| Message ID | 20201202033329.21759-3-huangpei@loongson.cn |
|---|---|
| State | New |
| Headers | show |
| Series | [V2,1/2] mips: add hp-timing support for MIPS R2 | expand |
On 02/12/2020 00:33, Huang Pei wrote: > Before Linux/MIPS 2.6.36, kernel expected setting syscall number(aka > "li v0, #sys_number") right precedes "syscall", so the kernel syscall > restart sequence can use CP0 EPC - 4 to restart the syscall, because > kernel DID NOT save v0 during syscall handling. Linux 2.6.36 canceled > this restriction. > > See sysdeps/unix/sysv/linux/mips/{mips32/sysdep.h,mips64/sysdep.h,sysdep.h} > > Since glibc-2.24 the minimum kernel version is 3.2(much higer than > 2.6.36), I think it is OK to remove the ugly register spill in > syscall.S just because of the old convention > > This also remove the unaligned stack pointer operation LGTM, thanks. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org> > --- > sysdeps/unix/sysv/linux/mips/mips64/syscall.S | 14 ++------------ > 1 file changed, 2 insertions(+), 12 deletions(-) > > diff --git a/sysdeps/unix/sysv/linux/mips/mips64/syscall.S b/sysdeps/unix/sysv/linux/mips/mips64/syscall.S > index a9baff3c17..089524a40b 100644 > --- a/sysdeps/unix/sysv/linux/mips/mips64/syscall.S > +++ b/sysdeps/unix/sysv/linux/mips/mips64/syscall.S > @@ -27,14 +27,9 @@ > > .text > NESTED (syscall, SZREG, ra) > - .mask 0x00010000, -SZREG > + .mask 0x00000000, 0 > .fmask 0x00000000, 0 > - PTR_ADDIU sp, -SZREG > - cfi_adjust_cfa_offset (SZREG) > - REG_S s0, (sp) > - cfi_rel_offset (s0, 0) > - > - move s0, a0 > + move v0, a0 > move a0, a1 /* shift arg1 - arg7. */ > move a1, a2 > move a2, a3 > @@ -43,13 +38,8 @@ NESTED (syscall, SZREG, ra) > move a5, a6 > move a6, a7 > > - move v0, s0 /* Syscall number -> v0 */ > syscall /* Do the system call. */ > > - REG_L s0, (sp) > - cfi_restore (s0) > - PTR_ADDIU sp, SZREG > - cfi_adjust_cfa_offset (-SZREG) > bne a3, zero, L(error) > > ret >
On Wed, 2 Dec 2020, Huang Pei wrote: > Before Linux/MIPS 2.6.36, kernel expected setting syscall number(aka > "li v0, #sys_number") right precedes "syscall", so the kernel syscall > restart sequence can use CP0 EPC - 4 to restart the syscall, because > kernel DID NOT save v0 during syscall handling. Linux 2.6.36 canceled > this restriction. I object, as I previously noted. Maciej
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/syscall.S b/sysdeps/unix/sysv/linux/mips/mips64/syscall.S index a9baff3c17..089524a40b 100644 --- a/sysdeps/unix/sysv/linux/mips/mips64/syscall.S +++ b/sysdeps/unix/sysv/linux/mips/mips64/syscall.S @@ -27,14 +27,9 @@ .text NESTED (syscall, SZREG, ra) - .mask 0x00010000, -SZREG + .mask 0x00000000, 0 .fmask 0x00000000, 0 - PTR_ADDIU sp, -SZREG - cfi_adjust_cfa_offset (SZREG) - REG_S s0, (sp) - cfi_rel_offset (s0, 0) - - move s0, a0 + move v0, a0 move a0, a1 /* shift arg1 - arg7. */ move a1, a2 move a2, a3 @@ -43,13 +38,8 @@ NESTED (syscall, SZREG, ra) move a5, a6 move a6, a7 - move v0, s0 /* Syscall number -> v0 */ syscall /* Do the system call. */ - REG_L s0, (sp) - cfi_restore (s0) - PTR_ADDIU sp, SZREG - cfi_adjust_cfa_offset (-SZREG) bne a3, zero, L(error) ret
Before Linux/MIPS 2.6.36, kernel expected setting syscall number(aka "li v0, #sys_number") right precedes "syscall", so the kernel syscall restart sequence can use CP0 EPC - 4 to restart the syscall, because kernel DID NOT save v0 during syscall handling. Linux 2.6.36 canceled this restriction. See sysdeps/unix/sysv/linux/mips/{mips32/sysdep.h,mips64/sysdep.h,sysdep.h} Since glibc-2.24 the minimum kernel version is 3.2(much higer than 2.6.36), I think it is OK to remove the ugly register spill in syscall.S just because of the old convention This also remove the unaligned stack pointer operation --- sysdeps/unix/sysv/linux/mips/mips64/syscall.S | 14 ++------------ 1 file changed, 2 insertions(+), 12 deletions(-)