Converting from int to long, back to int and then to unsigned int is confusing at best.
None of this voodoo is required. Negative syscall numbers including -1 don't need any of this treatment and the low level ASM code already does the sign extension to 64-bit on a 64-bit kernel. The only point where signedness matters is the comparison against the maximum syscall number, but that can be simplified by just using a unsigned argument for the various syscall invocation functions. Signed-off-by: Thomas Gleixner <[email protected]> --- arch/x86/entry/syscall_32.c | 26 +++++++++++--------------- arch/x86/entry/syscall_64.c | 36 ++++++++++++++---------------------- arch/x86/include/asm/syscall.h | 2 +- 3 files changed, 26 insertions(+), 38 deletions(-) --- a/arch/x86/entry/syscall_32.c +++ b/arch/x86/entry/syscall_32.c @@ -41,6 +41,8 @@ const sys_call_ptr_t sys_call_table[] = #endif #define __SYSCALL(nr, sym) case nr: return __ia32_##sym(regs); + +/* The unsigned int @nr argument is intentional as it creates denser code in a 64-bit build */ static noinline long ia32_sys_call(const struct pt_regs *regs, unsigned int nr) { switch (nr) { @@ -49,7 +51,7 @@ static noinline long ia32_sys_call(const } } -static __always_inline int syscall_32_enter(struct pt_regs *regs) +static __always_inline long syscall_32_enter(struct pt_regs *regs) { if (IS_ENABLED(CONFIG_IA32_EMULATION)) current_thread_info()->status |= TS_COMPAT; @@ -70,17 +72,11 @@ early_param("ia32_emulation", ia32_emula /* * Invoke a 32-bit syscall. Called with IRQs on in CT_STATE_KERNEL. */ -static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, int nr) +static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, unsigned long nr) { - /* - * Convert negative numbers to very high and thus out of range - * numbers for comparisons. - */ - unsigned int unr = nr; - - if (likely(unr < IA32_NR_syscalls)) { - unr = array_index_nospec(unr, IA32_NR_syscalls); - regs->ax = ia32_sys_call(regs, unr); + if (likely(nr < IA32_NR_syscalls)) { + nr = array_index_nospec(nr, IA32_NR_syscalls); + regs->ax = ia32_sys_call(regs, (unsigned int)nr); } } @@ -126,7 +122,7 @@ static __always_inline bool int80_is_ext */ __visible noinstr void do_int80_emulation(struct pt_regs *regs) { - int nr; + long nr; /* Kernel does not use INT $0x80! */ if (unlikely(!user_mode(regs))) { @@ -205,7 +201,7 @@ static __always_inline bool int80_is_ext */ DEFINE_FREDENTRY_RAW(int80_emulation) { - int nr; + long nr; enter_from_user_mode_randomize_stack(regs); @@ -240,7 +236,7 @@ DEFINE_FREDENTRY_RAW(int80_emulation) /* Handles int $0x80 on a 32bit kernel */ __visible noinstr void do_int80_syscall_32(struct pt_regs *regs) { - int nr = syscall_32_enter(regs); + long nr = syscall_32_enter(regs); /* * Subtlety here: if ptrace pokes something larger than 2^31-1 into @@ -260,7 +256,7 @@ DEFINE_FREDENTRY_RAW(int80_emulation) static noinstr bool __do_fast_syscall_32(struct pt_regs *regs) { - int nr = syscall_32_enter(regs); + long nr = syscall_32_enter(regs); int res; enter_from_user_mode_randomize_stack(regs); --- a/arch/x86/entry/syscall_64.c +++ b/arch/x86/entry/syscall_64.c @@ -32,6 +32,8 @@ const sys_call_ptr_t sys_call_table[] = #undef __SYSCALL #define __SYSCALL(nr, sym) case nr: return __x64_##sym(regs); + +/* The unsigned int @nr argument is intentional as it creates denser code */ static noinline long x64_sys_call(const struct pt_regs *regs, unsigned int nr) { switch (nr) { @@ -52,39 +54,29 @@ static noinline long x32_sys_call(const #endif } -static __always_inline bool do_syscall_x64(struct pt_regs *regs, int nr) +static __always_inline bool do_syscall_x64(struct pt_regs *regs, unsigned long nr) { - /* - * Convert negative numbers to very high and thus out of range - * numbers for comparisons. - */ - unsigned int unr = nr; - - if (likely(unr < NR_syscalls)) { - unr = array_index_nospec(unr, NR_syscalls); - regs->ax = x64_sys_call(regs, unr); + if (likely(nr < NR_syscalls)) { + nr = array_index_nospec(nr, NR_syscalls); + regs->ax = x64_sys_call(regs, (unsigned int)nr); return true; } return false; } -static __always_inline void do_syscall_x32(struct pt_regs *regs, int nr) +static __always_inline void do_syscall_x32(struct pt_regs *regs, unsigned long nr) { - /* - * Adjust the starting offset of the table, and convert numbers - * < __X32_SYSCALL_BIT to very high and thus out of range - * numbers for comparisons. - */ - unsigned int xnr = nr - __X32_SYSCALL_BIT; - - if (IS_ENABLED(CONFIG_X86_X32_ABI) && likely(xnr < X32_NR_syscalls)) { - xnr = array_index_nospec(xnr, X32_NR_syscalls); - regs->ax = x32_sys_call(regs, xnr); + /* Adjust the starting offset of the table */ + nr -= __X32_SYSCALL_BIT; + + if (IS_ENABLED(CONFIG_X86_X32_ABI) && likely(nr < X32_NR_syscalls)) { + nr = array_index_nospec(nr, X32_NR_syscalls); + regs->ax = x32_sys_call(regs, (unsigned int)nr); } } /* Returns true to return using SYSRET, or false to use IRET */ -__visible noinstr bool do_syscall_64(struct pt_regs *regs, int nr) +__visible noinstr bool do_syscall_64(struct pt_regs *regs, long nr) { nr = syscall_enter_from_user_mode_randomize_stack(regs, nr); --- a/arch/x86/include/asm/syscall.h +++ b/arch/x86/include/asm/syscall.h @@ -164,7 +164,7 @@ static inline int syscall_get_arch(struc ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64; } -bool do_syscall_64(struct pt_regs *regs, int nr); +bool do_syscall_64(struct pt_regs *regs, long nr); void do_int80_emulation(struct pt_regs *regs); #endif /* CONFIG_X86_32 */
