From fac23fe4be23259a8eaa9bad822f5b14dd07d15c Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Tue, 24 Jun 2008 11:32:54 +1000 Subject: [PATCH] powerpc: Introduce infrastructure for feature sections with alternatives The current feature section logic only supports nop'ing out code, this means if you want to choose at runtime between instruction sequences, one or both cases will have to execute the nop'ed out contents of the other section, eg: BEGIN_FTR_SECTION or 1,1,1 END_FTR_SECTION_IFSET(FOO) BEGIN_FTR_SECTION or 2,2,2 END_FTR_SECTION_IFCLR(FOO) and the resulting code will be either, or 1,1,1 nop or, nop or 2,2,2 For small code segments this is fine, but for larger code blocks and in performance criticial code segments, it would be nice to avoid the nops. This commit starts to implement logic to allow the following: BEGIN_FTR_SECTION or 1,1,1 FTR_SECTION_ELSE or 2,2,2 ALT_FTR_SECTION_END_IFSET(FOO) and the resulting code will be: or 1,1,1 or, or 2,2,2 We achieve this by extending the existing FTR macros. The current feature section semantic just becomes a special case, ie. if the else case is empty we nop out the default case. The key limitation is that the size of the else case must be less than or equal to the size of the default case. If the else case is smaller the remainder of the section is nop'ed. We let the linker put the else case code in with the rest of the text, so that relative branches from the else case are more likley to link, this has the disadvantage that we can't free the unused else cases. This commit introduces the required macro and linker script changes, but does not enable the patching of the alternative sections. We also need to update two hand-made section entries in reg.h and timex.h Signed-off-by: Michael Ellerman Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/vdso32/vdso32.lds.S | 2 +- arch/powerpc/kernel/vdso64/vdso64.lds.S | 2 +- arch/powerpc/kernel/vmlinux.lds.S | 2 +- arch/powerpc/lib/feature-fixups.c | 2 + include/asm-powerpc/feature-fixups.h | 68 ++++++++++++++++++++----- include/asm-powerpc/reg.h | 2 + include/asm-powerpc/timex.h | 2 + 7 files changed, 64 insertions(+), 16 deletions(-) diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S index 9352ab5200..271793577c 100644 --- a/arch/powerpc/kernel/vdso32/vdso32.lds.S +++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S @@ -24,7 +24,7 @@ SECTIONS . = ALIGN(16); .text : { - *(.text .stub .text.* .gnu.linkonce.t.*) + *(.text .stub .text.* .gnu.linkonce.t.* __ftr_alt_*) } PROVIDE(__etext = .); PROVIDE(_etext = .); diff --git a/arch/powerpc/kernel/vdso64/vdso64.lds.S b/arch/powerpc/kernel/vdso64/vdso64.lds.S index 7d6585f902..e608d1bd3b 100644 --- a/arch/powerpc/kernel/vdso64/vdso64.lds.S +++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S @@ -24,7 +24,7 @@ SECTIONS . = ALIGN(16); .text : { - *(.text .stub .text.* .gnu.linkonce.t.*) + *(.text .stub .text.* .gnu.linkonce.t.* __ftr_alt_*) *(.sfpr .glink) } :text PROVIDE(__etext = .); diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S index 0c3000bf8d..3c07811989 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -35,7 +35,7 @@ SECTIONS ALIGN_FUNCTION(); *(.text.head) _text = .; - *(.text .fixup .text.init.refok .exit.text.refok) + *(.text .fixup .text.init.refok .exit.text.refok __ftr_alt_*) SCHED_TEXT LOCK_TEXT KPROBES_TEXT diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c index f6fd5d2ff1..973d547ef0 100644 --- a/arch/powerpc/lib/feature-fixups.c +++ b/arch/powerpc/lib/feature-fixups.c @@ -22,6 +22,8 @@ struct fixup_entry { unsigned long value; long start_off; long end_off; + long alt_start_off; + long alt_end_off; }; static void patch_feature_section(unsigned long value, struct fixup_entry *fcur) diff --git a/include/asm-powerpc/feature-fixups.h b/include/asm-powerpc/feature-fixups.h index 35f927888f..ab30129dce 100644 --- a/include/asm-powerpc/feature-fixups.h +++ b/include/asm-powerpc/feature-fixups.h @@ -29,24 +29,35 @@ #define FTR_ENTRY_OFFSET PPC_LONG #endif +#define START_FTR_SECTION(label) label##1: + +#define FTR_SECTION_ELSE_NESTED(label) \ +label##2: \ + .pushsection __ftr_alt_##label,"a"; \ + .align 2; \ +label##3: + #define MAKE_FTR_SECTION_ENTRY(msk, val, label, sect) \ -99: \ - .section sect,"a"; \ +label##4: \ + .popsection; \ + .pushsection sect,"a"; \ .align 3; \ -98: \ +label##5: \ FTR_ENTRY_LONG msk; \ FTR_ENTRY_LONG val; \ - FTR_ENTRY_OFFSET label##b-98b; \ - FTR_ENTRY_OFFSET 99b-98b; \ - .previous - + FTR_ENTRY_OFFSET label##1b-label##5b; \ + FTR_ENTRY_OFFSET label##2b-label##5b; \ + FTR_ENTRY_OFFSET label##3b-label##5b; \ + FTR_ENTRY_OFFSET label##4b-label##5b; \ + .popsection; /* CPU feature dependent sections */ -#define BEGIN_FTR_SECTION_NESTED(label) label: -#define BEGIN_FTR_SECTION BEGIN_FTR_SECTION_NESTED(97) +#define BEGIN_FTR_SECTION_NESTED(label) START_FTR_SECTION(label) +#define BEGIN_FTR_SECTION START_FTR_SECTION(97) -#define END_FTR_SECTION_NESTED(msk, val, label) \ +#define END_FTR_SECTION_NESTED(msk, val, label) \ + FTR_SECTION_ELSE_NESTED(label) \ MAKE_FTR_SECTION_ENTRY(msk, val, label, __ftr_fixup) #define END_FTR_SECTION(msk, val) \ @@ -55,12 +66,27 @@ #define END_FTR_SECTION_IFSET(msk) END_FTR_SECTION((msk), (msk)) #define END_FTR_SECTION_IFCLR(msk) END_FTR_SECTION((msk), 0) +/* CPU feature sections with alternatives, use BEGIN_FTR_SECTION to start */ +#define FTR_SECTION_ELSE FTR_SECTION_ELSE_NESTED(97) +#define ALT_FTR_SECTION_END_NESTED(msk, val, label) \ + MAKE_FTR_SECTION_ENTRY(msk, val, label, __ftr_fixup) +#define ALT_FTR_SECTION_END_NESTED_IFSET(msk, label) \ + ALT_FTR_SECTION_END_NESTED(msk, msk, label) +#define ALT_FTR_SECTION_END_NESTED_IFCLR(msk, label) \ + ALT_FTR_SECTION_END_NESTED(msk, 0, label) +#define ALT_FTR_SECTION_END(msk, val) \ + ALT_FTR_SECTION_END_NESTED(msk, val, 97) +#define ALT_FTR_SECTION_END_IFSET(msk) \ + ALT_FTR_SECTION_END_NESTED_IFSET(msk, 97) +#define ALT_FTR_SECTION_END_IFCLR(msk) \ + ALT_FTR_SECTION_END_NESTED_IFCLR(msk, 97) /* Firmware feature dependent sections */ -#define BEGIN_FW_FTR_SECTION_NESTED(label) label: -#define BEGIN_FW_FTR_SECTION BEGIN_FW_FTR_SECTION_NESTED(97) +#define BEGIN_FW_FTR_SECTION_NESTED(label) START_FTR_SECTION(label) +#define BEGIN_FW_FTR_SECTION START_FTR_SECTION(97) -#define END_FW_FTR_SECTION_NESTED(msk, val, label) \ +#define END_FW_FTR_SECTION_NESTED(msk, val, label) \ + FTR_SECTION_ELSE_NESTED(label) \ MAKE_FTR_SECTION_ENTRY(msk, val, label, __fw_ftr_fixup) #define END_FW_FTR_SECTION(msk, val) \ @@ -69,6 +95,22 @@ #define END_FW_FTR_SECTION_IFSET(msk) END_FW_FTR_SECTION((msk), (msk)) #define END_FW_FTR_SECTION_IFCLR(msk) END_FW_FTR_SECTION((msk), 0) +/* Firmware feature sections with alternatives */ +#define FW_FTR_SECTION_ELSE_NESTED(label) FTR_SECTION_ELSE_NESTED(label) +#define FW_FTR_SECTION_ELSE FTR_SECTION_ELSE_NESTED(97) +#define ALT_FW_FTR_SECTION_END_NESTED(msk, val, label) \ + MAKE_FTR_SECTION_ENTRY(msk, val, label, __fw_ftr_fixup) +#define ALT_FW_FTR_SECTION_END_NESTED_IFSET(msk, label) \ + ALT_FW_FTR_SECTION_END_NESTED(msk, msk, label) +#define ALT_FW_FTR_SECTION_END_NESTED_IFCLR(msk, label) \ + ALT_FW_FTR_SECTION_END_NESTED(msk, 0, label) +#define ALT_FW_FTR_SECTION_END(msk, val) \ + ALT_FW_FTR_SECTION_END_NESTED(msk, val, 97) +#define ALT_FW_FTR_SECTION_END_IFSET(msk) \ + ALT_FW_FTR_SECTION_END_NESTED_IFSET(msk, 97) +#define ALT_FW_FTR_SECTION_END_IFCLR(msk) \ + ALT_FW_FTR_SECTION_END_NESTED_IFCLR(msk, 97) + #endif /* __ASSEMBLY__ */ #endif /* __ASM_POWERPC_FEATURE_FIXUPS_H */ diff --git a/include/asm-powerpc/reg.h b/include/asm-powerpc/reg.h index 079999b032..7256efb5c1 100644 --- a/include/asm-powerpc/reg.h +++ b/include/asm-powerpc/reg.h @@ -732,6 +732,8 @@ " .llong %1\n" \ " .llong 97b-98b\n" \ " .llong 99b-98b\n" \ + " .llong 0\n" \ + " .llong 0\n" \ ".previous" \ : "=r" (rval) : "i" (CPU_FTR_CELL_TB_BUG)); rval;}) #else diff --git a/include/asm-powerpc/timex.h b/include/asm-powerpc/timex.h index 92dedde761..c55e14f7ef 100644 --- a/include/asm-powerpc/timex.h +++ b/include/asm-powerpc/timex.h @@ -38,6 +38,8 @@ static inline cycles_t get_cycles(void) " .long 0\n" " .long 97b-98b\n" " .long 99b-98b\n" + " .long 0\n" + " .long 0\n" ".previous" : "=r" (ret) : "i" (CPU_FTR_601)); return ret; -- 2.39.5