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powerpc: Use gas sections for arranging exception vectors
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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>
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Nicholas Piggin authored and Michael Ellerman committed Oct 4, 2016
1 parent 573819e commit 57f2664
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2 changes: 1 addition & 1 deletion arch/powerpc/include/asm/exception-64s.h
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Original file line number Diff line number Diff line change
Expand Up @@ -91,7 +91,7 @@
*/
#define LOAD_HANDLER(reg, label) \
ld reg,PACAKBASE(r13); /* get high part of &label */ \
ori reg,reg,((label)-_stext)@l; /* virt addr of handler ... */
ori reg,reg,(FIXED_SYMBOL_ABS_ADDR(label))@l;

/* Exception register prefixes */
#define EXC_HV H
Expand Down
261 changes: 245 additions & 16 deletions arch/powerpc/include/asm/head-64.h
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Original file line number Diff line number Diff line change
Expand Up @@ -3,28 +3,218 @@

#include <asm/cache.h>

/*
* We can't do CPP stringification and concatination directly into the section
* name for some reason, so these macros can do it for us.
*/
.macro define_ftsec name
.section ".head.text.\name\()","ax",@progbits
.endm
.macro define_data_ftsec name
.section ".head.data.\name\()","a",@progbits
.endm
.macro use_ftsec name
.section ".head.text.\name\()"
.endm

/*
* Fixed (location) sections are used by opening fixed sections and emitting
* fixed section entries into them before closing them. Multiple fixed sections
* can be open at any time.
*
* Each fixed section created in a .S file must have corresponding linkage
* directives including location, added to arch/powerpc/kernel/vmlinux.lds.S
*
* For each fixed section, code is generated into it in the order which it
* appears in the source. Fixed section entries can be placed at a fixed
* location within the section using _LOCATION postifx variants. These must
* be ordered according to their relative placements within the section.
*
* OPEN_FIXED_SECTION(section_name, start_address, end_address)
* FIXED_SECTION_ENTRY_BEGIN(section_name, label1)
*
* USE_FIXED_SECTION(section_name)
* label3:
* li r10,128
* mv r11,r10
* FIXED_SECTION_ENTRY_BEGIN_LOCATION(section_name, label2, start_address)
* FIXED_SECTION_ENTRY_END_LOCATION(section_name, label2, end_address)
* CLOSE_FIXED_SECTION(section_name)
*
* ZERO_FIXED_SECTION can be used to emit zeroed data.
*
* Troubleshooting:
* - If the build dies with "Error: attempt to move .org backwards" at
* CLOSE_FIXED_SECTION() or elsewhere, there may be something
* unexpected being added there. Remove the '. = x_len' line, rebuild, and
* check what is pushing the section down.
* - If the build dies in linking, check arch/powerpc/kernel/vmlinux.lds.S
* for instructions.
* - If the kernel crashes or hangs in very early boot, it could be linker
* stubs at the start of the main text.
*/

#define OPEN_FIXED_SECTION(sname, start, end) \
sname##_start = (start); \
sname##_end = (end); \
sname##_len = (end) - (start); \
define_ftsec sname; \
. = 0x0; \
start_##sname:

#define OPEN_TEXT_SECTION(start) \
text_start = (start); \
.section ".text","ax",@progbits; \
. = 0x0; \
start_text:

#define ZERO_FIXED_SECTION(sname, start, end) \
sname##_start = (start); \
sname##_end = (end); \
sname##_len = (end) - (start); \
define_data_ftsec sname; \
. = 0x0; \
. = sname##_len;

#define USE_FIXED_SECTION(sname) \
fs_label = start_##sname; \
fs_start = sname##_start; \
use_ftsec sname;

#define USE_TEXT_SECTION() \
fs_label = start_text; \
fs_start = text_start; \
.text

#define CLOSE_FIXED_SECTION(sname) \
USE_FIXED_SECTION(sname); \
. = sname##_len; \
end_##sname:


