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LibC: Fix sigsetjmp on i686

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Calling sigprocmask() through the PLT requires setting the ebx register
to the address of the global offset table, otherwise chaos ensues. Also
the value of the ecx register was assumed to be preserved across that
function call despite the fact that it is caller-saved in the x86
calling convention.
This commit is contained in:
Jean-Baptiste Boric 2021-08-24 20:24:08 +02:00 • committed by Andreas Kling
parent 04694ae682
commit c87aa6d908
1 changed files with 14 additions and 2 deletions
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16
Userland/Libraries/LibC/arch/i386/setjmp.S
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@ -10,31 +10,43 @@
// /!\ Read setjmp.h before modifying this file!
//
.Lget_pc:
mov (%esp), %ebx
ret
.global setjmp
setjmp:
mov 4(%esp), %ecx // Grab jmp_buf argument
xor %eax, %eax // Grab val argument (hardcoded to zero)
jmp .Lsigset_common
.global sigsetjmp
sigsetjmp:
mov 4(%esp), %ecx // Grab jmp_buf argument
mov 8(%esp), %eax // Grab val argument
.Lsigset_common:
mov 4(%esp), %ecx // Grab jmp_buf argument
mov %eax, 24(%ecx) // Store val into did_save_signal_mask
movl $0, 28(%ecx) // Clear saved_signal_mask
test %eax, %eax
jz .Lsaveregs
push %ebp // Prepare ABI-compliant call to sigprocmask
mov %esp, %ebp
push %ebx
call .Lget_pc // Grab the GOT pointer
addl $_GLOBAL_OFFSET_TABLE_, %ebx
lea 28(%ecx), %eax // Set argument oldset
push %eax
push $0 // Set argument set
push $0 // Set argument how
call sigprocmask@plt
add $12, %esp
pop %ebx
pop %ebp
.Lsaveregs:
mov 4(%esp), %ecx // Grab jmp_buf argument
mov (%esp), %edx // Grab return address
mov %ebx, (0 * 4)(%ecx) // Save registers
mov %esi, (1 * 4)(%ecx)