_*`` enumerated above. This section covers ``SYM_FUNC_*`` and ``SYM_CODE_*`` enumerated above.
``objtool`` requires that all code must be contained in an ELF symbol. Symbol
names that have a ``.L`` prefix do not emit symbol table entries. ``.L``
prefixed symbols can be used within a code region, but should be avoided for
denoting a range of code via ``SYM_*_START/END`` annotations.
* ``SYM_FUNC_START`` and ``SYM_FUNC_START_LOCAL`` are supposed to be **the * ``SYM_FUNC_START`` and ``SYM_FUNC_START_LOCAL`` are supposed to be **the
most frequent markings**. They are used for functions with standard calling most frequent markings**. They are used for functions with standard calling
conventions -- global and local. Like in C, they both align the functions to conventions -- global and local. Like in C, they both align the functions to

15
arch/x86/entry/thunk_64.S
View File

@ -10,7 +10,7 @@
#include <asm/export.h> #include <asm/export.h>
/* rdi: arg1 ... normal C conventions. rax is saved/restored. */ /* rdi: arg1 ... normal C conventions. rax is saved/restored. */
.macro THUNK name, func, put_ret_addr_in_rdi=0 .macro THUNK name, func
SYM_FUNC_START_NOALIGN(\name) SYM_FUNC_START_NOALIGN(\name)
pushq %rbp pushq %rbp
movq %rsp, %rbp movq %rsp, %rbp
@ -25,13 +25,8 @@ SYM_FUNC_START_NOALIGN(\name)
pushq %r10 pushq %r10
pushq %r11 pushq %r11
.if \put_ret_addr_in_rdi
/* 8(%rbp) is return addr on stack */
movq 8(%rbp), %rdi
.endif
call \func call \func
jmp .L_restore jmp __thunk_restore
SYM_FUNC_END(\name) SYM_FUNC_END(\name)
_ASM_NOKPROBE(\name) _ASM_NOKPROBE(\name)
.endm .endm
@ -44,7 +39,7 @@ SYM_FUNC_END(\name)
#endif #endif
#ifdef CONFIG_PREEMPTION #ifdef CONFIG_PREEMPTION
SYM_CODE_START_LOCAL_NOALIGN(.L_restore) SYM_CODE_START_LOCAL_NOALIGN(__thunk_restore)
popq %r11 popq %r11
popq %r10 popq %r10
popq %r9 popq %r9
@ -56,6 +51,6 @@ SYM_CODE_START_LOCAL_NOALIGN(.L_restore)
popq %rdi popq %rdi
popq %rbp popq %rbp
ret ret
_ASM_NOKPROBE(.L_restore) _ASM_NOKPROBE(__thunk_restore)
SYM_CODE_END(.L_restore) SYM_CODE_END(__thunk_restore)
#endif #endif

5
include/linux/linkage.h
View File

@ -178,6 +178,11 @@
* Objtool generates debug info for both FUNC & CODE, but needs special * Objtool generates debug info for both FUNC & CODE, but needs special
* annotations for each CODE's start (to describe the actual stack frame). * annotations for each CODE's start (to describe the actual stack frame).
* *
* Objtool requires that all code must be contained in an ELF symbol. Symbol
* names that have a .L prefix do not emit symbol table entries. .L
* prefixed symbols can be used within a code region, but should be avoided for
* denoting a range of code via ``SYM_*_START/END`` annotations.
*
* ALIAS -- does not generate debug info -- the aliased function will * ALIAS -- does not generate debug info -- the aliased function will
*/ */