#define __FIXED_SECTION_ENTRY_BEGIN(sname, name, __align) \
USE_FIXED_SECTION(sname); \
.align __align; \
.global name; \
name:

#define FIXED_SECTION_ENTRY_BEGIN(sname, name) \
__FIXED_SECTION_ENTRY_BEGIN(sname, name, 0)

#define FIXED_SECTION_ENTRY_BEGIN_LOCATION(sname, name, start) \
USE_FIXED_SECTION(sname); \
name##_start = (start); \
.if (start) < sname##_start; \
.error "Fixed section underflow"; \
.abort; \
.endif; \
. = (start) - sname##_start; \
.global name; \
name:

#define FIXED_SECTION_ENTRY_END_LOCATION(sname, name, end) \
.if (end) > sname##_end; \
.error "Fixed section overflow"; \
.abort; \
.endif; \
.if (. - name > end - name##_start); \
.error "Fixed entry overflow"; \
.abort; \
.endif; \
. = ((end) - sname##_start); \


/*
* These macros are used to change symbols in other fixed sections to be
* absolute or related to our current fixed section.
*
* - DEFINE_FIXED_SYMBOL / FIXED_SYMBOL_ABS_ADDR is used to find the
* absolute address of a symbol within a fixed section, from any section.
*
* - ABS_ADDR is used to find the absolute address of any symbol, from within
* a fixed section.
*/
#define DEFINE_FIXED_SYMBOL(label) \
label##_absolute = (label - fs_label + fs_start)

#define FIXED_SYMBOL_ABS_ADDR(label) \
(label##_absolute)

#define ABS_ADDR(label) (label - fs_label + fs_start)

/*
* Following are the BOOK3S exception handler helper macros.
* Handlers come in a number of types, and each type has a number of varieties.
*
* EXC_REAL_* - real, unrelocated exception vectors
* EXC_VIRT_* - virt (AIL), unrelocated exception vectors
* TRAMP_REAL_* - real, unrelocated helpers (virt can call these)
* TRAMP_VIRT_* - virt, unreloc helpers (in practice, real can use)
* TRAMP_KVM - KVM handlers that get put into real, unrelocated
* EXC_COMMON_* - virt, relocated common handlers
*
* The EXC handlers are given a name, and branch to name_common, or the
* appropriate KVM or masking function. Vector handler verieties are as
* follows:
*
* EXC_{REAL|VIRT}_BEGIN/END - used to open-code the exception
*
* EXC_{REAL|VIRT} - standard exception
*
* EXC_{REAL|VIRT}_suffix
* where _suffix is:
* - _MASKABLE - maskable exception
* - _OOL - out of line with trampoline to common handler
* - _HV - HV exception
*
* There can be combinations, e.g., EXC_VIRT_OOL_MASKABLE_HV
*
* The one unusual case is __EXC_REAL_OOL_HV_DIRECT, which is
* an OOL vector that branches to a specified handler rather than the usual
* trampoline that goes to common. It, and other underscore macros, should
* be used with care.
*
* KVM handlers come in the following verieties:
* TRAMP_KVM
* TRAMP_KVM_SKIP
* TRAMP_KVM_HV
* TRAMP_KVM_HV_SKIP
*
* COMMON handlers come in the following verieties:
* EXC_COMMON_BEGIN/END - used to open-code the handler
* EXC_COMMON
* EXC_COMMON_ASYNC
* EXC_COMMON_HV
*
* TRAMP_REAL and TRAMP_VIRT can be used with BEGIN/END. KVM
* and OOL handlers are implemented as types of TRAMP and TRAMP_VIRT handlers.
*/

#define EXC_REAL_BEGIN(name, start, end) \
. = start ; \
.global exc_real_##start##_##name ; \
exc_real_##start##_##name:
FIXED_SECTION_ENTRY_BEGIN_LOCATION(real_vectors, exc_real_##start##_##name, start)

