The sc and scv 0 system calls have different ABI conventions, and
ptracers need to know which system call type is being used if they want
to look at the syscall registers.
Document that pt_regs.trap can be used for this, and fix one in-tree user
to work with scv 0 syscalls.
Fixes: 7fa95f9ada ("powerpc/64s: system call support for scv/rfscv instructions")
Cc: stable@vger.kernel.org # v5.9+
Reported-by: "Dmitry V. Levin" <ldv@altlinux.org>
Suggested-by: "Dmitry V. Levin" <ldv@altlinux.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210520111931.2597127-1-npiggin@gmail.com
Commit 209b44c804 ("docs: powerpc: syscall64-abi.rst: fix a malformed
table") attempted to fix the formatting of tables in syscall64-abi.rst, but
inadvertently changed some register names.
Redo the tables with the correct register names, and while we're here,
clean things up to separate the registers into different rows and add
headings.
Fixes: 209b44c804 ("docs: powerpc: syscall64-abi.rst: fix a malformed table")
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Link: https://lore.kernel.org/r/20210225060857.16083-1-ajd@linux.ibm.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
As reported:
Documentation/powerpc/syscall64-abi.rst:53: WARNING: Malformed table.
Text in column margin in table line 2.
=========== ============= ========================================
--- For the sc instruction, differences with the ELF ABI ---
r0 Volatile (System call number.)
This table requires a different notation to be valid.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Fix malformed table warning in powerpc/syscall64-abi.rst by making
two tables and moving the headings.
Documentation/powerpc/syscall64-abi.rst:53: WARNING: Malformed table.
Text in column margin in table line 2.
=========== ============= ========================================
--- For the sc instruction, differences with the ELF ABI ---
r0 Volatile (System call number.)
r3 Volatile (Parameter 1, and return value.)
r4-r8 Volatile (Parameters 2-6.)
cr0 Volatile (cr0.SO is the return error condition.)
cr1, cr5-7 Nonvolatile
lr Nonvolatile
--- For the scv 0 instruction, differences with the ELF ABI ---
r0 Volatile (System call number.)
r3 Volatile (Parameter 1, and return value.)
r4-r8 Volatile (Parameters 2-6.)
=========== ============= ========================================
Fixes: 7fa95f9ada ("powerpc/64s: system call support for scv/rfscv instructions")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/e06de4d3-a36f-2745-9775-467e125436cc@infradead.org
Add support for the scv instruction on POWER9 and later CPUs.
For now this implements the zeroth scv vector 'scv 0', as identical to
'sc' system calls, with the exception that LR is not preserved, nor
are volatile CR registers, and error is not indicated with CR0[SO],
but by returning a negative errno.
rfscv is implemented to return from scv type system calls. It can not
be used to return from sc system calls because those are defined to
preserve LR.
getpid syscall throughput on POWER9 is improved by 26% (428 to 318
cycles), largely due to reducing mtmsr and mtspr.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Fix ppc64e build]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200611081203.995112-3-npiggin@gmail.com
Convert docs to ReST and add them to the arch-specific
book.
The conversion here was trivial, as almost every file there
was already using an elegant format close to ReST standard.
The changes were mostly to mark literal blocks and add a few
missing section title identifiers.
One note with regards to "--": on Sphinx, this can't be used
to identify a list, as it will format it badly. This can be
used, however, to identify a long hyphen - and "---" is an
even longer one.
At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com> # cxl
Nicholas Piggin