diff options
author | Nicholas Piggin <npiggin@gmail.com> | 2016-09-28 11:31:48 +1000 |
---|---|---|
committer | Michael Ellerman <mpe@ellerman.id.au> | 2016-10-04 13:06:56 +1100 |
commit | 57f266497d81e16141bd2c9009e91dad34ea5f70 (patch) | |
tree | cfe7f69e2945f26758dcb6a81c1a40b4ecfb73e9 /arch/powerpc/kernel/vmlinux.lds.S | |
parent | 573819e3433278cde17e7b93e101e59e96f19ccf (diff) | |
download | linux-57f266497d81e16141bd2c9009e91dad34ea5f70.tar.bz2 |
powerpc: Use gas sections for arranging exception vectors
Use assembler sections of fixed size and location to arrange the 64-bit
Book3S exception vector code (64-bit Book3E also uses it in head_64.S
for 0x0..0x100).
This allows better flexibility in arranging exception code and hiding
unimportant details behind macros.
Gas sections can be a bit painful to use this way, mainly because the
assembler does not know where they will be finally linked. Taking
absolute addresses requires a bit of trickery for example, but it can
be hidden behind macros for the most part.
Generated code is mostly the same except locations, offsets, alignments.
The "+ 0x2" is only required for the trap number / kvm exit number,
which gets loaded as a constant into a register.
Previously, code also used + 0x2 for label names, but we changed to
using "H" to distinguish HV case for that. Remove the last vestiges
of that.
__after_prom_start is taking absolute address of a label in another
fixed section. Newer toolchains seemed to compile this okay, but older
ones do not. FIXED_SYMBOL_ABS_ADDR is more foolproof, it just takes an
additional line to define.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel/vmlinux.lds.S')
-rw-r--r-- | arch/powerpc/kernel/vmlinux.lds.S | 53 |
1 files changed, 50 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S index b59d75e194a5..2d1cfafd1404 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -44,11 +44,58 @@ SECTIONS * Text, read only data and other permanent read-only sections */ - /* Text and gots */ + _text = .; + _stext = .; + + /* + * Head text. + * This needs to be in its own output section to avoid ld placing + * branch trampoline stubs randomly throughout the fixed sections, + * which it will do (even if the branch comes from another section) + * in order to optimize stub generation. + */ + .head.text : AT(ADDR(.head.text) - LOAD_OFFSET) { +#ifdef CONFIG_PPC64 + KEEP(*(.head.text.first_256B)); +#ifdef CONFIG_PPC_BOOK3E +# define END_FIXED 0x100 +#else + KEEP(*(.head.text.real_vectors)); + *(.head.text.real_trampolines); + KEEP(*(.head.text.virt_vectors)); + *(.head.text.virt_trampolines); +# if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_PPC_POWERNV) + KEEP(*(.head.data.fwnmi_page)); +# define END_FIXED 0x8000 +# else +# define END_FIXED 0x7000 +# endif +#endif + ASSERT((. == END_FIXED), "vmlinux.lds.S: fixed section overflow error"); +#else /* !CONFIG_PPC64 */ + HEAD_TEXT +#endif + } :kernel + + /* + * If the build dies here, it's likely code in head_64.S is referencing + * labels it can't reach, and the linker inserting stubs without the + * assembler's knowledge. To debug, remove the above assert and + * rebuild. Look for branch stubs in the fixed section region. + * + * Linker stub generation could be allowed in "trampoline" + * sections if absolutely necessary, but this would require + * some rework of the fixed sections. Before resorting to this, + * consider references that have sufficient addressing range, + * (e.g., hand coded trampolines) so the linker does not have + * to add stubs. + * + * Linker stubs at the top of the main text section are currently not + * detected, and will result in a crash at boot due to offsets being + * wrong. + */ .text : AT(ADDR(.text) - LOAD_OFFSET) { ALIGN_FUNCTION(); - HEAD_TEXT - _text = .; /* careful! __ftr_alt_* sections need to be close to .text */ *(.text .fixup __ftr_alt_* .ref.text) SCHED_TEXT |