#define EXC_REAL_END(name, start, end)
#define EXC_REAL_END(name, start, end) \
FIXED_SECTION_ENTRY_END_LOCATION(real_vectors, exc_real_##start##_##name, end)

#define EXC_VIRT_BEGIN(name, start, end) \
. = start ; \
.global exc_virt_##start##_##name ; \
exc_virt_##start##_##name:
FIXED_SECTION_ENTRY_BEGIN_LOCATION(virt_vectors, exc_virt_##start##_##name, start)

#define EXC_VIRT_END(name, start, end)
#define EXC_VIRT_END(name, start, end) \
FIXED_SECTION_ENTRY_END_LOCATION(virt_vectors, exc_virt_##start##_##name, end)

#define EXC_COMMON_BEGIN(name) \
USE_TEXT_SECTION(); \
.align 7; \
.global name; \
DEFINE_FIXED_SYMBOL(name); \
name:

#define TRAMP_REAL_BEGIN(name) \
.global name ; \
name:
FIXED_SECTION_ENTRY_BEGIN(real_trampolines, name)

#define TRAMP_VIRT_BEGIN(name) \
FIXED_SECTION_ENTRY_BEGIN(virt_trampolines, name)

#ifdef CONFIG_KVM_BOOK3S_64_HANDLER
#define TRAMP_KVM_BEGIN(name) \
Expand All @@ -33,9 +223,13 @@ exc_virt_##start##_##name:
#define TRAMP_KVM_BEGIN(name)
#endif

#define EXC_REAL_NONE(start, end)
#define EXC_REAL_NONE(start, end) \
FIXED_SECTION_ENTRY_BEGIN_LOCATION(real_vectors, exc_real_##start##_##unused, start); \
FIXED_SECTION_ENTRY_END_LOCATION(real_vectors, exc_real_##start##_##unused, end)

#define EXC_VIRT_NONE(start, end)
#define EXC_VIRT_NONE(start, end) \
FIXED_SECTION_ENTRY_BEGIN_LOCATION(virt_vectors, exc_virt_##start##_##unused, start); \
FIXED_SECTION_ENTRY_END_LOCATION(virt_vectors, exc_virt_##start##_##unused, end);


#define EXC_REAL(name, start, end) \
Expand Down Expand Up @@ -77,13 +271,21 @@ exc_virt_##start##_##name:
TRAMP_REAL_BEGIN(tramp_real_##name); \
STD_EXCEPTION_PSERIES_OOL(vec, name##_common); \

#define EXC_REAL_OOL(name, start, end) \
__EXC_REAL_OOL(name, start, end); \
__TRAMP_REAL_REAL_OOL(name, start);

#define __EXC_REAL_OOL_MASKABLE(name, start, end) \
__EXC_REAL_OOL(name, start, end);

#define __TRAMP_REAL_REAL_OOL_MASKABLE(name, vec) \
TRAMP_REAL_BEGIN(tramp_real_##name); \
MASKABLE_EXCEPTION_PSERIES_OOL(vec, name##_common); \

#define EXC_REAL_OOL_MASKABLE(name, start, end) \
__EXC_REAL_OOL_MASKABLE(name, start, end); \
__TRAMP_REAL_REAL_OOL_MASKABLE(name, start);

#define __EXC_REAL_OOL_HV_DIRECT(name, start, end, handler) \
EXC_REAL_BEGIN(name, start, end); \
__OOL_EXCEPTION(start, label, handler); \
Expand All @@ -96,43 +298,67 @@ exc_virt_##start##_##name:
TRAMP_REAL_BEGIN(tramp_real_##name); \
STD_EXCEPTION_HV_OOL(vec, name##_common); \

#define EXC_REAL_OOL_HV(name, start, end) \
__EXC_REAL_OOL_HV(name, start, end); \
__TRAMP_REAL_REAL_OOL_HV(name, start);

#define __EXC_REAL_OOL_MASKABLE_HV(name, start, end) \
__EXC_REAL_OOL(name, start, end);

#define __TRAMP_REAL_REAL_OOL_MASKABLE_HV(name, vec) \
TRAMP_REAL_BEGIN(tramp_real_##name); \
MASKABLE_EXCEPTION_HV_OOL(vec, name##_common); \

#define EXC_REAL_OOL_MASKABLE_HV(name, start, end) \
__EXC_REAL_OOL_MASKABLE_HV(name, start, end); \
__TRAMP_REAL_REAL_OOL_MASKABLE_HV(name, start);

#define __EXC_VIRT_OOL(name, start, end) \
EXC_VIRT_BEGIN(name, start, end); \
__OOL_EXCEPTION(start, label, tramp_virt_##name); \
EXC_VIRT_END(name, start, end);

#define __TRAMP_REAL_VIRT_OOL(name, realvec) \
TRAMP_REAL_BEGIN(tramp_virt_##name); \
TRAMP_VIRT_BEGIN(tramp_virt_##name); \
STD_RELON_EXCEPTION_PSERIES_OOL(realvec, name##_common); \

#define EXC_VIRT_OOL(name, start, end, realvec) \
__EXC_VIRT_OOL(name, start, end); \
__TRAMP_REAL_VIRT_OOL(name, realvec);

#define __EXC_VIRT_OOL_MASKABLE(name, start, end) \
__EXC_VIRT_OOL(name, start, end);

#define __TRAMP_REAL_VIRT_OOL_MASKABLE(name, realvec) \
TRAMP_REAL_BEGIN(tramp_virt_##name); \
TRAMP_VIRT_BEGIN(tramp_virt_##name); \
MASKABLE_RELON_EXCEPTION_PSERIES_OOL(realvec, name##_common); \

#define EXC_VIRT_OOL_MASKABLE(name, start, end, realvec) \
__EXC_VIRT_OOL_MASKABLE(name, start, end); \
__TRAMP_REAL_VIRT_OOL_MASKABLE(name, realvec);

#define __EXC_VIRT_OOL_HV(name, start, end) \
__EXC_VIRT_OOL(name, start, end);

#define __TRAMP_REAL_VIRT_OOL_HV(name, realvec) \
TRAMP_REAL_BEGIN(tramp_virt_##name); \
TRAMP_VIRT_BEGIN(tramp_virt_##name); \
STD_RELON_EXCEPTION_HV_OOL(realvec, name##_common); \

#define EXC_VIRT_OOL_HV(name, start, end, realvec) \
__EXC_VIRT_OOL_HV(name, start, end); \
__TRAMP_REAL_VIRT_OOL_HV(name, realvec);

#define __EXC_VIRT_OOL_MASKABLE_HV(name, start, end) \
__EXC_VIRT_OOL(name, start, end);

#define __TRAMP_REAL_VIRT_OOL_MASKABLE_HV(name, realvec) \
TRAMP_REAL_BEGIN(tramp_virt_##name); \
TRAMP_VIRT_BEGIN(tramp_virt_##name); \
MASKABLE_RELON_EXCEPTION_HV_OOL(realvec, name##_common); \

#define EXC_VIRT_OOL_MASKABLE_HV(name, start, end, realvec) \
__EXC_VIRT_OOL_MASKABLE_HV(name, start, end); \
__TRAMP_REAL_VIRT_OOL_MASKABLE_HV(name, realvec);

#define TRAMP_KVM(area, n) \
TRAMP_KVM_BEGIN(do_kvm_##n); \
KVM_HANDLER(area, EXC_STD, n); \
Expand All @@ -141,6 +367,9 @@ exc_virt_##start##_##name:
TRAMP_KVM_BEGIN(do_kvm_##n); \
KVM_HANDLER_SKIP(area, EXC_STD, n); \

/*
* HV variant exceptions get the 0x2 bit added to their trap number.
*/
#define TRAMP_KVM_HV(area, n) \
TRAMP_KVM_BEGIN(do_kvm_H##n); \
KVM_HANDLER(area, EXC_HV, n + 0x2); \
Expand Down
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